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Proyecto mtbe indonesia Proyecto mtbe indonesia Document Transcript

  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR MEMBER OF GROUP AND SUPERVISORS 1
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR ACKNOWLEDGEMENT First and foremost, thank you to Allah S.W.T for giving us the strength to finish up this project report. Without Your Willingness we would not be able to complete this project. It would be impossible to acknowledge adequately all the people who have been influential, directly or indirectly in forming this project. We would like to take this opportunity to express our deepest gratitude to our supervisors, Encik Mohd Imran Bin Zainuddin and Puan Sunita Binti Jobli who has given us his constant encouragement constructive advises and his patient in monitoring our progress in this project. Our appreciation and special thanks goes, Puan Hasnora Binti Jafri, Puan Junaidah Binti Jai, Encik Aziz Bin Ishak for supplying the valuable information and guidance for this project. We greatly indebted to Encik Napis Bin Sudin for his cooperation and willingness to be interviewed and for provide us with invaluable information and for his resourcefulness in gathering material. Special thanks owe to Puan Masni Bt Ahmad for her willingness to be interviewed and for the painstaking care she has shown in assisting us throughout the project. We also would like to express our appreciation to the Malaysia Industrial Development Authority (MIDA), Pusat Informasi Sirim Berhad, Petronas Resource Center, Jabatan Perangkaan Malaysia and Tiram Kimia Sdn.Bhd. (Kuala Lumpur) for their generous supply of relevant documents and material needed research. Last but not least to all my lecturers, family, friends and collegues for their encouragement and kind support when we need it most. 2
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR ABSTRACT The purpose for this MTBE or Methyl tertiary Butyl Ether plant is to produce 300,000 metric tonne/year. MTBE is the simplest and most cost effective oxygenate to produce, transport and deliver to customers. The additive works by changing the oxygenate / fuel ratio so that gasoline burns cleaner, reducing exhaust emissions of carbon monoxide, hydrocarbons, oxides of nitrogen, fine particulates and toxic. Two units will be considered which are the fluidizations, (Snamprogetti) Unit and the Etherification Unit. The raw materials used are isobutane, methanol, and water as feedstock. In addition, two types of catalysts are chromia alumina catalyzed compound in Snamprogetti Unit, while sulphonic ion exchanged resin catalyzed is used in the MTBE reactor. A good deal of catalyst has been devoted to improve the activity, selectivity, and the lifetime of the catalysts. In the Design Project 2, we emphasize in the individual chemical and mechanical designs for selected equipments in the plant. The chosen equipments are Catalytic Cracking Reactor, Multitubular Fixed Bed Reactor, MTBE Distillation Column, LiquidLiquid Extraction Column and Heat Exchanger. Design Project 2 also includes Process Control, Safety, Economic Evaluation, Process Integration and as well as Waste Treatment, which are considered as group works. 3 View slide
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR CONTENTS TITLE PAGE DECLARATION II CERTIFICATION III ACKNOWLEDGEMENT V ABSTRACT VI LIST OF TABLES LIST OF FIGURES LIST OF NOMENCLATURES REPORT 1 CHAPTER 1 PROCESS BACKGROUND AND INTRODUCTION 1.1 Introduction 1.2 Historical Review of MTBE Production Process 1.2.1 UOP Oleflex Process 1.2.2 Philips Star Process 1.2.3 ABB Lummus Catofin Process 1.2.4 Snmprogetti Yartsingtez FBD Process 1 2 3 3 3 4 CHAPTER 2 PROCESS SELECTION 2.1 2.2 Method Consioderation Detailed Process Description 2.2.1 Snaprogetti Yarsingtez fbd Process 2.2.2 MTBE Unit 2.2.3 Distillation Column Unit 2.2.4 Liquid-Liquid Extraction Unit 5 7 7 8 8 9 CHAPTER 3 ECONOMIC SURVEY 3.1 3.2 3.3 3.4 Market Survey 3.1.1 World Market Asia Market Demand Production Capacity 10 10 11 11 14 4 View slide
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 3.5 3.6 3.7 Supply Market Price 3.6.1 Methanol 3.6.2 Isobutane 3.6.3 Catalyst 3.6.4 Conclusion Economic Analysis 3.7.1 Break Even Analysis 3.7.2 Data Calculation1 14 15 15 16 16 16 17 17 20 CHAPTER 4 PLANT LOCATIONS & SITE SELECTION 4.1 4.2 4.3 4.4 Plant Location 24 General Consideration On the site Selection 24 4.2.1 Location with Respect To Marketing Area 25 4.2.2 Raw Material supply 25 4.2.3 Transport Facilities 25 4.2.4 Availability Of Labor 25 4.2.5 Availability Of Utilities 26 4.2.6 Environmental Impact and Effluent Disposal 26 4.2.7 Local Community Considerations 26 4.2.8 Land (Site Consideration) 26 4.2.9 Political and Strategic Consideration 27 Overview on Prospective Locations 27 4.3.1 Teluk Kalong 28 4.3.2 Tanjung Langsat 28 4.3.3 Bintulu 29 Conclusion 33 CHAPTER 5 ENVIRONMENTAL CONSIDERATION 5.1 5.2 5.3 Introduction Stack gas 5.2.1 Gas Emission treatment Wastewater Treatment 5.3.1 Wastewater characteristic 5.3.1a) Priority pollutants 5.3.1b) Organic 5.3.1c) Inorganic 5.3.1d) pH and Alkalinity 5.3.1e) Temperature 5.3.2 Liquid waste treatment 5.3.2a) Equalization treatment 5.3.2b) Solid waste treatment 5.3.3 Waste Minimization 34 35 35 35 35 36 36 37 37 38 38 38 39 41 5
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR CHAPTER 6 SAFETY CONSIDERATION 6.1 6.2 6.3 Introduction 42 Material Safety Data Sheet 43 6.2.1 Isobutane 43 6.2.1.1 Product Information 43 Physical & Chemical Properties 43 6.2.1.2 Immediate Health Effects 44 6.2.1.3 First Aid Measure 44 6.2.2 N-Butane 44 6.2.2.1 Handling and Storage 45 6.2.3 Methanol 45 6.2.4 MTBE 46 6.2.4.1 Physical State and Appearance46 6.2.4.2 Physical Dangers 46 6.2.4.3 Chemical Dangers 47 6.2.4.4 Inhalation Risks 47 6.2.5 TBA 47 6.2.5.1 Recognition 48 6.2.5.2 Evaluation 48 6.2.5.3 Controls 48 Hazard Identification & Emergency Safety & Health Risk 49 CHAPTER 7 MASS BALANCE 7.1 7.2 7.3 7.4 7.5 7.6 7.7 7.8 7.9 Snamprogetti -Yarsingtez FBD Unit Separator Mixer MTBE Reactor 7.4.1 1st Reaction in rector 7.4.2 2nd Reaction in reactor 7.4.3 3rd Reaction in reactor 7.4.4 Overall reaction Distillation Column Liquid Extraction Column Distillation Column Overall reaction system; flow diagram Scales Up Factor 51 53 53 54 55 56 57 58 59 60 61 62 63 CHAPTER 8 ENERGY BALANCES 8.1 8.2 Energy Equation Energy balance: Sample of calculation 8.2.1 Pump 1 8.2.2 Cooler 1 8.2.3 Separator 8.2.4 MTBE Reactor 8.2.5 Pump 2 64 65 73 75 76 78 79 6
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 8.2.6 8.2.7 8.2.8 8.2.9 8.2.10 8.2.11 8.2.12 8.2.13 8.2.14 8.2.15 8.2.16 Mixer Expander 1 Cooler 1 Distillation Column 1 Cooler 2 Pump 3 Extraction Column Pump 4 Pump 5 Distillation Column 2 Cooler 3 CHAPTER 9 HYSYS 80 81 82 84 86 87 88 89 91 92 93 95 APPENDICES REPORT 2 CONTENTS PAGE CHAPTER 1 CHEMICAL DESIGN AND MECHANICAL DESIGN SECTION 1 CATALYTIC CRACKING DESIGN 2.2 1.1 Introduction 1.2 Estimation of Cost Diameter of Reactor 1.3 Calculation of TDH Height 1.4 Minimum Fluidization Velocity 1.5 Calculation for Terminal Velocity 1.6 Find the Value Kih 1.7 Find the value Eo 1.8 Calculation of Solid Loading 1.9 Calculation for Holding Time 1.10 Calculation for Pressure Drop 1.11 Determine the Direction and Flowrate 1.12 Design of Cyclone 1.13 Calculation for Mechanical Design Mechanical Design 2.2.1 Introduction 2.2.2 Design stress 2.2.3 Welded Joint Efficiency 1 3 4 4 5 8 9 10 12 14 15 17 21 58 59 59 7
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 2.2.4 2.2.5 2.2.6 2.2.7 2.2.7.1 2.2.8 2.2.9 2.2.10 2.2.11 2.2.12 2.2.13 2.2.14 2.2.15 2.2.16 2.2.17 2.2.18 2.2.19 2.2.20 2.2.21 Corrosion allowance Minimum thickness of cylindrical section of shell Minimum thickness of domed head Loading stress Dead weight load 1.2.7.1 Dead Weight of Vessel 1.2.7.2 Weight of the Tubes 1.2.7.3 Weight of Insulation 1.2.7.4 Weight of Catalyst 1.2.7.5 Total Weight 1.2.7.6 Wind Loading 1.2.7.7 Analysis of Stresses Dead Weight Stress Bending Stress Radial Stress Check Elastic Stability Vessel Support Skirt Thickness Height of the Skirt Bending Stress at Base of the Skirt Bending Stress in the Skirt Base Ring and Anchor Bolt Design Compensation for Opening and Branches Compensation for Other Nozzles Bolted Flange Joint 2.2.20.1 Type of Flanges Selected 2.2.20.2 Gasket Flange face SECTION 3 3.1 3.2 3.3 3.4 59 59 60 61 61 61 62 62 63 63 63 64 65 65 66 67 68 68 69 70 70 71 73 74 74 74 75 75 MTBE DISTILLATION COLUMN Introduction Selection f Construction Material Chemical Design 3.3.1 Determine the Number of Plate 3.3.2 Determination of Number of Plate 3.3.3 Physical Properties 3.3.4 Determination of Column Diameter 3.3.5 Liquid Flow Arrangements 3.3.7 Plate Layout 3.3.8 Entrainment Evaluation 3.3.9 Weeping Rate Evaluation 3.3.13 Number of Holes 3.3.14 Column size Mechanical Design 3.4.1 Material construction 3.4.2 Vessel Thickness 3.4.3 Heads and closure 3.4.4 Total Column Weight 78 79 79 81 88 89 89 90 91 91 94 95 96 98 98 99 8
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 3.5 3.4.5 Wind Loads 3.4.6 Stiffness Ring Vessel Support Design SECTION 4 4.1 4.2 4.3 5.1 5.2 5.3 DESIGN OF LIQUID-LIQUID EXTRACTION COLUMN Introduction Chemical Design 4.2.1 Choice of Solvent 4.2.2 Estimation the Physical Properties 4.2.3 Determination the Number of Stage 4.2.4 Sizing of Sieve Tray 4.2.5 Number of Holes 4.2.6 Column Parameter 4.2.7 Weeping Evaluation Mechanical Design 4.3.1 Material Construction 4.3.2 Vessel Thickness 4.3.3 Design of Domed Ends 4.3.4 Column Weight 4.3.4.1 Dead Weight of Vessel 4.3.4.2 Weight of Plate 4.3.4.3 Weight of Insulation 4.3.4.4 Total weight 4.3.4.5 Wind Loading 4.3.5 Analysis of Stress 4.3.5. 1 Longitudinal & Circumferential Pressure Stress 4.3.5.2 Dead weight 4.3.5.3 Bending Stress 4.3.5.4 Buckling 4.3.6 Vessel Support Design 4.3.6.1 Skirt Support 4.3.6.2 Base Ring and Anchor 4.3.7 Piping Sizing SECTION 5 100 100 100 103 104 104 104 105 107 107 107 108 110 111 111 112 112 113 113 113 114 114 115 115 115 115 116 117 117 119 122 HEAT EXCHANGER DESIGN Introduction 5.1.1 Designing the heater Chemical Design 5.2.1 Physical Properties of the Stream 5.2.2 The Calculation 5.2.3 Number of Tubes Calculation 5.2.4 Bundle and Shell Diameter 5.2.5 Tube Side Coefficient 5.2.6 Shell Side Coefficient 5.2.7 Overall Heat Transfer Coefficient 5.2.8 Tube Side Pressure Drop 5.2.9 Shell Side pressure Drop Mechanical Design 5.3.1 Design Pressure 127 129 130 130 131 133 134 135 137 139 140 140 142 142 9
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 5.3.2 5.3.3 5.3.4 5.3.5 5.3.6 5.3.7 5.3.8 5.39 5.3.10 5.3.11 5.3.12 5.3.13 5.3.14 5.3.15 Design Temperature Material of Construction Exchanger Type Minimum Thickness Longitudinal Stress Circumferential Stress Minimum Thickness of Tube wall Minimum Thickness of Head and Closure Minimum Thickness of the Channel Cover Design Load Pipe Size Selection for the Nozzle Standard Flanges Design Of Saddles Baffles 142 142 143 143 144 144 144 145 146 147 150 150 152 152 CHAPTER 2 PROCESS CONTROL AND INSTRUMENTATION 2.1 2.2 2.3 Introduction Objective of control Control system design sheet 2.3.1 Heat Exchanger 2.3.2 Catalytic cracking fluidized bed reactor 2.3.3 Compressor 2.3.4 Condenser 2.3.5 Separator 2.3.6 Fixed bed reactor 2.3.7 Distillation Column 2.3.8 Liquid -liquid extraction Column 2.3.9 Distillation Column 2.3.10 Mixer 2.3.11 Expander 154 155 156 156 157 158 159 160 161 162 163 164 165 166 CHAPTER 3 SAFETY CONSIDERATION 3.1 3.2 3.3 3.4 Introduction Hazard and Operability Study Plant Start Up and Shut Down Procedure 3.3.1 Normal Start Up and Shut Down the Plant 3.3.1.1 Operating Limits 3.3.1.2 Transient Operating and Process Dynamic 3.3.1.3 Added Materials 3.3.1.4 Hot Standby 3.3.1.5 Emergency Shut Down 3.3.2 Start up and Shut down Procedure for the main Equipment 3.3.2.1 Reactor 3.3.2.2 Distillation Column 3.3.2.3 Liquid-Liquid Extraction Column 3.3.2.4 Heat Exchanger Emergency Response Plan (ERP) 167 168 170 171 171 172 172 172 172 172 172 173 174 175 175 10
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 3.5 3.4.1 Emergency Response Procedures 3.4.2 Evacuation Procedures 3.4.3 Fires 3.4.4 Explosion, Line Rupture or Serious Leak 3.4.5 Other Emergencies Plant Layout 176 176 177 177 177 178 CHAPTER 4 ECONOMIC EVALUATION 4.1 4.2 4.3 4.4 Introduction Cost Estimation Profitability Analysis 4.3.1 Discounted Cash flow 4.3.2 Net Present Value 4.3.3 Cumulative Cash flow Diagram 4.3.4 Rate of Return 4.3.5 Sensitivity Analysis 4.3.6 Payback Period Conclusion 184 187 199 199 202 203 204 205 206 208 CHAPTER 5 PROCESS INTEGRATION AND PINCH TECHNOLOGY 5.1 5.2 5.3 5.4 5.5 Introduction Pinch Technology The Problem Table Method The Heat Exchanger Network Minimum number of exchangers 209 209 210 214 216 CHAPTER 6 WASTE TREATMENT 6.1 6.2 6.3 6.4 6.5 6.6 Introduction Wastewater Treatment Wastewater Treatment Plant Design Sludge Treatment Waste Treatment Plant Layout Absorption tank using granular activated carbon 6.6.1 Analysis of the absorption process 6.6.2 Breakthrough Absorption capacity 220 221 224 229 230 231 232 233 APPENDICES 11
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR LIST OF TABLES OF DESIGN I TABLE TITLE 1.1 The Physical and Chemical Properties of MTBE 2.1 PAGE 2 The Comparison of the UOP Oleflex, Philips Star SP-Isoether FBD Process 6 3.1 Trade Balance of MTBE in Asia and Pacific 12 3.2 MTBE Balances for Asia and Pacific 13 3.3 Production, Import, Export & Consumption in Europe in Year 2000 14 3.4 Supplies MTBE Plant in Asia & Pacific 15 3.5 Standard Price for Isobutane 16 3.6 Cost of Producing MTBE 500000 tonne/year 18 3.7 Value in US Dollar Converted to RM 20 3.8 Value in US Dollar Converted to RM per tonne 20 3.9 Data Calculation by using Microsoft Excel in RM 23 4.1 The Comparison of the Potential Site Location 30 4.2 The Comparison of Location in term of Weightage Study 31 4.3 The Electricity Tariffs (Industrial Tariff) for Peninsular Malaysia and Sarawak 33 12
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR LIST OF TABLES OF DESIGN II TABLE TITLE PAGE Chapter 1 Section 1 1.1 Calculation for Terminal Velocity in Different Size of dp. 8 1.2 Correlation of Three Investigators 10 1.3 Data Calculation to Find Solid Loading 12 1.4 Summary of Mechanical Design 40 3.1 The Composition in Feed Stream 80 3.2 The Composition in Top Stream 80 3.3 The Composition in Bottom Stream 80 3.4 The Average Relative Volatility, 3.5 The Non-key Flow of the Top Stream 82 3.6 The Non-key Flow of the Bottom Stream 83 3.7 MTBE Equilibrium Curve 85 3.8 Provisional Plate Design Specification 97 3.9 Summarized Results of Mechanical Design 101 3.10 Design Specification of the Support Skirt 102 4.1 Provisional Plate Design Specification 106 4.2 Summary of the Mechanical Design 118 4.3 Stress Analysis for Liquid-Liquid Extraction Column 119 4.4 Design Specification of the Support Skirt 119 4.5 Piping Sizing for Liquid-liquid Extraction Column 120 Section 3 α 82 Section 4 Section 5 5.1 Properties of Raw Material (Isobutane and N-butane) and Steam for (E100) 5.2 130 Summary of Chemical Design For Heat Exchanger In Series 5.3 141 By taking D = 100 mm, the selected tube nozzle 149 13
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR TABLE TITLE PAGE 5.4 By taking D = 500 mm, the selected tube nozzle is: 149 5.5 Standard Flange for Inlet isobutene 150 5.6 Standard Flange for Outlet isobutene 151 5.7 Standard Flange for Inlet Steam 151 5.8 Standard Flange for Outlet Steam 151 5.9 Using Ds = 600mm, the Standard Steel Saddles for Vessels up to 1.2m 5.10 152 Summary of Mechanical Design For Heat Exchanger in Series 153 2.1 Parameter at Heat Exchanger 151 2.2 Parameter at Catalytic Cracking Fluidized Bed Reactor 152 2.3 Parameter at Compressor 153 2.4 Parameter at Condenser 154 2.5 Parameter at Separator 154 2.6 Parameter at Fixed Bed Reactor 155 2.7 Parameter at MTBE Distillation Column 156 2.8 Parameter at Liquid-liquid Extraction Column 157 2.9 Parameter at Distillation Column 158 2.10 Parameter at Mixer 159 2.11 Parameter for Expander 160 Important Features in a HAZOP Study 170 4.1 Labor Cost 189 4.2 Estimation Cost of Purchase Equipment 197-198 4.3 Annual Cash flow Before Tax 200 4.4 Annual Cash flow After Tax 201 4.5 Present Worth Value 202 Chapter 2 Chapter 3 3.1 Chapter 4 14
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 4.6 After Tax Cumulative Cash Flow TABLE 203 TITLE PAGE 4.7 Present Value (RM) When i = 30% & i = 40% 204 4.8 Future Value (RM) When MARR = 15% 205 4.9 Simple Payback Period 206 4.10 The Interpolation Simple Payback Period 206 4.11 Discounted Payback Period 207 4.12 The Interpolation Discounted Payback Period 207 5.1 Shows the process data for each stream. 210 5.2 Interval Temperature for ΔTmin = 10oC 211 5.3 Ranked order of interval temperature 212 5.4 Problem Table 213 Chapter 5 Chapter 6 6.1 Parameter Limits for Wastewater and Effluent under the Environmental Quality Act 1974 6.2 208 Functions of Pumps in the Waste Treatment Plant 215 15
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR LIST OF FIGURES OF DESIGN I FIGURE 3.1 TITLE PAGE MTBE’s Role in US Gasoline grew rapidly Through 1995 10 3.2 World MTBE Demand (1998-2010) – Mod Scenario 11 3.3 MTBE supply & Demand Asia and Pacific 13 3.4 Breakeven Analysis Chart Calculated by using Excel 19 5.1 . Functional Elements in a Solid-Waste Treatment System 40 16
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR LIST OF FIGURES OF DESIGN II FIGURE TITLE PAGE Chapter 1 Section 1 1.1 Illustration Diagram of the Reactor 2 1.2 CDRe2 and CD/Re vs. Reynolds Number 6 Analysis of Stresses 67 3.1 MTBE Distillation Column 78 3.2 McCabe-Thiele Diagram 86 5.1 Heat Exchanger in Series for the Heating Process 129 5.2 Steel Pipe Nozzle 149 5.3 Standard Flange 150 2.1 Control Scheme for the Heat Exchanger 156 2.2 Control Scheme for Catalytic Cracking Section 2 2.1 Section 3 Section 5 Chapter 2 Fluidized Bed Reactor 157 2.3 Control Scheme for the Compressor 158 2.4 Control Scheme for the Condenser 159 2.5 Control Scheme for the Separator 160 2.6 Control Scheme for the Fixed Bed Reactor 161 2.7 Control Scheme for the MTBE Distillation Column 162 2.8 Control Scheme for the Liquid-liquid Extraction Column 163 2.9 Control Scheme for the Distillation Column 164 2.10 Control Scheme for the Mixer 165 2.11 Control Scheme for the Expander 166 17
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR FIGURE TITLE PAGE Chapter 3 3.1 Methyl tert-Butyl Ether (MTBE) Plant Layout 180 3.2 Methyl tert-Butyl Ether (MTBE) Plant Evacuation Routes 181 3.3 PID before HAZOP 182 3.4 PID after HAZOP 183 Cumulative Cash Flow (RM) Versus Year 203 5.1 Diagrammatically representation of process stream 210 5.2 Intervals and streams 211 5.3 Heat Cascade 212 5.4 Grid for 4 stream problem 213 5.5 Grid for 4 Stream Problem 214 5.6 Proposed Heat Exchanger Network 216 6.1 The Sludge Treatment System 229 6.2 Waste Treatment Plant Layout 231 Chapter 4 4.1 Chapter 5 Chapter6 18
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Ar - Archimedes number a - acceleration B - settling chamber longitudinal cross-sectional area b - dimension C - constant CD - drag coefficient c - concentration D - system diameter d - particle diameter de - effective fiber diameter E, - field intensity F - cross-sectional area Pr - Fronde number g - gravitational acceleration H - height K - precipitation constant , A - Cross sectional area of catalytic reactor Aor - Area of orifice C Ag - Concentration of gas reactant CD - Drag coefficient d Bv - Diameter of bubble in the bed dp - Particle diameter D - Diffusivity Dt - Diameter of catalytic reactor e - Thickness E - Activation energy 19
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR FBo - Mass flow of coal to the catalytic reactor FC - Fixed carbon mass fraction Hbed - Height of bed Hh - Height of Catalytic reactor J - Joint factor k” - Reaction rate constant k - Reaction rate constant K eq - Equilibrium constant L - Height above the bed n - Total no of orifice N - No of holes in 1 m2 area Nor - No of orifice in 1 m2 area PCO , PH 2 O - Pi Design stress - Partial pressure rC , rS - Rate of reaction R - Ideal gas constant Ret - Reynolds number Rp - Radius of particle t - Total holding time T - Temperature Uo - Superficial gas velocity Umf - Minimum fluidization velocity Ut - Terminal velocity VBed - Volume of bed WBed - Weight of coal in bed WC - Total mass of carbon X - Conversion factor α - Fitting parameter (for this design is 0.21) β - Fitting parameter (for this design is 0.66) ρg - Gas density ρB - Molar density ρs - Bulk density of catalyst ρp - Particle density 20
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR µg - Gas viscosity τ - Time for complete conversion of reactant particle ∆ p - Pressure drop E - total elutriation rate of particles Ef - frictional force of particles Ei - entrainment rate of panicle size i Ei∞ - elutriation rate of particle size i Eo - total entrainment rate at bed surface E∞ - total elutriation rate of particles g - gravitational acceleration constant gc - gravitational conversion constant, m kg/s2 kg -force Gi - solids flow rate h - height above dense bed surface Rep - particle Reynolds Number = ρ g (U o − U ts ) d p / µ Ret - dpU ρ / µ g t - time Umf - minimum fluidization velocity Uo - superficial gas velocity Usi - solid velocity (upward) Us - single particle terminal velocity of particle size i W - weight fraction of bed Ws - weight of solid particles in verlical pipe having length h Xi - weight fraction of particle size i in bed Greek Symbols ε - voidage in freeboard 21
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR εi - voidage in freeboard for system having only particle size i λ - solid friciion coefficient ρg - gas density ρp - particle density 22
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR CHAPTER 1 PROCESS BACKGROUND AND INTRODUCTION 1.1 INTRODUCTION Methyl tertiary butyl ether (MTBE) is produced by reacting isobutene with methanol over a catalyst bed in the liquid phase under mild temperature and pressure. Isobutene can be obtained from stream cracker raffinate or by the dehydrogenation of isobutane from refineries. Ether in general is a compound containing an oxygen atom bonded to two carbon atoms. In MTBE one carbon atom is that of a methyl group – CH3 and the other is the central atom of a tertiary butyl group, -C (CH3)). At room temperature, MTBE is a volatile, flammable, colorless liquid with a distinctive odour. It is miscible with water but at high concentrations it will form an air-vapour explosive mixture above the water, which can ignite by sparks or contact with hot surfaces. MTBE has good blending properties and about 95% of its output is used in gasoline as an octane booster and an oxygenate (providing oxygen for cleaner combustion and reduced carbon monoxide emissions). It is also used to produce pure isobutene from C4 streams by reversing its formation reaction. It is a good solvent and extractant. Table 1.1: The Physical and chemical properties of MTBE 23
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Chemical formula Molecular structure Oxygen content Physical state (at normal C5H12O (CH3)4CO 18.2 wt% Colorless liquid temperature and pressure) Boiling point Melting point Flash point Autoignition temperature Flammable limits in air Relative density Vapour pressure Reactive index Color Water solubility 55.2oC -108.6 oC 30 oC 425 oC 1.5 – 8.5% 0.7405g/ml at 20 oC 245 mm Hg at 25 oC 1.3690 at oC Colorless 42000mg/l at 25 oC (<10% in water, miscible with ethanol and Partition coefficient noctanol/water (log10) Henry’s Law Constant 1.2 diethyl ether) 1.06 65.4 Pa/m3/mol HISTORICAL REVIEW OF MTBE PRODUCTION PROCESS The MTBE plants actually consist of six units: Isomerization Unit (including deisobutanizer), Dehydrogenation Unit, MTBE Unit, Methanol Recovery Unit, Oxygenate Removal Unit and Olefin Saturation Unit. A common offsite utility system will be incorporated to distribute the required utilities to each unit. There are four method of producing MTBE implemented under license as the following: 1. UOP-Oleflex Process 2. Phillips STAR Process 3. ABB Lummus Catofin Process 4. Snamprogetti-Yarsingtez FBD (SP-Isoether) Process. 1.2.1 UOP-Oleflex Process 24
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR The UOP-Oleflex process uses multiple side-by-side, radial flow, moving-bed reactors connected in series. Preheated feed and interstage heaters supply the heat of reaction. The reaction is carried out over platinum supported on alumina, under near isothermal conditions. The catalyst system employs UOP's Continuous Catalyst Regeneration (CCR) technology. The bed of catalyst slowly flows concurrently with the reactants and is removed from the last reactor and regenerated in a separate section. The reconditioned catalyst is then returned to the top of the first reactor. processes involved are the deisobutenization, the isomerisation The typical and the dehydrogenation process that has been commercial in Malaysia. 1.2.2 Philips Star Process The second one is the Philips Steam Active Reforming (STAR) Process. The Phillips Steam Active Reforming (STAR) Process uses a noble metal-promoted zinc aluminate spinel catalyst in a fixed-bed reactor. The reaction is carried out with steam in tubes that are packed with catalyst and located in a furnace. The catalyst is a solid, particulate noble metal. Steam is added to the hydrocarbon feed to provide heat to the endothermic reaction, to suppress coke formation, and to increase the equilibrium conversion by lowering partial pressures of hydrogen and propane. 1.2.3 ABB Lummus Catofin Process The ABB Lummus Catofin Process uses a relatively inexpensive and durable chromium oxide–alumina as catalyst. This catalyst can be easily and rapidly regenerated under severe conditions without loss in activity. Dehydrogenation is carried out in the gas phase over fixed beds. Because the catalyst cokes up rapidly, five reactors are typically used. Two are on stream, while two are being regenerated and one is being purged. The reactors are cycled between the reaction and the reheat/regeneration modes, and the thermal inertia of the catalyst controls the cycle time, which is typically less than 10 minutes. The chromium catalyst is reduced from Cr6+ to Cr3+ during the dehydrogenation cycle. The raw materials used to produce MTBE by using this method are butanes, hydrogen and as well as recycled isobutene from the system itself. In this process, there is an isostripper column, which separates the heavies, and the light ends from which then could produce MTBE. 25
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 1.2.4 Snamprogetti-Yartsingtez FBD (SP-Isoether) The Snamprogetti-Yarsingtez SP-Isoether (FBD) Process uses a chromium catalyst in equipment, which is the fluidized bed that resembles conventional fluidized catalytic cracking technology used in the oil refinery. The catalyst is recirculated from the reactor to the regeneration section on a 30–60-min cycle. The process operates under low pressure and has a low-pressure drop and uniform temperature profile. Snamprogetti has been presenting and marketing their hydrogenation technology, ISOETHER 100, since 1997. This process is to be used to convert MTBE units by utilizing Snamprogetti’s MTBE Water Cooled Tubular Reactor Technology. In this SPIsoether Process, the products are MTBE and isooctagenas (iso octane gas). In this SP-Isoether Process the catalyst used in the isoetherification reactor is the same as those other typical processes, which is Platinum. (Please refer Appendix A – Figure 1.3). Four method processes of the MTBE above are favorable among the petrochemical firms. CHAPTER 2 PROCESS SELECTION 26
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Suitable process, which is gives a lot of profit and less problem is an important in order to determinant for the success of a plant. This chapter will briefly discuss the best process selected based on a few criteria. It covers general consideration, detailed consideration for process selection and conclusion on the process selection. 2.1 METHOD CONSIDERATION. From the processes mentioned earlier, there are many ways to produce MTBE. It is essential to choose the best method that will be used to produce MTBE. The selection of the method must consider the safety of the plant, minimum waste or by product generated, efficient and economical. Snamprogetti-Yarsingtez SP- Isoether FBD process will be chosen as the method to produce MTBE. More detailed reasons for the selection of this process are: High conversion (greater than 98 %) with few by-products compared to other process. From the economy aspect,Snamprogetti-Yarsingtez FBD Process can reduce the cost of setting up the plant as it can be implied in any of typical MTBE-produced plant, known as “Financial Safety Net”.(When an MTBE plant faces an oversupplied MTBE market, Isoether makes it possible to switch production from MTBE to a superior Alkylate.). As for the safety aspects of the plant, as the Snamprogetti-Yarsingtez FBD is a safe process as it just use the fluidize bed to the process of producing MTBE. The process operates under low pressure and has a lowpressure drop and this means that the fluidized bed is physically not harmful to anyone. As for the temperature, it operates under uniform temperature profile. As the temperature is not high, this means that the process is not as dangerous as other hightemperature-operated process. But, precautions should be taken seriously all the time, as we do not know when an accident could happen even in the safest place. As for the waste by using the Snamprogetti-Yarsingtez FBD Process, the product of the process is only MTBE and other effluent and as well as flue gas which are not harmful to the environment. Table 1.1 The comparison of the UOP-Oleflex, Philips Star, ABB Lummus Catofin and Snamprogetti- Yartsingtez SP-Isoether FBD process. 27
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Method and UOP-Oleflex STAR Philip ABB Lummus Snamprogetti- Consideration Process process Process Yarsingtez FBD Investment cost Investment cost Lower capital process Reduce the cost is very modest were evaluated investment of setting up the Economic for 700 BPSD plant as it can be Consideration (650tonne/day) implied in any of feed capacity typical MTBE- 97-99% 98% 99 .99% produced Greater than 98% 1. Higher per 1. The Stabilized 1.CD Tech 1.Environmental pass Product Is Near Efficiently Uses Friendly conversion and Equilibrium The Heat 2.”Financial at least 1-2% Mixture Of Released By An Safety Net”. higher catalyst Isobutane. Exothermic (When an MTBE selectivity as a 2.The Light-End Reaction. plant faces an result of lowest Yield Fr. Cracker 2.Conducting 2 oversupplied operating Is Less Than 1 Unit Operations MTBE market, pressure and Wt% Butane In 1 Equipment Isoether makes it temperature. Efficiency Feed (Isobutylene Selectivity) Advantages possible to switch 2. No catalyst production from losses. MTBE to a superior Alkylate.) Disadvantages 1. Less 1. Much heat is 1. The Reaction 1. Not widely efficiencies needed as Must Take Place practiced in furnace is used. In The Liquid industry, as it Phase –Catalyst needs thorough Must Remain research to Completely implement it. Wetted. 2.The Reaction Cannot Be Overly 28
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Endothermic 2.2.1 DETAILED PROCESS DESCRIPTION 2.2.2 Snamprogetti-Yartsingtez SP-Isoether (FBD) Process The Snamprogetti-Yarsingtez SP-Isoether (FBD) Process uses a chromium catalyst in equipment, which is the fluidized bed that resembles conventional fluidized catalytic cracking technology used in the oil refinery with 65% isobutane (i-C4H10) conversion to produce isobutene. Dehydrogenation reaction that occur in this process: iC4H10 iC4H8 + H2 The main feature of this process is that the catalyst filled annuli are connected in such a way that small, discrete amounts of catalyst can be withdrawn from the bottom of a reactor, and sent to the top of the reactor. Catalyst withdrawn from the bottom of the reactor is sent to a separate regeneration section for regeneration prior to being sent to the top of the reactor. The catalyst is recirculated from the reactor to the regeneration section on a 30–60-min cycle. The reactor and regeneration sections are totally independent of each other. The regeneration section can be stopped, even for several days, without interrupting the dehydrogenation process in the reactor section. The vaporized isobutane is fed along with fresh catalyst to the first, called reactor, and the spent catalyst is separated from the products and sent to the regenerator, where air (O 2) is added to oxidize the carbon. The reactor cracks the isobutane and forms coke on the catalyst. Then in the regenerator the coke is burned off and the catalyst is sent back into the reactor. The “magic” of this process is that the reactor-regenerator combination solves both the heat management and coking problems simultaneously. Burning off the coke is strongly exothermic, and this reaction in the regenerator supplies the heat (carried with the hot regenerated catalyst particles) for the endothermic cracking reactions in the reactor. The process operates under low pressure and has a low-pressure drop and uniform temperature profile. Products that have been produced from this unit are 29
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR isobutene. Isobutene available in the C4 stream from the Snamprogetti-Yarsintez FBD unit will be combining with methanol, which is sourced from the Sabah Gas Industries methanol plant in Labuan to produce, fuel-grade MTBE with a high-octane value in the MTBE unit. 2.2.3 MTBE Unit The MTBE unit includes two sections such as the main reaction section and the finishing reaction. In the main reaction section, 98% conversions of isobutene occurs mainly in the main reactor which are designed to provide the mechanical ands thermal conditions required by the expanded catalyst bid technology. Reactions occur in this unit are: 1. iC4H8 (isobutene) + CH3OH (methanol) 2. CH3OH + CH3OH (CH3)2O + H2O (DME) 3. iC4H8 + H2O C4H10O (TBA) C5H12O (MTBE) The reactor is operated in an up-flow direction with an external liquid recycle to remove the heat of reaction and to control the expansion of the catalyst bed. This selective reaction of methanol with isobutene is conducted in liquid phase at moderate temperature on an ion exchange resin type catalyst. The expansion of the catalyst bed in the reactor is ensured by pump around circulation loop with a cooling water cooler to control the reactor feed temperature to remove the heat of reaction. Resin traps on top of each reactor to trap resin in case of carryover with the liquid. In the finishing reactor section, isobutene final conversion is achieved in a catalytic column where reaction and distillation are performed simultaneously. 2.2.4 Distillation Column Unit 30
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR This column includes a separation column yielding MTBE product at the bottom and (isobutene, isobutene, normal butane, water and DME) with methanol entrained by azeotropy at the top. The reaction section bed is contained in the upper part of this column. An excess of methanol is maintained corresponding to the amount leaving the tower in the azeotrope. The required methanol is passed through guard beds and filtered prior to being charged to the catalytic column to achieve final conversion. Bottom MTBE product and the other by-product such as TBA, DME is sent to rundown tanks under level control after cooling in feed/bottom exchanger and trim cooler. The overhead of the column is condensed in the air-cooled condenser under pressure control. One part of the liquid is sent to the column as reflux and the other part to the liquid-liquid extraction unit after cooling. 2.2.5 Liquid-Liquid Extraction Unit In this unit methanol will extract from the isobutene, isobutene, normal butane to produce C4 raffinate from the overhead of the column and at the bottom, methanol and water are produced. C4 raffinate from this unit we decided to sell to the Korea. CHAPTER 3 ECONOMIC SURVEY 31
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 3.1 MARKET SURVEY 3.1.1 World Market The MTBE market has been in strong continuous growth since 1992. For instance, the 1998 world consumption was approximately 19.5 million tonnes, about double that of 1992, representing an annual growth rate of about 12%. Present trends indicate a mild growth in 2000, up to 20 million tonnes, with US consumption slightly declining and other parts of the world growing (EEA 2000). The MTBE’s role in U.S. gasoline grew rapidly through 1995 given away in figure 3.1. Figure 3.1 MTBE’s role in U.S. gasoline grew rapidly through 1995 (Sources: Local Issues, Global Implications) 3.2 ASIA MARKET Most Asia countries such as South Korea, Japan, Hong Kong, Taiwan, China, Malaysia, Singapore, Philippines and Thailand, have already phased lead out of their gasoline pool and are replacing it with oxygenates such as MTBE. Due to MTBE’s relative ease in blending into gasoline, easy transportation and storage, as well as relatively cheap and abundant supply, MTBE is the most widly use oxygenate in Asia. However, the use of MTBE in gasoline blending is not mandatory for countries like South Korea and Thailand. South Korea, for instance, requires a 1.3% - 2.3% 32
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR oxygenate content in gasoline during the winter, compared to a minimum of 0.5% for the summer. In other Asian Countries, MTBE is mainly use as an octane booster to replace lead. (source: features mtbe asias.html). 3.3 DEMAND World demand of MTBE mod scenario is about 4.1 mil ton per annum consumption in US West Coast at stake due to the legislation from 1998 to 2010. It has as an impact on 80% of PETRONAS MTBE exports to the US. This mod scenario is representing in figure 3.2. Figure 3.2: World MTBE demand (1998-2010) – mod scenario (Sources: Petronas’s Library Kuala Lumpur City Center (KLCC) U.S. demand is about 250,000b/d, dominates MTBE consumption. Most MTBE is used to comply with mandated oxygen content rules for gasoline supplied to either RFG or wintertime carbon monoxide areas. A small amount may be utilized for octane enhancement. In Europe, MTBE demand is estimated about 60,000 b/d. MTBE use in Europe is essentially confined to Octane enhancement, and about 6,000 b/d is exported to the United States. Eastern Europe currently consumed about 10,000 b/d of MTBE. In Asia, demand for MTBE in this region is expected to grow at much more rapid rate than elsewhere in the world. The rate will taper off late in decade from about 12% per year to about 8% by the turn of the century, since the early rapid growth has 33
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR been fed by the lead phase down which should be nearly complete by 2000. Throughout the period, the region will be a net importer of MTBE, mostly obtained from the Middle East. The trade balance of MTBE in Asia and Pacific is expected to be in table 3.1. (Sources: MTBE annual Report) Table 3.1 Trade Balance of MTBE in Asia and Pacific (Sources: MTBE annual Report) Capacities listed are the average available during the year. Details for 1995 and 1999 of MTBE Balance for Asia and Pacific are shown in table 3.2. These data are also shown graphically in figure 3.3 which indicate for MTBE supply and demand Asia and Pacific. (Sources: MTBE annual Report) Table 3.2: MTBE Balance for Asia and Pacific (Sources: MTBE annual Report) 34
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR MTBE supply and demand Asia and Pacific Figure 3.3: MTBE supply and demand Asia and Pacific (Sources: MTBE annual Report) Demand for MTBE expected to be marginally firmer in the near future as Asian Countries such as Indonesia and India are working totally phase out lead from their gasoline pool. Supply on other hand is expected to remain abundant, as Asia is able to produce about 3 million Mt/yr of MTBE for its Captive consumption. In addition to this, Asia attracts a regular supply of about 500,000 ton/yr of MTBE from Middle Eastern and Europe sources.(Reference: features mtbe asias.html). 35
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 3.4 PRODUCTION CAPACITY Commercial production of MTBE started in Europe in 1973 and in the US in 1979. Total worldwide production capacity in 1998 was 23.5 million tones and the actual production was 18 million tones The annual production volume of MTBE in the year 2000 in the Europe was 2,844,000 tons. About 129,000 tonnes was imported and about 479 000 tonnes were exported outside the Europe in the year 2000 ((Dewitt & Company Inc. 2002). The majority of the exported volume (> 83%) was exported to USA and Canada. The majority of exported volume (> 80%) was transported as non-blended MTBE and minority as a component of petrol (blended). The annual consumption of MTBE within the Europe was hence 2,495,000 tons in the year 2000 (see table below). For the future no substantial increase in MTBE usage is expected. (Dewitt & Company Inc. 2002). Table 3.3: Production, import, export and consumption in Europe in year 2000 (tonnes/year) souces: (Dewitt & Company Inc. 2002). Production 2 844 000 Import into Europe 129 000 Export outside Europe 479 000 Consumption 2 495 000 The world's MTBE industry today is operating at about 80% of capacity. The US is by far the largest market, having about 43% of the production capacity but consuming 63% of total global output. On stability, the Middle East is the swing producer, exporting more than 50,000 bbl/day to the US and elsewhere. 3.5 SUPPLY DeWitt’s Company estimates for local production of MTBE a summarized in table 3.4. Most of plants unit are refinery-based units taking isobutylene from FCCU units, or as Raffinate I from olefins plants. Since olefin plants in the region a mostly naphthabased, they produce significant quantities of C4 olefins for this purpose. There is one butane-based plant in Malaysia. Table 3.4 also shown for MTBE plants suppliers to Asia and Pacific. 36
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Table 3.4 Suppliers MTBE plant in Asia and Pacific (Sources: MTBE annual Report) 3.6 MARKET PRICE 3.6.1 Methanol Price of methanol, as feedstock in Asia is $240 - $280 /ton. While in Europe, the prices is $265 - $270 / ton free on board (fob) Rotterdam. In U.S. the price of methanol is 76 cts – 77cts/ gal in fob. Global Methanol demand is expected to increase to 3.5 % per year over the next 5 years, compared to 1.0% - 1.5% growth in 2002 and 2003. Those lower growth rates are attributable to the phase-out of Methyl tert-butyl ether (MTBE) as oxygenate in gasoline in California, and slower economic growth in China caused by SARS. Methanol growth in China is forecast at 7% - 8.5% per year, fueled by formaldehyde and acetic acid demand. (Chemicals Week) 3.6.2 Isobutane Standard price for isobutene is stated by followed: 37
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Table 3.5 : Standard price for isobutane Grade Purity Grade 4.0 99.99% Grade 3.0 99.9% Instrument 99.5% 3.6.3 Cylinder Size LP30 LP15 LP05 LP01 1/2 Ton LP30 LP15 LP05 LP01 1 Ton LP30 LP15 LP05 LP01 Volume lbs 117 60 23 6 490 117 60 23 6 490 117 60 23 6 Price per Cylinder RM900.00 RM600.00 RM370.00 RM200.00 RM1225.00 RM380.00 RM240.00 RM170.00 RM100.00 RM890.00 RM293.00 RM185.00 RM100.00 RM75.00 Catalyst Price of Chromia catalyst Compound – USD60 000/Rottedam (Rdam) from the existing plant. (En Mohd. Napis, from MTBE plant, Gebeng ) 3.6.4 Conclusion Our company will import the methanol and isobutane as feedstock, from Petronas Malaysia and United State (US) respectively. Methanol feedstock will be supplied from Gurun, Kedah production capacity of 66,000 ton/year. For the second feedstock, isobutane (instrument grade) will be supplied by Chevron Phillips Chemical Company LP, 10001 Six Pines Drive, The Woodlands, Texas, US by shipping method. MTBE is suitable as a gasoline additive which simultaneously increases the octane rating of the fuel and adds oxygen which promotes cleaner burning. When used in place of lead-based octane enhancers, dual environmental benefits are realized, a reduction in atmospheric lead concentrations and reduced emissions of carbon monoxide and other smog forming chemicals. Since the 1970s, the worldwide 38
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR consumption of MTBE has increased significantly and many new facilities have been constructed to support the growing market (Kirschner, 1996; Riddle, 1996). MTBE production will increase in future in Asia, Asia Pacific, Middle East and Europe even though MTBE is banned in California but not in the entire nation of the United States. 3.7 ECONOMIC ANALYSIS An economic analysis used to smooth the progress of based on existing plant. This analysis is important to ensure that the chemical plants converge and the economics is satisfactory before the plant operate. All the data taken from MTBE Annual 1994, DeWitt & Company Incorporated, 16800 Greenpoint Park, Suite 120 N, Houston, Texas, that given by Petronas Library, KLCC. 3.7.1 Break-Even Analysis When chemical engineers determine outlay for any type commercial process, they want these costs to be enough accuracy to provide reliable decision. To accomplish this, they must have a complete understanding of the many factors that can affect costs. Break-even analysis is important to ensure that the plant can give profit before the plant can run. The objective of break even analysis is to find the point, in dollars or in ringgits and units, at which costs equal revenues. This point is the break even point. Break even analysis requires an estimation of fixed costs, variable costs and revenue. Fixed costs are costs that continue even if no units are produced. Examples include depreciation, taxes, debt, and mortgage payments. Variable costs are those that vary with the volume units produced. The major components of variable costs are labor and materials. However, others cost, such as the portion of the utilities that varies with volume, are also variable cost. The different between selling price and variable cost is contribution. Only when total contribution exceeds total fixed cost will there be profit. 39
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Another element in break-even analysis is the revenue function. From the graph, revenue begins at the origin and proceeds upward to the right, increasing by selling price of each unit. Where the revenue function crosses the total cost line (the sum of fixed and variable costs), is the break even point, with a profit corridor to the right and a loss corridors to the left. Table 3.6: Cost of producing MTBE 500,000 ton/year (Sources: DeWitt & Company Incorporated, Annual Report) Table 3.6 showed that the cost of production of MTBE based on existing plant producing 500,000 ton/year. From table 3.6, given data, break-even analysis can be calculated to know the break-even point figure. Figure below indicate that break-even chart, where it has been calculated by using excel that shown in table 3.8 and based on the data given from table 3.6. 40
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Figure 3.4 : Break even analysis chart calculated by using excel. From the break even chart figure above, the value of break-even point at the existing capacity of 500,000 ton/year is 185,629.85 tons in units and RM 244,679,817.14 in Ringgit Malaysia (RM). This value indicates the minimum units and values needed to be sold. The given capacity of 500,000 tons/year can give profit to the company. The margin of safety (MOS) calculated from the graph, which is 314,370.15 tons and RM414,373,182.86. Margin of safety (MOS) in percentage of sales is 62.87%. The sale is allowed to drop about 62.87% before the company will incurred a loss. In other word, at selling 300,000 tons/year capacity will also give profit to our company. The margin of safety from the graph for 300,000 ton/year calculated is 114,370.15 tons and RM150,751,982.86. The margin of safety (MOS) as percentage of sales is 38.12%. The sale is allowed to drop about 38.12% before the company will incurred a loss. All the data calculation is shown in the next section. 41
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 3.7.2 Data Calculation All the data based on 500,000 tons/year producing MTBE from existing plant. Table 3.7 Values in USD converted to RM (Sources: Data collected from table 3.6) Total revenue, TR Total variable cost, TVC Total fixed cost, TFC RM 659,053,000.00 RM 504,754,000.00 RM 57,285,000.00 Total Revenue (TR), MTBE (500,000 ton), TR = Quantity of MTBE X Price of MTBE = QMTBE X PMTBE = 500,000 tons X USD346.87 X 3.8 = RM 659,053,000 Total cost TC = total fixed cost + total variable cost = TFC + TVC Where, Total fixed cost = 500,000 ton X USD30.13 X 3.8 = RM 57,285,000.00 Total variable cost = 500,000 ton X USD (226.4 + 39.26) X 3.8 = RM 504,754,000.00 ∴ Total cost, TC = RM57,285,000.00 + RM 504,754,000.00 = RM 562,039,000.00 Tables 3.7 represent cost per unit ton converted into Ringgit Malaysia (RM), taking data’s directly from the table 3.6. Table 3.8 Values in USD converted to RM per ton (Sources: Data collected from table 3.6) Revenue (RM) per ton RM1,318.00 Variable cost (RM) per ton RM 1,009.51 Fixed cost (RM) per ton RM114.57 Break-even point in ton can be calculated based on formula equation, which given by follow: 42
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Break-even point, BEP (tons) = Total Fixed cost Contribution/ton where, Contribution/ton = revenue / ton - variable cost / ton ∴ BEP (tons) = ______RM 57,285,000.00_____ (RM1, 318.00 - RM 1,009.51) = 185,629.85 tons (the minimum capacity) Next, Break-even point in RM can be calculated based on formula equation, which given by follow: ∴ BEP (RM) = Break-even point, BEP (tons) X revenue / ton = 185,629.85 tons X RM1, 318.00 = RM 244,679,817.14 Beside that, margin of safety and percentage of sale can be calculated as follows: For 500,000 ton/year production, ∴ Margin of safety (MOS) in units = Budgeted sale (units) - BEP (units) = 500,000 tons - 185,629.85 tons = 314,370.15 tons ∴ Margin of safety (MOS) in RM = Budgeted sale (RM) - BEP (RM) = RM 659,053,000.00 - RM 244,679,817.14 = RM 414,373,182.86 ∴ Margin of safety (MOS) as percentage of sales = MOS (RM) x 100% Sales(RM) = RM 414,373,182.86 x 100% RM 659,053,000 = 62.87% 43
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR For 300,000 ton/year production, ∴ Margin of safety (MOS) in units = Budgeted sale (units) - BEP (units) = 300,000 tons - 185,629.85 tons = 114,370.15 tons ∴ Margin of safety (MOS) in RM = Budgeted sale (RM) - BEP (RM) = RM 395,431,800 - RM 244,679,817.14 = RM 150,751,982.86 ∴ Margin of safety (MOS) as percentage of sales = MOS (RM) x 100% Sales(RM) = RM150,751,982.86 x 100% RM 395,431,800 = 38.12% Table 3.9 shown that the calculation of break-even point by using excel. Table 3.9: Data calculation by using excel in RM (Sources: Data taking from table 3.7) 44
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR CAPACITY TFC1 0 57,285,000.00 10000 57,285,000.00 20000 TVC1 0 TR1 TC1 0 57,285,000.00 10,095,080.00 13,181,060 67,380,080.00 57,285,000.00 20,190,160.00 26,362,120 77,475,160.00 40000 57,285,000.00 40,380,320.00 52,724,240 97,665,320.00 60000 57,285,000.00 60,570,480.00 79,086,360 117,855,480.00 80000 57,285,000.00 80,760,640.00 105,448,480 138,045,640.00 100000 57,285,000.00 100,950,800.00 131,810,600 158,235,800.00 120000 57,285,000.00 121,140,960.00 158,172,720 178,425,960.00 140000 57,285,000.00 141,331,120.00 184,534,840 198,616,120.00 160000 57,285,000.00 161,521,280.00 210,896,960 218,806,280.00 180000 57,285,000.00 181,711,440.00 237,259,080 238,996,440.00 200000 57,285,000.00 201,901,600.00 263,621,200 259,186,600.00 220000 57,285,000.00 222,091,760.00 289,983,320 279,376,760.00 240000 57,285,000.00 242,281,920.00 316,345,440 299,566,920.00 260000 57,285,000.00 262,472,080.00 342,707,560 319,757,080.00 280000 57,285,000.00 282,662,240.00 369,069,680 339,947,240.00 300000 57,285,000.00 302,852,400.00 395,431,800 360,137,400.00 320000 57,285,000.00 323,042,560.00 421,793,920 380,327,560.00 340000 57,285,000.00 343,232,720.00 448,156,040 400,517,720.00 360000 57,285,000.00 363,422,880.00 474,518,160 420,707,880.00 380000 57,285,000.00 383,613,040.00 500,880,280 440,898,040.00 400000 57,285,000.00 403,803,200.00 527,242,400 461,088,200.00 420000 57,285,000.00 423,993,360.00 553,604,520 481,278,360.00 440000 57,285,000.00 444,183,520.00 579,966,640 501,468,520.00 460000 57,285,000.00 464,373,680.00 606,328,760 521,658,680.00 480000 57,285,000.00 484,563,840.00 632,690,880 541,848,840.00 500000 57,285,000.00 504,754,000.00 659,053,000 562,039,000.00 CHAPTER 4 45
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR PLANT LOCATIONS AND SITE SELECTION 4.1 PLANT LOCATION The location of the plant can have a crucial effect on the profitability of a project and the scope for future expansion. Many factors must be considered when selecting a suitable site. A good location is required to optimise the production of the plant. It is important to know that, not all Malaysian industrial park caters the need of a chemical plant. Also not all industrial park allows the building of chemical plants. Our industrial parks are divided into categories such as: 1. Light industrial 2. Medium industrial 3. Heavy industrial 4. General industrial 5. Hi-tech industrial 4.2 GENERAL CONSIDERATION ON THE SITE SELECTION All the information about plant locations are based on the data gathered from the Malaysian Industrial Development Authority (MIDA). And we refer detail information on important factors that need to be considered in the site selection. In the process of selecting the location, we did some evaluation. Among the principle factors considered are: 4.2.1 Location With Respect To Marketing Area For materil that are produced in bulk quantities, such as cement, fertilizer, raw material of petrochemical product, where the cost of product per tone is relatively low and the cost of transport a significant fraction of the sales price, the plant must located close to the primary market. This consideration will be less important for low volume production, high priced products; such as pharmaceuticals, plastisizer and etc. in an international 46
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR market, there may be an advantage to be gained by locating the plant within an area with preferential tariff agreement. 4.2.2 Raw Material Supply The availability and price of suitable raw materials will often determine the site location. Plant producing bulk chemicals are best located close to the source of the major raw material, where this is also close to the marketing area. 4.2.3 Transport Facilities The transport of materials and products to and from the plant will be an overriding consideration in site selection. If practicable, a site that we are consider that close to at least two major forms of transport: road, rail, waterway or a sea port. Road transport being increasing used, and is suitable for local distribution from central warehouse. Rail transport will be cheaper for the long distance transport of bulk chemicals . Air transport is convenient and efficient for the movement of personnel and essential equipment and supplies and the proximity of the site to a major airport also considered. 4.2.4 Availability of Labour Labour that will be needed for construction of the plant and its operation. Skilled construction workers will usually be brought in from outside the site area, but there should be an adequate pool of unskilled labour available locally and labour suitable for training to operate the plant. Skill tradesman will be needed for plant maintenance. Local trade union customs and restrictive practices will have to be considered when assessing the availability and suitability of the local labour for requirement and training . 4.2.5 Availability of Utilities 47
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Chemical processes invariably require large quantities of water for cooling and general process used and the plant must be located near a source of water of suitable quality. Process water may be drawn from a river, wells or purchased from a local authority. At some site, the cooling water required can be taken from a river or lake or from the sea; at other locations cooling towers will be needed. Electrical power will be needed at all sites. Electrochemical processes that required large quantities of power: for example, aluminium smelters need to be located close to a cheap source of power. A competitively priced fuel must be available onsite for steam and power generation. 4.2.6 Environmental Impact and Effluent Disposal All industrial processes produce waste products and full consideration must be given to the difficulties and cost of their disposal. The disposal of toxic and harmful effluents will be covered by local regulations and the appropriate authorities must be consulted during the initial site survey to determine the standards that must be met. An environmental impact assessment should be made for each new project or major modification of addition to an existing process. 4.2.7 Local Community Considerations The proposed plant must fit in with and be acceptable to the local community. Full consideration must be given to the safe location of the plant so that it does not impose a significant additional risk to the community. On a new side, the local community must be able to provide adequate facilities for the plant personnel: schools, banks, housing and recreational and cultural facilities. 4.2.8 Land (site consideration) 48
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Sufficient suitable land must be available for the proposed plant for future expansion. The land should ideally be flat, well drained suitable load-bearing characteristics. A full site evaluation should be made to determine the need for piling or other special foundations. 4.2.9 Political and Strategic Considerations Capital grants, tax concessions and other inducements are often given by government to direct new investment to preferred locations such as areas of high unemployment. The availability of such grants can be the overriding factor in site selection. 4.3 OVERVIEW ON PROSPECTIVE LOCATIONS Our process is a petrochemical base process; therefore we choose to locate our plant in a petrochemical complex. The reason is quite simple; a petrochemical complex could simplify the formation and the maintenance of a chemical plant. It could also cut the daily operation cost and saving us the hassle of transportation. In Malaysia there are only three such places, known as the Integrated Petrochemical Complexes. These complexes are situated in each of the site below: 1. Telok Kalong Industrial Park. 2. Tanjung Langsat Industrial Park. 3. Bintulu Industrial Park. Other than the above factors, the capacity of plant was also taken into consideration in determining the suitability of site. Plant capacity will determine how big the space required to build the plant and the storage area and also the mode of transportation to be use. The manufacture of MTBE is classified as a petrochemical project. Several locations of industrial area particular at Teluk Kalong Industrial Area in Terengganu, Tanjung Langsat Industrial Area in Johor and Bintulu Industrial Area, Sarawak that we are refer for location. 49
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 4.3.1 Teluk Kalong Teluk Kalong Industrial Estate located 9.6 km from Kemaman. Total area available 167.46 hectares. The price of land in ranges RM 0.46 to RM 4.18 per Feet Square. This area is proposed for petrochemical and heavy industry petrochemical. The Electricity is generated at the following station. Total generation capacity is 900 MW. Local consumption is less than 1/3. No major breakdown, low frequency of interruption. Water most plentiful with surplus capacity. Water supply capacity at various treatment plants total 331000-meter cube per day, with planned upgrading for additional requirement. Kenyir Lake with 39000 hectares of water with 134 metre average depth, make Terengganu a potential export of water middle East. Water supply is in Bukit Shah. Water tariffs (industrial) are RM1.15 metre cube. The raw materials supplier of isobutene is availability from Chevron Philips Chemical Company LP, United State and methanol is availability from Petronas Malaysia, Labuan. 1. • Airport facilities Terengganu major industrial locations are serve by 3 airports - Kuantan - Kerteh - Kuala Teregganu • 2. • 4.3.2 Kuala Teregganu Port Facilities Kemaman Port, Kerteh Port and Kuantan Port Tanjung Langsat Industrial Park Tanjung Langsat is designed as hub for heavy/medium industries with all the necessary infrastructure and service facilities. 91.43 km distance from Johor Baharu. The infrastructure works such as the Pasir Gudang – Segamat Highway. Sungai Johore Bridge and dedicated Port in Tanjung Langsat. Tanjung Langsat Industrial Complex is a sprawling area just a stone’s through from Pasir Gudang Industrial Area. A total hectare still available is 1,085.95. Selling price is RM8 to RM22 square feet. In term of seaport two seaports are currently being constructed at Tanjung Pelepas, 50
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR located 40 km west of Johore Baharu city and Tanjung Langsat located 10 km east of the Johore Port. Tenaga Nasianal Berhad (TNB) provides electricity. Two airports in the 50km radius. There is the Sultan Ismail International Airport (common known locally as Senai Airport) in Johore Baharu and the Changi International Airport in Singapore. The Sultan Ismail International Airport, which is located about 30km to the north west of JB city, is currently being expended and upgrades to become the regional airport for southern peninsular Malaysia. 4.3.3 Bintulu The distance from nearest town is 224.29 km from Sibu. Type of industries is light and medium petrochemical. Area available is 77 hectares. Selling price RM2.5 to RM10 per feet square. Electricity supplies by Sarawak Electricity Supply Cooperation (SESCO). • Airport facilities - Bintulu Airport • Port Facilities - Bintulu Port 51
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Table 4.1 The Comparison of The Potential Site Location: Teluk Kalong Industrial Park Tanjung Langsat Industrial Park Bintulu Industrial Park 9.6 km from Kemaman 91.43 km from Johor Baharu 224.29 km from Sibu Types of Industry Isobutane from US and methanol from Labuan Petrochemical and heavy industry Isobutane from US and methanol from Labuan Petrochemical light and medium Isobutane from US and methanol from Labuan Petrochemical light and medium Area Available 167.46 hectares 1085.98 hectares 77 hectares RM 0.46 - 4.18 RM 8.00 - 22.00 RM 2.50 - 10.00 Electricity Supply Tenaga National Berhad Tenaga National Berhad Sarawak Electrycity Supply Cooperation (SESCO) Water Supply Bukit Shah Water Treatment Road Facilities Kuala TerengganuKuantan-Kuala LumpurKuala Terengganu-KertehTeluk Kalong-KuantanKuala Lumpur Distance from the nearest town Raw Material Land Price 2 (RM/ft ) Airport Facilities Port Facilities Water Tariffs 3 (RM/m ) Kuala Terengganu Airport Kerteh Airport Kemaman Port, Kerteh Port Kuantan Port RM 1.15 Syarikat Air Johor and Logi Air Sg. Layang Syarikat Air Sarawak North-South Highway from Bukit Kayu Hitam to Singapore- Major Road : Bintulu Sibu and Bintulu - Miri Senai International Airport Bintulu Airport Pasir Gudang Port Bintulu Port RM 1.68 (0-20 m 3) RM2.24 (more than 20 m 3) RM 0.95 (0 -25 m 3) RM1.20 (more than 25 m 3) (Source: MIDA) A few proposed plant sites were narrowed down based on the above factors (table 4.2). Table 4.2 is a summary of location and factors being considered. After detailed study of 52
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR the factors, each was given weightage and was estimated. The result tabulated in table 4.2 for the purpose of comparison. Table 4.2 The Comparison of Location in term of Weightage Study Weightage Telok Kalong Industrial Area Tanjung Langsat Industrial Area Bintulu Industrial Area Marketing Area 10 8 7 7 Raw Material 10 8 9 9 Transport 10 8 7 6 Availabillity of Labour 10 8 8 7 Utilities 10 8 9 7 Total Land Available 10 8 9 8 Climate 10 9 9 9 Price of Land 10 9 5 7 Local Community Consideration 10 6 8 9 Incentives 10 8 8 8 TOTAL 100 80 79 77 ∴ 0 to 10 with 10 is the best Table 4.3 The Electricity Tariffs (Industrial Tariff) for Peninsular Malaysia and Sarawak 53
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Tariff Peninsular Malaysia Tariff D (Low Voltage, and less than 6.6 supply) for all consumptions Cost per kWh kV Tariff E1 (Medium Voltage General, 6.6 kV - 66 kV supply) for all consumptions. For each kW of maximum demand per month: RM 17.30 25.8 19.8. Tariff E2 (Medium Voltage Peak/Off-Peak, 6.6 kV 66kV supply) Peak period (0800-2200 hours), 20.8 Off-Peak period (2200-0800 hours). 12.8 For each kW of maximum demand per month during peak period: RM21.70 Tariff E3 (High Voltage Peak/Off-Peak, more than 132 kV supply) Peak period (0800 -2200 hours), Off-Peak period (2200 - 0800) hours). For each kW of maximum demand per month during peak period: RM 20.80 Sarawak Tariff 11 1st 100kWh In excess of 100kWh to 3000 kWh In excess of 3000 kWh Minimum charge per month: RM 10.00 Tariff 12 All units 17.8 10.8 40 30 21 17 For each kW of maximum demand per month: RM12.00 Minimum charge : RM 12.00 per kW x billing demand Tariff 13 (Peak/Off-Peak) Peak period ( 0700 - 2400 hours) Off-Peak period ( 0000 - 0700 hours) For each kW of maximum demand per month during peak period: RM20.00 Minimum charge: RM 20.00 per kW x billing demand. 17 10 (Source: MIDA) 54
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 4.4 CONCLUSION Based on the factor weightage studied, it can be concluded that Telok Kalong Industrial Estate is the most suitable and practical location to choose as a site for MTBE plant. The philosophy of in situ consumption of much of the production MTBE, together with remaining product aimed directly at the export market and also makes the need for port facilities of paramount importance. The Tanjung Langsat and Bintulu Industrial Area are not impressive for MTBE plant. There are many other reasons influences our decision including: • Nearest of the Kuantan Port, Kemaman Port and Kerteh Port facilities is more convenient and economically for export and import purposes. • Excellent and consistent support from bulky oil, gas and chemical supplier from Kerteh. Constantly upgrading existing and developing new infrastructure, facilities and supporting industries. These include the construction of roads; to increase accessibility to and from the estates are scheduled. 55
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR CHAPTER 5 ENVIRONMENTAL CONSIDERATION 5.1 INTRODUCTION Nowadays, environmental issues become very important. Besides this, a good waste treatment system is also important in order to reduce and minimize environmental pollutants. The chemical waste in the form of solid, liquid and gases must be treated before being discharged into sewage, drain and atmospheres. Any chemical plant to be set up in Malaysia must follow the rules and regulations under the Department of Environment (DOE) Malaysia, which includes the Environmental Quality Act 1974. Under Environmental Quality Act (Sewage and Industrial Effluents) Regulation 1979 and Environment Quality Act (Clean Air) 1978. The plant owner or waste generator must ensure that waste generated disposed appropriately to prevent environmental pollution. The proper and suitable methods should be implemented in dealing with the waste disposal. Kualiti Alam Sdn. Bhd is one of the licensed contractors specialized in the industrial waste disposal in Malaysia. MTBE plant is not excluded from these regulations. As our plant produces MTBE and other byproducts like raffinate but generally they are not hazardous to the environment and human if safety measures are taken into consideration. These environmental considerations depend on the location of our plant. The plant will follow the Standard B of water quality measurement and also need some waste treatment facilities to minimize the pollution from our plant. 56
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR STACK GASES Gas Emission Treatment Direct flame combustion was used to burn the excess gas. Flare is usually open ended combustion unit. Therefore, the combustion process will be controlled by flow rate of gases mixture to prevent incomplete combustion. Another treatment is thermal combustion. It is an incinerator used in the cases where the concentration of combustible gases is too low to make direct flame incineration insufficient condition. The temperature of operation depends upon the type of pollutant in waste gas. Thermal combustion must be carefully designed to provide safe, efficient operation and to prevent incomplete combustion. Time, temperature, and oxygen must be carefully monitored. (Howard et. al 1985) Stack gas means the product of combustion process usually occur at machine or generator. It is usually the fuels used occurred in the complete combustion process, but it produced unwanted gas such as carbon monoxide, sulphur oxide and other gases. In our MTBE plant, the stack gases is only Hydrogen and it is stored in a special tank before being sold to interested company at market price. 5.3 5.3.1 WASTEWATER TREATMENT Wastewater Characteristics Wastewater characteristics vary widely from industry to industry. Obviously, the specific characteristics will affect the treatment techniques chosen for use in meeting discharge requirements. Because of the large number of pollutant substances, wastewater characteristics are not usually considered on a substance-by-substance basis. Rather, substances of similar pollution effects are grouped together into classes of pollutants or characteristics are indicated below. 5.3.1(a) Priority Pollutants 57
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Recently, greatest concern has been for this class of substances for the reasons given previously. These materials are treated on an individual-substance basis for regulatory control. Thus each industry could receive a discharge permit that lists an acceptable level for each priority pollutant. 5.3.1(b) Organics The organic composition of industrial wastes varies widely, primarily due to the different raw materials used by each specific industry. These organics include proteins, carbohydrates, fats and oils, petrochemicals, solvents, pharmaceutical, small and large molecules, solids, and liquids. Another compilation is that a typical industry produces many diverse waste streams. Good practice is to conduct a material balance throughout an entire production facility. This survey should include a flow diagram, location and sizes of piping, tanks, and flow volumes, as well as an analysis of each stream. An important measure of the waste organic strength is the 5-day biochemical oxygen demand (BOD5). As this test measures the demand for oxygen in the water environment caused by organics released by industry and municipalities, it has been the primary parameter in determining the strength and effects of a pollutant. This test determines the oxygen demand of a waste exposed to biological organisms (controlled seed) for an incubation period of five days. Usually this demand is caused by degradation of organics according to the following simplified equation, but reduced inorganics in some industries may also cause demand (i.e., Fe2+, S2- and SO32-). Organic waste + O2 CO2 +H2O In general, low-molecular-weight water-soluble organics are biodegraded readily. As organic complexity increases, solubility and biodegrability decrease. Soluble organics are metabolized more easily than insoluble organics. Complex carbohydrates, proteins and fats and oils must be hydrolyzed to simple sugars, aminos, and other organics acids prior to metabolism. Petrochemicals, pulp and paper, slaughterhouse, 58
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR brewery, and numerous other industrial wastes containing complex organics have been satisfactorily treated biologically, but proper testing and evaluation is necessary. 5.3.1(c) Inorganics The inorganics is most industrial wastes are the direct result or inorganic compounds in the carriage water. Soft-water sources will have lower inorganics than hard-water or saltwater sources. However, some industrial wastewaters can contain significant quantities of inorganics which result from chemical additions during plant operation. Many food processing wastewaters are high in sodium. While domestic wastewaters have a balance in organics and inorganics, many process wastewaters from industry are deficient in specific inorganic compounds. Biodegration of organic compounds requires adequate nitrogen, phosphorus, iron, and trace salts. Ammonium salts or nitrate salts can provide the nitrogen, while phosphates supply the phosphorus. 5.3.1(d) pH and Alkalinity Wastewaters should have pH values between 6 and 9 for minimum impact on the environment. Wastewaters with pH values less than 6 will tend to be corrosive as a result of the excess hydrogen ions. On the other hand, raising the pH above 9 will cause some of the metal ions to precipitate as carbonates or as hydroxides at higher pH levels. Alkalinity is important in keeping Ph values at the right levels. Bicarbonate alkalinity is the primary buffer in wastewaters. It is important to have adequate alkalinity to neutralize the acid waste components as well as those formed by partial metabolism or organics. Many neutral organics such as carbohydrates, aldehydes, ketones, and alcohols are biodegraded through organics acids which must be neutralized by the available alkalinity. If alkalinity is inadequate, sodium carbonate is a better form to add than lime. Lime tends to be hard to control accurately and results in high pH levels and precipitation of the calcium which forms part of the alkalinity. In a few instances, sodium bicarbonate may be the best source of alkalinity. 59
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 5.3.1(e) Temperature Most industrial wastes tend to be on the warm side. For the most part, temperature is not a critical issue below 37oC if wastewaters are to receive biological treatment. It is possible to operate thermophilic biological wastewater-treatment systems up to 65oC with acclimated microbes. Low-temperature operations in northern climates can result in very low winter temperatures and slow reaction rates for both biological treatment systems and chemical treatment systems. Increased viscosity of wastewaters at low temperatures makes solid separation more difficult. Increased viscosity of wastewaters at low temperatures makes solid separation more difficult. Efforts are generally made to keep operating temperatures between 10 and 30oC if possible. 5.3.2 Liquid Waste Treatment 5.3.2(a) Equalization Treatment Liquid treatment generally is necessary in any plant. In our plant, we also have liquid treatment but in general, we only state the general method, as our plant does not produce any significant liquid waste. In any liquid waste treatment, we need equalization treatment. The equalization treatment is an initial procedure in liquid waste treatment. The purpose of equalization is to minimize and control the fluctuation in liquid waste characteristic. Besides it provides the suitable and optimum condition for biological and chemical treatment. It also provides adequate damping to minimize the chemical consumption. The procedure will occur in the equalization tank. The size of tank and time of equalization process depend on the liquid waste amount. The Activated Sludge process will be used for this treatment. It is carried out in Aerobic condition. The main purpose of activated sludge process is to remove soluble and insoluble organic matter that converted into flocculants microbial suspension and settable microbial. It also permits the use of gravitational solid liquid separation technique for the above requirement. The organic matter where measured in the form of BOD and COD serves as food and energy source for microbial growth. It converts the pollutant into microbial cell 60
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR and oxidized end product such as CO2 and H2O by microbial activities. Therefore, Submersible Aerator as mixing device will supply the oxygen and nutrient into aeration tank and therefore improves the quality of the liquid. (Howard et. al, 1985) 5.3.2(b) Solid Waste Treatment The solid waste treatment will be minimized by regenerating the catalyst. Regeneration processes depend on the characteristic of catalyst after whole reaction. Licensed contractor will dispose the solid waste to follow the DOE regulation. By the way, the scheduled maintenance activities will be implemented. Dewatering system will be used to solidify and extract the catalyst. Therefore, clarifier and filter press were used in these treatments. Clarifier is used to clarify any impurities before going through the filters. The size of equipment depends on the flow rate and holding time of these processes. Maintenance activities will be scheduled based on the availability of workers and machines. Skilled and experienced workers will do the maintenance activities, (Bailed, 1995). 61
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Industrial Process Waste Reduction Waste Generation Re-use Storage Transfer/ Transport Processing/ Recovery Collection Disposal Recycling/ Reuse Figure 5.1 Functional Elements in a Solid-waste Treatment System. 62
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 5.3.3 Waste Minimization Waste minimization means the optimization process to minimize the waste come out of the plant. It will be done by source reduction and recovery of the sources. The source reduction refers to preventative measured taken to reduce the amount of waste, which produced in this process. Recovery of the sources is aimed to reuse the excess methanol to produce the MTBE. Waste production from the plant could be reduced by implementing these procedures: - Raw material modification, - Product reformulation, - Process modification, - Improvement in operating practices. The most important is by improving the product yield and this means minimization of waste generation. It will be accomplished through improvement in catalyst efficiency and proper maintenance activities. 63
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR CHAPTER 6 SAFETY CONSIDERATION 6.1 INTRODUCTION For years, those employed in the chemical industry have known that the safe operation of chemical plant is essential to the industry’s continued ability to survive. The human, political and financial costs of having accidents are just too high for the chemical industry to not exhibit excellence in their efforts to operate plants in safe and environmentally responsible ways. The chemical industry has an outstanding record in both transportation safety and the safe operations of its processes. That effort has resulted in a dramatic and steady decline in releases and waste produced at chemical sites. Actions that should be taken to avoid serious chemical plant accidents are as follows: 1. In most cases involving large volumes of highly hazardous chemicals, excess flow valves are in place that would stop a rapid flow of the chemicals 2. When highly hazardous chemicals are involved, processes have fixed protection, as well as trained emergency response teams that could handle the incident. 3. Appropriate reaction control or inhibiting systems are in place to interrupt runaway reactions if cooling, heating and pressure relief are not considered adequate. 4. Control systems are designed to detect heat or pressure of a chemical reaction and to control that reaction. 5. Work more closely with local and state law enforcement groups. 64
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 6.2 MATERIAL SAFETY DATA SHEET 6.2.1 Isobutane (Instrument Grade) Product Number(S): 0001020533, 0001020534, 0001020535, 0001020536 Synonyms: Methylpropane; Iso Company Identification: Chevron Phillips Chemical Company Lp 10001 Six Pines Drive The Woodlands, Tx 77380 6.2.1.1 Product Information: Msds Requests: (800) 852-5530 Technical Information: (800) 852-5531 Colorless liquefied gas, odorless. - Flammable gas. May cause flash fire - Contents under pressure - Detection of leak via sense of smell may not be possible if odorant has degraded - Contact with liquefied gas can cause frostbite - Liquid can cause eye and skin injury - Reduces oxygen available for breathing 6.2.1.2 Physical And Chemical Properties Appearance and odor: colorless liquefied gas, odorless. Ph: na Vapor pressure: 72 psia @ 37.8 ºc Vapor density (air=1): 2.1 Boiling point: -12°c (10.4°f) Solubility: negligible Percent volatile: 100 % volume Specific gravity: 0.564 @ 15.6 ºc Evaporation rate: >1 65
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 6.2.1.3 Immediate Health Effects: Eye: Because the liquid product evaporates quickly, it can have a severe chilling effect on eyes and can cause local freezing of tissues (frostbite). Symptoms may include pain, tearing, reddening, swelling and impaired vision. Skin: Because the liquid product evaporates quickly, it can have a severe chilling effect on skin and can cause local freezing of tissues (frostbite). Symptoms may include pain, itching, discoloration, swelling, and blistering. Not expected to be harmful to internal organs if absorbed through the skin. Ingestion: Material is a gas and cannot usually be swallowed. Inhalation: This material can act as a simple asphyxiant by displacement of air. Symptoms of asphyxiation may include rapid breathing, in coordination, rapid fatigue, excessive salivation, disorientation, headache, nausea, and vomiting. Convulsions, loss of consciousness, coma, and/or death may occur if exposure to high concentrations continues. 6.2.1.4 First Aid Measures Eye: Flush eyes with water immediately while holding the eyelids open. Remove contact lenses, if worn, after initial flushing, and continue flushing for at least 15 minutes. Get immediate medical attention. Skin: Skin contact with the liquid may result in frostbite and burns. Soak contact area in tepid water to alleviate the immediate effects and get medical attention. Ingestion: No specific first aid measures are required because this material is a gas and cannot usually be swallowed. Inhalation: For emergencies, wear a niosh approved air-supplying respirator. Move the exposed person to fresh air. If not breathing, give artificial respiration. If breathing is difficult, give oxygen. Get immediate medical attention. 6.2.2 N-Butane N-Butane synonym with I-Butane, Butane, and Normal Butane is a flammable gas. NButane is heavier than air and may travel considerable distance to an ignition source. 66
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR N-Butane is listed under the accident prevention provisions of section 112(r) of the Clean Air Act (CAA) with threshold quantity (TQ) of 10000 pounds. Physical and Chemical Properties Parameter value Physical state units : Gas o Vapor pressure at 70 F : 31 psia Vapor density at STP : 2.07 Evaporation point : not available Boiling point : 31.1 o Freezing point : -0.5 o pH : not available Solubility : insoluble Odor and appearance : a colourless and odourless gas Stability : stable Condition to avoid : high temperature F C 6.2.2.1 Handling and storage Protect cylinders from physical damage. Store in cool, dry, well- ventilated area away from heavily trafficked areas and emergency exits. Do not allow the temperature where cylinders are stored to exceed 130oF. Cylinders should be stored upright and firmly secured to prevent falling or being knocked over. Full and empty cylinders should be segregated. Use a “first in first out” inventory systems to prevent full cylinders from being stored for excessive periods of time. Never carry a compressed gas cylinder or a container of a gas in cryogenic liquid form in an enclosed space such as a car trunk, van or station wagon. A leak cans re4sult in a fire, explosion, asphyxiation or a toxic exposure. 6.2.3 Methanol Methanol synonyms with Methyl alcohol and in chemical family alcohol with the formula CH3OH. Methanol is a clear, colourless, mobile, volatile, flammable liquid and it’s soluble in water, alcohol and ether. 67
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Physical and Chemical properties: Parameter value Physical state : liquid Boiling Point : 64.7oc Vapor Pressure (20oc) : 128 mb Vapor Density (air=1) : 1.11 Solubility in water ,%wt : full Specific Gravity : 0.792 g/cm3 Appearance and odor : liquid-colorless-odor specific Fire and Explosion Hazard data: Flash point : closed cup: 12oc Flammable limits, % vol : Lel: 6, Uel : 36.5 Extinguishing media : Foam – CO2 –halogenated agents Special fire fighting : Avoid contact with oxidizing materials Unusual fire and explosion : Moderate Reactivity Data: Stability : Medium Conditions to avoid : Oxidizing materials Incompatibility : Sulfo-chromic mixtures Special Precautions Precaution to be taken in handling and storing Methanol: store in iron or steel containers or tanks. Small quantities can be stored in reinforced glass containers. 6.2.4 MTBE 6.2.4.1 Physical state, appearance MTBE is chemically stable; it does not polymerize, nor will decompose under normal conditions of temperature and pressure. Unlike most ether, MTBE does not tend to form peroxides (auto-oxidize). The physical state of MTBE is that MTBE is in the form of liquid at room temperature (25oC). It is a colourless liquid with the billing point at 68
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 55.2oC 131.4oF. The freezing point of MTBE is –108.6oC –163.5oC. The density of MTBE at 25oC is 735g/cm3. 6.2.4.2 Physical dangers MTBE is non-reactive. It does not react with air, water, or common materials of construction. The reactivity of MTBE with oxidizing materials is probably low. However, without definitive information, it should be assumed that MTBE reacts with strong oxidizers, including peroxides. 6.2.4.3 Chemical dangers MTBE is highly flammable and combustible when exposed to heat or flame or spark, and it is a moderate fire risk. Vapours may form explosive mixtures with air. It is unstable in acid solutions. Fire may produce irritating, corrosive or toxic gases. Runoff from fire control may contain MTBE and its combustion products. Occupational exposure limits (OELs) Routes of Exposure 6.2.4.4 Inhalation risk Like other ethers, inhalation of high levels of MTBE by animals or humans results in the depression of the central nervous system. Symptoms observe red in rats exposed to 4000 or 8000 ppm in air included labored respiration, ataxia, decreased muscle tone, abnormal gait, impaired treadmill performance, and decreased grip strength. These symptoms were no longer evident 6 hours after exposure ceased. A lower level of MTBE, 800ppm did not produce apparent effects (Daughtrey et al., 1997). A number of investigations have been conducted to examine the self-reported acute MTBE in gasoline vapors during use by consumers. This research includes both epidemiological studies and studies involving controlled exposure of volunteers to MTBE at concentrations similar to those encountered in refueling an automobile (Reviewed in USEPA, 1997, and California EPA, 1998). In general, the studies involving controlled human exposures in chambers to levels of MTBE similar to those experienced during refueling and driving an automobile have not shown effects of 69
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR MTBE on physical symptoms (e.g. irritation), mood, or performance based tests of neurobehavioral function. 6.2.5 TBA (TERT - BUTYL ACOHOL) CAS Number: 75-65-0 Synonyms: tert-Butanol 2-methyl-2-propanol TBA t-butylhydroxide 1,1-dimethylethanol trimethylmethanol trimethylcarbinol 6.2.5.1 Recognition NIOSH/OSHA Health Guideline. Summarizes pertinent information about for workers and employers as well as for physicians, industrial hygienists,and other occupational safety and health professionals who may need such information to conduct effective occupational safety and health programs. 6.2.5.2 Evaluation 1. Health Hazards. Routes of exposure, summary of toxicology, signs and symptoms, emergency procedure. 2. Workplace Monitoring and Measurement. 3. Medical Surveillance. Workers who may be exposed to chemical hazards should be monitored in a systematic program of medical surveillance that is intended to prevent occupational injury and disease. The program should include education of employers and workers about work-related hazards, placement of workers in jobs that do not jeopardize their safety or health, early detection of adverse health effects, and referral of workers for diagnosis and treatment. 70
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 6.2.5.3 Controls 1. Exposure Sources and Control Methods. 2. Personal Hygiene Procedures. 3. Respiratory Protection. Conditions for respirator use, respiratory protection program. 4. Personal Protective Equipment. Protective clothing should be worn to prevent any possibility of skin contact. Chemical protective clothing should be selected on the basis of available performance data, manufacturers' recommendations, and evaluation of the clothing under actual conditions of use. 5. Emergency Medical Procedures. Material Safety Data Sheets (MSDS's) include chemical specific information on emergency medical and first aid procedures as referenced under the OSHA Hazard Communication standard, 29 CFR 1910.1200, (g)(2)(X). This standard requires chemical manufacturers and importers to obtain or develop an MSDS for each hazardous chemical they produce or import. Employers shall have an MSDS in the workplace for each hazardous chemical, which they use. 6. Storage. 7. Spills and Leaks. In the event of a spill or leak, persons not wearing protective equipment and clothing should be restricted from contaminated areas until cleanup has been completed. 6.3 HAZARD IDENTIFICATION & EMERGENCY SAFETY & HEALTH RISK ASSESSMENT Safety & Health Risks vary with the type of industry & the magnitude of the emergency. The severity of the risk too will vary with especially where there are chemicals, combustible gases, potential for fire & explosion etc. These hazards may not only pose a danger to the health of working in a particular plant but also the adjacent community. In the event of a major disaster property both within and outside the plant will be damaged. The real and potential hazards at the work place must be identified and the Safety & Health Risks that they pose assessed. This will require a close scrutiny of all 71
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR work place buildings, their design, electrical wiring, transport and storage facilities, the work processes, workstation design, safe operating procedures, list of chemicals substances used, their quantity, storage, daily transfer, safe usage and disposal. MSDS’s of the chemical too have to be studied as regards their toxicity, volatility, and their potential for a fire and/or explosion and adverse health affects both short term and long term. The possible emergencies/disaster in a industry could be: • Fire/ explosion • Chemical spill • Radioactive material spill • Biological material spill • Personal injury The best action plan is prevention from an emergency. This is where one has to work closely with operation personnel to make sure that all operations are safe and comply with OSH Legislations. All persons at work are aware of the safe procedure and also follow those procedures. Unfortunately in the real world, mostly human factors- accident & emergency do occur. This is why emergency response plans have to be written up, communicated to all concerned and tested for effectiveness. Depending on the gravity the workplace emergency can be categorized in to Level 1, Level 2, or Lever 3 emergency. Level 1 Emergency- the first responder without having to call the disaster response team or outside help can effectively manage such incident. Examples; a small fire easily smothered, chemical spill easily contained and cleaned, injury minor and treated at site by rendering first aid. Level 2 Emergency - an incident that requires technical assistance from the disaster response team and may need outside help. Examples; fire that need technical from trained personnel and specialized equipment spill that can only be properly contained by specialized equipment. 72
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Level 3 Emergency- these are major disaster that are difficult to contain even with trained personnel and outside help. Examples, spill that cannot be properly contained or abated even by highly trained team and the use of sophisticated special equipment. Fire involving toxic material that is too large to control and are to burn. This may require the evacuation of civilians across jurisdictional boundaries 73
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR CHAPTER 7 MASS BALANCE 7.1 SNAMPROGETTI UNIT (REACTOR AND REGENERATOR) Stream S5 = 164.74 kgmole/hr 0.393 C4H8 0.393 H2 0.212 iC4H10 0.002 nC4H10 100 kgmole/hr 0.996 iC4H10 0.004 nC4H10 S2 Given from MSDS Assume steady-state system, Basis = 100 kgmole/hr of S2 74
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR The fraction at stream S2 acquired from isobutane instrument grade, MSDS. Reaction occurred in the reactor, iC4H10 C4H8 + H2 Flowrate in kgmole/hr of iC4H10 in the feed stream of S2 = 0.996 (100) = 99.6 kgmole/hr iC4H10 Balanced Based upon the stoichoimetric ratio with 65% conversion of iC4H10 to obtain C4H8. Since, 65% conversion in the reactor, ∴ kgmole/hr of C4H8 obtained = 0.65 (99.6) = 64.74 kgmole/hr ∴ 35% of iC4H10 unreacted = 99.6 - 64.74 = 34.86 kgmole/hr Based upon stoichiometric ratio (inert) (unreacted) n C4H10 + iC4H10 0.4 C4H8 99.6 H2 64.74 (kgmole/hr) + iC4H10 64.74 + n C4H10 34.86 0.4 (kgmole/hr) Input S2 Stream Component + (inert) MW Molar flow Output S5 Mass flow kg/hr Molar flow Mass flow kg/hr kg/kgmole kgmole/hr C4H8 56 - - kgmole/hr 64.74 3625.44 H2 2 - - 64.74 129.4 iC4H10 58 99.6 5776.8 34.86 2021.88 n C4H10 Total 58 0.4 23.2 5800 0.4 23.4 5800 75
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 7.2 SEPARATOR Stream S10 = 64.74 kgmole/hr 1 H2 Stream S9 = 164.74 kgmole/hr 0.393 C4H8 0.393 H2 0.212 iC4H10 Stream S11 = 100 kgmole/hr 0.002 nC4H10 0.6474 C4H8 0.3486 iC4H10 0.0040 nC4H10 Input S9 Stream Component Output S10 S11 MW Molar flow Mass flow Molar flow Mass flow Molar flow Mass flow kg/kgmole kgmole/hr kg/hr kgmole/hr kg/hr kgmole/hr kg/hr C4H8 56 - - - - 64.74 3625.44 H2 2 - - 64.74 129.4 64.74 129.4 iC4H10 58 99.6 5776.8 - - 34.86 2021.88 n C4H10 Total 58 0.4 23.2 5800 - 129.4 0.4 23.4 5670.6 7.3 MIXER S13 = 64.74kgmole/hr S14 = 71.62 kgmole/hr 1 CH3OH 0.996 CH3OH 0.004 H2O S27 = 0.406 kgmole/hr 0.3596 CH3OH 0.6404 H2O 76
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Input Stream Component S13 MW Molar flow Output S14 S27 Mass flow Molar flow Mass flow Molar flow Mass flow kg/kgmole kgmole/hr kg/hr kgmole/hr kg/hr kgmole/hr kg/hr CH3OH 32 71.214 2278.848 0.146 4.67 71.36 2283.52 H2O Total 18 - 2278.848 0.26 4.68 9.356 0.26 4.685 2288.205 7.4 MTBE REACTOR Assumption : 98% conversion of C4H8 (2% remains unconverted) Reactions involve in the reactor, 1. C4H8 + CH3OH 2. 2CH3OH 3. C4H8 + C5H12O C2H6O H2O + H2O C4H10O Stream S11 = 100 kgmole/hr 0.6474 C4H8 0.3486 iC4H10 0.0040 nC4H10 R e ac to r S15 kgmole/hr C4H8 iC4H10 nC4H10 S14 = 71. 214 kgmole/hr CH3OH CH3OH H2O C5H12O C4H10O C2H6O H2O 7.4.1 1st REACTION IN REACTOR C4H8 + CH3OH C5H12O 77
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR kgmole/hr of C4H8 in the stream S11 = 100(0.6474) = 64.74 kgmole/hr C4H8 Balance based upon stoichiometric ratio with 98% conversion. CH3OH is classified an excess. The unreacted of CH3OH (excess) = (71.36 - 64.74) = 6.62 kgmole/hr Since 98% conversion in the reactor, kgmole/hr of C5H12O obtained = 0.98 (64.74) = 63.44 kgmole/hr C5H12O obtained From the stoichiometric ratio, 98% C4H8 64.74 + CH3OH 71.214 C5H12O + C4H8 63.44 conv. + 1.3 CH3OH 7.92 unconverted kgmole/hr kgmole/hr 64.74 kgmole/hr 1 C4H8 R e ac to r kgmole/hr C4H8 CH3OH C5H12O 64.74 kgmole/hr 1 CH3OH Component MW Input Molar flow Mass flow Output Molar flow Mass flow 78
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR C4H8 (kg/kgmole) 56 (kgmole/hr) 64.74 (kg/hr) 3625.44 (kgmole/hr) 1.3 (kg/hr) 72.8 CH3OH 32 71.36 2283.52 7.92 253.44 C5H12O Total 88 - 5908.96 63.44 5582.72 5908.96 7.4.2 2nd REACTION IN REACTOR From 2nd reaction, stoichiometric ratio shown below: Since the ratio between methanol and dimethylether is 2CH3OH : 1C2H6O , 98% conversion methanol (CH3OH) into dimethylether (C2H6O) = 1.3 (0.98) 2 = 0.637 kgmole/hr 98% 2CH3OH conv. 7.92 C2H6O + 3.88 H2O + 2CH3OH 3.88 0.16 unconverted kgmole/hr 7.92 kgmole/hr 1 CH3OH kgmole/hr R e ac to r kgmole/hr CH3OH C2H6O H2O Input Output 79
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Component MW Molar flow Mass flow Molar flow Mol Mass flow kg/kgmole kgmole/hr (kg/hr) (kgmole/hr) Fraction (kg/hr) CH3OH 32 7.92 253.44 0.16 0.02 5.12 C2H6O 46 - - 3.88 0.49 178.48 H2O 18 - - 3.88 0.49 69.84 1.0 253.44 Total 7.4.3 253.44 3rd REACTION IN REACTOR The 3rd reaction and its stoichiometric below, From 1st reaction, kgmole/hr of C4H8 remain is 1.3 and 3.88 kgmole/hr of H2O is obtained in 2nd reaction. Since C4H8 is limiting reactant to react with H2O, only 1.3 kgmole/hr of H2O needed to react with C4H8 H2O is classified an excess. The unreacted of H2O (excess) = (4.14 - 1.3) = C4H8 + 1.3 H2O 4.14 2.84 kgmole/hr C4H10O + 1.274 C4H8 0.026 + H2O 2.866 unconverted kgmole/hr kgmole/hr 1.3 kgmole/hr 1 C4H8 80
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR R e ac to r 4.166 kgmole/hr 0.3058C4H8 0.3058C4H10O 0.688H2O 4.14 kgmole/hr 1 H2O Input Component Output MW Molar flow Mass Molar Mass Molar Mass kg/kgmole kgmole/hr flow flow flow flow flow kgmole/hr - (kg/hr) - kgmole/hr 0.026 (kg/hr) 1.456 4.14 74.52 2.866 51.588 1.274 94.276 4.166 147.32 C4H8 56 1.3 (kg/hr) 72.8 H2O 18 - - C4H10O 74 Total 7.4.4 1.3 72.8 4.14 74.52 OVERALL MASS BALANCE ON MTBE REACTOR S11 = 100 kgmole/hr 0.6474 C4H8 0.3486 iC4H10 0.0040 nC4H10 81
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR R e ac to r S15 = 100.676 kgmole/hr 0.0002 C4H8 0.3261 iC4H10 0.0037 nC4H10 0.0015CH3OH 0.5934 C5H12O S14 = 71.36 kgmole/hr 0.0119 C4H10O 1 CH3OH 0.0363 C2H6O 0.0268 H2O Input Input Output S11 S14 S15 MW Molar flow Mass Molar flow Mass Molar flow Mass (kg/kg (kgmole/hr) flow (kgmole flow (kgmole/h flow C4H8 mole) 56 64.74 (kg/hr) 3625.44 /hr) - (kg/hr) - r) 0.026 (kg/hr) 1.456 iC4H10 58 34.86 2021.88 - - 34.860 2021.88 n C4H10 58 0.4 23.2 - - 0.4 23.2 CH3OH 32 - - 71.36 2283.52 0.16 5.12 C5H12O 88 - - 63.44 5582.72 C2H6O 46 - - 3.88 178.48 C4H10O 74 - - 1.274 94.276 H2O 18 - 0.26 2.866 51.588 106.906 7958.72 Component Total 7.5 100 5670.52 71.62 4.68 2288.2 DISTILLATION COLUMN Assume that 90% of methanol in bottom. 82
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR S17 = 40.321 kgmole/hr 0.0006 C4H8 S15 = 100.906 kgmole/hr 0.0002 C4H8 0.8646 iC4H10 0.3261 iC4H10 0.0099 nC4H10 0.0037 nC4H10 0.0037 CH3OH 0.0015 CH3OH 0.0249 H2O 0.5934 C5H12O 0.0962 C2H6O 0.0119 C4H10O S16 = 66.585 kgmole/hr 0.0363 C2H6O 0.9528 C5H12O 0.0268 H2O 0.0191 C4H10O 0.0279 H2O 0.0002 CH3OH S15 Component MW kg/kgmole Molar Mass S16 Molar flow Mass S17 Molar flow Mass flow flow (kgmole/hr) flow (kgmole/hr) flow C4H8 56 kgmole/hr 0.026 (kg/hr) 1.456 - (kg/hr) - 0.026 (kg/hr) 1.456 iC4H10 58 34.86 2021.88 - - 34.86 2021.88 n C4H10 58 0.4 23.2 - - 0.4 23.2 CH3OH 32 0.16 5.12 0.011 0.352 0.003 4.768 C5H12O 88 63.44 5582.72 63.44 5582.72 - - C2H6O 46 3.88 178.48 - - 3.88 178.48 C4H10O 74 1.274 94..276 1.274 94..276 - - H2O Total 18 2.866 106.906 51.588 7958.72 1.860 66.585 33.48 5710.828 0.013 40.321 18.108 2247.892 7.6 LIQIUD –LIQUID EXTRACTION S 20 = 12.029 kgmole/hr 1 H2O S 21 = 39.166 kgmole/hr 0.0007 C4H8 0.8901 iC4H10 0.0102 nC4H10 0.0991 C2H6O 83
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR S18 = 40.321 kgmole/hr S23 = 13.184 kgmole/hr 0.0006 C4H8 0.0113 CH3OH 0.8646 iC4H10 0.9887 H2O 0.0099 nC4H10 0.0037 CH3OH C 0.0962 2H6O 0.0249 H2O Input Output S18 S20 Mass MW Molar flow kg/kgmole (kgmole/hr) C4 H8 56 0.026 (kg/hr) 1.456 Component flow Molar flow (kgmole/hr) S21 Mass flow - (kg/hr) - Molar flow (kgmole/hr) S23 Mass flow 0.026 (kg/hr) 1.456 Mass Molar flow flow (kgmole/hr) - (kg/hr) - iC4H10 58 34.86 2021.88 - - 34.86 2021.88 - - n C4H10 58 0.4 23.2 - - 0.4 23.2 - - CH3OH 32 0.149 4.768 - - - - 0.149 4.768 C5H12O 88 - - - - - - - - C2H6O 46 3.88 178.48 - - 3.88 178.48 - C4H10O 74 - - - - - - - - H2O Total 18 1.006 40.321 18.108 2247.892 12.029 12.029 216.522 216.522 39.166 2225.016 13.035 13.184 234.63 239.398 7.7 DISTILLATION COLUMN S26 = 0.407 kgmole/hr S24 = 13.185 kgmole/hr 0.0113 CH3OH 0.9887 H2O 0.146 CH3OH 0.260 H2O 84
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR S25 = 12.778 kgmole/hr 1 H2O S24 Component Molar MW kg/kgmole Mass S25 Molar flow Mass S26 Molar flow Mass flow flow (kgmole/hr) flow (kgmole/hr) flow C4H8 56 kgmole/hr - (kg/hr) - - (kg/hr) - - (kg/hr) - iC4H10 58 - - - - - - n C4H10 58 - - - - - - CH3OH 32 0.149 4.776 0.003 0.096 0.146 4.680 C5H12O 88 - - - - - - C2H6O 46 - - - - - - C4H10O 74 - - - - - - H2O Total 18 13.035 13.185 234.63 239.411 12.775 12.778 229.95 230.046 0.260 0.407 4.685 9.365 OVERALL REACTION SYSTEM, FLOW DIAGRAM S3 S17 S18 S9 Liquid d– liquid liquid extra extrac ction tion Liqui Distill ation colu mn S11 Distill ation colu mn 7.8 85 Re act or R Se ea pa rat ct or or Ca tal ytic rea cto r
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR S2 S10 S12 S15 Overall mass balance is shown below: Input S4 Molar flow Mass flow kgmole/hr (kg/hr) 5800 = output Input S13 Molar flow Mass flow Molar flow (kgmole/hr) (kgmole/hr) (kg/hr) 2278.848 Total input S20 Mass flow (kg/hr) 216.522 8295.37 Output S10 Molar flow Mass (kgmole/hr flow ) (kg/hr) 129.48 S16 Molar flow (kgmole/hr) Total S26 Mass flow (kg/hr) 5710.828 Molar flow (kgmole/hr) S21 Mass flow (kg/hr) 230.046 Molar flow (kgmole/hr) Mass flow (kg/hr) 2225.016 8295.37 output 7.6 SCALE-UP FACTOR Determination of the scale-up factor for the end product (MTBE) With a basis 100 kgmole/hr of feed at stream S2, the product at stream S12 acquired is 5658.934 kg/hr. This amount if converted to kg/yr, by conversion unit, 5582.72kg/hr * 7920 hr/yr = 44.215142 * 106 kg/yr of MTBE Targeted production of MTBE = 300 X106 kg/yr (300,000 metric tonnes/yr) 86
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR ∴ Therefore, the scale-up factor = Targeted Amount Actual Amount = 300,000 x103 kg/yr 44.8188 x106 kg/yr = 6.785005854 ≈ 6.785 To determined whether the scale-up factor can proceed or not, Target amount = Actual Production x Scale-up factor = 44.215 x 106 x 6.785 = 299.9997385 x106 ≈ 300 x106 kg/yr at stream S14 Therefore, the scale-up factor of 6.785 is acceptable for this process. CHAPTER 8 ENERGY BALANCE 8.1 ENERGY EQUATION The equation that we used to calculate the power Q or W at each equipment is: 87
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Q – W = ∆HR + (-∆Hin) + (∆Hout) + (∆KE) + (∆PE) To calculate ∆H, first we need to find the Cp values for every component in each of the stream. To find the Cp values, we need to use this equation to find the values of Cp C o P = a + bT + cT2 + dT3 The values of a, b, c and d are taken from Appendix D, Coulson and Richardson Chemical Engineering, Volume 6. If the temperature and pressure is more than the critical temperature and pressure of the component, we need to find the (C p – Cpo) for that specific component. But as for all of our temperatures and pressures none of them exceed the critical temperature and pressure; we need not to find the (Cp – Cpo). To find the value of ∆H, we use this equation: ∆H = T 2 ∫ C T 1 P dT x (n) Should there is any reaction in the process; we need also to find the values of ∆HR which takes place in the equipment. The equation, which we used to find ∆HR is: ∆HR = (∆ĤF product - ∆ĤF reactant) x n and if the equipment has ∆KE and ∆PE, we also need to calculate the values by using this equation: ∆KE = 0.5 m(vout2 - vin2) ∆PE = mg x (zout – zin) so, after we have calculated all the values of the energy for each and every of the stream, we then can calculate the value of Q or W. And for this sample of calculations, listed are the values of constants in the ideal gas heat capacity equation based on R. K Sinnot, Coulson & Richardson, Chemical Engineering, Volume 6, Third Edition, Butterworth Heinemann: 88
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Table 8.1 Table of Constant in the Ideal Heat Capacity Component C5H12O CH3OH H2O C4H8 i-C4H8 i-C4H10 C4H10O n-C4H10 (CH3)2O H2 8.2 a b c d Delta HF kJ/kmol.K kJ/kmol -1 -4 -8 2.53 5.14 x 10 -2.60 x 10 4.30 x 10 -292990 2.12 x 101 7.09 x 10-2 2.59 x 10-5 -2.85 x 10-8 -201300 32.243 1.93 x 10-3 1.06 x 10-5 -3.60 x 10-9 -242000 -2.994 3.53 x 10-1 -1.98 x 10-4 4.46 x 10-8 -130 16.052 2.8043 x 10-1 -1.091 x 10-4 9.098 x 10-9 -16900 -1.39 3.85 x 10-1 -1.85 x 10-4 2.90 x 10-8 -134610 1 -4.86 x 10 7.17 x 10-1 -7.08 x 10-4 2.92 x 10-7 -312630 9.85 3.31 x 10-1 -1.11 x 10-4 -2.82 x 10-9 -126.23 1.70 x 101 1.79 x 10-1 -5.23 x 10-5 -1.92 x 10-9 -184180 2.71 x 101 9.27 x 10-3 -1.38 x 10-5 7.65 x 10-9 0 ENERGY BALANCE: SAMPLE OF CALCULATIONS (Methods of calculations are based on, Coulson & Richardson, Chemical Engineering, Volume 6, page 78). 8.2.1 P-100 (Pump 1) S2 T = -150C P = 750 Kpa (liquid) S1 T = -180C P = are based Calculations450 Kpa on Yunus A. Cengel, Micheal A. Boles, Thermodynamics: (Liquid) An Engineering Approach, WCB/Mc Graw-Hill, 1989, page, 354-355. Assumptions: 1. Steady operating conditions exist 2. Kinetic and potential energy negligible 3. The process is to be isentropic Specific volume: Isobutane = 0.255 m3/mol n-butane = 0.263 m3/mol 89
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR (Data of these specific volumes are based on Coulson & Richardson, Chemical Engineering, Volume 6, Third Edition, Butterworth Heinemann, page 947) Isobutane 0.255m3/mol x 1000mol/kmol x 1kmol/58kg = 9.11 m3/kg n-butane 0.263m3/mol x 1000mol/kmol x 1kmol/58kg = 4.53 m3/kg Vavg = (9.11 + 4.53) m3/kg / 2 = 6.82 m3/kg (Which remains essentially constant during the process) 2 ∴Win = ∫ Vdp 1 = V1 (P2 − P1 ) = 6.82m 3 /kg(750 − 450)kpa(1k J/1kpa.m = 6.82(300) 3 ) = 2046.00kJ/ kg ∴2046kJ/kg x 39353kg/hr = 80516238kJ /hr = 22365.62kW 8.2.2 E-100 (Heat Exchanger 1) S2 T = -15 oC P = 750Kpa (Liquid) S3 T = 117 oC P = 450Kpa (Gas) Stream 2 Component i-C4H10 n-C4H10 Flowrates Kmol/hr 675.786 2.714 ∆ĤF kJ/Kmol -1.35 x105 -1.26 x105 To K 298 298 T, K 258 258 ∆H kJ/hr -690.04 -2.81 90
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR ∑ ∆H = -692.86 Stream 3 Component i-C4H10 n-C4H10 Flowrates Kmol/hr 676.786 2.714 ∆ĤF kJ/Kmol -1.35 x105 -1.26 x105 To K 298 298 T, K 390 390 ∆H kJ/hr 1902.85 7.66 ∑ ∆H = 1910.51 Sample of calculations for i-C4H10 at stream 3 ∆H = T 2 ∫ C T 1 T 2 ∫ C T 1 P P dT = dT x (n) T2 ∫ T1 a + bT + cT 2 + dT 3  b(T 2 − T1 ) 2 c(T 2 − T1 )3 d(T 2 − T1 ) 4  a(T2 − T1 ) + + + =   2 3 4   = ( 1.390 )( 390 − 298 ) + + 38 .473 ×10 2 (390 - 298 ) 2 2 + ( 1.846 ×10 4 )( 390 - 298 )3 3 28 .952 ×10 9 (390 - 298 ) 4 4 = 10100 kJ/kmol ∆H = 10100 kJ/kmol x 675.786 kmol/hr = 6825438.6 kJ/hr = 1902.85 kW (for i-C4H10) And as for n-C4H10, the ∆H So = 7.66 kW ∑ ∆H = 1910.51 Energy balance, 91
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Q=( ∑ H) out –( ∑ H) in = 1910.51- (-692.86) = 2603.37kW Steam flowrate, Q = mCpΔT Cp of isobutane, 2155 J/kg oC (Elementary Principles of Chemical Processes, W. Rousseau et. al) m= Q Cp ∆ T 2603370 J/s 2155J/g o C x (117 - (-15)) = 9.152g/s = o C Therefore the supply of steam flow rate required is 9.152 g/s. 8.2.3 E-101 (Heat Exchanger 2) S3 T = 117 oC P = 450 kPa (Gas) S4 T = 250 oC P = 325 kPa (Gas) Stream 3 Component i-C4H10 n-C4H10 Flowrates Kmol/hr 676.786 2.714 ∆ĤF kJ/Kmol -1.35 x105 -1.26 x105 To K 298 298 T, K 390 390 ∆H kJ/hr 1902.85 7.66 ∑ ∆H = 1910.51 Stream 4 Component i-C4H10 n-C4H10 Flowrates Kmol/hr 676.786 2.714 ∆ĤF kJ/Kmol -1.35 x105 -1.26 x105 To K 298 298 T, K 523 523 ∆H kJ/hr 5356.57 21.46 92
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR ∑ ∆H = 5378.03 Sample of calculations for i-C4H10 at stream 4 ∆H = T 2 ∫ C T 1 T 2 ∫ C T 1 P P dT x (n) T2 ∫ dT = T1 a + bT + cT 2 + dT 3  b(T 2 − T1 ) 2 c(T 2 − T1 )3 d(T 2 − T1 ) 4  a(T2 − T1 ) + + + =   2 3 4   = ( 1.390 )( 523 − 298 ) + + 38 .473 ×10 2 (523 - 298 ) 2 2 + ( 1.846 ×10 4 )( 523 - 298 )3 3 28 .952 ×10 9 (523 - 298 ) 4 4 = 28500 kJ/kmol ∆H = 28500 kJ/kmol x 675.786 kmol/hr = 19259901 kJ/hr = 5349.97 kW (for i-C4H10) And as for n-C4H10, the ∆H So = 21.46 kW ∑ ∆H t = 5371.43kW ou Energy balance, Q=( ∑ H) out –( ∑ H) in = 5371.43- (1910.51) = 3460.92kW Steam flowrate, Q = mCpΔT 93
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Cp of isobutane, 2155 J/kg oC (Elementary Principles of Chemical Processes, W. Rousseau et. al) m= Q Cp ∆ T 3460920 J/s 2155J/g o C x (250 - 118) o C = 12.17g/s = Therefore the supply of steam flow rate required is 12.17 g/s. 8.2.4 R-101 (Snamprogetti Fluidized Bed Reactor) S5 Air Out S4 T=250oC P=325kPa (gas) S6 Air In S7 T=180oC P=110kPa (Liquid) Stream 4 Component i-C4H10 n-C4H10 Flowrates Kmol/hr 676.786 2.714 ∆ĤF kJ/Kmol -1.35 x105 -1.26 x105 To K 298 298 T, K 523 523 ∆H kJ/hr 5356.57 21.46 ∑ ∆H = 5378.03 Stream 7 94
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Component i-C4H8 i-C4H10 n-C4H10 H2 Flowrates Kmol/hr 237 2.71 439 439 ∆ĤF kJ/Kmol -1.30 x10-1 -1.35 x105 -1.26 x105 0.00 To K 298 298 298 298 T, K 453 453 453 453 ∆H kJ/hr 1056.59 13.82 2236.41 549.84 ∑ ∆H = 3856.66 To calculate the value of ∆HR: 1) i-C4H10 →C4H8 + H2 so, ∆ĤR = (∆ĤF C4H8) + (∆ĤF H2) -(∆ĤF i-C4H10) = (-130) + (0) – (-134610) = 134480 kJ/kmol therefore, ∆HR = (∆ĤR kJ/kmol x 236.53 kmol/hr) = (134480 kJ/kmol x 236.53 kmol/hr) = 31808554.4 kJ/hr = 8835.71 kJ/s = 8835.71 kW Although there is stream flow, but the ∆KE is too small and negligible and there is also now work so, W is zero and as for the ∆PE, the value is neglected, as it is also too small. Now we calculate the value of Q, Q – W 0= ∆HR + (-∆Hin) +(∆Hout) +∆KE 0+ ∆PE0 Q = ∆HR + (∆Hout) - (∆Hin) Q = 8835.71 + (1980.66) - (3856.66) Q = 6959.71kW (heat have been absorbed) 8.2.5 C-100 (Compressor 1) 95
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR S7 T = 1800C P = 110 Kpa (Gas) S8 T = 1930C P = 120 Kpa (Gas-liquid) T7 = 453K T8 =? P7 = 1.1 bar P8 = 1.2 bar T4 = 453K, P4 = 1.1 bar, P8 = 1.2 bar is based on the literature review of process Snamprogetti fluidized bed. By assuming polytropic and ideal gas condition: T7= T6(P7/P6)m (Coulson & Richardson, Chemical Engineering, Volume 6, page 85) m = α – 1/ αEp α = CPmean/CV = CPm/CPm – R Where R = 8.314 kJ/kmol.K For hydrogen, a = 27.143, b = 97.38 x 10-4, c = -1.31 x 10-5, d = 76.451 x 10-10 1000K ∫ CPHydrogen = 453K a + bT + cT 2 + dT 3 = 16200 kJ/kmol.K For butene, a = -2.994 , b = 3.53 x 10-1 , c = -1.98 x 10-4 , d = 4.46 x 10-8 , CPbutene = 1000K ∫ 453K a + bT + cT 2 + dT 3 = 89400 kJ/kmol.K For Isobutane, a = -1.39 , b = 3.85 x 10-1 , c = -1.85 x 10-4 , d = 2.90 x 10-8 , CPisobutane = 1000K ∫ 453K a + bT + cT 2 + dT 3 = 103000 kJ/kmol.K For n-butane, a = 9.85 , b = 3.31 x 10-1 , c = -1.11 x 10-4 , d = -2.82 x 10-9, 1000K CPn-butane = ∫ Cpmean = 0.25 (Cp , Hydrogen + Cp , butene + Cpisobu tan e + Cp , n − bu tan e) (466 − 453 ) = 453K a + bT + cT 2 + dT 3 = 103000 kJ/kmol.K 0.25(16200 + 89400 + 103000 + 103000) = 167.5kJ/km ol.K 1000 − 453 So , α = CPm/CPm – R = 167.5/(167.5-8.314) = 1.07 96
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR To find Ep(efficiency), Flow rate = 1117.76kmo l 453 1 x22.4x x 3600s 273 0.5 = 23 .08 m 3 / s From Figure 3.6, Coulson & Richardson, Chemical Engineering, Volume 6, page 83, Ep = 75% m = α – (1/ αEp) = 1.07-(1/1.07 (0.75) ) = 0.3690 To determine T6, T8 = T7(P8/P7)m = 453(1.2/1.1)0.3690 = 466.83K (193oC) Tc and Pc for H2, isobutene, isobutane and n-butane, Tc = 417.07K, Pc = 38.17 bar Trmean = (T7 + T8)/2Tc = (453+ 466.83K)/2(417.07) = 1.10 K Prmean = (P5 + P6)/2Pc = (1.1+1.2)/2(38.17) = 0.030 bar From Figure 3.8, Compressibility factors (Coulson & Richardson, Chemical Engineering, Volume 6, page 87). Z = 1.00 Then find n, n = 1/(1-m) = 1/(1-0.3456) = 1.53 Polytropic work = zRT1(n/n-1)x((P1/P2)(n-1/n) – 1) = 1.5 3  1 0 1 5  .0 (8.3 4 )( 4 3 )( 0.5 3  0.5 3    1.2 1.53 )  x  − 1     1.1     = 332.69 kJ/kmol Actual work = Polytropic work / Ep = 332.69 /0.75 = 443.60 kJ/kmol Compressor power = 443.60 kJ/kmol x 1117.76 kmol/hr x 1hr/3600s = 137.73 kW Therefore the compressor power required to increase the pressure from 1.1 bar to 1.2 bar is 137.73kW. 8.2.6 E-102 (Cooler 1) S8 T = 193oC P = 120 Kpa (Liquid) S9 T = 530C P = 100 Kpa (Liquid) 97
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Sample of Calculation for Cooler 1 Stream 8 Component C4H8 i-C4H10 n-C4H10 H2 Flowrates Kmol/hr 4.39x1002 2.37x102 2.71x100 4.39x102 ∆ĤF kJ/Kmol -1.69x10-4 -1.35x105 -1.26x105 0.00 To K 298 298 298 298 T, K 466 466 466 466 ∆H kJ/hr 2155.41 1323.43 15.15 596.20 ∑ ∆H = 4090.20 Stream 9 Component i-C4H8 i-C4H10 n-C4H10 Flowrates Kmol/hr 6.47x101 3.49x 101 4.00x101 ∆ĤF kJ/Kmol -1.69x104 -1.35 x104 -1.26 x105 To K 298 298 298 T, K 326.3 326.3 326.3 ∆H kJ/hr 47.45 27.84 0.32 ∑ ∆H = 75.61 Energy balance, Q=( ∑ H) out –( ∑ H) in = 75.61– 4090.20 = -4014.59 kW (heat is being released to the surrounding) Steam flowrate, Q = mCpΔT 98
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Cp of pure water, 4.184 J/g oC (Elementary Principles of Chemical Processes, W.Rousseau et. al) Q m p ∆ C T 4014590J/s = 4.184J/g o C x (193 - 53.3) =6869.36 g/s m= o C Therefore the supply of steam flow rate required is 6869.36 g/s. 8.2.7 V-100 (Separator) S10 T = 53.3oC P = 90 kPa (gas) S9 T= 53.3oC P= 100kPa (liquid-gas) S11 T=53.3oC P=100kPa Sample of Calculation for Hydrogen Splitter Vessel Stream 9 Component C4H8 Flowrates Kmol/hr 2.37x102 i-C4H10 n-C4H10 H2 2.71x102 4.39x102 4.39x102 ∆ĤF kJ/Kmol -1.69x104 1.35Ex105 -1.26x105 0.00 To K 298 T, K 326.3 ∆H kJ/hr 166.03 298 298 298 326.3 326.3 326.3 2.17 353.50 99.88 99
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR ∑ ∆H = 621.57 Stream 10 Component Flowrates Kmol/hr To K T, K 4.39x102 0.00 298 326.3 99.88 Flowrates Kmol/hr 439.26 236.53 2.71 H2 ∆ĤF kJ/Kmol ∆H kJ/hr ∆ĤF kJ/Kmol -16910 -134610 -126230 To K 298 298 298 T, K ∆H kJ/hr 321.92 188.89 2.18 ∑ ∆H = Stream 11 Component C4H8 i-C4H10 n-C4H10 326.3 326.3 326.3 ∑ ∆H = 512.99 Energy balance, Q=( ∑ H) out –( ∑ H) in = (512.99)-(621.57+99.88) = -208.46 (heat is being released to the surroundings) 8.2.8 R-102 (MTBE Reactor) S11 T = 53.3oC P = 2000kPa (liquid) S14 T = 27oC P = 100kPa (liquid) S15 T = 101oC P = 2000kPa (liquid) 100
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR The pressure increases from 100kPa to 2000kPa. As there is a heat exchanger (heater) in the MTBE reactor. Stream 11 Component C4H8 i-C4H10 n-C4H10 Flowrates Kmol/hr 439.26 236.53 2.71 ∆ĤF kJ/Kmol -16910 -134610 -126230 To K 298 298 298 T, K 326.3 326.3 326.3 ∆H kJ/hr 321.92 188.89 2.18 ∑ ∆H = 512.99 Stream 14 Component CH3OH H2O Flowrates Kmol/hr 4.84x102 1.76 ∆ĤF kJ/Kmol -2.01x104 -2.42x105 To K 298 298 T, K 300 300 ∆H kJ/hr 11.81 -4.79 ∑ ∆H = 7.02 Stream 15 Component C5H12O CH3OH Flowrates Kmol/hr 4.30x102 1.09 ∆ĤF kJ/Kmol -2.93x105 -2.01 x105 To K 298 298 T, K 374 374 ∆H kJ/hr 1339.10 1.07 101
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR H2O i-C4H8 i-C4H10 C4H10O n-C4H10 (CH3)2O 1.94 0.176 2.37x102 8.64 2.71 26.3 -2.44 x105 -0.123 -1.35 x105 -3.13 x105 -1.26 x105 -1.84 x105 298 298 298 298 298 298 374 374 374 374 374 374 13.94 0.35 539.59 22.49 6.22 39.56 ∑ ∆H = 1962.32 Q=( ∑ H) out –( ∑ H) in = 1962.32 – 7.02 – 512.99 = 1442.31 kW To calculate the value of ∆HR: 1.) C4H8 + CH3OH 2.) 2CH3OH C5H12O C2H6O + H2O 3.) C4H8 + H2O C4H10O so, ∆ĤR 1 = (∆ĤF C5H12O) - (∆ĤF CH3OH) + (∆ĤF C4H8) = (-292990) – ((-201300) + (-130)) = -91820 kJ/kmol ∆ĤR 2 = (∆ĤF C2H6O) + (∆ĤF H2O) -(2 ∆ĤF CH3OH ) = (-242000) + (-184180) – (2 x -201300) = -23580 kJ/kmol ∆ĤR 3 = (∆ĤF C4H10O) – (∆ĤF H2O) -(∆ĤF C4H8) = (-312630) - (-184180) – (-130) = -128270 kJ/kmol Therefore, ∆HR = (∆ĤR 1kJ/kmol x (63.44kmol/hr) + (∆ĤR 2kJ/kmol x 0.039kmol/hr) + (∆ĤR 3kJ/kmol x 0.624kmol/hr) =(-91820kJ/kmolx63.44kmol/hr)+(-23580kJ/kmolx0.039kmol/hr) + 102
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR (-128270 kJ/kmol x 0.624kmol/hr) = -5906020.9 kJ/hr = -1640.56 kW Although there is stream flow, but the ∆KE is too small and negligible and there is also now work so, W is zero and as for the ∆PE, the value is neglected, as it is also too small Now we calculate the value of Q Q – W 0= ∆HR + (-∆Hin) +(∆Hout) +∆KE 0+ ∆PE0 Q = ∆HR + (-∆Hin) +(∆Hout) Q = -1640.56 + 1442.31 = -198.25 kW 8.2.9 P-101 (Pump 2) S13 T = 270C P = 115 Kpa (liquid) S12 T = 270C P = 110 Kpa (Liquid) Calculations are based on Yunus A. Cengel, Micheal A. Boles, Thermodynamics: An Engineering Approach, WCB/Mc Graw-Hill, 1989, page, 354-355. Assumptions: 4. Steady operating conditions exist, 5. Kinetic and potential energy negligible 6. The process is to be isentropic Specific volume: 103
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR methanol = 0.118 m3/mol (Data of these specific volumes are based on Coulson & Richardson’s) Methanol 0.118m3/mol x 1000mol/kmol x 1kmol/32kg = 3.6875 m3/kg Vavg = 1.78 m3/kg Which remains essentially constant during the process 2 ∴Win = ∫ Vdp 1 = V1 (P2 − P1 ) = 3.6875m 3 /kg(115 −110)kpa(1k J/1kpa.m = 18 .44 kJ/kg ∴18.44kJ/kg x 15462 kg/hr = 285080.63k J/hr = 79.19 kW 3 ) 8.2.10 M-101 (Mixer) S13 S14 T= 27oC P=115kPa (liquid) T= 27oC P= 115kPa (liquid) S29 T=27oC P=130kPa (liquid) Stream 13 Component ∆ĤF To Kmol/hr CH3OH Flowrates kJ/Kmol K 4.83 x102 -2.01 x102 298 T, K ∆H kJ/hr ∑ ∆H = 300 11.79 104
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Stream 29 Component ∆ĤF Kmol/hr CH3OH Flowrates kJ/Kmol 9.91 x10 H20 1 To T, K K ∆H kJ/hr 298 300 0.02 -2.42 x10 1.76 -2.01 x10 5 5 298 300 0.03 ∑ ∆H = 0.06 Stream 14 Component ∆ĤF Kmol/hr CH3OH Flowrates kJ/Kmol 4.84 x10 H20 1.76 5 To T, K K ∆H kJ/hr -2.01 x10 5 298 300 11.81 -2.42 x10 5 298 300 0.03 ∑ ∆H = 11.84 Energy balance = out - in Q=( ∑ H) out –( ∑ H) in = 11.84 – 0.06 – 11.79 = 0.04 kW 8.2.11 EX-100 (Expander 1) S15 S16 T = 1010C P = 2000 kPa (liquid) T = ?0C P = 450 Kpa (Gas-liquid) T15 = 453K T16 =? P15 = 2 bar P16 = 0.45 bar 105
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR By assuming polytropic and ideal gas condition: T16= T15(P16/P15)m (Coulson & Richardson, Chemical Engineering, Volume 6, page 85) m = α – 1/ αEp α = CPmean/CV = CPm/CPm – R Where R = 8.314 kJ/kmol.K For MTBE, a = 2.533 , b = 51.372 x 10-2 , c = -2.59 x 10-4 , d = 43.04 x 10-9 , CPMTBE = 1000K ∫ 374K a + bT + cT 2 + dT 3 = 151000 kJ/kmol.K For TBA, a = 3.266 , b = 41.80 x 10-2 , c = -2.242 x 10-4 , d = 46.85 x 10-9 , CP(TBA) = 1000K ∫ 374K a + bT + cT 2 + dT 3 = 126000 kJ/kmol.K For DME, a = 17.015 , b = 19.907x 10-2 , c = -5.23 x 10-5 , d = -1.918 x 10-9 , CP(DME) = 1000K ∫ 374K a + bT + cT 2 + dT 3 = 70700 kJ/kmol.K For CH3OH, a = 21.152 , b = 70.924 x 10-3 , c = 25.870 x 10-6 , d = -2.852 x 10-8 , CP(methanol) = 1000K ∫ 374K a + bT + cT 2 + dT 3 = 44900kJ/km ol.K For H2O, a = 27.143 , b = 92.738 x 10-4 , c = -1.381 x 10-5 , d = 76.451 x 10-10 , CP(water) = 1000K ∫ 374K a + bT + cT 2 + dT 3 = 23500kJ/km ol.K For butene, a = -2.994 , b = 3.53 x 10-1 , c = -1.98 x 10-4 , d = 4.46 x 10-8 , CPbutene = 1000K ∫ 374K a + bT + cT 2 + dT 3 = 113000 kJ/kmol.K For Isobutane, a = -1.39 , b = 3.85 x 10-1 , c = -1.85 x 10-4 , d = 2.90 x 10-8 , CPisobutane = 1000K ∫ 374K a + bT + cT 2 + dT 3 = 126000 kJ/kmol.K For n-butane, a = 9.85 , b = 3.31 x 10-1 , c = -1.11 x 10-4 , d = -2.82 x 10-9, CPn-butane = Cpmean= = 1000K ∫ 374K a + bT + cT 2 + dT 3 = 113000 kJ/kmol.K 0.125(Cp, M TBE+ Cp, TBA + Cp, DM E+ Cp, methanol Cp, H2 + Cp, butene+ Cpisobu + (1000− 453) 0.125(1510 00 + 126000 + 70700 + 44900 + 23500 + 113000 + 126000 + 113000) = 153.37kJ/k mol.K 1000 − 374 So , α = CPm/CPm – R = 153.37/(153.37-8.314) = 1.06 106
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR To find Ep(efficiency), Flow rate = 53999.92km ol 374 1 x22.4x x 3600s 273 0.5 = 920 .61m 3 / s From Figure 3.6, Coulson & Richardson, Chemical Engineering, Volume 6, page 83, Ep = 85% m = α – 1/ αEp = (1.06-1/1.06 (0.85)= 0.0665 To determine T6, T16 = T15(P16/P15)m = 374(0.45/2.0)0.0665 = 338.68K (65.6oC) Tc = 417.07K, Pc = 38.17 bar Trmean = (T15 + T16)/2Tc = (374+ 228.68K)/2(417.07) = 0.723 K Prmean = (P15 + P16)/2Pc = (2+0.45)/2(38.17) = 0.0321 bar From Figure 3.8, Compressibility factors (Coulson & Richardson, Chemical Engineering, Volume 6, page 87). Z = 0.8 Then find n, n = 1/(1-m) = 1/(1-0.0665) = 1.07 Polytropic work = zRT1(n/n-1)x((P15/P16)(n-1/n) – 1) = 1.0 7  1 0 1 7  .0 (8.3 4 )( 3 4 )( 0.0 7  0.0 7     2 1.07 )  x  − 1   5   0.4     = 4872.06 kJ/kmol Actual work = Polytropic work / Ep = 4872.06 /0.80 = 6090.07 kJ/kmol Compressor power = 6090.07 kJ/kmol x 53999.12x 1hr/3600s = 91349kW Therefore the compressor power required to decrease the pressure from 2 bar (2000kPa) to 0.45 bar (450kPa) is 91349kW. 8.2.12 E-103 (Cooler 1) S16 T = 193oC P = 120 Kpa (Liquid) S17 T = 64.50C P = 100 Kpa (Liquid) 107
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Sample of Calculation for Cooler 1 Stream 16 Component C5H12O CH3OH H2O i-C4H8 I-C4H10 C4H10O n-C4H10 (CH3)2O Flowrates Kmol/hr 4.30 x102 5.02 1.21 x102 8.16 2.37 x102 6.65 x101 2.71 1.21 x102 ∆ĤF kJ/Kmol -2.93 x105 -2.01 x105 -2.42 x105 -1.69 x105 -1.35 x105 -3.13 x105 -1.26 x105 -1.84 x105 To K 298 298 298 298 298 298 298 298 T, K 466 466 466 466 466 466 466 466 ∆H kJ/hr 3270.13 11.81 194.19 40.93 1323.40 4.26 15.17 438.54 ∑ ∆H = 5298.44 Stream 17 Component C5H12O CH3OH H2O i-C4H8 I-C4H10 C4H10O n-C4H10 (CH3)2O Flowrates Kmol/hr 4.30 x102 5.02 x102 1.21 x102 8.16 2.37 x102 0.665 2.71 1.21 x105 ∆ĤF kJ/Kmol -2.93 x105 -2.01 x105 -2.42 x105 -1.69 x105 -1.35 x105 -3.13 x105 -1.26 x105 -1.84 x105 To K 298 298 298 298 298 298 298 298 T, K 337.5 337.5 337.5 337.5 337.5 337.5 337.5 337.5 ∆H kJ/hr 665.50 2.50 44.96 8.45 267.64 0.85 3.09 91.16 ∑ ∆H = 1084.15 Energy balance, 108
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Q=( ∑ H) out –( ∑ H) in = 1084.15– 5298.44 = -4214.29 kW (heat is being released to the surrounding) Steam flowrate, Q = mCpΔT Cp of pure water, 4.184 J/g oC (Elementary Principles of Chemical Processes, W.Rousseau et. al) Q m Cp ∆ T 4214290J/s = 4.184J/g o C x (193 - 64.5) =7838.44 g/s m= o C Therefore the supply of steam flow rate required is 7838.44 g/s. 8.2.13 T-101 (Distillation Column 1) S19 P = 305 Kpa T = 53.3 oC (gas) S17 P = 450 Kpa T =64.5 oC ( liquid ) S18 P = 400 Kpa T = 103.3oC ( liquid ) Sample of Calculations: R = L/D Overall: (NL), L = D x 1.5 109
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR = 451.779 x 2.5 = 1129.45 kmol/hr (NV), V = L + D = 1129.45+ 451.779 = 1581.23 kmol/hr Stream 17 Component C5H12O CH3OH H2O i-C4H8 I-C4H10 C4H10O n-C4H10 (CH3)2O Flowrates Kmol/hr 4.30 x102 5.02 1.21 x102 8.16 2.37 x102 0.665 2.71 1.21 x102 ∆ĤF kJ/Kmol -2.93 x105 -2.01 x105 -2.42 x105 -1.69 x105 -1.35 x105 -3.13 x105 -1.26 x105 -1.84 x105 To K 298 298 298 298 298 298 298 298 T, K 337.5 337.5 337.5 337.5 337.5 337.5 337.5 337.5 ∆H kJ/hr 665.50 2.50 44.96 8.45 267.64 0.85 3.09 91.16 ∑ ∆H = 1084.15 Stream 19 Component Flowrates ∆ĤF To T, K ∆H CH3OH H2O i-C4H8 (CH3)2O i-C4H10 n-C4H10 Kmol/hr 1.01E+00 6.83E+00 1.76E-01 2.63E+01 2.37E+02 2.71E+00 kJ/Kmol -2.01 x105 -2.42 x105 -1.69 x104 -1.84E+05 -1.35 x105 -1.26 x105 K 298 298 298 298 298 298 376.3 376.3 376.3 376.3 376.3 376.3 kJ/hr 1.03 5.04 0.38 40.85 557.49 6.42 ∑ ∆H = 611.21 Stream 18 Component Flowrates Kmol/hr ∆ĤF kJ/Kmol To K T, K ∆H kJ/hr 110
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR CH5H12O CH3OH C4H10O H2O 4.30E+02 7.50E-02 8.64E+00 1.26E+01 -2.93 x105 -2.01 x105 -3.13 x105 -2.42 x105 298 298 298 298 326.3 326.3 326.3 326.3 469.97 0.03 7.82 3.35 ∑ ∆H = 481.17 Energy balance, Q=( ∑ H) out –( ∑ H) in = (481.17 + 611.21)– 1084.15 = 8.23 kW 8.2.14 Cooler 2 (E-104) S19 T = 53.3oC P = 305 Kpa (Liquid) S20 T = 400C P =100 Kpa (Liquid) Sample of Calculation for Cooler 1 Stream 19 Component Flowrates ∆ĤF To T, K ∆H CH3OH H2O i-C4H8 (CH3)2O i-C4H10 n-C4H10 Kmol/hr 1.01E+00 6.83E+00 1.76E-01 2.63E+01 2.37E+02 2.71E+00 kJ/Kmol -2.01 x105 -2.42 x105 -1.69 x104 -1.84x105 -1.35 x105 -1.26 x105 K 298 298 298 298 298 298 376.3 376.3 376.3 376.3 376.3 376.3 kJ/hr 1.03 5.04 0.38 40.85 557.49 6.42 ∑ ∆H = 611.21 Stream 20 Component Flowrates Kmol/hr ∆ĤF kJ/Kmol To K T, K ∆H kJ/hr 111
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR CH3OH 1.01E+00 H2O 6.83E+00 i-C4H8 1.76E-01 (CH3)2O 2.63E+01 I-C4H10 2.37E+02 N-C4H10 2.71E+00 -2.01 x105 -2.42 x105 -1.69 x104 -1.84 x105 -1.35 x105 -1.26 x105 298 313 0.19 298 313 0.96 298 313 0.07 298 313 7.33 298 313 98.29 298 313 1.14 ∑ ∆H = 107.97 Energy balance, Q=( ∑ H) out –( ∑ H) in = 107.97– 611.21 = -503.24 kW Steam flowrate, Q = mCpΔT Cp of pure water, 4.184 J/g oC (Elementary Principles of Chemical Processes, W.Rousseau et. al) Q m p ∆ C T 503240J/s = 4.184J/g o C x (53.3 - 40) o C =9043.40 g/s m= Therefore the supply of steam flow rate required is 9043.40 g/s. 8.2.15 P-102 (Pump 3) S22 T = 270C P = 30 kPa (liquid) S21 T = 270C P = 25 kPa (Liquid) 112
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Calculations are based on Yunus A. Cengel, Micheal A. Boles, Thermodynamics: An Engineering Approach, WCB/Mc Graw-Hill, 1989, page, 354-355. Assumptions: 7. Steady operating conditions exist, 8. Kinetic and potential energy negligible 9. The process is to be isentropic Specific volume: Water = 0.056m3/mol (Data of these specific volumes are based on Coulson & Richardson’s) (Which remains essentially constant during the process) Water 0.056m3/mol x 1000 mol/kmol x 1 kmol/18kg = 3.11 m3/kg Which remains essentially constant during the process. 2 ∴Win = ∫ Vdp 1 = V1 (P2 − P1 ) = 3.11m 3 /kg(30 − 25)kpa(1kJ /1kpa.m 3 ) = 3.11(5) = 15.55kJ/kg ∴15.55kJ/kg x 1469kg/hr = 22851 kJ/hr = 22.85kW 8.2.16 T-102 (Extraction Column) 113
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR S22 T=27oC P=30kPa (liquid) S23 T=40oC P=250kPa (liquid) S20 T=40oC P=100kPa (liquid) S25 T=27oC P=100kPa (liquid) Sample of Calculation for Extraction Column Stream 20 Component Flowrates Kmol/hr CH3OH 1.01E+00 H2O 6.83E+00 i-C4H8 1.76E-01 (CH3)2O 2.63E+01 I-C4H10 2.37E+02 N-C4H10 2.71E+00 ∆ĤF kJ/Kmol -2.01 x105 -2.42 x105 -1.69 x104 -1.84 x105 -1.35 x105 -1.26 x105 To K T, K ∆H kJ/hr 298 313 0.19 298 313 0.96 298 313 0.07 298 313 7.33 298 313 98.29 298 313 1.14 ∑ ∆H = 107.97 Stream 22 Component H2O Flowrates Kmol/hr ∆ĤF kJ/Kmol To K T, K 8.16E+01 -2.42 x105 298 300 ∆H kJ/hr ∑ ∆H = 1.53 114
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Stream 23 Component Flowrates Kmol/hr i-C4H8 1.76E-01 (CH3)2O 2.63E+01 i-C4H10 2.37E+02 n-C4H10 2.71E+00 ∆ĤF kJ/Kmol -1.69 x104 -1.84 x105 -1.35 x105 -1.26 x105 To K T, K ∆H kJ/hr 298 313 0.07 298 313 7.33 298 313 98.30 298 313 1.14 ∑ ∆H = 106.83 Stream 25 Component CH3OH H2O Flowrates Kmol/hr 1.01E+00 8.84E+01 ∆ĤF kJ/Kmol -2.01 x105 -2.42 x105 To K 298 298 T, K 300 300 ∆H kJ/hr 0.02 1.65 ∑ ∆H = 1.68 Energy balance, Q=( ∑ H) out –( ∑ H) in = (106.83+1.68) – (107.97+1.53) = -0.91 kW 8.2.17 Pump 4 (P-103) S24 T = 40OC P= 300 Kpa (liquid) 115
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Calculations are based on Yunus A. Cengel, Micheal A. Boles, Thermodynamics: An Engineering Approach, WCB/Mc Graw-Hill, 1989, page, 354-355. Assumptions: 1. Steady operating conditions exist, 2. Kinetic and potential energy negligible 3. The process is to be isentropic Specific volume: (Data of these specific volumes are based on Coulson & Richardson’s) Specific volumes: DME = 0.178m3/mol Butene = 0.240 m3/mol Isobutane = 0.255m3/mol n-butane =0.263 m3/mol DME 0.178m3/mol x 1000mol/kmol x 1kmol/46kg = 3.87 m3/kg butene 0.240m3/mol x 1000mol/kmol x 1kmol/56kg = 4.29 m3/kg Isobutane 0.255m3/mol x 1000mol/kmol x 1kmol/58kg = 9.11 m3/kg n-butane 0.263m3/mol x 1000mol/kmol x 1kmol/58kg = 4.53 m3/kg Vavg = (3.87 + 4.29 + 9.11 + 4.53) m3/kg / 4 = 5.45 m3/kg Which remains essentially constant during the process 116
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 2 ∴Win = ∫ Vdp 1 = V1 (P2 − P1 ) = 5.45m 3 /kg(300 − 250)kpa(1k J/1kpa.m = 5.45(50) 3 ) = 272.50kJ/k g ∴272.50kJ/k g x kg/hr = 4113932.50 kJ/hr = 1142.76kW 8.2.18 Pump 5 (P-104) S26 T = 27OC P= 150 Kpa ( liquid ) Calculations are based on Yunus A. Cengel, Micheal A. Boles, Thermodynamics: An Engineering Approach, WCB/Mc Graw-Hill, 1989, page, 354-355. Assumptions: 4. Steady operating conditions exist, 5. Kinetic and potential energy negligible 6. The process is to be isentropic Specific volume: Water = 0.056 m3/mol Methanol = 0.118m3/mol (Data of these specific volumes are based on Coulson & Richardson’s) Water 0.056 m3/mol x 1000mol/kmol x 1kmol/18kg = 4.26 m3/kg Methanol 0.118m3/mol x 1000mol/kmol x 1kmol/32kg = 3.6875 m3/kg 117
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Vavg = (4.26 m3/kg + 3.6875 m3/kg)/2 = 3.974 m3/kg Which remains essentially constant during the process. 2 ∴Win = ∫ Vdp 1 = V1 (P2 − P1 ) = 3.974m 3 /kg(150 −100)kpa(1k J/1kpa.m = 3.974(50) 3 ) = 198.7kJ/kg ∴198.7kJ/kg x 1624.32kg/ hr = 322752.384 kJ/hr = 322 .75 kW 8.2.19 T-102 (Distillation Column 2) S28 T=530C P=100kPa (liquid) S26 T=27oC P=150kPa (Liquid) Sample of Calculations: S27 T=30oC P=70kPa (liquid) R = L/D Overall: (NL), L = D x 1.5 = 88.44 x 1.5 = 132.66 kmol/hr (NV), V = L + D 118
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR = 132.66 + 88.64 = 221.30 kmol/hr Stream 26 Component Flowrates ∆ĤF To T, K ∆H CH3OH H2O Kmol/hr 9.91E-01 1.76E+00 kJ/Kmol -2.01 x105 -2.42 x105 K 298 298 300 300 kJ/hr 0.02 -4.79 ∑ ∆H = -4.77 Stream 27 Component Flowrates ∆ĤF To T, K ∆H CH3OH H2O Kmol/hr 2.00E-02 8.67E+01 kJ/Kmol -2.01 x105 -2.42 x105 K 298 298 300 300 kJ/hr 0.00 -235.48 ∑ ∆H = -235.48 Stream 28 Component Flowrates ∆ĤF To T, K ∆H CH3OH H2O Kmol/hr 1.10E-02 8.84E+01 kJ/Kmol -2.01 x105 -2.42 x105 K 298 298 326 326 kJ/hr 0.00 -240.26 ∑ ∆H = -240.26 Energy balance, Q=( ∑ H) out –( ∑ H) in = (-235.48+(-240.26))– (-4.77) = -470.97 kW 8.2.20 Cooler 3 (E-105) S28 T = 53oC P = 100Kpa (Liquid) S29 T = 270C P = 130 Kpa (Liquid) 119
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Sample of Calculation for Cooler 1 Stream 28 Component Flowrates ∆ĤF To T, K ∆H CH3OH H2O Kmol/hr 1.10E-02 8.84E+01 kJ/Kmol -2.01 x105 -2.42 x105 K 298 298 300 300 kJ/hr 0.00 -240.26 ∑ ∆H = -240.26 Stream 29 Component Flowrates ∆ĤF To Kmol/hr kJ/Kmol K T, K ∆H CH3OH 9.91E-01 -2.01 x105 298 300 0.02 H20 1.76E+00 -2.42 x105 298 300 0.03 kJ/hr ∑ ∆H = 0.06 Energy balance, Q=( ∑ H) out –( ∑ H) in = 0.06– (-240.26) = 240.32 kW Steam flowrate, Q = mCpΔT Cp of pure water, 4.184 J/g oC (Elementary Principles of Chemical Processes, W.Rousseau et. al) Q m Cp ∆ T 240320 J/s = 4.184J/g o C x (53 - 27) o C = 2209.15 g/s m= 120
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Therefore the supply of steam flow rate required is 2209.15 g/s. CHAPTER 9 121
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR HYSYS 9.0 THE DESIGN MADE BASED ON HYSYS SIMULATION There are two method that was used in calculating the mass balance and energy balance for the process which is: i) Manual calculation ii) Hysys simulation Hysys program was used to see whether the design could be run or not. Using Hysys the calculation of the process was calculated automatically when the parameter that needed was insert. Then if the parameter that was insert is logic so Hysys program can calculated the result and the equipment can converge. If the data that was inserted was illogical the equipment cannot converge and the calculation cannot be done. At the back of this page show the simulation using Hysys that was converge and include with the manual log book. REFERENCES Alber V.G Hahn (1970). The Petrochemical Industry – Market & Economics, USA Mc Graw Hill Book Company. 363- 372. 122
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Coulson & Richardson’s, Chemical Engineering Volume 6 Third Edition, Butterworth Heinemann. Norman N. Barish and Seymour Kaplan, Economic Analysis for Engineering and Managerial Decision Making, Second Edition, Mc Graw Hill Robert H. Perry and Don W. Green, Perry’s Chemical Engineering’s Handbook, Seventh Edition, Mc Graw Hill. Encik Mohd Napis Bin Sudin. 2003, Production of MTBE, Malaysia, Kuantan. Interview, 8 July Puan Masri. 2003. Information of MTBE production, Malaysia, Kuantan. Interview, 28 Jun. Lanny P. Schmidt (1998), The Engineering of Chemical Reaction, Oxford University Press. James, G. Speight, Baki Ozum (1985). Petroleum Refining Process, Apex Engineering Inc. Marcell Dekkir New York. MTBE and Oxygenates (1990), An International Marketing Guide Dewitt & Company Incorporated 16800 Greenport park, Suite 120N Houston, Texas 77060-2386. Page 51-62. The 1992-1995 Worldwide Catalyst Product, Process Licensing & Service DirectoryTechnical articl-1992/3. Page 9. Annual Report 1994, Section 4. Area Summary for asia and the Pacific. Page 135-169. Ray/Johnston (1989). Chemical Engineering Design Project, a case study approach, volume 6. Gordon and Breach Science Publishers. Wentz (1998). Safety, Health, And Environmental Protection, Mc Graw Hill Companies, Inc. Wiley (2000). Elementary Principles of Chemical Processes, John Willey & sons, Inc. Chemical Week June 11, 2003 Volume 165 page 31 George S. Brandy ,Henry R.Clauser & John A. Vaccari. ”Material Handbook – 4th edition”Joshua D.Tayloy, Jerrey I. Steinfeld and Jefferson W.Tester “ Ind. Eng. Chem. Res 2001,40, 67-74 page 71. Monica Bianchi & Rachl Uctas,ECN “ACN/CMR/ ECN NPRA Supplement, March 2002. Petronas Resource Center, Tingkat 4, Menara 2, Menara Berkembar Petronas, Kuala Lumpur City Center. 123
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Malaysia Industrial Development Authority (MIDA), Plaza Central, K L Sentral. Kuala Lumpur. Pusat Informasi SIRIM Berhad. 1, Persiaran Dato’ Menteri, PO Box 7035, Seksyen 2, 40911 Shah Alam. Jabatan Perangkaan Malaysia, Pusat Pentadbiran Kerajaan, Putrajaya. Tiram Kimia Sdn. Bhd, Tingkat 1, Bangunan Shell, Off Jalan Semantan, Damansara Heights, 50490 Kuala Lumpur. http://www.Manufacturing.net/pur/index.asp http://www.ceh.sric.sri.com/Public…html http://ww2.cemr.wvu/edu/~wwwche/publications/project/index.html http://www.illallc.com/engarticle.html http://www.huntsman.com/pertochemicals/ShowPage.cfm http://www.cmt.anl.gov/science_technology/basicci/onestep_phenol.shtml http://www.illallc.com/engpatent3am.html http://www.wikipedia.org/w/wiki.phtml http://www.ccohs.ca/oshanswers/chemicals/chem_profiles/acetone/basic_ace http://www.atsdr.ede.gov/toxfag.html http://www.shellchemicals.com/chemicals/products/1,1184,806,00.html http://www.mida.gov.my http://eneken.ieej.or.jp/en/data/pdf/142.pdf http://www.matheson-trigos.com/mathportal/-pdfs/product/isobutane.pdf http://www.specialgas.com/isobutane.html http://www.gas.com.pdf/gas.pdf http://www.boc.com/microsite/america/products/gases/mixed/isobutane.html http://www.boc.com/microsite/america/products/gases/aps/geiger.html http://www.airliquide.com/safety/msds/en/129-AlEn.pdfhttp://www.cpchem/msds/specchem/isobutaneinstrumengradi.pdf 124
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR DESIGN PROJECT II 125
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR SECTION 1 Catalytic Cracking Design 1.1 INTRODUCTION A bed of solid particles can be fluidized by a stream of gas through it. The fluidization of solids in a stream of gas occurs only if the gas velocity achieved a certain value which is called minimum fluidization velocity Umf. Once the gas velocity achieved this value, the bed expands and pressure drop across the fluidized bed remains constant once fluidization occurred. In this commercial fluidized-bed catalytic cracking reactor, catalysts flow up through the reaction regeneration section in a riser type of flow regime. The over head catalyst captured by cyclones is returned to the hopper where it is fluidized with air to recapture any entrained hydrocarbon vapor. The catalyst was then discharged from the hopper, down through a standpipe. The solids flow through the standpipe was controlled by slide valve located at the base. From there, the solids went into the riser where they are carried by stream of air to the regenerator vessel. The regenerator operation in these plants resembled that of the reactor except for the system’s use of air instead of oil vapor. A portion of the catalyst from the regenerated catalyst hopper was returned to the regenerator through catalyst fresh feed exchangers. This action controlled the regenerator temperature and served to preheat the feed. Another bypass line from the hopper to the regenerator was used to control the dense bed level or holdup in the regenerator. Catalyst from the regenerated catalyst hopper flowed through a standpipe back into riser where the feed was injected. The commercial cracking catalysts used most widely is silica-alumina. High content catalysts are characterized by higher equilibrium activity level and surface area. These 126
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR catalysts could be offered at a lower price. An advantage of this catalyst grade is that a lesser amount of adsorbed, unconverted, heavy products on the catalyst were carried over to the stripper zone and regenerator. As a result, a higher yield of more valuable products and also smoother operation of the regenerator was achieved. Basically the design of the fluidized bed system can be divided into several sections: 1. Reaction vessel which included:  Fluidized bed portion  Gas disengaging space or freeboard  Gas distributor 2. Solids feeder or flow control 3. Solids discharge 4. Dust separator for the exit gas 5. Instrumentation and control 6. Gas supply Figure 1.1 : Illustration diagram of the reactor 127
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 1.2 Estimation of diameter of reactor The fluidized bed diameter depends on the operating gas velocity. A larger diameter is required for a low gas velocity while for a high gas velocity, a small diameter is required. However the gas velocity must exceed the terminal velocity (Ut) of the particle transport of solid particles may occur. The operating velocity should be between minimum fluidization velocity and terminal falling velocity to maintain fluidization of solids. Operating gas velocity, Uo = Where 2 d p g ( ρ p − ρg ) 18 µg dp = diameter of particle ρ p = density of particle ρ g = density of gases µ = viscosity of gases g = gravitational acceleration so, the value of Uo = (80 ×10 −6 ) 2 × 9.81 × (1282 −1.484 ) 18 × (1.15 ×10 −5 ) = - 0.388 m/s (rising) = 0.388 m/s Flowrate of gas stream , Q = 39353 kg/hr = 39353 m3/s 1.484 ×3600 = 7.366 m3/s The bed diameter will be depending on the area of reactor used: Cross sectional area, A = = Q V 7.366 0.388 = 18.985 m2 128
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Diameter of bed, D = = 4×A π 4 ×18 .985 π = 4.9164 m ≈5m 1.3 Calculation of the Transport disengagement height, TDH According to M. Rhodes (1998), the TDH region is considered as the region where located above the bed surface to the top of disengagement zone. While the disengagement zone is the region above the splash zone or region just above the bed surface in which the upward flux and suspension concentration of fine particles decrease with increasing in height. There are so many correlations that can be used to find the TDH value. For this design Amitin et al. (1968) was used. TDH ( F ) = 0.85U 0 TDH ( F ) = 7.740968 1 .2 ( 7.33 − 1.2 log 10 U 0 ) (1.1) ≅ 8m 1.4 Minimum fluidization Velocity The minimum fluidization velocity (Umf) is determined from Ergun equation: For Reynolds number, 0.01 < Re < 1000: According to the Martin Rhodes (1999), Ar = Re = 2 d p g ( ρ p − ρg ) ρg 18 µg and U mf D p ρ f µ 129
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Ar = 150 And (1 − ε ) Re + 1.75 ε 3 1 Re 2 3 ε (1.2) By rearranging the equation (1.2) above we can get the new equation for minimum fluidization, Umf. As a result, the equation is becomes: Re = U mf D p ρ f U mf = µ = µ ρg d p (1135 .7 + 0.0408 Ar ) 0.5 − 33 .7 1.15 ×10 −5 (1135 .7 + 0.0408 × 72 .44 ) 0.5 − 33 .7 −6 1.484 × 80 ×10 U mf = 0.00425 m / s 1.5 Calculation for the value of terminal velocity U t e The value of R t need to be calculated first, then the value of U t can be calculated. The range of particle size is 65 μm to 95 μm. The mean particle size is 250 μm. −6 When d p = 80 ×10 m 4 ρ g ( ρ p − ρ g ) gd p C D Ret = 2 3 µg 3 2 C D Re t 2 ( 4 1.484 × (1282 − 1.484 ) × 9.81 × 80 ×10 −6 = × 2 3 1.15 ×10 −5 ( ) ) 3 2 C D Re t = 96.227883 2 From the chart of C D Re t and CD vs Reynolds number, for value of Re t 130
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Figure 1.1 : CDRe2 and CD/Re versus Reynold number 2 C D Re t = 96.227883 the value of Re t = 3 Now from this we can calculate the value of U t , where Re t = 3= ρg U t d p µg 1.484 ×U t ×8 ×10 −6 1.15 ×10 −5 U t = 0.290599 ms −1 131
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR −6 when d p = 85 ×10 m C D Re t 2 C D Re t 2 4 ρ g ( ρ p − ρ g ) gd p = 3 µ2 3 ( 4 1.484 × (1282 −1.484 ) × 9.81 × 85 ×10 −6 = × 2 3 1.15 ×10 −5 ( ) ) 3 2 C D Re t = 115.421775 5 2 From the chart of C D Re t and CD vs Reynolds number from figure 1.1 for value Re t 2 of C D Re t = 115.421775 5 the value of Re t = 3.5 Now from this we can calculate the value of U t , where Re t = 3= ρg U t d p µg 5.54 ×U t ×85 ×10 −6 5.0 ×10 −5 U t = 0.3190899 ms −1 Table 1.1 : Calculation for terminal velocity in different size of dp. 132
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Sieve Weight, Weight size dp, %, xi fraction, 3.5 7.5 24 44 9.5 7 4.5 xi 0.035 0.075 0.24 0.44 0.095 0.07 0.045 m 0.000095 0.00009 0.000085 0.00008 0.000075 0.00007 0.000065 1.6 Reynold CDReT2 161.1394175 137.0119672 115.4217755 96.22788368 79.28933286 64.46516426 51.61441905 Terminal number 4.5 4 3.5 3 2.5 2 1.8 velocity, Vt 0.367073344 0.344414495 0.3190899 0.29059973 0.258310872 0.221409318 0.214596724 Find the value of K i*∞ Using the correlation for estimating entrainment rates are reported in the literature. The entrainment rate can be expressed by the following equation, as follows: Ei = Ei∞ + (Eio -Ei∞)exp (-afh) ( 1.3) Where Ei = entrainment rate at a point h above bed surface af = a constant in freeboard Ei∞ = rate of elutriation of the fines with diameter dpi above the TDH Ei∞ = K i∞ Xi (1.4) Where Ki∞ is the elutriation rate constant for which numerous correlations have been reported. Table 2.2 from Appendix lists various published correlations for the elutriation rate constant. The constant, af, in equation (1.2) is independent of the bed’s composition and can be evaluated from experimental data for Fi as a function of h. Following Chen et al. (1979), is the entrainment rate of particles at the bed surface, where: Eio = KoXi (1.5) Where Ko = Elutriation rate constant at bed surface Xi = weight fraction of the particle cut size dpiA 1.7 Find the value of Eo 133
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 3.07 ×10 −9 ρ g Eo = Ad eqmt µ 2 .5 Eo = 3.5 g 0 .5 (U − U ) 2..5 mf 3.07 ×10 −9 × (1.484 ) 3.5 (9.81) 0.5 ( 0.388 − 0.00425416 7 ) (1.15 ×10 −5 ) 2..5 2.5 (18 .98 )( 5) Eo = 10.676 kg/m2s The following correlation is used to calculate the value of E i*∞ by using three different investigators which is : Merrick and Highley (1974) 0.5  E i∞  v   U mf = A +130 exp −10 .4 t   ρg U   U   U −U mf       0.25     Geldart et al. (1979) revised E i∞ v   = 23 .7 exp  − 5.4 t  ρgU U  and Colakyan et al (1979) E i∞ v   = 331 − t   U 2 From this correlation we find that the average of the correlation for these three investigators, shown in the table below: 134
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Table 1.2 : Correlation of three investigators Merrick and Highley Geldart et al. (1974) Ki*∞ 2.810456563 3.115064954 3.509080841 4.035580234 4.76909596 5.849694145 6.085514067 (1981) Ki*∞ 0.008247282 0.011304929 0.016081902 0.023907858 0.037471784 0.062625124 0.068853496 Colakyan (1979) Ki*∞ 10.27741771 8.238989106 6.227114828 4.299839595 2.545780992 1.100824216 0.8993437 1.8 Ki*∞, average 4.36537385 3.788452996 3.25075919 2.786442562 2.450782912 2.337714495 2.351237088 Calculation of solid loading First find the value of Kih , K ih = K i* + ( E o − K i* ) exp( −a i h) ∞ ∞ = 4.36537385 = 4.36537385 + (10.676996 53 - 4.36537385 )(2.69398E - 12) kg/m 2 s R = Σ Ri = Σ RmRi m Bi = Fm Fi ( F − R ) + K i∞ A 135
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR m Bi = 10 .93 × 0.035 (10 .93 − R ) + 4.36537385 ×18 .98 + 10 .93 × 0.075 (10 .93 − R ) + 3.78845299 6 ×18 .98 + 10 .93 × 0.024 (10 .93 − R ) + 3.25075919 + 10 .93 × 0.0095 10 .93 × 0.07 + (10 .93 − R ) + 2.45078291 2 ×18 .98 (10 .93 − R ) + 2.33771449 5 ×18 .98 + 10 .93 × 0.0045 (10 .93 − R ) + 2.35123708 8 ×18 .98 ×18 .98 + 10 .93 × 0.044 (10 .93 − R ) + 2.78644256 2 ×18 .98 So the value of Rih calculated by excel is = 0.564147556 kg/s Eih = RT A 0.5641475 = 18.98 = 0.0297 kg / m 2 s Rti = Kih* A = 4 6335 .3 5 7 8 × 8 8 1 .9 2 8426 .7 6 4 5 2 × 8 8 1 .9 2 5278 .3 1 3 0 +3 8429 .7 8 5 9 +2 5721 .4 0 8 9 6 × 8 8 1 .9 2× 8 8 1 .9 +3 5799 .2 0 5 1 +2 3749 .3 7 1 4 × 8 8 1 .9 + 5 × 8 8 1 .9 + 8 × 8 8 1 .9 = 404.8578835 kg/s Ri = Kih A. Xi =4 6335 .3 5 7 8 2 8426 .7 6 4 5 2 5278 .3 1 3 0 = 5 .9 3 6 5 08 × 8 8 ×0 3 1 .9 .0 5 + 3 8429 .7 8 5 9 6 × 8 8 ×0 7 1 .9 .0 5 +3 5799 .2 0 5 1 ×8 8 × 1 .9 2 × 8 .9 ×0 4 1 8 .4 +2 5 7 2 1 .4 0 8 9 2 × 8 8 ×0 9 1 .9 .0 5 + 2 3749 .3 7 1 4 5 × 8 8 ×0 1 .9 8 × 8 8 ×0 4 1 .9 .0 5 k /s g 136
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Table 1.3 : Data calculation to find solid loading Total Mbi 0.004103705 0.009964059 0.03640034 0.076031739 0.018254549 0.013978087 0.008943974 0.167676452 MRi 0.602699773 1.269994045 3.981014237 7.127685256 1.505148839 1.099367014 0.707506537 16.2934157 Ki*η 4.36537385 3.788452996 3.25075919 2.786442562 2.450782912 2.337714495 2.351237088 Rti 82.85479568 71.90483787 61.69940943 52.88667983 46.51585967 44.36982112 44.62647993 Ri 2.899918 5.392863 14.80786 23.27014 4.419007 3.105887 2.008192 55.90386 a) Solid loading unreturned = 0.029723 / 0.388 = 0.076606351kg/s b) solid loading return = = 55.90386 / 18.98 2.94540903 kg/s 1.9 Calculation of holding time and residence time The outlet concentration of a plug flow reactor is related to the inlet concentration of the reactant by the same equation as in a batch reactor with the same residence time -. For an equilibrium reaction between A and B, is first order. Based on studied of Khabtou, S., Chevreau, T., and Lavalley, J.C., Micropor. Mat. 3, 133 (1994), express the rate per catalyst mass instead of reactor volume. k mA = − = 1 0.75 0.35   ⋅ ⋅ ln  − 0.35 − 1 151 .92 0.75 +1 0.75    4.785 ×10 −3 m 3 kg − 1 hr − 1 where x is the conversion in this process, x = ([A] 0 - [A]) / [A]0 = 0.35, 137
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR [A] is experssed in concentration in mol/m3, K the rate mol m-3 s-1, kA in s-1. The value K = [i-C4=]eq/[i-C4]eq = 0.75 and ST = 151.94 g.hr/m3 based on study by Yamamoto, S. Asaoka, et al (1997). Then from below equation given, w can find τ : kτ = (1 − ε A ) ln 1 −ε A X A 1− X A 1 − 0.41(065 ) 1 − 0.65 τ = (1 − 0.41 ) ln τ = 2256.48/ 4.785x10-3 τ = 417574.39 hr τ = 115.99 s when the total holding time are calculate then the weight of the bed of fluidized bed can be calculated. The formula used is as below: t= W Bed FB 0 WBed 830 = 3600 39353 W Bed = 95679.7761 7 kg 1.10 P Calculation for the pressure drop ∆ B The equation that can be used to calculate the pressure drop across the bed is: 138
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR  ρg W Bed − W Bed  ρp  ( − ∆p ) = A ( − ∆p ) = ( 95679.78     1.484  × 9.81 ) − ( 95679.78 ×9.81 ) ×    1282  18 .985 ( − ∆p ) = 49382 .78 Pa ≅ 49 .383 kPa p According to Kunii and Levenspield, the pressure drop across the distributor ∆ d is P 10% from the value of pressure drop across the bed when fluidized ∆ B . So the value p of ∆ d is: ( ∆p d ) = 10 %( − ∆p B ) ( ∆p d ) = 10 % × (49 .382 kPa ) ( ∆Pd ) = 4.938 kPa ≅ 0.5035 kgm −2 According to Kunii and Levenspield (1991), to determine the number of holes in the e distributor the R t need to be calculated first: Re t = ρg U 0 Dt µg Re t = 1.484 ×0.388 ×5.0 1.15 ×10 −5 Re t = 250344 1.11 Determine the direction and flow rate of gas passing between the vessels. 139
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Assuming that in fluidized flow the apparent weight of the solids will be supported by the gas flow, the equation below gives the pressure gradient for fluidized bed flow: ( − ∆P ) = (1 − ε ) × ( ρ − ρ ) × g p g H ( − ∆P ) = (1 − 0.42 ) ×(1282 −1.484 ) ×9.81 H = 7411.499 Pa / m Actual pressure gradient = ( 3.25 − 2.89 ) ×10 5 10 = 3600 Pa / m Since the actual pressure gradient is well below that for fluidized flow, the standpipe is operating in packed bed flow. The pressure gradient in packed bed flow is generated by the upward flow of gas through the solids in the standpipe. The Ergun equation above provides the relationship between gas flow and pressure gradient in packed bed. Knowing the required pressure gradient, the packed bed voidage and the particle and gas properties, equation below can solve for IUrelI, the magnitude of the relative gas velocity: ( − ∆P ) H 2 ρ f (1 − ε )    µ (1 − ε )  2 = 150 2  !U rel ! + 1.75  !U rel ! 2 x sv ε  x sv ε    For standpipes it is to take downward velocities as positive. In order to create the pressure gradient in the required direction, the gas must flow upwards relative to the solids. Hence, IUrelI is negative: IUrelI = -0.291 m/s 140
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR From the continuity for the solid, Solid flux, = Gp A = U p (1 − ε ) ρ p The solid flux calculated is 55.9 kg/m2s as and so Up = 55 .9 (1 −0.41 ) ×1282 = 0.072715 m /s Solids flow is downward, so Up = + 0.072715 m/s The relative velocity, Urel = Uf - Up Hence, actual gas velocity, Uf = - 0.291 + 0.072715 = - 0.21829 m/s (upwards) Therefore the gas flows upwards at a velocity of 0.21829 m/s relative to the standpipe walls. The superficial gas velocity is therefore : U = ε Uf = -0.0895 m/s (upward ) From the continuity for the gas, mass flow rate of gas, Mf = ε U f ρp A = -0.10431 kg/s So, for the standpipe operate as required, 0.10431 kg/s of gas must flow from the lower vessel to the upper vessel. 1.12 Design of cyclone Size a cyclone separator for removing particles above 80µ m in diameter entrained in a flue gas stream. The following information is supplied: 141
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR α = β 0.21 = 0.66 dp = 0.00008 m gas volumetric flow = 1.8 m3/s particle density = 1282 kg/m3 gas density = 1.484 kg/m3 viscosity gas = 0.0000115 Ns/m kinematic viscosity v = 0.0000278 m2/s inlet gas velocity = 0.388 m/s specific wall thickness δ = 5 mm The particles are approximately round with a shape factor of 0.77 All dimensions of a cyclone of any design are selected depending on the width of inlet duct b or on the diameter of cyclone Dc. The problem is to properly select one of these dimensions from which the other dimensions are proportionally evaluated. The cyclone diameter, settling velocity, gas velocity, and parameters of the suspension to be separated are all interrelated parameters. Therefore, we select a preliminary diameter for approximate calculations and then refine our estimate to a more exact design. According Nicholas P. Cheremisinoff at al. (1984), the relative dimensions of the cyclone are specified as: b = α DC and hin = β DC For the chosen cyclone α = 0.21 and β = 0.66 The continuity equation for the inlet nozzle is: bh = Vsec Win (1.5) 142
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR where win is the inlet gas velocity; which for a primary cyclone operation is typically 18 to 22 m/s. Expressing b and hin in terms of diameter DC, equation above is rearranged to solve for the cyclone diameter: V DC =  sec w  in 0.5     0.5 1.8   =    0.21 × 0.66 ×18  = 0.85 m For design purposes, assume a value of 0.9 m for DC. The diameter of the discharge pipe is: Dd = 0.58Dc = 0.58 x 0.9 = 0.52 m The gas velocity in discharge pipe is thus: Wd = 4 Vsec 4 × 1.8 = 2 πDd 3.142 × 0.52 2 = 8.5m / s Specifying a wall thickness δ = 5 mm for the gas discharge pipe, its outside diameter will be: Dd ,out = Dd + 2δ = 0.52 + 2(0.005 ) = 0.53 m The width of the circular gap between the pipe and cyclone shell is:  = Dc Dd ,out − 2 2 = 0.45 − 0.265 = 0.185 m The height of the circular gap from a spiral surface to the lower edge of discharge pipe is: H = 0.775 Dc = 0.775 X 0.9 = 0.7 m The calculated dimensions of the cyclone can be checked by comparing the particle settling time: 143
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR τ0 = Rc − Rd ,out wo =  wo to the residence time of gas in the cyclone: τ= 2 π Rav n wg where Rc and Rd,out are the radii of the cyclone and discharge pipe, respectively; n = number of gas rotations around the discharge pipe (we may assume n = 1.5) The peripheral velocity of gas is: wg = Vsec = H  1 .8 0.7 × 0.185 = 13 .9 m / s For this cyclone, this value must be in the range of 12 to 14 m/s The average radius of the gas rotation is : Rav = Dd ,out + 2  2 = 0.53 0.185 + 2 2 = 0.357 m The centrifugal acceleration (at the average radius) is: a= 2 wg Rav 2 = 13.9 = 542 m / s 2 0.357 The separation criterion is: Ks = a g = 542 9.81 = 55 .2 In this case, the centrifugal field in the cyclone is 55.2 times more intensive than the gravitational. The Archimedes number is: 144
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR g d 3 ρ p − ρg × Ar = ρg ν2 9.81 × (80 ×10 −5 ) 3 × (1282 −1.484 ) ×1.484 = (1.15 ×10 −5 ) 2 = 77.44 The settling number is: S1 = Ar x 1 x Ks = 72.44 x 55.08843 = 3999 Because 3.6 < S1 < 82,500 the flow regime through the cyclone is transitional. Therefore, the theoretical velocity of the particles is: (  α ρf 2 w = 0.22 d   µρ  )  0.333   (  α ρf 2 = 0.22 d   µρ  )  0.333   5.42 ×10 2 ×1282  = 0.22 ×10 ×10 −5   1.15 ×10   = 4.638 m / s The particles have a shape factor ofψ = 0.77 and the gas inlet gas stream contains a low volume of solid particles. Based on the operating conditions specified, the settling velocity is Ws = R ψ w = 0.77 x 4.634 = 3.568 m/s Because the concentration of the suspension is low, we may assume R = 1 145
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR The settling time is therefore:  w τ0 = = 0.0518s The residence time for the gas is: τ= 2πRavg n wg = 2 × 3.142 × 0.357 ×1.5 = 0.2424 s 13 .9 Since τ0 < τ the diameter of the cyclone selected is acceptable and we may now specify the other dimensions as based on the recommended proportions. As a final calculation for the design, we evaluate the hydraulic resistance of the cyclone: ∆ P= 1 2 C D ρ win Where CD is the typical number of cyclone. 2 = 0.5 x 1 x 1.484 x 182 = 240.4 N/m2 1.13 Calculation for mechanical design For mechanical design, the temperature and pressure are imperative properties in calculate the thickness and the stress of the material. For that reason, the safety factor also required as safeguard and determined by certain consideration such as corrosion factor, location and process characteristic. From Hysys data, the operating temperature inlet into the reactor is 250oC and regenerator is 180oC. The design temperature is related to the operating temperature. The design pressure and temperature for this reactor are showed as follow: Reactor 1. Design Pressure Operating pressure = 2.89 bar = 0.289 N/mm2 146
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR For safety reason take pressure 10% above operating pressure Design Temp. , T = 0.289 N/mm2x 1.1 = Design Pressure, Pi 0.3179 N/mm2 = 200ºC 2. Material Construction The material used is stainless steel (18Cr/8Ni, 304). For this material, the design stress at 200 ºC, R.K.Sinnot (1999). Design stress, f = 115 N/mm2 Diameter vessel, Di = 5.0 m Tensile strength, = 510 N/mm2 3. Vessel Thickness = P D i i 2 jf − P i = (0.3179 )( 5000 ) 2(1)(115 ) − (0.3179 ) = 7 mm + 4 mm = e 11 mm From R.K.Sinnot (1999), this value should not be less than 12 mm (including 2 mm of corrosion allowance). For vessel diameter around 5 m, this take e = 15 mm. A much thicker wall will be needed at the column base to withstand the wind and dead weight loads. 4. Heads and Closure This section covers the choice of closure to be used in the design. Basically there are two types of ends, which are domed ends. A standard torispherical heads and ellipsoidal heads as well as the flat heads are calculated in order to select the most economical head regarding its thickness. All the calculation is referring to the R.K. Sinnot, Coulson and Richardson Vol.6 page 815-817. Take, crown radius, Rc = Di = 5.0 m 147
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Knuckle radius, Rk = 6% Rc = 0.03 m A head of this size would be form by pressing: no joints, so J = 1.0 = 1 3 + 4  Rc Rk = Cs     1 3 + 4  5 .0   0 .3   = 1.77 Therefore, minimum thickness: e = = Pi Di 2 Jf − Pi ( Cs − 0.2) ( 0.3179 )( 5000 ) 2(1)(115 ) − 0.3179 (1.77 − 0.2 ) = 11 mm 5. Column Weight Dead weight of vessel, Wv For a steel vessel, Wv = 240 Cv Dm (Hv + 0.8Dm) t = mean diameter, m = (Di + t) Cv = a factor, take 1.15 Hv = height or length between tangent lines, m t = wall thickness, m Where, Dm 148
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR To get a rough estimate of the weight of this vessel is by using the average thickness, 11mm Therefore, Dm = 5 + 2 x 0.011 = 5.022 m = 240 (1.15) (5.022) [7.6 + 0.8(5.022)] 0.011 = 177.13 N = 0.17713 kN So, Wv Weight of insulation, WI Assume material is Mineral wool. ρ of Mineral wool = thickness 75 mm = 130 kg/m3 Volume of insulation = π = π (5.022) (7.622) (0.075) = 9.018967m3 x Dm x Hv x thickness of insulation Weight of insulation, WI = Volume of insulation x ρ x g = 9.018967 x 130 x 9.81 = 11501.89N = 11.50189kN Double this value to allow fittings, so weight of insulation will be = 23.004 kN Weight of bed 149
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Weight of bed in reactor WB = 95679.78 x 9.81 = 938618.6 N = 938.6186 kN Weight of cyclone Volume of cyclone in reactor = 2.438 m3 Weight of cylone = 2.438 x 9.81 x 1282 = 30661.31 N = 30.661 kN There fore, Total weight = Wv +WI +WB + Wc = (177.1311 + 23003.78 + 938618.6 + 30661.31)N = 992.461 kN For Regenerator 1. Design Pressure Operating pressure = 2.6 bar = 0.26 N/mm2 For safety reason take pressure 10% above operating pressure Design Temp. , T 2. = 0.26 N/mm2x 1.1 = Design Pressure, Pi 0.286 N/mm2 = 180ºC Material Construction The material used is stainless steel (18Cr/8Ni, 304). For this material, the design stress at 200 ºC, R.K.Sinnot (1999). Design stress, f = 121 N/mm2 Diameter vessel, Di = 6.5 m 150
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Tensile strength, 3. 510 N/mm2 = Vessel Thickness Pi D i 2 f − Pi (0.286 )( 6500 ) 2(1)(121 ) − (0.286 ) = 8 mm + 4 mm = 4 = = e 12 mm Heads and Closure This section covers the choice of closure to be used in the design. Basically there are two types of ends, which are domed ends. A standard torispherical heads and ellipsoidal heads as well as the flat heads are calculated in order to select the most economical head regarding its thickness. All the calculation is by referring to the R.K. Sinnot, Coulson and Richardson Vol.6 page 815-817 Take, crown radius, Rc = Di = 6.5 m Knuckle radius, Rk = 6% Rc = 0.39 m A head of this size would be form by pressing: no joints, so J = 1.0 = 1 3 + 4  Rc Rk = Cs     1 3 + 4  6.5 0.39     = 1.77 Therefore, minimum thickness: e = Pi Di 2 Jf − Pi ( Cs − 0.2) 151
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR = ( 0.286 )( 5000 ) 2(1)(121 ) − 0.286 (1.77 − 0.2 ) = 14 mm 5. Column Weight Dead weight of vessel, Wv For a steel vessel, Wv = 240 Cv Dm (Hv + 0.8Dm) t = mean diameter, m = (Di + t) Cv = a factor, take 1.15 Hv = height or length between tangent lines, m t = wall thickness, m Where, Dm To get a rough estimate of the weight of this vessel is by using the average thickness, 12 mm Therefore, Dm = 6.5 + 2 x 0.012 = 6.524 m = 240 (1.15) (6.524) [8 + 0.8(6.524)] 0.012 = 285.6337 N = 0.2856 kN So, Wv Weight of insulation, WI Assume material is Mineral wool. ρ of Mineral wool = 130 kg/m3 152
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR thickness = 75 mm Volume of insulation = π = π (6.524) (8) (0.075) = 12.29745 m3 x Dm x Hv x thickness of insulation Weight of insulation, WI = Volume of insulation x ρ x g = 12.29745 x 130 x 9.81 = 15682.94N = 15.68294kN Double this value to allow fittings, so weight of insulation will be = 31.36588kN Weight of bed Weight of bed in reactor WB = 75060.19 x 9.81 = 736340.5 N = 736.3405 kN Weight of cyclone Volume of cyclone in reactor = 2.438 m3 Weight of cylone = 2.438 x 9.81 x 1282 = 30661.31 N = 30.661 kN There fore, Total weight = Wv +WI +WB + Wc = 0.2856 + 31.36588 + 736.3405 + 30.661 = 798.652 kN 153
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Total weight for reactor and regenerator = 992.461 + 798.652 kN = 1791.113 kN 6. Wind Loads Take, Win speed, Uw = 160 km/hr For a smooth cylindrical column stack, the following semi-empirical equation can be used to estimate wind pressure. = 0.05Uw2 = 0.05(160)2 = Pw 1280 N/m2 Loading per Unit Length of column, Fw Fw = Pw Deff] Where, Deff = Effective column diameter = Diameter + 2(tshell + tinsulation ) = 6.5 + 2(12 + 75 ) x 10-3 = 6.68 m Therefore, Fw = 1280 x 6.68 = 8550.4 N/m Bending Moment Mx = Fw ( X ) 2 2 154
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Where, X = Distance measure from the free end =8m Therefore, 8550 .4 (18 ) 2 2 1385164.8 Nm = 7. = = Mx 1385.1648 kNm Analysis of Stress From bottom tangent line, Longitudinal pressure stress, σ h = P Deff i 2t = (0.286 )( 6680 ) 2(12 ) = 79.6033N/mm2 Circumferential pressure stress, σ L = P Deff i 4t = (0.286 )( 6680 ) 4(12 ) = 39.802 N/mm2 Dead weight stress, σ w = W π( Di + t )t 155
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR = 1791 .113 ×10 3 π(6500 +12 )12 = 7.2958 N/mm2 Bending Stress, σ b ± = M  Di  + t  Iv  2  where, M = total bending moment Iv = Iv = second moment of area π 64 (D 4 o − Di 4 ) which, Di = 6500 mm Do = (6500+ 2(12)) = 6524 mm so, π = (6524 64 = Iv 1.3013 x 1012 mm4 4 − 6500 4 ) Therefore, σ 1385164 .8 ×1000  6500  + 12   12 1.3013 ×10  2  = ± = b ± 3.47 N/mm2 The resulted longitudinal stress, σ z is: σ z(upwind) = σ = 39.802 - 7.2958 + 3.47 = 35.9762 N/mm2 L - σ w + σ b 156
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR σ σ = z(downwind) L - σ = w - σ b 39.802 - 7.2958 - 3.47 29.0363 N/mm2 = 8. Elastic Stability Critical bulking stress σ 1  t = 2 x 104  D  m      12   = 2 x 104   6512  = 36.855 N/mm2 Maximum compressive stress will occurs when the vessel not under pressure =σ w + σ b = 7.2958 + 3.472 = 10.768 N/mm2 This is below critical bulking stress, so acceptable. 9. Vessel Support Design (Skirt Design) Type of support : Straight cylindrical skirt θs : 80º Material construction : Carbon steel Design stress, fs : 135 N/mm2 at ambient temperature, 20ºC Skirt height : 4.0 m Young modulus : 200, 000 N/mm2 Therefore, The total weight of vessel from calculation before = 1791.113 kN Wind load, Fw = 8550.4 N/m = 8.5504 kN/m 157
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Bending moment at skirt base, Ms  ( H v + H skirt ) 2  = Fw   2   (18 + 2 ) 2  = 8.5504   2   = 1710.08 kNm As a first trial, take skirt thickness as same as the thickness of the bottom section of the vessel, ts = 12 mm Bending stresses in skirt, σ = bs 4 Ms [π ( Ds + ts )ts Ds ] Where, Ms = maximum bending moment (at the base of the skirt) ts = skirt thickness Ds = inside diameter of the skirt base = 3.0 m Therefore, σ bs = 4(1710 .08 )(1000 )(1000 ) [π ( 6500 +12 ) (12 )( 6500 )] = 4.287 N/mm2 Dead weight stress in the skirt, σ ws = 2W [π ( D s + t s ) t s ] Where, 158
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR W = Total weight of the vessel and content = 1791.113 kN Therefore, σ (test) ws = 2 ×1791 .113 ×1000 [π( 6.5 + 0.012 ) (0.012 )] = 14591753.05 N/m2 = 14.592 N/mm2 σ bs, (operating) = 1791 .113 ×1000 [π( 6.5 + 0.012 ) (0.012 )] = 7295876.525 N/m2 = 7.2958 N/mm2 Thus, the resulting stress in the skirt, σ Maximum σ s (compressive) = σ ws s : (test) + σ bs = 14.592 + 4.287 = 18.879 N/mm2 Maximum σ s (tensile) =σ bs - σ ws (operating) = 4.287 - 7.2958 = 0.0323 N/mm2 10. General consideration for design Take the joint factor J as 0.85, 159
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR σ s (tensile) < fs J sin θ s σ s (compressive) < 0.125 E ts sin θs Ds Where , fs = maximum allowable design stress for the skirt material = 135 N/mm2 J = weld joint factor θs = base angle of a conical skirt E = modulus young = 200, 000 N/mm2 Therefore, σ s (tensile) < 135 x 0.85 sin 80 0.1892 N/mm2 < 113.007 N/mm2 σ s (compressive) < (0.125)(200,000) 0.4014 N/mm2 < .1214.473 N/mm2 148 sin 80 3000 Both criteria are satisfied, add 2 mm for corrosion, give design thickness of 150 mm 11. Base Rings and Anchor Bolts Assume pitch circle diameter = 5.0 m Circumference of bolt circle = 5000π Bolt stress design, fb = 125 N/ mm2 Recommended spacing between bolts = 600 mm 160
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Minimum number bolt required, Nb = 5000 π 600 = 26.18 Closest multiple of 4 = 28 Bending moment at base skirt, Ms = 212.101 kNm Total weight of vessel, W = 236.7534 kN Area of bolt, =  4M s    D −W   Nb fb  b  = Ab 1  4( 212 .101 )(1000 )  − (184 .046 )(1000 )   28 (125 )  3. 0  1 … E.1.19 = 28.22 mm2 bolt root diameter, d 28 .22 × 4 = π = 6 mm Total compressive load on the base ring per unit length, Fb  4M s =  πDs 2 + W   πDs  4 (212 .101 ) ×1000 236 .7534 ×1000  + =   2 π (3) π (3.0)   = 55.12 kN/m Assuming that a pressure of 4 N/mm2 is one of the concrete foundation pad, fc Minimum width of the base ring, Lb = Fb 1 × 3 fc 10 161
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR = 55 .12 ×10 3 4 ×10 3 = 13.78 mm 12. Feed Nozzle Sizing Optimum duct diameter, dopt,t = 293G0.53ρ -0.37 Where, G = flow rate = 1.32121 x 105kg/hr = 36.7 kg/s ρ = density = 30.698 kg/ m3 Therefore, Dopt = 293 (36.7)0.53 (30.698)-0.37 = 500 mm Nozzle thickness, t = Ps d opt 20 σ + Ps Where, Ps = Operating pressure = 2.74945 N/mm2 σ = Design stress at working temperature = 30 N/mm2 Therefore 162
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR t = ( 2.74945 )(118 ) 20 (30 ) + 2.74945 = 0.2 mm So, thickness of nozzle = corrosion allowance + 0.2 mm = 4 + 0.2 mm = 4.2 mm ∼ 5 mm 13. Top Product Nozzle Sizing Optimum duct diameter, dopt,t = 260G0.52ρ -0.37 Where, G = flowrate = 223938.68 kg/hr = 62.205 kg/s ρ = density = 56.69 kg/m3 Therefore, dopt = 226(62.205)0.50 (56.69)-0.35 = 500 mm Nozzle thickness, t = Ps d opt 20 σ + Ps σ 163
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Where Ps = Operating pressure = 2.74945 N/mm2 σ = Design stress at working temperature = 30 N/mm2 Therefore t = ( 2.74945 )(1000 ) 20 (30 ) + 2.74945 = 2 mm So, thickness of nozzle = corrosion allowance +2 mm =4 +2 = 6 mm ∼ 6 mm Table 1.4 : Summary of the Mechanical Design Design Pressure Reactor Operating Pressure 2.89 bar Reactor Operating Temperature 160 Reactor Design Pressure 0 C 3.179 bar 164
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 0 Reactor Design Temperature 200 C Regenerator Operating Pressure 2.6 bar Regenerator Operating Temperature 150 Regenerator Design Pressure 2.86 bar Regenerator Design Temperature 180 Safety Factor 0.10 0 C 0 C Design of Domed Ends Types Torispherical head Crown Radius Knuckle Radius Joint Factor Stress Concentration Factor Minimum Thickness Corrosion Allowance Column Weight Dead Weight of Vessel Weight of Bed Weight of cyclone Weight of Insulation Total Weight reactor and regenerator Wind Pressure Loading Bending Moment 6.5 0.039 1 1.77 14 4 389 736.34 30.66 31.366 1791.11 1280 8550.4 1385.1648 m m mm mm kN kN kN kN kN N/m2 N/m kNm REFERENCES Cheremisinoff, Nicholas P., 1984, Hydrodynamics of Gas-Solids Fluidization, 279 - 231 Amitin et al. 1985, The Hydrodynamic of Fluidization, Powder Technology,(42): 67-78 Geldart, D ,. et al., 1979, Transition Institute Chemical Engineers, 57-269. Dolignier J. C, Marty E., Martin G. & Delfosse L., 1998, Modelling of gaseous pollutants emission in circulating fluidized bed of municipal refuse. Elsevier Science Ltd(77): 1399-1409 Gregory et al, 1985, The design of distributor for gas-fluidized bed, Powder Technology. (42): 100-145 165
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Horio et al. 1980, The Hydrodynamic of Fluidization, Powder Technology,(42): 67-78 Sinclair, J.L. and R. Jackson, “Gas-Particle Flow in a Vertical Pipe with Particle-Particle Interactions, AIChE J., 35, 1473-1486 (1989) Sinclair, J.L., “Hydrodynamic Modeling”, in “Circulating Fluidized Beds”, ed. Grace, J.R., Avidan, A.A. and T. M. Knowlton, Chapman and Hall, Great Britain (1997) Wang, Z., D. Bai and Y. Jin, "Hydrodynamics of Concurrent Downflow Circulating Fluidized Bed (CDCFB)", Powder Technology, 70, 271-275 (1992) Wei, F., Wang, Z., Jin, Y., Yu, Z. and W. Chen, “Dispersion of Lateral and Axial Solids in a Cocurrent Downflow Circulating Fluidized Bed”, Powder Technology, 81, 2530 (1994) Himmelblau M. D. 1996, Basic Principles and calculation in Chemical Engineering. Sixth edition. United States of America: Prentice Hall International, Inc. Levinspiel O. 1999. Chemical reaction engineering. Third edition. United States of America: John Wiley & Sons. Rhodes, M. 1998. Introduction to particle technology. Chichester England. John Wiley & Sons 97-130. Sinnot, R.K. 1999.Chemical engineering volume 6. Third edition. Great Britain: Butterworth-Heinemann. Zhang H, “Hydrodynamics of a Gas-Solids Downflow Fluidized Bed Reactor”, Ph.D. thesis, The University of Western Ontario (1999) Zhang, H., Zhu, J-X., “Hydrodynamics in Downflow Fluidized Beds (2): Particle Velocity and Solids Flux Profiles”, Chemical Engineering Science, 55, 4367-4377 (2000) Matsen, J. M. "Some Characteristics of Large Solids Circulation Systems". In Fluidization Technology, Keairns, D. L., Ed.; Hemisphere: New York, Vol. 2, Chapter1 (1976) 166
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Ouyang, S. Potter, S.E., “Consistency of Circulating Fluidized Bed Experimental Data”, Ind. Eng. Chem. Res., 32, 1041-1045 (1993) Wei, F., R. Xing, Z. Rujin, L. Guohua, J. Yong, “A Dispersion Model for Fluid Catalytic Cracking Riser and Downer Reactors”, Ind. Eng. Chem. Res., 36, 5049-5053 (1997) Yang Y.L., Y. Jin, Z.Q. Yu, Wang, Z.W., “Investigation on Slip Velocity Distribution in the Riser of Dilute Circulating Fluidized Bed”, Powder Tech., 73, 67-73 (1992) http://thor.tech.chemie.tu_muenchen.de/~tc2/eng/teaching/industr_chem_process/crac king%20lecture%201.pdf http://www.refiningonline.com/EngelhardKB/npra/NPR8851.htm http://iglesia.cchem.berkeley.edu/ChemicalCommunications_1764_2003.pdf http://www.caer.uky.edu/energeia/PDF/vol10-3.pdf http://www.netl.doe.gov/publications/proceedings/96/96ps/ps_pdf/96ps3_2.pdf http://tetra.mech.ubc.ca/CFD03/papers/paper29AF3.pdf http://www.netl.doe.gov/products/r&d/annual_reports/2001/stpt/cfb%20operating %20regimes%20cork.pdf http://www.flotu.org/~weifei/twophase-ces.pdf http://www.gtchouston.com/articles/GTC%20online%20reprint%2011-99.pdf 167
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR SECTION 2 MULTITUBULAR FIXED BED REACTOR 2.1 CHEMICAL DESIGN 2.1.1 INTRODUCTION 168
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Fixed bed reactors are the most important type of the reactor for the synthesis of large scale basic chemicals and intermediates. In these reactors, the reaction takes place in the form a heterogeneous catalyst. In addition to the synthesis of valuable chemicals, fixed bed reactors have been increasingly used in recent years to treat harmful and toxic substances. The most common arrangement is the multi tubular fixed bed reactor, in which the catalyst is arranged in the tubes, and the heat carrier circulates externally around the tubes. Fixed bed reactor for industrial synthesis are generally operated in a stationary mode under constant operating conditions over prolonged production runs, and design therefore concentrates on achieving an optimum stationary operation. However, the non stationary dynamic operation mode is also great importance for industrial operation control. CATALYST FORM FOR FIXED BED REACTOR The heart of fixed bed reactor and the site of the chemical reaction is the catalyst. The processes taking place on the catalyst may formally be subdivided into the following separate steps: 1. Mass transfer of reactants from the main body of the fluid to the gross exterior surface of the catalyst particle. 2. Molecular diffusion /Knudsen flow of reactants from the exterior surface of the catalyst particle into the interior pore structure. 3. Chemisorption of at least of the reactants on the catalyst surface. 4. Reaction of the surface 5. Desorption of absorbed species from the surface of the catalyst. 6. Transfer of products from the interior catalyst pores to the gross exterior surface of the catalyst by ordinary molecular diffusion/Knudsen flow. 7. Mass transfer of products from the exterior surface3 of the particle into the bulk of the fluid. 169
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR For industrial use, a particle size is a compromise between the speed of the exchange reaction (which is greater with small beds) and high flow rates (which require coarse particles to minimize the head loss). Standard resins contain particle with diameter from 0.3 to 1.2 mm, but coarser or finer grades are available. For the MTBE production process, the fine sulphonic ion exchange resin particles with its size less than 1.0 mm have to be enveloped in various conceivable shapes The catalyst properties are as below: Shape of Catalyst = Spheres Diameter of catalyst (dc) = 0.6 mm (ref: Jon J.Ketta) Effective Diameter surface d’p = 0.5mm Bulk Density of Catalyst (ρb) = 810 kg/m3 Specific Solid Sphere surface = 34.25 m2/g (ref:Perry’sHandbook,pg 16.10) Voidage (εb) 0.32 (ref:Tech Info.Buletin) Surface Area (Sa) = 45 m2/g Specific Surface = 0.034 m2/g Specific Gravity = in range 1 to 1.4 Internal Void Fraction (εp) = 0.54 Molecular Weight 2.1.2 = = 98 g/mole PARTICLES SOLID DENSITY Particle solid density (ρp) can be obtained from the equation below (ref: Particle Technology’s book): ρp = ρb 1-εb = 810 1 - 0.32 = 1191.2 kg/m3 170
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 2.1.3 VOID VOLUME OF CATALYST Void volume of catalyst, Vg can be determined as below: Vg = εp ρp = 2.1.5 0.32 1191.2 = (2.1) 0.268 cm3/g PORE RADIUS OF CATALYST Pore radius of particle, r is the determined, r = 2. Vg Sa = 2.1.6 2 * 0.268 45 x 104 = (2.2) 1.194 x10-5 m KNUDSEN DIFFUSIVITY Knudsen Diffusivity is given by the equation below: Dk where M = 9.7 x103 r (T)1/2 (M) 98 g/mole = operating temperature = Dk molecular weight of the catalyst = T = 393 K = (2.3) 9.7 * 103 * 1.194 *10-5 *( 393)1/2 171
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 98 = 0.013 cm2/ s The effectiveness factor is given in term of Thiele Modulus as: η = η 2.1.7 = 3 (Φ - 1) Φ2 tan h Φ (ref: Jon J.Mc Ketta) (2.4) 0.928 where Φ = 1.1 (ref: Perry,s Handbook) REACTION RATE The synthesis of MTBE from methanol and isobutylene catalyzed by Amberlyst-15 or similar sulphonic ion exchange resin catalyst is a reversible etherification as shown in equation 1: iC4H8 (isobutene) + CH3OH (methanol) C5H12O (MTBE) k1 CH3C(CH3)=CH2(B) + CH3OH CH3C(CH3)2OCH3 (M) K2 Reaction kinetics: According to Yang et al, the forward reaction of reaction above is first order with respect to the isobutylene concentration and zero order with respect to the methanol concentration, respectively, and the reverse reaction is first order with respect to the MTBE concentration as shown below: Table 1: Arhenius parameters of rate constant K1 and K2 for MTBE synthesis catalyzed by Sulphonic ion exchange acidic resin catalyst. (Ref: Chem. Eng. Journal) 172
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR A1 A2 E1(J/mole) E2(J/mole) 6.50E+05 1.36E+08 4.74E+04 7.04E+04 -rB = k1CB – k2CM where: k1 = A1 exp (-E1/RT) & k2 = A2 exp (-E2/RT) k1 = A1 exp (-E1/RT) (2.5) = 6.5 * 105 exp (-4.74*104/ 8.314 * 326 K) = 0.0165 / min k2 = A2 exp (-E2/RT) (2.6) = 1.36 * 108 exp (-7.04 * 104 / 8.314 * 326 K) = 0.00071/ min The main side reactions are the dimerization of isobutylene to diisobutylene, and the hydration of isobutylene to tert-butyl-alcohol (TBA) as shown below: 2CH3C(CH3)=CH2 CH3C(CH3)=CH2 + H2O CH2=C(CH3)CH2C(CH3)2CH3 (DIB) CH3C(CH3)2OH (TBA) (3) (4) The kinetic study shows that reaction (3) can only take place when the addition of methanol is unsufficient. Since the methanol addition is carefully arranged to allow the molar ratio of methanol to isobutylene to be higher than 0.8, the reaction (3) can be 173
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR neglected. For reaction (4), the minor water in hydrocarbon and methanol feedstock is consumed in the pre-reactor before it is fed into reactor. Therefore, reaction (4) can also neglect. The products of the two side reaction are considered in the vapor-liquid equilibrium calculation, whereas the reaction kinetics is not included in the calculation. -rB = k1CB – k2CM = k1(CBo –CBXB) – k2( MCBo –CBXB) CB = CBo since Pi = 2000Kpa and Ti = 326 K CBo = Pi /RT = 73.79 mol /m3 M = CMo / CBo = 0.138 Substitute all the value, -rB = 173.8 mole/ m3hr 2.1.8 WEIGHT OF CATALYST The weight of catalyst can be determined from the equation, W = ∫ dX F r 2.7) Where r = overall reaction rate W = weight of catalyst needed for the conversion F = mole flow rate of the feed to the reactor Substitute all the value and the by integration, the weight of catalyst is found to be 2998 kg. 2.1.9 DETAIL DESIGN OF THE REACTOR 2.1.9.1 Heat Exchanger for Reactor 174
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR For isothermal operation, heat may be supplied or removed continuously along with the reaction path. In order to accomplish effective heat transfer with the packed bed, the width of the bed must be small. In other words, isothermal reactors usually consist of a number tube arranged as in large heat exchangers with the catalyst inside the tubes and the cooling or heating medium outside the tubes. 2.1.9.2 Direction of the Reactant Flow For the fixed bed reactor to be designed so that reactants remain isothermal, the rate of heat required for the exothermic reaction must be exactly balance the heat transfer from the heating medium. For any isothermal reaction of positive order, the reaction rate falls as the reaction approaches equilibrium. Therefore a more rapid heating is need at the reactant entrance than the reactant exit. Therefore the reactors have to be designed as co-current to match the requirement and heat transfer. 2.1.9.3 Volume of Catalyst Bed Volume of catalyst bed (Vb) = W / ρb = 2998 810 = 3.70 m3 (2.8) 2.1.9.4 Pressure Drop in the Bed Pressure drop is an important variable in the rate equations. The maximum allowable pressure drop criteria below have to be concerned. 1. The resulting force must not be exceeding the crushing strength of the particle. For the down flow bed this force created by the pressure drop is transmitted by contacting solid to the bottom of the bed. 2. Mass velocity through the bed must be high enough to minimize interphase gradients and assure good distribution. Incremental increases in pressure 175
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR drop however should not exceed savings release from improved reactor performance. In many bed systems the maximum economical pressure drop is in the range of 3 to 5% of the total pressure. 2.1.9.5 Estimating Pressure Drop (ΔP) L Where ƒ = ƒ u2 ρf d’p (2.9) = friction factor, the correlation of Ergun (1952) will be used = [1.75 + 150 / (1-εb) / Re] (1-εb)/ εb3 Re = d’p u ρf = d’p G μf μf (2.10) Where G is mass velocity = m/ A since m= 12.12 kg/s and G = 1.968 kg/m2s μf = ( 0.28 E-6 + 1.001 E-3 +7.86 E-6)/3 = 3.36 E-4 kg/ms Substitute the value, so Re = 2.928 (transition region) and ƒ = 73.75. Since ρf = 796.57 kg/m3 and u= 0.0178x4/ πx2.82 =0.003 m/s, (ΔP) will be 1060 N/m2 2.1.9.6 Height of Bed From the criteria shown above, the optimum value of pressure drop is between 3 to 15% of the total pressure. Let the height of bed equals to 4 m, the pressure drop in the bed is 4240 N/m2 which is equal to 4.2% of the operating pressure. Therefore, the height of bed is taken as 4m 2.1.9.7 Total cross Section Area of the Tube Total cross section area of the tube can be obtained by dividing the volume of the bed with the height of the bed. At = 3.70 176
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 4 = 0.925 m2 (2.11) 2.1.9.8 Tube Diameter If the tube diameter to particle diameter ratio is less than 10, the effect of wall can become predominate, the void fraction and thus fluid velocity near the wall become more dominant. However, if high value of tube to particle diameter ratio is obtained, the heating effects through the tube wall will not be efficient. Therefore, tube with the inside diameter Di =0.1143m and thickness 0.005m is used in this reactor, where the ratio is approximately 11.5. The inside diameter of the tube (Di) = = 0.1143 – 2 x 0.005 0.1043 m The cross section of the tube is then obtained from the equation: = π Di 2 /4 = At 0.009 m2 (2.12) 2.1.9.9 Total Number of Tubes Total number of tube can then obtained by dividing the total cross section area of one tube. Nt = 0.925 0.009 = 103 tubes (2.13) 2.1.9.10 Tube Arrangement The tubes in an exchanger are usually arranged in an equilateral triangular, square or rotated square pattern. Since the triangular pattern gives higher heat transfer rates, it is recommended for this reactor. 177
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 2.9.1.11 Pitch of the Tube From reference (Process Heat Transfer’s book), the pitch of the tube is recommended to be 1.25 times of the outside tube diameter Do. Therefore, Pitch of the tube (Pt) = 1.25Do = 1.25 x 0.1143 = 0.143 m (2.14) 2.1.9.12 Bundle Diameter The bundle diameter depends not only on the number of tubes but also can also on the number of tube passes. For a single pass heat exchanger type reactor, the bundle diameter can be obtained from the empirical equation base on standard tube layout as shown: Bundle diameter, Db = Do ( Nt)n-1 K1 (2.15) Where n1 and K1 = constant for use in the equation above given in reference (Process Heat Transfer’s book). For single pass, n1 and K1 is given as 2.142 and 0.319 respectively. Hence, Db = = 0.1143 x (103 / 0.319) (1/2.142) 1.70 m 2.1.9.13 Number of Tubes In the Centre Row The number of tubes in the centre row is then given by equation: Nc = = Db / Pt 1.70/ 0.143 178
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR = 11.8 or 12 tubes (2.16) 2.1.9.14 Shell Diameter By using split ring floating head type from Fig 12.6 in Reference (Chem. Eng. Vol.6’s book), Ds – Db = 95.14 mm Where Ds = Shell Diameter Ds = 1.7 + 0.09 = 1.79 m 2.1.10 Baffles Baffles are used in the shell to direct the fluid stream across the tubes, increase the fluid viscosity and create turbulence so as to improve the rate of heat transfer. The baffles used in this reactor are a common type i.e the single segmented baffles with baffles cut 35 %. 2.1.11 Baffles Spacing The optimum baffles spacing will usually be between 0.3 to 0.5 times of the shell diameter. Here, it is taken as 0.3 times of the shell diameter. Bs = 0.3 Ds = 0.3 x 1.79 = 0.55 m say 0.6 m (2.17) 2.1.12 Number of Crosses Number of crosses in the shell side, 179
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Nc = = L -1 Bs 4 (2.18) (Pt – Do) * Ds * Bs Pt (2.19) Area for Cross Flow As = = = (0.143 - 0.114) * 1.79 * 0.6 0.143 2 0.218 m 2.1.14 Shell side heat transfer and pressure drop calculation The flow pattern in the shell of a segmental baffled heat exchanger type of reactor is complex, and this makes the prediction of the shell side heat transfer coefficient and pressure drop much more difficult than for the tube side. However, Kern has developed a method base on experimental work on commercial exchangers with standard tolerances and gives a reasonably satisfactory prediction of the heat transfer coefficient and pressure drop for standard design. 2.1.15 Shell side Mass Velocity Mass velocity, Gs Gs = Ws As G = 2.211 0.218 G s =10.14 kg / m 2 s (2.20) Shell side velocity 180
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Gs us = us = ρ 10.14 1209 u s = 0.01 m / s (2.21) Shell side equivalent diameter for triangular pitch arrangement = 4(Pt/2).0.87.Pt – π.Do2/8 π. Do/2 Das = 0.084 m (2.22) Reynolds number Re = Re = G s d as µ (10.14)(0. 084) 0.00034 (2.23) Re = 2505 Prandtl number Pr = Pr = CP µ kf (3124.5)(0 .00034) 0.086 (2.24) Pr =12.3 Choose buffle cut of 35%, from figure 12.30 (Coulson & Richardson’s Chemical Engineering), we can obtained Jf =1.3 x 10-1 181
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Assumed that the viscosity correction is negligible hs = k f jf Re Pr 1 / 3 de hs = (0.086)(0. 13)(2505)( 12.3 1/3 ) 0.084 h s = 763.2 W / m 2 o (2.25) C Shell side pressure drop Reynolds number Re = 2505 From figure 12.30 (Coulson & Richardson’s Chemical Engineering), Jf = 1.3 x 10-1 Shell side pressure drop can be calculated using equation below ∆P =8j f ( D d / d e )( L/I B )( ρµ / 2 )( µ / µw ) s ∆P =8.93kPa -0.14 (2.26) 2.1.16 Tube side coefficient, hi Mean temperature of the tube 182
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR t mean = t1 + t 2 2 t mean = 53 + 27 2 (2.27) t mean = 80 o C cross sectional area = π d12/ 4 = (3.142)(0.10432) / 4 = 0.009 m2 Tube / pass = 103 / 1 = 103 tube / pas (2.28) Total flow rate area = (cross sectional area)(tube / pass) = (0.009)(103) = 0.927 m2 velocity, Gt = (2.211)/(0.927) = 2.05 kg / sm2 v = 0.002 kg / ms Ratio of L / di = 4 / 0.104 (2.29) = 38.46 Reynolds number, Re Re = ρν d i µ Re = (1209) (0.002 ) (0.1043) 0.00034 Re =1000 183
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Heat transfer factor figure 12.31 (Coulson & Richardson’s Chemical Engineering), Jh = 2 x 10-2 Prandtl number, as 12.3 Pr =12.3 Tube side coefficient, hi can be calculated using equation below. hi = jh k f Re Pr 0.33 di hi = (2x 10 -1 )(0.086)(1 000)(12.3) 0.104 (2.30) 0.33 h i = 393 W / m o C Tube side pressure drop Reynolds number, Re = 1000 From figure 12.24 (Coulson & Richardson’s Chemical Engineering), jf = 2 x 10-1 Neglect the viscosity correction term [ ∆Pt = N p 8 jf ( L/d i )( µ / µW ) - m + 2.5 [ ∆Pt = 2 8(5 x 10 -3 )(4/0.104) + 2.5 µ ] ρ2 i 2 i . ] (1209 )( 0200034 ) 2 (2.31) ∆Pt =10.89 kPa 2.1.17 Correction for Tube Heat Transfer Coefficient 184
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Since the tube side heat transfer coefficient calculated is based on the inside diameter of the tube, correction has to be done to obtain the heat transfer coefficient for outside diameter of tube. HO = = hI . Di Do 192 W/ moC (2.32) 2.1.18 Overall Heat Transfer Coefficient Uc = HO . hS HO + hS = 100.1 W/ moC (2.33) 2.1.19 Reactor cooling system mfCPf (t1 - t2) = mcCpc (t1 - t2) (2.34) Log Mean Temperature difference (LMTD) : TLMTD = = Ti –To ln(Ti-To)/(Ti-To) (2.35) 45 oC From this value can get mc = 39.63 kg/s where CPc=4220 and ti-t2 =135 oC 2.2 MECHANICAL DESIGN 2.2.1 INTRODUCTION The mechanical design of chemical plant are of particular interest to chemical engineers, but not usually be called on to undertake the detailed mechanical design of 185
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR the plant, especially the reactor vessels. However, the chemical engineer will be responsible for developing and specifying the elementary design information for the reactor, and need to have a general appreciation of pressure vessel design to work effectively with the specialist designer. Therefore, the design of wall thickness, head, column support, flange joint, reinforcement and maximum allowable pressure are considered here. Material of construction: In this design, reference will mainly be based on the current British Standard BS 5500 and Bs 1515 where the current addition of Bs 5500 covers vessels fabricated in carbon steel. The most common types used in the petroleum industry are Types 304, 316,321, and 347.Because of their inherent high temperature strength propertied and high corrosion resistance, they are particularly suitable for use in this process, in areas of moderate and high temperature, and where substantial resistance such as in heater tubes, reactors, reactor effluent exchangers and piping. In this design, material of construction: can be constructed by using carbon steel. Type 304 DESIGN STRESS It is necessary to decide a value for the maximum allowable stress that can be accepted in the material of construction, for example, it can withstand without failure under standard test conditions. The nominal design strengths (allowable design stress) for the range of materials covered are listed in BS 5500. By using carbon steel (semi killed or silicon Killed), the design stress is given, σD as 125 N /mm2 at design temperature. WELDED JOINT EFFICIENCY The strength of a welded joint will be depending on the type of joint and the quality of the welding. The soundness of welds is checked by visual inspection and non destructive testing (radiography). For the reactor, it is assumed that the joint is equally as strong as the virgin plate; this is achieved by radio graphing the complete weld length and cutting out and remarking 186
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR any defects. Therefore, the non destructive testing is assumed to be 100% and the joint efficiency, J is taken as 1.0. 2.2.4 CORROSION ALLOWANCE 1. Corrosion and erosion or scaling will cause material lost, so an additional thickness of material called “corrosion allowance” must be added to be calculated wall thickness. MINIMUM THICKNESS OF CYLINDRICAL SECTION OF SHELL The minimum thickness of cylindrical section of shell to resist the internal pressure can be determined by using equation below: e = PD DIs 2J σD - PD = 2.0*1.8 2.125-2 = 0.015 m (2.36) By adding corrosion allowance 2 mm, e = 0.015 + 0.002m = 0.017 m MINIMUM THICKNESS OF DOMED HEAD There are three types of commonly used domed head: 1. Hemispherical heads 2. Ellipsoidal heads 3. Torispherical heads 187
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR The selection of head depends on the cost and the thickness required for the head. The design equations and charts for the various types of domed head are given in the codes and standards (BS 5500) used in this design. A standard dished head (torisphere) is used as first trial. The crown radius of this head equals to the diameter of the shell, DIS. On the other hand, the knuckle radius is taken as 6% of the crown radius. Since this type of head is formed by pressing, no joint is needed. Therefore, the joint factor is taken as 1. For the torispherical head, the minimum thickness of the head can be determined from equation below: eh = P D RC CS 2 J TD + PD(CS – 0.2) (2.37) where Rc is the crown radius, equal to DIS in this case. CS = stress concentration factor for torispheriical head. It is given by equation below: CS = 1 / 4(3 + (Rc + Rk) 1/2) (2.38) Since Rk is 0.06 of Rc, = 1 / 4 (3 + (1/ 0.06)1/2) = 1.771 = 2.0 x1.8 x1.771 2 x 1x125 + 2.0 (1.771 - 0.2) = CS 0.025 m Therefore, eh However, for a standard ellipsoidal head, eh = PDDIs 2J σD - 0.2PD = 0.014 m (2.39) Therefore, an ellipsoidal head would probably be the most economical to be used. For convenience, the thickness is taken to be as same of wall thickness 17 mm. 188
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR LOADING STRESSES 2.2.7.1 Dead Weight of Loading 2.2.7.2 Dead Weight Of vessel The major source of dead weight loads are: 1. vessel shell 2. vessel fitting : manway, nozzles 3. internal fittings: where the main item is tube 4. insulation 5. catalyst The preliminary calculation of the approximate weight of a cylindrical vessel with domed ends, and uniform wall thickness can be estimated from the following equation, Wv = Cv.Л.ρm.Dm.g.(Hv + 0.8Dm)t x 10-3 Where Wv = total weight of the shell, excluding internal fitting Cv = a factor to account for the weight of nozzles, internal support etc. Cv is given as 1.08 for vessels with only a few internal fitting. Hv = height between 2 tangent lines, 4m in this case g = gravitational acceleration, 9.81 m/s2 t = wall thickness, mm ρm = density of vessel material, kg/m3. by using carbon steel, ρm = 6870 kg/m3 Dm = mean diameter of vessel = DIs + t * 10-4 Since the wall thickness = 0.017 m Therefore, Dm = 1.8 + 0.014 = 1.817 m As a result, by substituting into the equation above: Wv = 39000 N = 39 KN 189
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Weight of the Tubes From BS 3059, the mass per length of tubes is equal to 13.5 kg/ m for carbon steel. Therefore, the weight of one tube = 13.5 x 3 x g = 4.529 * 104 N ≈ 45 KN (2.40) Total weight of the tubes, Wt = 103 x 13.5 x3 x9.81 = 4.1x104 Weight of Insulation To avoid heat loss from the surface of the shell, mineral wool is used as the insulator. From (Chem. Eng. Vol. 6’s book), Density of mineral wool = 130 kg/m3 Let the thickness of mineral wool = 75 mm The approximate weight of the insulator, Wi = 2ЛHvtiρig = 2 Л x3 x0.075 x30 x9.81 = (2.41) 1.803 x103 N This value should be double to allow for fittings, etc. = 3.6 x103 N 190
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Weight of Catalyst Weight of catalyst, Wc = 2998 kg = 2.998 x104 N Total Weight Since only 4 baffles are used in the reactor, their weight is neglected compared to others. W = Wv + Wi + Wt +Wc = 39000N+ 4.1x104 N+ 3.6x103 N +2.998x104 N = 1.1x 105 N Wind Loading Take dynamic wind pressure as 1300 N/m2 Mean Diameter, including insulation = 2+2(17+75) x10-3 = 2.18 m The wind loading is then given by equation below: Fw = P w Dm = 1300 x2.18 m = 2.8 x 103 N/m (2.42) Therefore, the bending moment at bottom tangent line can be determined from equation below: Mx = Fw L2 191
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 2 (2.43) = 2.8 x 103 x 42 2 = 2.24 x104 N 2.2.7.8 ANALYSIS OF STRESSES Uniform thickness is used for analyzing stresses in the column. If it is found satisfactory at the bottom of the vessel which is the highest loading point, then the entire column structure is feasible. At bottom tangent line, the longitudal and circumferential stresses due to pressure is given by: Longitudal, σL = P i Di 4t = 2.0 x1.8 4 x 0.017 = 53 N /mm2 = P i Di 4t = 2.0 x1.8 2 x 0.017 = Circumrerential, σh (2.44) 106 N /mm2 Dead Weight Stress The direct stress is mainly due to the weight of vessel, its contents and any attachment which is often called the dead weight stress. The stress is compressive since it is at the bottom of the vessel to support the direct loading. 192
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Dead Weight stress, σW = = = W Л (Di + ti) * t 1.1 x 105 Л (1800 + 17) x 17 (2.45) 1.13 N /mm2 (compressive) Bending Stress The second moment of area of the vessel about the plane of bending, = outer diameter of vessel Di + 2t 1.8 + 2 x 0.017 = Iv Л (Do4 – Di4) 64 = Where Do = = Iv 1.834 m = Л (18344 – 18004) 64 4.0 x1010 mm4 = (2.46) Therefore, the bending stress is then given by equation below: σb = = ± Mx (Di /2 + t) Iv (2.47) ± 0.51 N/mm2 The resultant longitudal stress σZ = σ L + σW + σb σZ = 53 – 1.13 + 0.51 = 52.38 N/mm2 For upwind, For downwind, 193
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR σZ = 53– 1.13 - 0.51 = 51.36 N/mm2 = Pi = 2.0 2 2 Radial Stress (2.48) 1.0 N/mm2 = Since radial stress obtained is a small value and there are torsional stress in the system, therefore the principle stress will be σZ and σh 52.38 N/mm2 Figure 2.1: 51.36 N/mm2 Analysis of Stresses 194
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Therefore, the greatest difference between the principles stresses, σd = σh - σZ ( downward) = 106 – 51.36 = 54.64 N/mm2 The value obtained is well bellow the maximum allowable design, 125 N/mm2. 2.2.11 CHECK ELASTIC STABILITY The design of this vessel have to be checked to ensure that the maximum value of the resultant axial stress does not exceed the critical value at which buckling will occur. By applying a factor of safety of 12, the critical buckling stress gives: = 2x104 (t/Do) = σC 185.4 N/mm2 (2.49) The maximum compressive stress will occur when the vessel is not under pressure, = σ W + σb = 1.13 + 0.51 = 1.64 N/mm2 Which is well below the critical buckling stress, σC . 2.2.12 VESSEL SUPPORT The method used to support a vessel will depend on the size, shape and weight of the vessel; the design temperature and pressure; the vessel location and arrangement; and the internal and external fittings and attachment. Since the reactor is a vertical vessel, skirt support is used in this design. 195
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR A skirt support consists of a cylindrical or conical shell welded to the base of the vessel. A flange at the bottom of the skirt transmits the load to the foundations. The skirt may be welded to the bottom, level of the vessel. Skirt supports are recommended for vertical vessels as they do not imposed concentrated loads on the vessel shells; they are particularly suitable for use with tall columns subject to wind loading. 2.2.13 SKIRT THICKNESS The skirt thickness must be sufficient to withstand the dead weight loads and bending moments imposed on it by the vessel; it will not be under the vessel pressure. The resultant stresses in the skirt will be: σS (tensile) = σbS - σWS σS (compressive) = σbS + σWS and where σbS = = σWS = = bending stress in the skirt 4Ms Л(Ds + ts) tsDs (2.50) the dead weight stress in the skirt W Л(Ds + ts) ts Where Ms = maximum bending moment, evaluated at the base of the skirt. W = total weight of the vessel and contents Ds = inside diameter of the skirt, at the base ts = skirt thickness 196
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR The skirt thickness should be such that under the worst combination of wind and dead weight loading the following design criteria are followed: σS (tensile) < fs.J sin θs σS (compressive) < 0.125 E (ts/Ds) sin θs Where fs is the maximum allowable design stress for the skirt material, normally taken at ambient temperature, 20oC. J = weld joint factor θs = base angle of conical skirt, 90o is used in this design The maximum thickness should not less than 6mm. 2.2.14 HEIGHT OF THE SKIRT The height of the skirt, Hs is taken to be 1m. 2.2.15 BENDING STRESS AT BASE OF THE SKIRT Mbs = = = Fw (Hv + Hs)21 2 (2.51) 2.8x 103 (4 + 1)2 2 3.5 x 104 Nm BENDING STRESS IN THE SKIRT As the first trial, the thickness of skirt is taken to be 20 mm. Substitute into the equation (19), σbS = = 4 x 2.24 x104 Л (1.9 + 0.020) 1.9x0.020 3.9 x 105 N/m2 197
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR = 1.1 x 105 Л (1.9 +0.020)*0.020 = σWS 9.1 x 105 N/m2 The maximum stress (compressive), σS = σbS + σWS = 3.9 x 105 N/m2 +9.1x 105 N/m2 = 1.3 x 106 N/m2 The maximum stress (tensile), σS = σbS - σWS = 3.9 x 105 N/m2 – 9.1 x 105 N/m2 = 5.2 x 105 N/m2 (negative) Let the joint factor for skirt support, J = 0.85 Criteria for design, = 125 x 0.85 xsin( 90o) = 10.63 * 107 N/m2 > fs.J sin θs σS (tensile) , therefore it satisfied. (2.52) Modulus Young = 200,000 N/mm2 at ambient temperature, (from Bs 5500:1998), 0.125 E (ts/Ds) sin θs = 0.125x2x105 (0.02/1.9) sin 90o = 26.3 x 107 N/m2 > σS (compressive) , therefore it satisfied Both criteria are satisfied, add 2mm for corrosion allowance, and give a design thickness of 22 mm. 198
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR BASE RING AND ANCHOR BOLT DESIGN The loads carried by the skirt are transmitted to the foundation slab by the skirt base ring (bearing plate). The moment produced by wind and other lateral loads will tend to overturn the vessel. Since the reactor can be considered as the small vessel, the simplest types, rolled angle ring are used. The preliminary design of base ring is done by using Scheiman’s short cut method. The anchor bolts are assumed to share the overturning load equally, and the bolt area required is given by: = 1 (4.Mbs – W) Nbfb Db (2.53) Where Ab = area of one bolt at the root of the thread, mm2 Nb = number of bolts fb = maximum allowable bolts stress, typical design = 125 N/mm2 Mbs = bending (overturning) moment at the base, Nm W = weight of the vessel, N Db = bolt circle diameter, m Scheiman gives the following guide rules which can be used for the selection of the anchor bolts. 1. bolts smaller than 25 mm diameter should not be used 2. minimum number of bolts = 8 3. use multiples of 4 bolts 4. bolts pitch should not be less than 600 mm The base ring must be sufficiently wide to distribute the load to the foundation. The total compressive load on the base ring is given by: fb = (4 Mbs + W ) = 28255 N/mm ЛDs2 ЛDs (2.54) Where Fb is the compressive load on the base ring and Ds = skirt diameter, m The minimum width of the base ring is given by: 199
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Lb Where Lb fc = fb fc 1 103 (2.55) = base ring width, mm = the maximum allowable fc on the concrete foundation pad, And typically range from 3.5 to 7 N/mm2 fb = 28255 N/mm Take the bearing pressure as 5 N/mm2, fc = 5 N/mm2 Substitute into the equation above, Lb = = 28255 5 x103 5.65 mm This is the minimum width required; actual width will depend on the chair design Actual width required= Lr + ts +50 mm Where Lr = the distance from the edge of the skirt to the outer edge of the ring, mm = 64 mm (from BS 4190:1967) Therefore, actual width required = 64 + 22 +50 = 136 mm Actual bearing pressure on concrete foundation: f’c = = tb = 28255 136 x103 0.21 N/mm 64 ( 3 x 0.21) ½ 140 (2.56) 200
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR = 4.3 mm COMPENSATION FOR OPENING AND BRANCHES All process vessels will have opening for connections, man ways, sight holes, hand holes and instrument fittings. The presence of an opening weakens the shell, and gives rise to stress concentrations. The stress at edge of a hole will be considerably higher than the average stress in the surrounding plate. To compensate for the effect of an opening, the wall thickness is increased in the region adjacent to the opening. Sufficient reinforcement must be provided to compensate for the weakening effect of opening without altering the general dilation pattern of the vessel opening. 2.2.19 COMPENSATION FOR OTHER NOZZLES Pipe size for inlet and outlet of the reactor are all less than 10 mm, therefore, the reinforcement area can be usually is provided by increasing the wall thickness of the branch pipe. This already done on piping, where extra thickness is provided, thus no compensation area needed. 2.2.20 BOLTED FLANGE JOINT Flanged joints are used to connect pipes and instruments to vessels and from removable vessel heads when ease of access is required. Flanges may also be used on the vessel body, when it is necessary to divide the vessel into section for transport or maintenance. Flanged joints are also used to connect pipes to other equipment, such as pumps, valves. 2.2.20.1 Type of Flanges Selected a) Welding neck Flanges 201
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Have a long tapered lub between the flange ring and the welded joint. This gradual transition of the section reduces discontinuity stresses between flange and branch, and increases the strength of the flange assembly. Welding neck flanges are suitable for extreme service conditions, where the flange is likely to be subjected to temperature, shear and vibration loads.. For this reactor, the welding neck flanges are suitable for use in connecting the inlet and outlet piping of reactor. b) Gasket Gaskets are used to make a leak tight joint between two surfaces. It is impractical to machine flanges to the degree of surface finish that would be required to make a satisfactory seal under pressure without a gasket. Gasket are made from “semi plastic” materials, which will deform and flow under load to fill the surface inequalities between the flange faces, yet retain sufficient elasticity to take up the changes in the flange arrangement that occur under load. Several factors must be considered when selecting a gasket material: 1. The process condition: pressure, temperature, corrosive nature of process fluid. 2. Whether repeated assembly and disassembly of the joint is required 3. The type of flange and flange face. Judging from process conditions, where the operating temperature is quite high, 393K, metal reinforced gaskets is recommended, since it have a quite good heat resistance property. 2.2.21 Flange Face The raised face, narrow feed flange are used for all the flanges. Where the flange has a plain face, as for the flange faces mentioned above, the gasket is held in place by friction between the gasket and flange surface. 202
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR S SUMMARY OF CHEMICAL DESIGN PARAMETERS Reactor Design Catalyst weight required 2998 kg Volume of Catalyst bed 3.7 m3 Height of Bed 4.0 m Diameter of Bed 1.817 m Tube inside pressure drop 1.06E-4 N/m2 % of pressure drop 0.042 Tube inner diameter 0.1043 m Total number of tubes 103 tubes Tube arrangement equivalent triangular pitch Tube side heat transfer coefficient 293 W/moC Pitch of tube 0.143 m Bundle diameter 1.70 m 203
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Shell diameter 1.79 m Baffles cuts 0.35 Baffles Spacing 0.6 m Number of crosses 4 Inlet flow rate 0.647 kg/s Inlet temperature 326 K Outlet temperature 373 K Shell side heat transfer coefficient 191 W/moC Shell side pressure drop 0.557 kPa Design overall heat transfer area 100.1 W/moC SUMMARY OF MECHANICAL DESIGN PARAMETERS 204
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Operating Conditions and Material of construction Design pressure 2.0 bar Design temperature 323 K Material of construction Carbon Steel plate (Type 304) Design Stress 125 N/mm2 Welded joint efficiency 1 Corrosion allowance 2 mm Designed Column Diameter Shell thickness 17 mm Domed end thickness(ellipsoidal heads) 17 mm Vessel Support (skirt) Skirt thickness 22 mm Skirt diameter 1.9 m Skirt height 1m Base Ring and Anchor Bolt Base ring Rolled angle rings Minimum ring thickness 4.5 mm Minimum base ring width 7.06 mm Anchor bolt M24 Number of bolts 8 Bolt root diameter 21.2 m 205
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR SECTION 3 MTBE DISTILLATION COLUMN 3.1 INTRODUCTION Distillation is a method used to separate the components of a liquid solution, which depends upon the distribution of these various components between a vapor and a liquid phase. All components are present in both phases. The vapor phase is created from the liquid phase by vaporization at the boiling point. MTBE is our main product that needs to be separated. For individual design, MTBE distillation column was chosen. The characteristics required in the chosen types of distillation column are the separation objective satisfied in the column, the cost of construction and the design of the selected distillation column. R e lief Va lve C on den se r T=53.3oC T=6 4.5oC TC LC R e bo iler T=10 3 oC .3 Figure 3.1 MTBE Distillation Column 3.2 SELECTION OF CONSTRUCTION MATERIAL 206
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Materials chosen are based on the characteristics of the component in the distillation column, the location and the environmental consideration of the MTBE plant. Stainless steel 304 is used in construction of the MTBE distillation column - ‘The stainless steels are the most frequently used corrosion resistant materials in the chemical industry’ – Coulson & Richardson, Chemical Engineering, Volume 6, page 295. Carbon steel is used in skirt support material and the insulation material used is fiberglass. The selection is based on the chemical and mechanical design as stated in Coulson & Richardson, Chemical Engineering, Volume 6. Most parameters used in design were referred to mass, energy balance data and also data generated by Chemical Engineering Simulation Software; HYSIS Version 3.2. Other materials chosen were based on the British Standard BS 5500, BS4505 and BS 750. 3.3 CHEMICAL DESIGN In the MTBE distillation column design, the McCabe-Thiele method in determining the number of stages needed was used. The McCabe-Thiele method is based upon representation of the material-balance equations as operating lines on the X-Y diagram. The lines are made straight (and the need for the energy balance obviated) by the assumption of constant molar overflow. The liquid-phase flow is assumed to be constant from tray to tray in each section of the column between addition (feed) and withdrawal (product) points. If the liquid rate is constant, the vapour rate must also be constant. Table 3.1 The Composition in Feed Stream FEED Component T (K) Operating Op Pressure, Feed Flowrate Fraction, zi 207
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR T (K) kPa kmol/hr i-C4H10 313 337.5 450 34.860 0.3261 n-C4H10 313 337.5 450 0.400 0.0037 C4H8 DME 313 313 337.5 337.5 450 450 0.026 3.880 0.0002 0.0363 CH3OH 313 337.5 450 0.160 0.0015 H2O 313 337.5 450 2.866 0.0268 MTBE TBA 380 380 337.5 337.5 450 450 63.44 1.274 ∑ =106.906 0.5934 0.0119 ∑ = 1.0000 Table 3.2 The Compositions in Top Stream Top Component T (K) Operating T (K) Op Pressure, kPa Top Flowrate Yi kmol/hr i-C4H10 326.3 305 33.860 0.839760919 n-C4H10 313 326.3 305 0.400 0.009920389 C4H8 313 326.3 305 0.026 0.000644825 DME 313 326.3 305 3.880 0.096227772 CH3OH 313 326.3 305 0.149 0.003695345 H2O 313 326.3 305 1.006 0.024949778 MTBE 313 326.3 305 1.000 0.024800972 ∑ =40.321 S16 (top) 313 ∑ =1.0000 Table 3.3 The Composition in Bottom Stream T (K) Operating T (K) Op Pressure, kPa Bttm Flowrate kmol/hr Xi 380 376.3 400 1.000 0.015018398 MTBE 380 376.3 400 62.44 0.937748742 TBA 380 376.3 400 1.274 0.019133438 CH3OH 380 376.3 400 0.011 0.000165202 H2O S14 (bttm) Component i-C4H10 Bttm 380 376.3 400 1.860 ∑ =66.59 0.027934219 ∑ =1.0000 * The T(K) is the stream temperature, while the Operating T(K) temperature is the temperature which should be achieved by controlling the pressures. 208
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 3.3.1 DETERMINATION OF THE NUMBER OF PLATES USING McCABETHIELE METHOD The components in the feed to the MTBE distillation column are i-C4H10, n-C4H10, C4H8, DME, CH3OH, H2O, MTBE and TBA, and the feed is assumed as multicomponents feed. By using the Hengstebeck’s and McCabe-Thiele method, the number of stages required and the position of the feed in the MTBE distillation column can be determined. The determination of the plate by using McCabe-Thiele method was simply because as explained in J.M Coulson, J.F Richardson, Chemical Engineering Volume 2, Third Edition, the Pergamon Textbook, page 429, which stated that “This method is one of the most important concepts in chemical engineering and is an invaluable tool for the solution of distillation column. The assumptions of constant molar overflow is not limiting since in very few systems do the molal heats of vaporizations differ by more than 10 percent. The method does have limitations, however, and should not be employed when the relative volatility is less than 1.3 or greater than 5, when the reflux ratio is less than 1.1 times the minimum, or when more than twenty-five theoretical trays are required. In these circumstances, the Ponchon-Savarit method should be employed”. The vapor pressure can be determined by using the Antoine’s equation as follows: Log10 P* = A - B T +C (3.1) With related at equilibrium, constant K, Ki = P* x P (3.2) And related with concentration, 209
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Ki = yi xi (3.3) Where yi = concentration in vapor phase xi = concentration in liquid phase Calculation for the relative volatility, α , α = KLK / KHK (3.4) Where KLK = Light key component KHK = Heavy key component In this case, MTBE is as the heavy key and i-C4H10 is as the light key components. By using goal seek in the excel programme, the value of the bubble point at bottom column = 103.3oC and dew point at the top column is = 53.3 oC, from the values of Ki related to the pressure, the values of relative volatilities could be determined, listed are values of the relative volatilities for components at the top and bottom of the distillation column. Table 3.4 Average Relative Volatility, α α Bttm, α Top, i-C4H10 (LK) 7.699631 n-C4H10 5.654994 - 2.827496955 C4H8 DME MTBE (HK) TBA 6.948741 14.10614 1.00000 - 1.0000 0.149333 3.474370398 7.05306993 1.00000 0.074666444 CH3OH 0.67395 0.99561 0.834780143 H2O 0.152422 0.288322 0.220371796 5.084017 Avg, α Component 6.39182391 Calculations for the non-key flows, Table 3.5 The Non-key Flow of the Top Stream 210
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR di 0.4 0.026 3.88 0.149 1.006 li = di / (α i-1) 0.218878614 0.010507724 0.640997055 -0.901828648 -1.290358653 Vi = li + di 0.618878614 0.036507724 4.520997055 -0.75282865 -0.28435865 ∑ = -1.321803909 αi 2.827497 3.47437 7.05307 0.83478 0.220372 TOP n-C4H10 C4H8 DME CH3OH H2O ∑ = 4.139 Table 3.6 The Non-Key Flow of the Bottom Stream BOTTOM αi bi TBA CH3OH H2O 0.074666 0.83478 0.220372 1.27 0.01 1.86 Vi’=α ibi / (α - LK li’ = vi’ + bi’ α i) 0.01506000 0.001652422 0.066417357 ∑ = 0.083127984 1.2900 0.0100 1.9300 ∑ = 3.23 Flows of combine key, Le = L - ∑ li (3.5) = (2.5 X 40.321) – (- 1.3218) = 102.1243 Ve = V - ∑Vi (3.6) = (2.5+1) x 40.321 – 4.139 = 136.985 Calculation of the slope for top operating line, L e V e = 102 .1243 136 .984 (3.7) = 0.7455 Ve’ = V’ - ∑ Vi’ (3.8) = (2.5+1) x 40.321 – 0.08313 = 141.04 Le’ = L’ - ∑ li’ (3.9) = (2.5+1) x 40.321 + 66.59 – 3.23 = 204.48 211
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Calculation of the slope for bottom operating line, L ' e V ' e = 141 .04 204 .48 (3.10) = 1.45 = flow .LK flow ( LK + HK ) = Xb 1 (1 +62 .47 ) at bottom, (3.11) at top, (3.12) at feed, (3.13) = 0.016 Xd = flow .LK flow ( LK + HK ) Xd = 33 .86 (33 .86 +1) = 0.9713 Xf = Xf = flow .LK flow ( LK + HK ) 34 .86 (34 .86 +63 .44 ) = 0.3546 For vapor – liquid equilibrium curve, we use the equation of Y = α.x [1 + (α − 1) x] = 6.391 x [1 + ( 5.391 ) x] α from LK component (3.14) Table 3.7 MTBE Equilibrium Curve y= x 6.391 x 1 + 5.391 x y 212
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 0 0.41527398 0.61508201 0.73257407 0.80992987 0.86471539 0.9055511 0.93716326 0.96235974 0.9829137 1.0000 So from the data as above, the McCabe-Thiele diagram was constructed to determine the number of plates. The top operating line and the bottom operating line were determined first before the number of plates required could be calculated. And from the graph plotted, the number of stages needed for the MTBE distillation column is 11 with the feed point location is at stage number six from bottom. 213
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR McCabe-Thiele Diagram 1 0.9 0.8 Top Operating Line 0.7 Y 0.6 Equilibrium Curve 0.5 Line for Number Stages 0.4 0.3 Bottom Operating Line 0.2 0.1 0 0 0.2 0.4 0.6 0.8 1 X Xb = 0.016 Xf = 0.35 Xd = 0.97 At bottom At feed At top 214 the of
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Figure 3.2 McCabe-Thiele Diagram From the graph plotted, the number of plate can be determined by calculating the stage plotting at graph and the number of stages needed is 11 stages. The feeding stage also can be determined from the graph, feed at stage 6 from bottom. Calculation for minimum reflux ratio, Rmin, To get the value of minimum reflux ratio, use the Underwood equation was used, (J. Douglas, 1988), Rmin  1   =   α −1        X D.L K   X D.H K    − α      X F .H K  X F .H K  (3.15) 1  1.0    33 .86 =   63 .44 − 6.391 63 .44  6.391 −1     = 0.0803 Optimum reflux ratio is 0.0803 x 1.5 = 0.1204 Where, XD.LK = Light key component at top flow XD.HK = Heavy key component at top flow XF.LK = Light key component at feed flow XF.HK = Heavy key component at feed flow In the calculation, the optimum reflux ratio as 2.5 was used (based on Coulson & Richardson, Chemical Engineering, Volume 6, and J.M Coulson, J.F Richardson, Chemical Engineering, Volume Two, Third Edition) as 0.1204 is too low for the calculation, based on statement from R. K. Sinnot, Coulson & Richardson, Chemical Engineering, Volume 6, Butterworth Heinemann, 2001, page 495 – “At low reflux ratios the calculated number of stages will be very dependent on the accuracy of the vapor-liquid equilibrium data available. If the data are suspect a higher than normal ratio should be selected to give more confidence in the design”. 215
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 3.3.2 DETERMINATION OF THE NUMBER OF PLATES USING FENSKE’S EQUATION The Fenske’s equation (1932) can be used to estimate the minimum stages required at total reflux. The derivation of the equation is for binary system and applies equally to multicomponents system. But in the design only the calculation of plates using McCabe-Thiele method as the design plate number was taken into consideration.  33 .86  62 .44  log     1.000  1.000  log 6.392 = Nmin = = Nmin  x   x   log   LK   HK     x HK  d  x LK  b    log α LK 4.13 ≈ 5 stages (3.16) Normally after using the Fenske’s Equation, the value of Nmin is given by the equation below to get the number of stages, NT, NT = 2 (Nmin) = 2 (5) = 10 stages To get the real number of stages, the efficiency of the process must be considered, and the efficiency is calculated based on the equation by O’Connell’s (J. Douglas, 1988), Eo = 0.5 ( µ α) 0.25 = 0.5 ( 0.224 x 6.392 ) 0.25 = (3.17) 0.457 216
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR N = NT Eo = = 24.07 ≈ 3.3.3 11 0.457 24 plates THE PHYSICAL PROPERTIES The properties consider in this design are liquid flow rate, LW, vapor flow rate, VW, liquid surface tension, σ, liquid density, ρl and vapor density, ρv. This physical properties evaluated at the system temperature by using HYSIS generated data or by manual calculations the from mass and energy balance data. The useful properties data are from HYSIS, mass and energy balance data is given as below: Liquid flow rate, LW = 38747.97 kg/hr (10.7633 kg/s) Vapor flow rate, VW = 15251.95 kg/hr (4.2367 kg/s) Liquid surface tension, σ = 0.0351 N/m Liquid density, ρl = 746.74 kg/m3 Vapor density, ρv = 3.8402 kg/m3 Data evaluated are at system temperatures and pressures. 3.3.4 DETERMINATION OF COLUMN DIAMETER The principal factor that determines the columns diameter is the vapour flow-rate. The vapour velocity must be below that which would cause excessive liquid entrainment or a high-pressure drop. The equation below which is based on the well-known Souders and Brown equation, Lowenstein (1961), Coulson & Richardson, Chemical Engineering, Volume 6, page 556, can be used to estimate the maximum allowable superficial vapour velocity, and hence the column area and diameter, 217
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR ( σ L −σ v)  u = (− 0.171 l2 + 0.27 lt − 0.047 )  σ t   v   1/ 2 (3.18) v ( 746 .74 −3.8402 = −0.171 ( 0.9 ) 2 +0.27 ( 0.9) −0.047    3.8402    1/ 2 )   = 0.7997 m/s Where, u v = maximum allowable vapour velocity, based on the gross (total) column cross-sectional area, m/s, l t = plate spacing, m (range 0.5 – 1.5). Based on the equation below, the column diameter could be determined, Dc = Dc = 4 vw π vρu v 4(0.6244 ) π(3.8402 )( 0.7997 ) = 0.51 m = 0.51 x 1.5 = Dc (3.19) 0.765 m For safety reason, the approximate diameter was increased 50% more than the calculated value, as it deals with vapour, which is in high pressure. 218
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 3.3.5 DETERMINATION OF PLATE SPACING The overall height of the column will depend on the plate spacing. Plate spacings from 0.15 m (6 in.) to 1m (36 in.) are normally used. The spacing chosen will depend on the column diameter and the operating conditions. Close spacing is used with smalldiameter columns, and where head room is restricted, as it will be when a column is installed in a building. In the MTBE distillation column, the plate spacing was assumed 0.9 m as it is in the range of 0.5 m to 1 m recommended by Coulson and Richardson, Chemical Engineering, Volume 6. 3.3.6 LIQUID FLOW ARRANGEMENTS Before deciding liquid flow arrangement, maximum volumetric liquid rate were determined by using equation below, VL = Lw ρ (3.20) L VL = 38747 .97 746 .74 VL = 51.89 m3/hr = 0.0144 m3/s Based on the values of volumetric flow rate and column diameter, Dc. Figure 11.28 from Coulson & Richardson, Chemical Engineering, Volume 6, page 568. Therefore, types of liquid flow could be considered as single pass. 3.3.7 PLATE LAYOUT The value of downcomer area, active area, hole area, hole size, and weir height were determined based on above value calculated, trial plate layout column area determined by using the equation below, 219
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR U m U (0.9) v 4.181 0.7997 (0.9) = Where Um = = Column area, Ac 5.81 m2 = Velocity at below plate, (3.21) Down comer area were found by assume 20% of column area and using equation below, Down comer Area Ad = 0.2 Ac = 0.2(5.81 m2) = 1.162 m2 Net area and active area were determined by using equations below, Net Area, An Ac - Ad = 5.181 -1.162 = 4.02 m2 = Ac - 2Ad = 5.181 - 2(1.162) = Active area, Aa = 2.857 m2 Hole Area, AH are determine with trial value of 10% active area by equation below, Hole Area, Ah = 0.10(Aa) = 0.10(2.857) = 0.2857 m2 Weir Length, lw was calculated by referring Figure 11.31 from Coulson Richardson, Chemical Engineering, Volume 6, page 572 which was determined based on the value of the ratio of Ad/Ac to get the ratio of lw/ Dc . The weir height determined and other dimensions are as below: 220
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Weir Height, hw 50 mm (standard) Hole diameter, dh = 5 mm (standard) Plate Thickness = 5 mm (standard) Weir Length, Iw 3.3.8 = = 612 mm (80% x 765) ENTRAINMENT EVALUATION The entrainment checking can be done by determine actual flooding percentage, Uv by using equation below, = Um Ac = 4.181 5.181 = Uv 0.807 m/s (3.22) Liquid flow rate were determine by using below equation by using liquid vapor flow factor. 0.5  ρv    ρl     = Lw Vw = 38747 .97 3.8402  15251 .95 746 .74    = FLV 0.182 (3.23) 0.5 Where FLV is liquid vapor factor. Based on value of FLV and assumption made for initial tray spacing (0.9m) by referring to Figure 11.27 from Coulson & Richardson, Chemical Engineering, Volume 6, page 567, the data were used to determine the constant, K1 for the estimation of flooding velocity. Before that, correction factor are used as equation below: 0.2 K1 =  σ    k1  0.02  (3.24) 221
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 0 .2 =  0.0351  0.1    0.02  = 0.112 And flooding velocity, Uf determine by equation below (correlation given by Fair, Coulson & Richardson, Chemical Engineering, Volume 6, page 567, = =  ρl − ρv      0.112  ρv  0.5 =  746 .74 − 3.8402    3.8402  0.112  = Uf  ρl − ρv      K1  ρv  1.56 m/s (3.25) 0 .5 Actual % of flooding = Uv ×100 Uf = 0.807 ×100 1.560 = (3.26) 51.8% Fractional entrainment is calculated based on this percentage and FLV by referring to Figure 11.29 from Coulson & Richardson, Chemical Engineering, Volume 6, page 570, if unsatisfied, recalculation were done based on chosen diameter and plate spacing acceptable to determine the lowest value. However, fractional entrainment Ψ = 0.02, is below the initial guest of 0.1 and entrainment is acceptable. 3.3.9 WEEPING RATE EVALUATION 222
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Weir liquid crest were determined by using values of maximum liquid flow rate and minimum flow rate based on the process condition and also assumption of turndown percentage based on the liquid characteristic. Each weir liquid crest value was determined by using equations as follow, the Francis weir formula (see also Volume 1, Chapter 5), 2/3  Lw max 750   ρl (lw )  750   = 13.49 mm liquid =  Lw min 750   ρl (lw )  =   10 .7633 750   (746 .74 )( 0.88 )     = Min how = = Max how     48.37 mm liquid (3.27) 2/3   1.5860    (746 .74 )( 0.88 )      2/3 (3.28) 2/3 Where, Iw = Weir length, 0.88 (standard) how = weir crest Lw = liquid flow rate At minimum liquid flow rate, the value was determined by adding weir height H w and weir crest, how the constant, K2 where it is found based on the value by referring to Figure 11.30 from Coulson & Richardson, Chemical Engineering, Volume 6, page 571. Minimum vapor velocity Uh, were determined by using the equation as below, Uh = K 2 − 0.90 ( 25 .4 − d h ) ρv 0.5 = = (3.29) 28 .60 − 0.90 (25 .4 − 0.005 ) (3.8402 ) 0.5 2.931 m/s (3.3.10, 3.3.11 and 3.3.12: Please refer to the Appendix) 223
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 3.3.13 NUMBER OF HOLES Area of hole, AH = = πd h 4 2 (3.30) π × (0.05 ) 2 4 = Ah AH 0.2857 1.9634 ×10 −3 = 145.49 ≈ 3.3.14 = = Number of Holes 1.9634 x 10-3 m2 146 units (at every sieve plate). (3.31) COLUMN SIZE The column height will be calculated based on the equation given below. The equation determines the height of the column without taking the skirt or any support into consideration. Its determination is based on condition in the column. Column Height = (No stage –1) (tray spacing) +(Tray spacing x 2) +(No stage-1) (Thickness of Plate) = (11 -1)(0.9)+(0.9)(2) + (11-1)(0.005) = 10.85 m ≈ 12.00 m (including 10% safety factor) The overall height from the calculation is 10.85 m, but in a real construction it will be added slightly more (about 10%) because of vapor and liquid area at top and bottom column. The space for vapor and liquid are required if uncertain condition occur 224
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR in the column, such as over flooding, over vapor pressure or upset in reaction situation. The calculated result is tabulated in the Table 5.8 as below. Table 3.8 Provisional Plate Design Specification Item Column Diameter, Dc No of Plates Plate Spacing Plate Thickness Total Column Height, Ht Plate Pressure Drop, ht Plate Material Down Comer Area, Ad Down Comer Material Column Area, Ac Net Area, An Active Area, Aa Hole Area, Ah Number of Holes Weir Length Weir Height (standard) Resident Time Value 0.765 m 11 units 0.9 m 5 mm* 12.00 m 192.81 mm liquid* SS 304 0.8348 m2 SS 304 5.181 m2 4.020 m2 2.857 m2 0.2857 m2 146 units 0.612 m 0.05 m 13.37 seconds* * For the determination of these values, they are shown in the Appendix section. 3.4 MECHANICAL DESIGN In the mechanical design, the temperature and pressure are important properties in evaluating the thickness and the stress of material. Therefore, the safety factor also is 225
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR also added as precaution and determined by certain consideration such as corrosion factor, location and process characteristic. The safety factor is usually 10% above the operating pressure and as for this MTBE distillation column, the operating pressure is 450 kPa. The chosen safety factor is based on the process characteristics of the system. The design temperature is related to the operating temperature. Based on the calculated result, the temperature at the top of the column is 53.3oC and the temperature at the bottom of the column is 107oC. Design Temperature, T 3.4.1 = 0.450 N/mm2 x 110% = Design Pressure, Pi 0.495 N/mm2 = 117.70 ºC (10% more than design temp.) MATERIAL OF CONSTRUCTION The material used in the construction of the distillation column is stainless steel (18Cr/8Ni, 304) as the material is suitable in high temperature and less corrosive. For this material, the design stress at 150 ºC is obtained from Table 13.2, page 809 Coulson & Richardson, Chemical Engineering, Volume 6. Design stress, f 130 N/mm2 Diameter vessel, Di = 860 mm Tensile strength, 3.4.2 = = 510 N/mm2 VESSEL THICKNESS The minimum thickness of column required and other designs are calculated based on equation below (Coulson & Richardson, Chemical Engineering, Volume 6, page 812): 226
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR = P D i i 2Jf − P i = (0.495 )( 765 ) 2(1)(145 ) −(0.495 ) = e 1.31 mm (3.32) Based on Table 13.4, Coulson & Richardson, Chemical Engineering, Volume 6, page 811, this minimum thickness should be added 5 mm to withstand its own weight and any incidental loads. e 1.31 mm + 5 mm = Assumed = 6.31 mm ≈ 7.00 mm Where, Pi = Design pressure Di = Column diameter f = Design Stress J = Joint factor (assumed = 1) From Table 13.4, Coulson and Richardson, Chemical Engineering, Volume 6, page 811, for diameter 1 m to 2 m the minimum thickness should not be less than 7 mm (including 2 mm of corrosion allowance). For vessel diameter around 0.5 m to 1 m, a much thicker wall will be needed at the column base to withstand the wind and dead weight loads. A much thicker wall is needed at the column base to withstand the wind and dead weight loads. As a first trial, divide the column into five sections, with the thickness increasing by 2 mm per section. Try 7, 9, 11, 13 and 15 mm. The average wall thickness is 11 mm. 3.4.3 HEADS AND CLOSURE 227
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Torispherical head had been chosen because of operating pressure below 10 bars and suitable for liquid vapor phase process in inconsistent high pressure. The calculations as below is considered, Crown radius, Rc = Di = 0.765 m Knuckle radius, Rk = 6% Rc = 0.046 m Minimum Thickness = Pi R c C s 2Jf + Pi (C s − 0.2) = 0.2137mm (The method of calculations is shown in the Appendix section) 3.4.4 TOTAL COLUMN WEIGHT Total Weight, Tw Total weight is the summation of the weight of dead weight, the weight of plates and the weight of insulation. The calculations for the dead weight, the weight of plates and the weight of the insulation are shown in the Appendix. Total weight, Wt W v + Wp + WI = (28.46 + 68.53 + 10.63) kN = 3.4.5 = 107.62 kN WIND LOADS The wind load is calculated based on location and the weather of surrounding. Therefore, the value of wind speed is assumed as below and wind load is calculated shown in the appendix. The wind load for the MTBE column is 62.91kN (methods of calculation in shown in the appendix. 3.4.6 – STIFFNESS RING (Please refer to the Appendix) Table 3.9 Summarized Results of Mechanical Design 228
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Operating pressure, Po 0.45 N/mm2 Design Pressure, Pi 0.495 N/mm2 Safety factor 0.15 Design Temperature, TD 88.78 oC Operating Temperature, To 80.71 oC Heads and Closure Types Torispherical head. Crown Radius, Rc = Di 0.765 m Knuckle Radius, Rk = 6% Rc 0.046 m Joint Factor, J 1.00 Cs 1.77 Minimum thickness head, e 0.2317 mm Column Weight Dead weight of vessel, Wv 28.46 kN Weight of a plate, Wp 6.23 kN Weight of 11 plates,Wp 68.53 kN Weight of insulation, WI 10.63 kN Total weight 107.62 kN Win speed, Uw 160 km/hr Wind pressure. Fw 1068.8 N/m2 Bending Moment (Mx) 62.91 kN Stiffness Ring Critical buckling pressure for ring, Pc 15 x 106 N/m2 229
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 3.5 VESSEL SUPPORT DESIGN (SKIRT DESIGN) Type of Support : Straight cylindrical skirt θs : 90º Material of Construction : Carbon steel Design Stress, fs : 135 N/mm2 at ambient temp. 20ºC Skirt Height, Hv : 2.5 m (standard) Young’s Modulus : 200, 000 N/mm2 Approximate Weight : 8.418 kN Total Weight : 36.88 kN 230
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR (The method of calculations for other parameters in the vessel support design in shown in the Appendix section) Table 3.10 Design Specification of the Support Skirt Support Data Type of Support Straight cylindrical skirt Material of Construction Carbon steel Design Stress, at T 20ºC (ambient) 135 N/mm2 Skirt Height 2.50 m Young’s Modulus 200000 N/mm2 σ 746.74 kg/m3 L Approximate Weight, Wapprox 8.418 kN Total Weight 107.62 kN Wind Load, Fw 1068.8 N/m2 Skirt Thickness, ts 15 mm REFERENCES J. M. Coulson, J. F. Richardson, Chemical Engineering, Volume Two, Third Edition, The Pergamon Press, 1977. R. K Sinnot, Coulson & Richardson’s Chemical Engineering, Chemical Engineering Design, Volume Six, Butterworth Heinemann, 1999. Robert H. Perry, Don W. green, Perry’s Chemical Engineer’s Handbook, Seventh Edition, McGraw-Hill, 1998. James, M. Douglas, Conceptual Design of Chemical Processes, McGraw-Hill Book Company, 1988. Martyn S. Ray and David, W. Johnston, Chemical Engineering, Design Project: A Case Study Approach, Gordon and Breach Science Publishers, 1989. Carl R. Branan, Rules of Thumb for Chemical Engineers, Gulf Publishing Company, 1994. 231
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Billet, R., Distillation Engineering, Heydon Publishing, 1979. King, C. J., Separation Processes, Second Edition, McGraw-Hill, 1992. Kister, H. Z., Distillation Design, McGraw-Hill, 1992. Lockett, M. J., Distillation Tray Fundamentals, Cambridge University Press, 1986. Normans, W. S., Absorption, Distillation and Cooling Towers, Longmans, 1961. Oliver, E. D., Diffusional Separation Procesess, John-Wiley, 1966. Robinson, C.S., and Gilliland, E.R., Elements of Fractional Distillation, McGrawHill, 1950. Smith, R., Chemical Process Design, McGraw-Hill, 1995. Van Winkle, M., Distillation, McGraw-Hill, 1967. Micheal J. Barber, Handbook of Hose, Pipes, Couplings and Fittings, First Edition, The Trade & Technical Press Limited, 1985. Louis Gary Lamit, Piping Systems: Drafting and Design, Prentice-Hall, Inc., 1981. David H. F. Liu, Bela. G. Liptak, Wastewater Treatment, Lewis Publishers, 2000. SECTION 4 DESIGN OF LIQUID-LIQUID EXTRACTION COLUMN 4.1 INTRODUCTION Liquid-liquid extraction has become an important separation technique in modern process technology. This is has resulted in the rapid development of a great variety of 232
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR extractor types, in the evaluation of which the chemical engineer must primarily depend on manufacturers’ literature. To the design, only three components that are considered, - methanol, water and isobutene- this is because of for most system containing more than four components, the display of equilibrium data and the computation of stages is very difficult. In such cases, the requirements are best obtained in the laboratory without detail study of the equalibria. (Treybal, Mass Transfer Operations, 1987). Beside that for multicomponent separations also, special computer programs for these multistage operations embodying heat and material balances and sophisticated phase equilibrium relations are best left to professionals. Most such work is done by service organizations that specialize in chemical engineering process calculations or by specialize in chemical engineering organizations. (Stanley M. Walas, Chemical Process Equipment, 1988). Sieve tray (perforated plate) Column were choose for the extraction of these components. These multistage, countercurrent columns are very effective, both with respect to liquid-handling capacity and with respect to extraction efficiency, particularly for system of low interfacial tension, which do not require mechanical agitation for good dispersion. 4.2 CHEMICAL DESIGN OF LIQUID – LIQUID EXTRACTION COLUMN 4.2.1 Choice of Solvents There is usually a wide choice of liquids to be used as solvent for extraction operations. It is unlikely that any particular liquid will exhibit all the properties considered desirable for extraction, and some compromise is usually necessary. The following factors need to be considered when selecting a suitable solvent for a given extraction – affinity for solute, partition ratio, density, miscibility, safety and cost. Based on the factors that need to be considered water was choosing as a solvent in this system. 4.2.2 Estimation or Gather the Physical Properties 233
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Most of the design parameter used were refer to mass balance, energy balance data and generated by chemical Engineering Simulation Software, HYSIS. The properties data as state below: Flowrate at the dispersed phase, QD = 1254.92 ft3/hr Flowrate at the continuous phase, QC = 1.785 ft3/hr Density at the dispersed phase, ρD = 24.10 lb/ ft3 Density at the continuous phase ρC = 41.45 lb/ft3. The data was evaluated at system temperature and pressure. 4.2.3 Determination of Number of Stages To determine the theoretical stages required, by assuming the minimum solvent to feed ratio required to remove all the minimum component, so that is the extraction factor, ε = 1(Schweitzer, Separation Handbook). Equation 4.1 was used. The value for X f = 0.0195 kg CH3OH/ kg water, Ys = 1.57 x 10-6 kg CH3OH/ kg water was compute from the mass balance at this system. Number of theoretical stage, Nf = Xf – Ys/m Xr – Ys/m Nf = 0.0195 – (1.57 x 10-6 / 0.001) (1.57 x 10-6 / 0.001) -1 (4.1) -1 = 10.42 stages = 10 stages Where, Xf = weight solute /weight feed solvent in the feed phase Ys = weight solute / weight extraction solvent in extract Xr = weight solute /weight feed solvent in the raffinate phase m = slope at the equilibrium line dY/dX 234
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR The number of mass transfer unit, Nor is identical to the number of the theoretical stages when extraction factor, ε = 1. Nor = Xf – Ys/m -1 (4.2) Xr – Ys/m Nor = 10 units By assuming column efficiency, E is 80%, the number of real stages, N was determining by using equation 4.3. N = (Nf -1)/ E (4.3) = (10 – 1)/ 0.8 = 11 stages 4.2.4 Sizing of Sieve Tray The sieve tray sizing was base on the manufacturer’s literature. Usually the tray spacing is from (6 to 24) in, and perforation diameter, do usually from (0.32 to 0.64) cm or (1/8 to 1/4) in diameter. By take 2 ft tray spacing, Zt, 0.25 in holes on 0.75 in triangular spacing. The downcomer area is found with equation 4.4. h = 4.5 Vd2 ρC / 2gc ∆h = 2 (4.4) = 4.5 Vd2 ρC / 2gc ∆ρ 2 = 4.5(41.45) 2(4.18 x 108) 17.35 Vd = 12471 ft/hr Ad = QD/ Vd Vd2 (4.5) = 1254.92 / 12471 = 0.1006 ft2 235
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Dd Where, = 4.2948 in (Downcomer diameter) Vd = Velocity of the dowmcomer ρC = Density at the continuous phase gc = gravitational constant To determine the total holes area in a tray used equation 4.6 and set the velocity through the holes, Uh are kept below 0.8 ft/sec or 2880ft/ hr to avoid formation of very small droplet. Total hole area, AHT = QD/ Uh (4.6) = (1254.92 / 2880) = 0.4357 ft2 To find the tray area, by using ratio of the tray area to hole area as state below: Tray area, AT = 0.866 (ds) 2 ½ (Л/4) (do) 2 Hole area, AH = 2.21( ds/ do) 2 = 2.21 (0.75/0.25)2 = 19.89 = 19.89(0.4357) = 8.666 ft2 = 3.32 ft do = perforation diameter ds = triangular spacing Tray Area, AT Tray Diameter, DT Where, 4.2.5 Number of Holes Hole area, AH = ½ (Л/4) (do) 2 (4.7) 236
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR =½ (Л/4) (0.25) 2 =0.0245 in2 Number of hole, NH = AHT/AH (4.8) 2 = 0.4357ft / 0.0245 in 2 = 2560 units 4.2.6 Column Parameter Number of tray, NT required and the tower high, HT is determining by using equation 4.9 and 4.10 respectively. The efficiency of the tray is base on assumption of the column efficiency. Number of trays, NT = Nf / ET (4.9) = 10 / 0.8 = 13 trays Column Height, CT = Zt x NT (4.10) = 2 (13) = 26 ft + 3 ft (including 1.5 ft at each end) = 29 ft Column diameter same with the tray diameter, so Column diameter, DC = 3.32 ft. Column area, AC = 8.67 ft2 Net area and active are were determined by using equation 4.11 and 4.12 respectively. Net area, AN = AC - Ad (4.11) = 8.67 – 0.1739 = 28.4961ft 2 Active area, Aa = AC - 2Ad (4.12) = 8.67 – (2 x 0.1739) = 8.322 ft2 Where, Ad = downcomer area 237
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR The height equivalent to theoretical stages, (HETS) and height of transfer unit, Hor are calculated by using equation 4.13 and 4.14 respectively. HETS 29 / 10 = 2.9 = CH / Nor = 4.2.7 CH / Nf = Hor = (4.13) 2.9 (4.14) Weeping Evaluation By analogy with distillation. Weir length, lw is calculated by referring to Figure 11.31 from Coulson and Richardson Vol.6 page 572, which determined the value is base on the ratio of Ad/AC to get the ratio of lw/DC. The weir height determine from standard form as follows: Weir height = 50 mm Hole diameter = 5 mm Plate thickness = 5 mm Weir crest were determined by using value of maximum flowrate and minimum flowrate based on process condition. Each weir crest value determine by using equation 4.15 and equation 4.16 respectively. Max how 2/3 750 Lw max / ρD( lw) = 750 3.8106/ (380.048 x 1.2705) = Min how = 29.73 mm liquid = 750 Lw min / ρD( lw) = 750 0.4512/ (380.048 x 1.2705) (4.15) 2/3 2/3 (4.16) 2/3 238
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR = 7.17 mm liquid At minimum rate hw + how = 50 + 7.17 =57.17 mm Where, lw = weir length how = weir crest Lw = liquid flowrate Orifice coefficient, Co was referring from figure 11.34 Coulson and Richardson Vol. 6 pg 576 and by assuming. 1. Plate thickness : hole diameter =1 2. Ah/Ap =5 Plate pressure drop, h h = 51 (Uh / Co)2 (ρC/ρD) (4.17) 2 = 51 (0.2438/0.805) (640/380.048) = 7.88 mm liquid = (12.5 x 103) / ρD Residual head, hr hr (4.18) 3 = 12.5 x 10 / 380.048 = 32.89 mm liquid Total plate pressure drop, ht ht = h + (hw + how) + hr = 7.88 + 57.17 + 32.89 = (4.19) 97.94 mm liquid Plate pressure drop, ∆Pt ∆Pt = 9.81 x 10-3 ht ρD (4.20) = 9.81 x 10-3 (97.94) (380.048) = 365.147 Pa (N/m2) Table 4.1: Provisional Plate Design Specification Column Diameter 1011 mm 239
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Number of Trays Tray Spacing Plate Thickness Total Column Height Plate Pressure Drop Plate Material Downcomer Area Column Area Net Area Active Area Hole Area Number of Holes Weir Length Weir Height (standard) Number of manhole Manhole Diameter (BS 470:1984) 4.3 13 0.6 5 9 7.88 SS304 9.3 x 10-3 0.805 2.647 0.773 1.58 x 10-5 2560 1.2705 50 2 700 trays m mm m mm liquid m2 m2 m2 m2 m2 units m mm mm MECHANICAL DESIGN OF LIQUID – LIQUID EXTRACTION COLUMN In mechanical design, the temperature and the pressure are important properties in evaluate the thickness and the stress of material. Therefore, the safety factor also need as precaution and determined by certain consideration such as corrosion factor, location and process characteristic. Based on Hysis data, the operating pressure is 2.75 kPa and the safety factor is 10% above operating pressure. The design temperature related to the operating temperature. The temperature of column operated in 400C at top of column and 270C at the bottom of the column. The design pressure and design temperature of the system as follows: Design Temperature, T 4.3.1 = 0.275 N/mm2 x 1.1 = Design Pressure, Pi 0.3025 N/mm2 = 500C Material Construction The material used is stainless steel (18Cr/8Ni, 304). Design stress at 500C is gain from table 13.2, pg 809 Coulson & Richardson Vol.6. 240
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Design stress, f 165 N/mm2 Diameter Vessel, Di = 1011 mm Tensile Strength, 4.3.2 = = 510 N/mm2 Vessel Thickness The thickness of column is calculated based on the equation below: e = PiDi (4.21) 2f – Pi = 0.3025(1011) 2(165) – 0.3025 = 0.9276 mm Add corrosion allowance 4mm, so the thickness: e = 4.9276 mm = 5 mm From Coulson & Richardson, value for vessel diameter (m), 1 m, the minimum wall thickness required should not be less than 5mm including corrosion allowance. A much thicker wall will be needed at the column base to withstand the wind and dead weight loads. As a first trial, divide the column into five sections (courses) with thickness increasing by 2mm per section. Try 10,12,14,16, and 18mm. The average is 14 mm. 4.3.3 Design of Domed Ends Standard torispherical head are the most commonly used end closure for vessel up to operating pressure of 15 bar. Torispherical head had been choose because of operating pressure below 10 bar. Crown Radius, RC = Di = 1.011m Knuckle Radius, Rk = 6%RC = 0.061 m 241
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR A head of this size would be formed by pressing: no joint, so J = one. Stress concentration factor for torispherical heads, Cs: Cs = ¼ (3 + √ (RC / Rk)) = ¼ (3 + √ (1.011/0.061)) = (4.22) 3.053 Therefore the minimum thickness: e = PiRCCs (4.23) 2fJ + Pi (Cs – 0.2) = 0.3025(1011) (3.053) (2 x 165) + (0.3025(3.053 -0.2)) = 4.3.4 2.821 mm Column Weight 4.3.4.1 Dead Weight of Vessel, Wv Wv = 240 Cv Dm(Hv + 0.8Dm) t Where;Cv = a factor take 1.15, vessel with plates Dm = mean diameter, m = (Di + t) Hv = height or length between tangent line t = (4.24) wall thickness, m To get a rough estimate of the weight of this vessel by using the average thickness 14 mm. Dm = 1.011 + 0.014 = 1.025 m = 240(1.15) (1.025) (9 +0.8(1.025)) 14 = 38933.69N Hence, Wv 242
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR = 4.3.4.2 389 kN Weight of plate, Wp From Nelson (1963) pg 833 in Coulson & Richardson Vol. 6 rough guide to weight of fittings, take contacting plates, steel including typical liquid loading, 1.2 kN/m2 plate areas. The total of weight of plate determine by multiply the value with number of tray design. Tray area, AT = 0.805 m2 Weight of plate = 1.2 x AT = 1.2(0.805) = 0.966 kN Weight of 13 trays, Wp 0.966(13) = 4.3.4.3 = (4.25) 12.558 kN Weight of Insulation, Wi The insulating material is mineral wool; Density of mineral wool = 130 kg/m3 Thickness of insulation, ti = 75 mm Volume of insulation, Vi = ЛDiHv x ti = Л (1.0110) (9) (75 x 10-3) = 2.144m3 = Viρg = 2.144(130) (9.81) = 2734.11 N Weight of Insulation, Wi (4.26) (4.27) Double this value to allow fittings, so weight of insulation, Wi = 5.468 kN 4.3.4.4 Total weight, W 243
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR W Wv + Wp + Wi = 389 + 12.56 + 5.47 = 4.3.4.5 = (4.28) 407.03 kN Wind Loading Take dynamic wind pressure, Pw as 1280 N/m2. Mean diameter, including insulation, Deff: = 1.011 + 2(0.014 + 0.075) = 2.791 m Loading (per linear meter) Fw; Fw = PwDeff (4.29) = 1280 (2.791) = 3572.48 N/m Bending moment at bottom tangent line. MX MX = FwX2 (4.30) 2 = 3572.48 (9)2 2 = Where; X 144685 Nm = Distance measured from the free end The calculated value as the result tabulated in table 4.2. The value requires determining in strength and suitability of column while in construction and operation. It also required the safety consideration operation. The operating procedure of the column should base on this value. 4.3.5 Analysis of Stress At bottom tangent line, 244
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 4.3.5.1 Longitudinal and Circumferential Pressure Stress; σh = PiDi (4.31) 2t = 0.3025 (1011) 2 (14) = σL 10.92 N/mm2 = PiDi (4.32) 4t = 0.3025 (1011) 4 (14) = 4.3.5.2 5.46 N/mm2 Dead Weight Stress σL = W (4.33) Л (Di + t) t = 407030 Л (1011 + 14) 14 = 4.3.5.3 9.03 N/mm2 Bending Stress σb = ± MX / IV ((Di/2) + t) Where;MX = Total bending moment = Second bending moment = Л / 60 (Do4 –Di4) = 1011 + 2(14) = 1039 mm = Л / 60 (10394 –10114) = 6.32 x 109 mm4 IV (4.34) Which; Do IV Therefore, 245
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR σb = ± 144685000 ((1011 / 2) + 14) 6.32 x 109 = ± 11.89N/mm2 The result longitudinal stress, σZ is: σZ = σ L + σW ± σ b σZ (upwind) = σ L - σ W + σb = 5.46 – 11.15 + 11.89 = 6.2 N/mm2 = σL - σW - σb = 5.46 – 11.15 – 11.89 = -17.58 N/mm2 σZ(downwind) 4.3.5.4 Elastic Stability (Buckling) Critical buckling stress, σC: σC = 2 x 104 (t / Do) (4.35) 4 = 2 x 10 (14 / 1039) = 269.48 N/mm2 The maximum compressive stress will occurs when the vessel is not under pressure: σ W + σb = 11.15 + 11.89 = 23.04N/mm2 This value is below critical buckling stress, so design is satisfactory. Stresses analysis is tabulate in the table 4.3. 4.3.6 4.3.6.1 Vessel Supports Design Skirt Supports At ambient temperature. 246
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Type of support : Straight cylindrical skirt (θS = 900) Material construction : Plain carbon steel Design stress : 135 N/mm2 Young’s Modulus : 200000 N/mm2 Skirt height, Hs : 3m The maximum dead weight load on the skirt will occur when the vessel is full of the mixture. Approximate weight, Wapprox (Л / 4) Di2 HVρLg = = (Л / 4) (1.011 ) (9) (380.048) (9.81) = 26936.56 N = 26.9 kN = W + Wapprox = 407.03 + 26.9 = Total weight (4.36) 2 433.93kN Bending moment at base of skirt, MS: MS = Fw (HV + HS)2 (4.37) 2 2 = 3.572 (12 / 2) = 257.184 kNm As a first trial, take the skirt thickness as the same as that of the bottom section of the vessel, ts = 14 mm. Bending stresses in skirt, σbs Where; Ms = 4Ms / (Л (Ds + ts) tsDs) = Maximum bending moment at the base of the skirt. ts = Skirt thickness Ds = (4.38) Inside diameter of the skirt at the base So, 247
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR = 4 (257184 x 103) / Л (1011+14) (14) (1011) = σbs 22.5710 N/mm2 Dead weight stress in the skirt, σWs: σWs(test) = = 26900 / Л (1011+14) (14) = 0.60 N/mm2 = 407030 / Л (1011+14) (14) = σWs(operating) W / (Л (Ds + ts) ts) (4.39) 9.03 N/mm2 Thus, the resulting stress in the skirt, σs: Max σs (compressive) = σWs(test) + σbs = 0.60 + 22.57 = 23.17 N/mm2 = σbs - σWs(operating) = 22.57 – 9.03 = 13.54 N/mm2 Max σs (tensile) (4.40) (4.41) Take the joint factor, J as 0.85. Criteria for design σs (tensile) > fs J sin θ 13.54 > 0.85 (135 sin 900) 13.54 > 114.75 248
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR σs (compressive) > 0.125 E (ts/DS) sin θ 23.17 > 0.125 (200000) (14/1011) sin 900 23.17 > 346.19 Both criteria are satisfied; add 2mm for corrosion gives a design thickness of 16 mm. 4.3.6.2 Base Ring and Anchor Bolt Approximate pitch circle diameter, say 2.2 m. Circumferences of bolt circle = 2200 Л Л of bolt required, at minimum recommended bolt spacing: = 2200 Л / 600 = 11.5 Closet multiple of 4 = 12 bolts Take bolt design stress = 125 N/mm2 Bending moment at skirt, MS = 301.834 kNm Total weight vessel, W 502.53 kN Area of bolt, Ab = = 1 Nbfb Where:Nb 4MS - W (4.42) Db = Number of bolts fb = Maximum allowable bolt stress MS = Bending moment at the base W = Weight of the vessel 249
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Db = Bolt Circle diameter Therefore, Ab = 1 4 (257184) 12 (125) = Bolt root diameter - 407030 2.2 40.35 mm2 = √ (40.38 x 4) / Л = 7.17 mm Total compressive load on the base ring per unit length. Fb = 4MS + Л DS2 = (4.43) Л DS 4 (257184) + Л (1.0112) = W 407030 Л (1.011) 448.5 x 103 N/m By taking the bearing pressure as 5 N/mm2. The minimum width of the base ring, Lb: Lb = Fb Fc + 1 103 = (4.44) 448.5 x 103 5000 = 89.7 mm Actual width can be calculated from this minimum width. Use M24 bolts (BS 4190:1967) root area = 353 mm2 (Figure 13.30 Coulson & Richardson Vol. 6) 250
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Actual width required = Lr + ts + 50mm = 150 + 14 + 50 = 214 mm Actual bearing pressure on concrete foundation: f’c = Fb actual width = 448500 214000 = 2.10 N/mm2 Actual minimum base thickness: tb Lr √ (3 f’c / fr) = 150 √ ((3 x 2.1) / 140) = Where: fr = (4.45) 25.98 mm = Allowable design stress in the ring material, typically 140 N/mm2 The design specifications of support are summarized in the table 4.4. 4.3.7 Piping Sizing The optimum diameter for carbon steel pipe: d, optimum = 293 G 0.53 ρ-0.37 Where:G = Flowrate (kg/s) ρ = (4.46) Density (kg/m3) Pipe thickness, t = P d, optimum (4.47) 251
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 20σ + P Where:P = Internal pressure, bar σ = Design stress at working temperature, N/mm2 The piping sizing for this system are shown in table 4.5 Table 4.2 : Summary of the Mechanical Design Design Pressure Operating Pressure 2.75 kPa Operating Temperature 40 0 C 0.3025 N/mm2 Design Pressure Design Temperature 50 Safety Factor 0 C 0.10 Design of Domed Ends Types Crown Radius Knuckle Radius Joint Factor Stress Concentration Factor Minimum Thickness Column Weight Dead Weight of Vessel Weight of Plate (per plate) Weight of Insulation Total Weight Wind Pressure Loading Bending Moment Torispherical head 1.011 m 0.061 m 1 3.053 2.821 mm 389 0.966 2734.11 407.03 1280 3572.48 144.685 kN kN N kN N/m2 N/m kNm 252
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Table 4.3: Stress Analysis for Liquid-Liquid Extraction Column Longitudinal Pressure Stress Circumferential Pressure Stress Dead Weight Stress Bending Stress σZ (upwind) σZ(downwind) Critical Buckling Stress 10.92 N/mm2 5.46 N/mm2 9.03 N/mm2 ± 11.89 6.2 -17.58 269.48 N/mm2 N/mm2 N/mm2 N/mm2 Table 4.4: Design Specification of the Support Skirt Types of Support θ Material Construction Design Stress Skirt Height Young Modulus ρL Approximate Weight Total weight Bending Moment at Skirt Skirt Thickness Bending Stress in Skirt σ ws (test) σ ws (operating) Maximum σs (compressive) Maximum σs (tensile) Straight cylindrical skirt 90 Plain Carbon steel 135 3 200000 380.048 26.9 433.93 257.184 14 22.57 0.60 9.03 23.17 13.54 0 C N/mm2 m N/mm2 kN kN kN kNm m N/mm2 N/mm2 N/mm2 N/mm2 N/mm2 253
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Table 4.5: Piping Sizing for Liquid-liquid Extraction Column Feed Pipe Sizing Flowrate, G Density, ρ Internal Pressure, P Design Stress, σ Diameter Optimum, d optimum Corrosion Allowance Pipe Thickness, t Solvent Pipe Sizing Flowrate, G Density, ρ Diameter Optimum, d optimum Extract Pipe Sizing Flowrate, G Density, ρ Diameter Optimum, d optimum Raffinate Pipe Sizing Flowrate, G Density, ρ Diameter Optimum, d optimum 4.4 13873.67 567.0445 2.75 165 55 4 4.05 kg/hr kg/hr bar N/mm2 mm mm mm 1469.1 kg/hr 998 kg/hr 15 mm 1624.37 kg/hr 992.8161 kg/hr 15 mm 15096.74 kg/hr 564.7173 kg/hr 30 mm PROCESS CONTROL AND INSTRUMENTATION OF THE LIQUID-LIQUID EXTRACTION COLUMN Control systems are very important in any of the chemical industries. It is essential for a process to meet the design specification and products purity that imposed by the designer or by external constrains such as government regulations and standards. 254
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Process parameters control is to compensate for the process changes with the existence of external disturbances. Normally, an overall control strategy is design to meet the following objectives: 1. Ensure stable plant operation conductive to power optimization 2. Maintain product quality according to specification 3. Operate the process and machinery in such a way as to estimate or minimize the possibility of activating last resort safety measures such as relief valve and surge system, thus ensuring safe plant operation. Compensate for perturbations cause by external factors such as ambient and cooling water temperature variations. Provide an intelligent man-machine interface capable of presenting process and control system information and interactive format. Typically, there are two types of control systems- feedback control and feed forward control. In this case, the feedforward control is applied; in feedforward control its take corrective action before they upset the process. In this system also, solvent use is lighter than the material being extract, the two input indicated are of course interchanged. Both inputs are on flow control. The light phase is removing from the tower on LC (level control) or at the top of level maintain with an internal weir. The bottom stream is removed on interfacial level control (ILC). The relative elevations of feed and solvent input nozzles depend on the nature of the extraction process. The temperature of an extraction process ordinarily is controlled by regulating the temperature of the feed stream. REFERENCES Buford D.Smith, 1963. Design of Equilibrium Stage Processes, United State of America. McGraw-Hill. Robert C.Reid,Prausnitz & Poling,1987.The properties of Gases and Liquid, United State of America. McGraw-Hill. 255
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Erneat J.Henley & J.D Seader, 1968.Equilibrium-Stages Separation Operations in Chemical Engineering. Canada. John Wiley & Sons Philip A.Schweitzer,1988. Handbook of Separations Techniques for Chemical Engineers,2nd Edition. United State of America. McGraw-Hill. J.D Seader & Erneat J.Henley, 1998.Separation Process Principles, United State of America. John Wiley & Sons R.K.Sinnott, 1999.Chemical Engineering Design, Coulson & Richardson Chemical Engineering .3rd Edition. Volume 6 .Britain. Butterworth Heinemann Robert H. Perry, Don W. Green, 1998 Perry’s Chemical Engineer’s Handbook, Seventh Edition, McGraw-Hill. J.R Backhurst & J.H Harker.1987.Chemical Engineering Design, Coulson & Richardson Chemical Engineering .3rd Edition. Volume 2 .United Kingdom. Pergamon Press. Stanley M. Walas. 1988. Chemical Process Equipment Selection and Design. United State of America. Butterworth’s Series in Chemical Engineering. Robert E.Treybal.1988. Mass-Transfer Operations,3rd Edition. Singapore, McGraw-Hill International Series. K.H Reissinger & Jurgen Schroter. 1980. Selections Criteria for Liquid-liquid Extractors. Chemical Engineering Magazine, November: 274-256. P.J Bailes,C.Hanson & M.A Hughes.1976. .Liquid-liquid Extraction: The process, the equipment. Chemical Engineering Magazine, January 217-231. Ariffin Marzuki & Nurul Izzi, 2004. PETRONAS Research Centre, Bangi. Interview,19 January. SECTION 5 256
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR DESIGN OF HEAT EXCHANGER INTRODUCTION Shell and tube heat exchangers are the most versatile type of heat exchangers. They are used in process industries, in conventional and nuclear power stations as condensers, in steam generators in pressurized water reactor power plants, in feed water heaters and in some air conditioning and refrigeration systems. They are also proposed for many alternative energy applications including ocean, thermal and geothermal. Shell and tube heat exchangers provide relatively large ratios of heat transfer area to volume and weight and they can be easily cleaned. Shell and tube heat exchangers offer great flexibility to meet almost any service requirement. The reliable design methods and shop facilities are available for their successful design and construction. Shell and tube heat exchangers can be designed for high pressures relative to the environment and high pressure differences between the fluid streams. Shell and tube heat exchangers are built of round tubes mounted in a cylindrical shell with the tubes parallel to the shell. One fluid flows inside the tubes, while the other fluid flows across and along the axis of the exchanger. The major components of this exchanger are tubes (tube bundle), shell, front-end head, baffles and tube sheets. Shell types-various front and rear head types and shell types have been standardized by Tubular Exchanger manufacturers Association (TEMA). The E-shell is the most common due to its cheapness and simplicity. In this shell, the shell fluid enters at one end of the shell and leaves at the other end that is there is one pass on the shell side. The tubes may have a single or multiple passes and are supported by transverse baffles. This shell is the most common for singlephase shell fluid applications. With a single-tube pass, a nominal counter flow can be obtained. The design of a shell and tube heat exchanger is an iterative process because heat transfer coefficients and pressure drop depend on many geometric factors, including shell and tube diameters, tube length, tube layout, baffle type and 257
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR spacing and the numbers of tube and shell passes, all of which are initially unknown and are determined as part of the design process. In production of MTBE, heat exchanger is very important equipment. Heat exchanger is used to increase or to decrease the mixture to the desired temperature. In order to make the process of production of MTBE taking place in the system, it is important to make the system at the correct environment. The heat exchanger that we used here is the shell and tube exchanger. Shell and tube heat exchanger is the most common type of heat exchanger used in the industry. This is because it has many advantages. The advantages are: 1. It provided a large transfer area in a small space. 2. Good mechanical layout: a good shape for pressure operation. 3. Used well-established fabrication techniques. 4. It can be constructed from a wide range of materials. 5. It can be clean easily. 6. Well-established design procedures. 7. Single phases, condensation or boiling can be accommodated in either the tubes or the shell, in vertical or horizontal positions. 8. Pressure range and pressure drop are virtually unlimited and can be adjusted independently for the two fluids. 9. Thermal stresses can be accommodated inexpensively. 10. A great variety of materials of construction can be used and may be different for the shell and tubes. DESIGNING THE HEATER In the production of MTBE, a heater is the most important heat exchanger in the system. Therefore this chapter is going to describes details for this heater and the design of this piece of equipment. 258
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Heater is used in the process to heated the raw material of MTBE consist of isobutane and a bit of normal butane. Isobutane and normal butane from the storage is in liquid form. The heating process is because to produce the isobutane and normal butane in the gases form before this material is feed to the Snamprogetti Fluidized Bed Reactor. Here the mixtures of this component initially are in the liquefied gas form at temperature of -15 oC. It will be heated in the Heater (E-100) and Heater (E101) until it converted into gas form at temperature of 250 oC using steam. For this heat exchanger we use the counter current process. The temperature difference between liquid and gas phase is quit big, so we need two heat exchanger in series. The shell and tube heat exchanger is the floating head type. T = 250OC T = 350OC STEAM IN T = -15 OC STREAM 2 STEAM IN STREAM 3 STREAM 4 T = 250 OC O T = 117 C E100 E101 STEAM OUT T = 120 OC STEAM OUT T = 250OC Figure 5.1 : Heat Exchanger In Series For The Heating Process 5.1 CHEMICAL DESIGN OF HEAT EXCHANGER The chemical engineering design for the heat exchanger is also known as thermal. The design requires the calculation of the heat transfer area required. From this value, design features of the unit such as the tube and shell size, tube counts and layout is determined. In addition, then pressure loss of the fluids across the unit is also calculated by determined the pumping capacity required. The calculation of the design 259
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR is base on the first heat exchanger (E100). The chemical design is based on Bell’s and Kern method. Bell’s method accounts for the major bypass and leakage streams. Kern method was based on experimental work on commercial exchangers with standard tolerances and will give a reasonably satisfactory prediction of heat-transfer coefficient for standard design. 5.1.1 Physical Properties Of The Stream Table 5.1: Properties of Raw material (Isobutane and N-butane) and Steam for (E100) Component Raw material (Isobutane Steam Temperature inlet, oC Temperature outlet, oC Specific heat, j/kg oC Thermal conductivity, W/mK Density, kg/m3 Viscosity, kg/ms Feed flowrate, kg/s and normal butane) t1 = -15 t2 = 117 2155 0.07 485 1.30005 x 10-4 10.9314 T1 = 250 T2 = 120 2010 0.0306575 0.49375 1.55263 x 10-5 1.7649 5.1.2 The Calculation Of ∆ Tm To determine the mean temperature, Tm ∆Tm = Ft ∆Tlm (5.1) Where ∆ Tm = true temperature difference 260
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Ft = temperature correction factor Before ∆ Tm can be obtained, logarithmic mean temperature ∆ Tlm must be calculated Using the equation: ∆Tlm = (T1 - t 2 ) - (T2 - t1 ) (T - t ) ln 1 2 (T2 - t1 ) (5.2) Where ∆ Tlm = log mean temperature difference T1 = inlet shell-side fluid temperature T2 = outlet shell-side fluid temperature t1 = inlet tube-side temperature t2 = outlet tube-side temperature ∆Tlm = ( 250 - 117 ) - (120 + 15 ) (250 - 117) ln (120 - (-15)) ∆Tlm = 134.00 0 C the temperature correction factor can be obtain by using figure 12.19 (Coulson & Richardson’s Chemical Engineering) 261
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR R= T1 - T2 t 2 - t1 R= (250 - 120) (117 - (-15)) (5.3) R = 0.98 S= t 2 - t1 T1 - t1 S= (117 - (-15)) (250 - (-15)) (5.4) S = 0.50 Using figure 12.19, (Coulson & Richardson’s Chemical Engineering) Ft = 0.82 Substitute the above value into equation (1.1) below : ∆Tm = Ft ∆Tlm ∆Tm = ( 0.82 )(134 .00 ∆Tm = 109.88 0 0 C) C From table 12.1 (Coulson & Richardson’s Chemical Engineering), we take overall Coefficient, U = 300 W/m2 0 C Duty for this heat exchanger is obtain from the energy balance. The duty is, Q = 3109542.883 W 262
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Then we need to calculate the surface area using equation below. A= Q U∆Tm A= 3109542.88 3 (300 )(109 .88 ) (5.5) A = 94.33 m2 5.1.3 Number Of Tubes Calculation From table 12.3 (Coulson & Richardson’s Chemical Engineering), we take standard pipe of: Inside diameter, di = 16 mm Outside diameter, do = 20 mm Length of pipe is assumed as 16 ft. Length, L = 4.88 m Area of the pipe can be calculated using equation below area = Lπ D (5.6) area = (4.88)(3.142)(0.02) area = 0.3067 m2 Using the area needed from the duty and area for each tube, the number of Tube, Nt that we get is, Nt = Nt = A a (5.7) 94.33 0.3067 Nt = 307.56 Therefore the number of tube, Nt = 308 tubes 263
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 5.1.4 Bundle And Shell Diameter Calculation The tubes in heat exchanger are usually arranged in an equilateral triangular, square or rotated pattern. The triangular and rotated square patterns give higher heat transfer rates. Here we use the triangular pattern. The triangular pitch of 1.25 is chosen as the tube arrangement. Bundle diameter Db = do (Nt / K1 )1 / n1 (5.8) From table 12.4 (Coulson & Richardson’s Chemical Engineering), for 1.25 triangular pitch, number of passes = 2, then we can obtain K1 = 0.249 n1 = 2.207 Db = do (Nt / K1 )1 / n1 Db = 0.02 (308 / 0.249 )1 / 2.207 Db = 0.50m Assume using pull-through floating head type. From figure 12.10 (Coulson & Richardson’s Chemical Engineering), for bundle diameter 0.33, bundle clearance is 93 mm. Shell diameter, Ds Ds = 0.50 + 0.093 = 0.60m 5.1.5 Tube Side Coefficient, hi 264
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Mean temperature of the tube t mean = t1 + t 2 2 t mean = - 15 + 117 2 (5.9) t mean = 51 o C cross sectional area = π d12/ 4 (5.10) 2 = (3.142)(0.016 ) / 4 = 0.0002 m2 Tube / pass = 308 / 2 (5.11) = 154 tube / pass Total flow rate area = (cross sectional area)(tube / pass) (5.12) = (0.0002)(154) = 0.0308 m2 Steam mass velocity, Gt = (steam flow rate)/(total flow rate area) (5.13) = (1.7649)/(0.0308) = 57.30 kg / sm2 Steam linear velocity, u1 = (Gt)/(steam density) (5.14) = (57.30)/(0.49375) = 116.05 kg / ms Ratio of L / di = 4.88 / 0.016 (5.15) = 305 Reynolds number, Re 265
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Re = ρ ν di µ Re = (0.49375) (116 .05 ) (0.016) 1.55263 x 10 - 5 (5.16) Re = 59047.87 Heat transfer factor figure 12.31 (Coulson & Richardson’s Chemical Engineering), Jh = 4.1 x 10-3 Prandtl number, Pr = Pr = Cp µ (5.17) kf (2.010 x 10 3 )(1.55263 x 10 - 5 ) 0.0306575 Pr = 1.0180 Tube side coefficient, hi can be calculated using equation below. jhk f Re Pr 0.33 hi = di hi = (4.1 x 10 - 3 )(0.030657 5)(59047.8 7)(1.0180) 0.016 (5.18) 0.33 hi = 466.62 W / mo C 266
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 5.1.6 Shell Side Coefficient, hs Take baffle spacing as 1/3 from the shell diameter, so Baffle spacing: lB = Ds / 3 (5.19) = 0.60 / 3 = 0.20 m Tube pitch, pt = 1.25 do (5.20) = (1.25)(0.02) = 0.025 m Flow area, As As = As = (Pt - do )(D s )(IB ) Pt (5.21) (0.025 - 0.02)(0.60 )(0.20) 0.025 A s = 0.0240 m2 Mass velocity, Gs Gs = Ws As Gs = 10.9314 0.0240 (5.22) Gs = 455.48 kg / m 2 s Shell side velocity 267
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR us = Gs ρ us = 455.48 485 (5.23) us = 0.9391 m / s Shell side equivalent diameter for triangular pitch arrangement de = 1.10 2 (p t - 0.917d o 2 ) do de = 1.10 (0.025 2 - 0.917(0.02 )2 ) 0.02 (5.24) de = 0.0142 m Calculate the Reynolds number Re = Re = Gs de μIsobutane (5.25) (455.48)(0 .0142) 0.00013000 5 Re = 49750.52 Prandtl number Pr = Pr = CpIsobutane μIsobutane kf (5.26) (2155)(0.0 00130005) 0.07 Pr = 4.0023 268
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Choose baffle cut of 25%, from figure 12.30 (Coulson & Richardson’s Chemical Engineering), we can obtained Jf = 2.70 x 10-2 Assumed that the viscosity correction is negligible hs = k f jf Re Pr 1 / 3 de hs = (0.07)(2.7 0 x 10 - 2 )(49750.52 )(4.0023 1/3 ) 0.0142 hs = 10513.35 W / m2 (5.27) o C 5.1.7 Overall Heat Transfer Coefficient, Uo Material of construction = carbon Steel Thermal conductivity of the tube wall Kw = 38 W/moC Assumed dirt coefficient as hid = 8500 W/m2 oC hod = 8500 W/m2 oC 1 1 1 d ln(d o /di ) 1 ( do /di ) + 1 (do /di ) = + + o + Uo hs hod 2k w hid hi 1 = 0.0039738 m2 Uo Uo = 322.85 W / m2 5.1.8 o C/W o (5.28) C Tube Side Pressure Drop 269
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Reynolds number , Re = 59047.87 From figure 12.24 (Coulson & Richardson’s Chemical Engineering), jf = 3.10 x 10-3 Neglect the viscosity correction term ∆Pt = Np [ 8 jf (L/d i )(μ/μ W )- m + 2.5 ] ρiμi 2 2 ∆Pt = 2[ 8(3.10 x 10 - 3 )(4.88/0.0 16) + 2.5 ] (5.29) ( 0.49375 )(116 .05 )2 2 ∆Pt = 66921.86 N / m2 ∆Pt = 66.92 kPa 5.1.9 Shell Side Pressure Drop Reynolds number Re = 49750.52 From figure 12.30 (Coulson & Richardson’s Chemical Engineering), Jf = 2.70 x 10-2 Shell side pressure drop can be calculated using equation below ∆P = 8j f ( Dd / de ) ( L/I B ) ( ρμ s / 2) ( μ/μ w ) -0.14 (5.30) ∆P = 47.63 kPa Table 5.2: Summary Of Chemical Design For Heat Exchanger In Series 270
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Heat Exchanger Temperature range, (o C) Feed flow rate, (kg/hr) Steam flow rate, (kg/hr) Log mean temperature E100 Shell side 250 →150 Tube side -15 → 117 39353 6353.64 134.00 difference, ,∆ Tm (o C) True temperature 109.88 difference, ∆ Tm (o C) Overall coefficient, U (W/m2 300 o C) Duty, Q (w) Surface are, A (m2) Length of tube or shell, L Tube diameter di (mm) Tube diameter do (mm) Area of pipe, a (m2) Number of tube, Nt Bundle diameter, Db(m) Shell diameter, Ds(m) Baffles spacing, IB(m) Tube side coefficient, hi 3109542.883 94.33 4.88m or 16 ft 16 20 0.3067 308 0.50 0.60 0.2000 466.62 (W/m2 o C) Shell side coefficient, 10513.35 hs(W/m2 o C) Overall heat transfer 322.85 coefficent, Uo (W/m2 o C) Tube side pressure drop, 66.92 ∆ P (kPa) Shell side pressure drop, 47.63 ∆ P (kPa) 5.2 MECHANICAL DESIGN OF HEAT EXCHANGER The mechanical engineering design of heat exchanger determines the physical elements that make up the unit as well as their respective dimensions. This design follows the procedures specified by the Tubular Heat Exchanger association (TEMA) Mechanical Standards. It is applicable to shell and tube exchangers with internal diameter not exceeding 60 in. (1524mm), a maximum design pressure of 3000psi (204 bar) or a maximum product of nominal diameter (in) and design pressure (psi) of 271
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 60000. In addition, the design also complies with the American Society of mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section VIII, Division 1. 5.2.1 Design Pressure For the design of tube and shell parts, a safety factor of 10% is included to determine the design pressures. Operating pressure = 1.1 bar 10% above the pressure for safety Pi = 1.1 x 10 = 11 bar = 1.1 N / mm2 5.2.2 Design Temperature For the shell side and tube side the operating temperature is at 250 oC, so: Shell-side design temperature = 1.1x 250 oC = 275 oC Adding 2 oC for uncertainties in temperature prediction TD = 275 + 2 = 277 oC 5.2.3 Material Of Construction For the heat exchanger, the material used for construction is carbon steel. This selection of material is depending on the economic factor and also level of corrosiveness of the fluid used. Since the properties of the fluid both in the tube and also in the shell are not corrosive fluid, therefore the carbon steel is used because it is more economics compared to stainless steel. 5.2.4 Exchanger Type For the heater design, pull through floating head exchanger is chosen as the exchanger type. Internal floating head is versatile than other type and also suitable for 272
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR high temperature different between shell and tubes. The tube for internal floating head also can be rod from end to ends and the bundle are easier to clean. 5.2.5 Minimum Thickness Of Cylindrical Section Of The Shell The minimum thickness of the cylindrical section of the shell to stand the pressure can be obtained from the calculation below. e= PiDi 2jf - Pi (5.30) Where, Pi = design pressure Di = shell diameter F = design stress (from table 13.2, Coulson & Richardson’s Chemical Engineering) e= (1.1)(600) 2(1)(85) - (1.1) e = 3.91 mm adding the corrosion allowance = 2 mm e = 3.91 + 2 e = 5.91 mm Take the round number of the thickness e = 6.00 mm 5.2.6 Longitudinal Stress σh = σh = PiDi 2t (5.31) (1.1)(600) 2(6) σ h = 55.00 / mm 2 273
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 5.2.7 Circumferential Stress σh = PiDi 4t (5.32) σ h = (1.1)(600) / 4(6) σ h = 27.50 N / mm 2 5.2.8 Minimum Thickness Of Tube Wall Minimum thickness of the tube wall can be calculated using the equation e= (5.30): PiDi 2jf - Pi e= (1.1)(600) 2(1)(85) - (1.1) e = 3.91 mm adding the corrosion allowance = 2 mm e = 3.91 + 2 e = 5.91 mm 5.2.9 Minimum Thickness Of Head And Closure The minimum thickness of the torispherical head can be calculated by , e= PiR c Cs 2jf + Pi (Cs - 0.2) (5.33) Rc = crown radius Rk = knuckle radius Cs = stress concentration factor for torispherical head 274
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR [ Cs = 1/4 3 + R c / Rk ] (5.34) Rc = Ds = 600 mm Rk = 0.06(500) = 36 mm Cs = 1.77 e= (1.1)(600) (1.77) 2(1)(85) + 1.1(1.77 - 0.2) e = 6.80 mm Adding corrosion allowance e = 6.80 + 2 = 8.80 mm 5.2.10 Minimum Thickness Of The Channel Cover e = (C p )(D e )(Pi /f) 1/2 (5.35) where Cp = a design constant, depend on the edge constraint (0.45) De = nominal plate diameter f = design stress e = (0.45)(600)(1.1/85)1/2 = 30.72 mm Adding corrosion allowance = 2 mm E = 30.72 + 2 = 32.72 ≈ 33 mm 5.2.11 Design Load Dead weight of vessel 275
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR W v = C v πρ mDm g(H v + 0.8D m )t x 10 -3 (5.36) where Wv = total weight of the shell Cv = 1.08 for vessels with only few internal fitting Wv = (1.08)π (7700)(0.602)(9.81)(4.88+0.8(0.602))(2 x 10-3) = 1654.45 N Weight of tubes 2 2 W t = Nt π(do - d1 )Lρmg W t = 308 π(0.02 2 (5.37) - 0.016 2 )(4.88)(77 00)(9.81) W t = 51362.08 N Weight of insulation Material used = mineral wool insulation Insulation thickness = 50 mm = 0.05 m Density = 130 kg / m3 Approximate volume of insulation V = πH v [ (r + r1 )2 - r 3 ] (5.38) V = π (4.88) [ (0.60 + 0.05) - (0.50) 2 2 ] V = 2.64 m3 W t = Vρ g (5.39) W t = (2.64)(130 )(9.81) W t = 3366.79 N Total weight of heat exchanger WT = Wv + Wt + Wi (5.40) 276
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR WT = 1654.45 + 51362.08 + 3366.79 = 56383.32 N = 56.38 kN 5.2.12 Pipe Size Selection For The Nozzle pipe size for isobutane inlet material of construction = carbon steel density inlet isobutane, ρ = 600 kg / m3 flow rate isobutane at inlet, Gisobutane = 10.9314 kg / s Diameter pipe for isobutane inlet, Disobutane Disobutane (in) = 293G0.53ρ -0.37 (5.41) Disobutane (in) = 293(10.9314) 0.53(600)-0.37 Disobutane (in) = 97.60 mm Pipe size for isobutane at outlet, material of construction = carbon steel density outlet isobutane, ρ = 370 kg / m3 flow rate isobutane at outlet, Gisobutane = 10.9314 kg / s Diameter pipe for isobutane outlet, Disobutane Disobutane (out) = 293G0.53ρ -0.37 Disobutane (out) = 293(10.9314) 0.53(370)-0.37 Disobutane (out) = 116.72 mm Diameter pipe for steam at inlet stream 277
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR material of construction = carbon steel density inlet steam, ρ = 0.5654 kg / m3 flow rate steam at inlet, Gsteam = 1.7649 kg / s Diameter of pipe Dsteam (in) = 293G0.53ρ -0.37 Dsteam (in) = 293(1.7649) 0.53(0.5654)-0.37 Dsteam (in) = 488.94 mm Diameter pipe for steam at outlet stream material of construction density outlet steam, ρ = carbon steel = 0.4221 kg / m3 flow rate steam at outlet, Gsteam = 1.7649 kg / s Diameter of pipe Dsteam (out) = 293G0.53ρ -0.37 Dsteam (out) = 293(1.7649) 0.53(0.4221)-0.37 Dsteam (out) = 544.79 mm 278
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Figure 5.2 : Steel pipe nozzle Table 5.3 : by taking D = 100 mm, the selected tube nozzle is : Nominal pipe size, inch 4 Outside diameter, inch 4.5 (114.30) Schedule no. 4OST Wall thickness, inch 0.237 (6.02 mm) Inside diameter, inch 4.026 (102.26 mm) Table 5.4 : by taking D = 500 mm, the selected tube nozzle is : Nominal pipe size, inch 20 Outside diameter, inch 20 (508) Schedule no. 4OST Wall thickness, inch 0.375 (9.53 mm) Inside diameter, inch 19.250 (488.95 mm) (From Perry R.H and Green, Don (1984), “Perry’s Chemical Engineer’s Handbook”, 7th Edition, McGraw-Hill Book) 5.2.13 Standard Flanges 279
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Flanges used in this design are chosen from the standard flanges. Here standard flanges are adapted from the British standard (BS 4504), nominal pressure 10 bar. Figure 5.3 Standard Flange Standard flange for inlet isobutane Diameter isobutane inlet pipe = 97.60 mm Used standard o.d pipe = 114.3 mm Table 5.5 : Standard Flange for Inlet isobutane nom. size 100 pipe o.d d1 D 114.3 Flange b 210 16 hi Raised face Bolting Drilling d4 f No. d2 45 148 3 M16 4 18 Neck h2 k d3 170 r 10 8 130 Standard flange for outlet isobutane Diameter isobutane outlet pipe = 116.72 mm Used standard o.d pipe = 114.3 mm 280
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Table 5.6 : Standard Flange for Outlet isobutane nom. size 100 pipe o.d d1 D 114.3 Flange b 210 16 hi 45 Raised face Bolting Drilling d4 f No. d2 148 3 M16 4 18 Neck h2 k d3 170 r 10 8 130 Standard flange for inlet steam Diameter steam inlet pipe = 488.94 mm Used standard o.d pipe = 508 mm Table 5.7 : Standard Flange for Inlet Steam nom. size pipe o.d d1 500 508 Flange D b 645 24 hi 68 Raised face Bolting Drilling d4 f No. d2 570 4 M20 20 22 Neck h2 k d3 600 538 15 r 12 Standard flange for outlet steam Diameter steam outlet pipe = 544.79 mm Used standard o.d pipe = 508 mm Table 5.8 : Standard Flange for Outlet Steam nom. size pipe o.d d1 500 508 Flange D b 645 24 hi 68 Raised face Bolting Drilling d4 f No. d2 570 4 M20 20 22 Neck h2 k d3 600 538 5.2.14 Design of Saddles Table 5.9: Using Ds = 600mm, the standard steel saddles for vessels up to 1.2m : 281 15 r 12
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Vessel Maximum diamete weight r (m) 0.9 (kN) 56.38 V Y Dimension (m) C E J G t2 0.63 0.15 0.81 0.34 0.275 0.095 10 t1 mm Bolt diameter 6 20 5.2.15 Baffles  Type : transverse baffle  Baffle diameter for plate shell is given as, Ds = the nominal diameter of the shell for plate shell. So baffle diameter = 0.600 m = 23.63’ = 600 mm  Diameter of tube holes in baffles, Dh Dh = outer diameter of the tube = (0.16 + 1/32) x 20.2 = 3.86 mm  Number of baffle segmental, Nb Nb = length tube / inside diameter shell = 4880 / 600 = 8.13 ≈ 8 baffles  Vent and drain -A drain and vent connection shall be provided on the shell side Table 5.10: Summary Of Mechanical Design For Heat Exchanger In Series Heat Exchanger E100 282
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Design pressure, bar 11 design temperature, oC 277 Material Of Construction Tube side: Carbon steel Shell side : Carbon steel 6.0 Minimum Thickness Of Cylindrical Section Of The Shell, mm Longitudinal Stress, 55.0 N/mm2 Circumferential Stress 27.5 N/mm2 Minimum Thickness Of Tube Wall, mm Minimum Thickness Of Head And Closure, 5.91 8.80 Minimum Thickness Of The Channel Cover,mm 33.0 Design Load, kN Diameter pipe for isobutene inlet and outlet, mm Diameter pipe for steam inlet and outlet, mm Vessel diameter, m Types of baffles Number of baffle segmental, Nb 56.38 100 500 0.9 transverse 8 REFERENCES D. Brian Spalding, J.Taborek, “Heat Exchanger Design Handbook, Volume 1 - Heat Exchanger Theory”, Hemisphere Publishing Corporation, Washington, New York, London, 1983. 283
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR D. Brian Spalding, J.Taborek, “Heat Exchanger Design Handbook, Volume 2 - Fluid Mechanics and Heat Transfer”, Hemisphere Publishing Corporation, Washington, New York, London, 1983. J. M. Chenoweth, D. Chisholm, R. C. Cowie, D. Harris, A. Illingworth, J. F. Lancaster, M. Morris, I. Murray, C. North, C. Ruiz, E. A. D. Sauders, K. V. Shipes, J. Dennis Usher, R. L. Webb, “Heat Exchanger Design Handbook, Volume 4 Mechanical Design of Heat Exchangers”, Hemisphere Publishing Corporation 1983, Washington, New York, London, 1983. D. K. Edwards, P. E. Liley, R. N. Maddox, Robert Matavosian, S. F. Pugh, M. Schunk, K. Schwier, Z. P. Shulman, “Heat Exchanger Design Handbook, Volume 5 - Physical Properties”, Hemisphere Publishing Corporation 1983, Washington, New York, London, 1983. E. A. D. Saunders, B. Sc. C. Eng., M. I. Mech. E. “Heat Exchangers, Selection, Design and Construction”, Longman Scientific and Technical, 1998. Yokell, Stanley, “A working Guide to Shell and Tube Heat Exchangers”, McGraw-Hill Publishing Company, 1990. Sadik Kakac, Hongtan Cin, “ Heat Exchangers, Selection, Rating, and Thermal Design”, CRC Press, Boca Raton, Boston London New York, Washington, D.C, 1998. Gupta, J. P., “Working With Heat Exchangers: question and answers”, Hemisphere Publishing Corporation, A member of the Taylor and Francis Group, 1990. Warren D. Seider, J.D. Seider, Daniel R. Lewin, “Process Design Principles, Synthesis, Analysis and Evaluation”, 1997. Stanley M. Wales, “Chemical Process Equipment, Selection and Design” , Butterworths Series in Chemical Engineering, 1990. Frank P. Incropera, David P. Dewitt, “Fundamentals of Heat and mass Transfer”, 5th Edition, John Wiley & Sons, Inc, 2002. Holman, J.P, “Heat Transfer”, 7th Edition, McGraw-Hill, Inc, 1992. Kern. D.Q, “Process Heat Transfer”, International Editions, McGraw-Hill, Inc, 1965. Perry R.H and Green, Don, “Perry’s Chemical Engineer’s Handbook”, 7th Edition, McGraw-Hill Book Company, Singapore, 1984. Bhattacharya, B.B, “Introduction to Chemical Equipment Design, Mechanical Aspects”, Indian Institute of Technology, 1976. 284
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Holman, J.P. “Heat Transfer”, 7th Edition, McGraw-Hill, Inc, 1992. Kern. D. Q “Process Heat Transfer”, International Editions, McGraw-Hill, Inc, 1965. Perry R.H and Green, Don, “Perry’s Chemical Engineer’s Handbook”, 7th Edition, McGraw-Hill Book Company, Singapore, 1984. Sinnott, R. K., Coulson & Richardson, “Chemical Engineering Volume 6, Chemical Engineering Design”, Butterworth Heinemann, 1999. Carl R. Branon, “Rules Of Thumb For Chemical Engineers”, Gulf Publishing Company, 1994. Perry R.H and Green, Don, “Perry’s Chemical Engineer’s Handbook”, 7th Edition, McGraw-Hill Book Company, Singapore, 1984. Sinnott, R. K., Coulson & Richardson, “Chemical Engineering Volume 6, Chemical Engineering Design”, Butterworth Heinemann, 1999. Peters, max Stone, “Plant Design and Economics for Chemical Engineers”, 2nd Edition, McGraw-Hill Chemical Engineering Series, 1968. CHAPTER 2 285
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR PROCESS CONTROL AND INSTRUMENTATION 2.1 INTRODUCTION All processes are subject to disturbances that tend to change operating conditions, compositions and physical properties of the streams. In order to minimize those ill effects that could result from such disturbances, chemical plants are implemented with substantial amounts of instrumentation and automatic control equipment. In critical cases and in especially large plants, moreover, the instrumentation is computer monitors for convenient, safety and optimization. A chemical plant is an arrangement of processing unit. The plant overall objective is to convert the raw materials into desired product using available sources of energy in the most economical way. All operating unit should be monitored. Methods of limiting hazard levels by control features include sensoring control on limits and various aspects of sequential and continuous monitoring. In control situations, the demand for speed of response may not be realizable with an overly elaborate mathematical system. Moreover, in practice, not all disturbances are measurable and the process characteristics are not known exactly. Accordingly, feedforward control is supplemented in most instances with feedback. In a well-designed system, typically, 90% of the corrective action is provided by feed forward and 10% by feedback with the result that the integrated error is reduces by a factor 10%. The main types of instrument used for chemical process plants are flow controller, temperature controller, pressure controller and level controller. 2.2 OBJECTIVES OF CONTROLL The most important objectives of the designer when specifying control and instrumentation schemes are: 1. Safe Plant Operation 286
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR • To keep the process variables within known safety operating limits and within allowable limits. • To detect dangerous situations as they develop and to provide alarms and automatic shut down system. • To provide interlocks and alarms to prevent unsafe operating procedures. 2. Production Specification • To achieve the design product output • To produce the desired quality of final product • To keep the product composition within the specified quality standards. 3. Economics • To operate at the lowest production cost, commensurate with the other objectives. • The operation of the plant must conform to the market condition, which is availability of raw materials and demand of the final product. 4. Environmental Regulations • Variable controlled must not exceed the allowable limits set by various federal and state laws. 5. Operational Constraint • Various type of equipments used in chemical plant have constrains inherent to their operation. Such constraints should be satisfied throughout the operation of plant. • Control systems are needed to satisfy all these operational constrains. In a typical chemical processing plant these objectives are achieve by combination of automatic control, manual monitoring and laboratory analysis. 2.3 CONTROL SYSTEM DESIGN SHEET 2.3.1 Heat Exchanger (E-100) 287
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Figure 2.1: Control Scheme for the Heat Exchanger Table 2.1: Parameter at Heat Exchanger Intention: To Heat Up the reactant Before Entering Reactor Objective : To heat up the reactants to 250 oC Objective Measurable Disturbances Action Variable 1. To control Temperature at Change in Control temperature temperature of outlet stream flow rate of the heating by V3 at outlet stream S4 feed steam inlet S3 2.3.2 Set Point E-100 Temperature 250oC Catalytic Cracking Fluidized Bed Reactor (op-100) 288
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Figure 2.2: Control Scheme for Catalytic Cracking Fluidized Bed Reactor Table 2.2: Parameter at Catalytic Cracking Fluidized Bed Reactor Intention: To Separate Vapor and Liquid from Stream Leaving Heat Exchanger Set Point Objective Measurable Disturbances Action 1. To control flow inside phase reactor 2. To control solid flow to relate speed and flow rate 3. To control pressure between reactor and regenerator 4. To control temperature in reactor 2.3.3 Variable Flow of gas in phase to reactor Solid in and out in the reactor and regenerator flow rate of feed into reactor and regenerator Temperature in reactor and regenerator Change in flow of gas in phase of reactor Change of solid flow rate moving to reactor and regenerator Change of feed flow rate Control flowrate of the Input stream S4 by controlling V3 Control solid in and solid out in the reactor and regenerator Control pressure by opening or closing valve by adjusting V5 Stream S4 Change of temperature In reactor and regenerator Control temperature by opening or closing valve at the air feed V4 and product V6 180oC 95679.8kg 2.89 bar Control at Compressor (C-101) S7 289
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR S8 Figure 2.3: Control Scheme for the Compressor Table 2.3: Parameter at Compressor Objective To maintain pressure inside compressor 2.3.4 Intention: To maintain the pressure inside the compressor Objective : To keep pressure maintain at bar Measurable Disturbances Action Variable Pressure Power or duty Control pressure inside of the by adjusting V8 at compressor compressor steam inlet S7 Set Point C-101 pressure bar Control at Condenser 290
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Figure 2.4: Control Scheme for the Condenser Table 2.4: Parameter at Condenser Intention: To maintain the pressure inside the compressor Objective : To keep pressure maintain at bar Objective Measurable Disturbances Action Variable 1. To control Temperature at Change in Control temperature temperature of outlet stream flow rate of the heating by V9 at outlet stream S9 feed steam inlet S8 Set Point E-100 Temperature 50oC 2.3.5 Separator (V-100) 291
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Figure 2.5: Control Scheme for the Separator Table 2.5: Parameter at Separator Intention: To Separate Vapor and Liquid from Stream Leaving Heat Exchanger Objective Measurable Disturbances Action Set Point Variable 1. To control level Level of liquid Change in level Control level by Stream inside phase in phase of liquid in phase V10 at inlet stream S9 of separator separator separator S9 liquid height 1. To control Maintain Change in Control pressure by Pressure pressure pressure pressure opening and closing 0.5 bar phase separator in phase of liquid in phase valve by V28 at separator separator stream S10 1. To control Flow rate at Change in the Control Flow at the Flow into Flow rate the bottom of flowrate of bottom by V27 at The feed inside phase the separator the separator stream S11 At stream separator S11 292
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 2.3.6 Fixed Bed Reactor (R-101) V29 V13 Figure 2.6: Control Scheme for the Fixed Bed Reactor Table 2.6: Parameter at Fixed Bed Reactor Objective Intention: To React Isobutene with Methanol to Produce MTBE Measurable Disturbances Action Set Point To regulate Variable Cooling Reactant feed Control temperature Set the reactor water make temperature and by V13 temperature temperature To maintain up rate Pressure in composition Pressure feed to Control the pressure at 53.3 oC Pressure at constant the fed of the reactor in the reactor by 1 bar pressure at the stream S15 control of V29 feed stream 2.3.7 Distillation Column (T-101) 293
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Figure 2.7: Control Scheme for the MTBE Distillation Column Table 2.7: Parameter at MTBE Distillation Column Intention: To Separate MTBE from Mixture Leaving Reactor Objective Measurable Disturbances Action Variable 1. To control level Level of liquid Change of level Control level by inside column in column of column Adjusting V17 valve at raffinate outlet Stream S19 2. To control Temperature Change of Control temperature by temperature inside column temperature Control V16 inside column in column 3. To control Level in drum Change of level Control level by V15 level in drum in drum to maintain the Product output 2.3.8 Set Point Stream S19 at 15251.9kg/hr 61.2oC Stream S17 at 38747.97kg/hr Liquid-Liquid Extraction Column (T-100) 294
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Figure 2.8: Control Scheme for the Liquid-liquid Extraction Column Table 2.8: Parameter at Liquid-liquid Extraction Column Objective To control flow at stream S20 To control flow at Intention: To Extract Methanol and Water from Hydrocarbon Measurable Disturbances Action Variable flow of liquid Change of level Control flow by adjust in column of column Valve V19 at bottom outlet stream Flow of liquid in Change of flow of Control at V20 to keep stream S21 To control level at the column Level of raffinate Set Point Stream S20 at 40.32kg/hr Flow inlet at liquid extraction Change of level in the flow inlet maintain Maintain the level by stream S21 Level output at going out of the the column control V21 at stream raffinate section Product of S24 To control the density column Density level Change of the S24 The bottom stream S24 Interfacial level intermediate between change between removed by control at bottom methanol and water water and between two V22 product at methanol phase 2.3.9 liquid interfacial of level stream S26 Distillation Column (T-102) 295
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Figure 2.9: Control Scheme for the Distillation Column Table 2.9: Parameter at Distillation Column Objective 1. To control level inside column 2. To control temperature inside column 3. To control level in drum Intention: To Separate Methanol and water Measurable Disturbances Action Variable Level of liquid Change of level Control level by in column of column opening and closing valve V25 at bottom outlet stream Temperature Change of Control temperature by inside column temperature opening or closing in column Valve 24 at top outlet stream Level in drum Change of level Control level by V23 in drum opening or closing valve at reflux stream Set Point Stream S28 : at 63.4453kg/hr 62.17oC Stream S27 296
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 2.3.10 Mixer (MIX-100) Figure 2.10: Control Scheme for the Mixer Table 2.10: Parameter at Mixer Intention: To Mix Methanol from Recycle and Make Up Methanol Measurable Disturbances Action Set Point Variable 1. To control the Flowrate of Change of Control flowrate M - 101 flowrate the reactant flowrate to the bypass valve Stream S14 reactor V12 at 2.88 m3/hr Objective 297
  • PRODUCTION OF 300,000 METRIC TON MTBE PER YEAR 2.3.11 Expander (EX-100) Figure 2.11: Control Scheme for the Expander Table 2.11: Parameter for Expander Intention: To Expand the Pressure Leaving the Reactor Measurable Disturbances Action Variable 1. To expand the Pressure Change of Control pressure by pressure inside the pressure adjusting valve V14 expander Objective Set Point Pressure 0.45 38
  • PRODUCTION OF 300,000 METRIC TON MTBE PER YEAR Figure 2.13 : PFD Diagram Before Control 39
  • PRODUCTION OF 300,000 METRIC TON MTBE PER YEAR Legend TC - Process Flow PC - Pressure Control Control Flow FC - Flow Control LC ILC - Temperature Control TI - Temperature Indicator DPC - - Interfacial Level Control Level control Differential Pressure Control Figure 2.13 : Process Control P and ID Diagram 40
  • PRODUCTION OF 300,000 METRIC TON MTBE PER YEAR 41
  • PRODUCTION OF 300,000 METRIC TON MTBE PER YEAR REFERENCES Luyben, W. l., (1990), Process Modelling simulation and Control for Chemical Engineers, 2nd Edition, McGraw-Hill Chemical Engineering Series Ogunnaike, B. A. and Ray, W. H. (1994), Process Dynamics, Modeling and Control, New York, Pxford. R.K.Sinnott, 1999.Chemical Engineering Design, Coulson & Richardson Chemical Engineering .3rd Edition. Volume 6 .Britain. Butterworth Heinemann J.R Backhurst & J.H Harker.1987.Chemical Engineering Design, Coulson & Richardson Chemical Engineering .3rd Edition. Volume 2 .United Kingdom. Pergamon Press. Stanley M. Walas. 1988. Chemical Process Equipment Selection and Design. United State of America. Butterworth’s Series in Chemical Engineering. Chemical Engineering Progress, February 2001, American Institute of Chemical Engineering. 42
  • PRODUCTION OF 300,000 METRIC TON MTBE PER YEAR CHAPTER 3 SAFETY CONSIDERATION 3.1 INTRODUCTION Any organization has a legal and moral obligation to safe guard the health and welfare of its employees and the public. Safety is also good business: the good management practices needed to ensure safe operation would also ensure efficient operation. All manufacturing processes there are additional, special, hazard associated with the chemical used and the process condition. The designer must be aware of these hazards and ensure through the application of sound engineering practices that the risks are reduced to acceptable levels. Safety and loss prevention in process design can be considered under the following broad headings :( Coulson and Richardson’s Volume 6) 1. Identification and assessment of the hazards 2. Control of the hazards; for example by containment of flammable and toxic materials 3. Control the process. Prevention of hazardous deviation in the process variables, (pressure, temperature, flow) by provision of automatic control system interlocks, alarms, trips, together with good operating practices and management. 4. Limitation of the loss. The damage and injury caused if an incident occurs, pressure relief, plant layout, provision of fire-fighting equipment. In Malaysia, The Occupational Safety and Health Act, 1994 is a tool which provided a new legal and administrative as a driving force to promote, encourage and stimulate the high quality standards of health and safety at work place. Both parties such as employers and employees must give their support and cooperate to 43
  • PRODUCTION OF 300,000 METRIC TON MTBE PER YEAR comply the law and not misuse safety in order to increasing the promotion of safety awareness and effective safety organization and performance in companies. 3.2 HAZARD AND OPERABILITY STUDY HAZOP stands for “hazard and operability studies.” This is asset of formal hazard identification and elimination procedures designed to identify hazard to people, process plants and the environment. The techniques aim to stimulate in a systematic way the imagination of designers and people who operate plants or equipment so they can identify potential hazard. In effect, HAZOP studies make the assumption that hazard or operating problem can arise when there is a deviation from the design or operating intention. Corrective actions can then be made before a real accident occurs. The primary goal in performing a HAZOP study is to identify, not analyse or quantify, the hazard process. The end product of a study is a list of concerns and recommendation for prevention of the problem, not an analysis of the occurrence, frequency, overall effects, and the definite solution. If HAZOP is started too late in a project, it can lose effectiveness because: 1. There may be a tendency not to challenge an already existing design. 2. Changes may come too late, possibly requiring redesign of the process. 3. There may be loss of operability and design decision data used to generate the design. HAZOP is a formal procedure that offers a great potential to improve the safety, reliability and operability of process plants by recognizing and eliminating potential problems at the design stage. It is not limited to the design stage, however. It can be applied anywhere that a design intention. (Perry’s Handbook, 1998) When using the operability study technique to vet a process design, the action to be taken to deal with a potential hazard will often be modification to the control system and instrumentation, the inclusion of additional alarms, trips or interlock. If major hazard are identified, major design changes may be necessary, alternatives processes, material and equipment. In order to have a safe process successfully producing to specification to the required product, a sound control system is necessary but not sufficient. (Coulson & Richardson’s, 1999). 44
  • PRODUCTION OF 300,000 METRIC TON MTBE PER YEAR The objectives of HAZOP study are: 1. To identify areas of the design that may posses a significant hazard potential 2. To identify and study features of the design that influences the probability of a hazardous incident occurring. 3. To familiarize the study team with the design information available. 4. To ensure that a systematic study is made of the areas of significant hazard potential. 5. To identify design information not currently available to the team. 6. To provide a mechanism for feedback to the client of the study team’s detailed comments. (Sydney Lipton and Jeremiah Lynch, 1994) The advantages of HAZOP study to the design application: • Early identification of problems areas when conceptual design stage. • Identifies need for emergency procedures to mitigate. • Provide essential information for safety case, such as on the hazards identified and effectiveness of safety systems. • Through examination of hazard and operability problems when applied at detailed stage. • Meets legislative requirements. • Identifies need for commissioning, operating and maintenance procedures for safe and reliable operations. 45
  • PRODUCTION OF 300,000 METRIC TON MTBE PER YEAR Table 3.1: A HAZOP study contains the following important features: Features : Intention Guide words Deviations Causes Consequences Action Meaning : Defines how the part or process is expected to operate. Simple word used to qualify the intention in order to guide and stimulate creative thinking. Departures from the intention discovered by systematic application of guide words. Reasons that deviations might occur. Results of deviations if they occur. Prevention, mitigation and control - Prevent causes. - Mitigate the consequences. - Control action such as provide alarms to indicate things getting out of control: define control actions to get back into control. The MTBE Plant HAZOP Study is included at Appendix: Safety. 3.3 PLANT START UP AND SHUT DOWN PROCEDURE Safe procedures must be well known for the start up and shut down of plant and deviations from normal operating conditions. Whenever process conditions are changed, opportunities are presented for hazardous situations to arise. Building up the process consistency may reduce the investigating breakdown and malfunction, availability, the design cycle, operability, flexibility including blending and recycling experience and known how personnel. The start-up and shutdown of the plant must proceed safely and easily, yet be flexible enough to be carried out in several ways. The operating limits of the plant must not exceed and dangerous mixtures must not be formed because of abnormal states of concentration, temperature, phase, reactant, catalyst and products. During start-up, the catalyst in the reactor should be activated and sufficiently warm for reaction to begin when the flow of reactant is started. Contaminants often enter the system at this stage. Materials are added by operations such as purging, drying and flushing. Water and other materials may 46
  • PRODUCTION OF 300,000 METRIC TON MTBE PER YEAR condense in unplanned location causing process levels to get out of control and other problems. The ignition of fuel to heat the high temperature fluid during start-up must be designed to accomplish this safely Some typical errors that could occur during start-up of the plant include : 1. Wrong routing, involving failure to ensure that correct valves are closed. This is especially crucial in the adsorption section where three different processes are occurring at any one time. 2. Drain valves are left open resulting in loss of material and possibly endangering the lives of workers. 3. Valves left closed resulting in over pressure in the vessel. 4. Failure to complete purging cycle before admission of fuel air mixture. 5. Backflow of material from high pressure to low pressure system. 6. Setting of wrong valves for operating parameters such as jacket temperature in the reactor and reflux in the distillation column. 3.3.1 Normal Start up and Shut down the Plant The study of the plant start up and shut down must include investigation of the operating limits, transient operating conditions, process dynamics, contamination and added material, emissions, hot standby and emergency shut down with plant protection control systems and alarms. 3.3.1.1 Operating Limits The operating limits of the plant are imposing by mechanical, electrical, civil and process design. Where necessary, it has to be introduce additional equipment, sampling points, instrumentation and lines, and identify their use on the engineering line diagram, 3.3.1.2 Transient Operating and Process Dynamic The transient operating conditions must be studied to safe time and operating cast. The process dynamics that to be investigated includes excessive heat transfer 47
  • PRODUCTION OF 300,000 METRIC TON MTBE PER YEAR when more or less floe in either energy exchanging streams through activations and warming of catalyst when the flow of reactant starts to entrance of contamination and others 3.3.1.3 Added Materials Materials are added by operations may not be tolerated in part of the system or clean material may be needed for the start up of the plant. Residues or unwanted products such as out of specification may be discharged or hold in tank for further treatment. 3.3.1.4 Hot Standby Time is save during restart up if plant are kept partially working such as when other unit operation are ceased to function temporarily, the converter can be left in hot standby conditions. 3.3.1.5 Emergency Shut Down Special plant protection known as process trip system or emergency shut down system is design to affect the emergency shut down through the push button by operator or from automatic activation of a relay when necessary. The trip systems should be reliable and operate when required to avoid a nuisance shut down of plant. 3.3.2 Start up and Shut down Procedure for the Main Equipment 3.3.2.1 Reactor 1. It is recommended that the internal reactor vessel measurements (ID, Bed Depth – not the overall vessel height, etc.) be verified, so that product loading is consistent with the "Estimated Performance Sheet" (EPS). 2. Prior to any loading, it is necessary to make an internal and external inspection of the reactor vessel. In other words, there should not be any pipes or hollow devices in the vessel, which could allow the gas to travel without contacting the product. 48
  • PRODUCTION OF 300,000 METRIC TON MTBE PER YEAR 3. There are two vessel types of bed supports that can be used; (1) has a support grid permanently installed about 2 inches below the throat of the lower manway; or (2) uses a level bed of washed gravel, ceramic balls, or pawl rings. The bed support must be leveled. 4. Close and secure the bottom manway. 5. Through the top manway, load the remaining feed to level as stated in the EPS. During the latter stages of loading level off the cone of the filled product bed and continue loading until finished. 6. Close and secure the top manway. Upon operational start-up, record the required measurements – temperature, pressure, and flow rate - from each bed (if applicable). This data should be kept on some routine basis (daily, weekly bi-weekly, etc.) so that any problems that might develop can be identified and corrected. 3.3.2.2 Distillation Column Start-Up Procedure 1. Turn the switch box indicator to Distillation Control setting. 2. Switch the column power source lever to the "on" position. Turn the Reboiler Heater Control knob clockwise. This prevents over heating of the reboiler. 3. Turn on the cold water supply ( CWS )valve until the computer stops telling the user to increase the volume of the CWS valve. 4. Adjust the Reflux Control to the desired setting. 5. Assure all computer settings are as desired. 6. Allow the tray temperatures to reach a steady-state value. 7. Turn on the feed and reboiler pumps as applicable. The pump settings can be adjusted on the computer. Caution: DO NOT ALLOW THE WATER LEVEL TO FALL BELOW THE CALROD HEATERS. 49
  • PRODUCTION OF 300,000 METRIC TON MTBE PER YEAR This will result in damage to the heaters. If the heaters are exposed turn off the column, this allows the vapor in the column to condense and return to the reboiler. If the liquid level is still below the heaters, more liquid must be added to the reboiler. Shut-Down Procedure 1. Turn the Reboiler Heater Control knob to zero. 2. Turn off the pumps (feed and reboiler). 3. Turn off the CWS valve when the temperature of the distillate is below the boiling point of the light component of the mixture. 4. Press the stop button. 5. Shut off the computer, by selecting the "Shut-down" option from the Special menu. 3.3.2.3 Liquid-Liquid Extraction Column Start Up Procedure 1. Check to see that all the drainage valves are closed. 2. Check to be sure the top water vent valve is open. 3. When the liquid level in the column reaches the top right nozzle(water in nozzle), turn the water flowrate down to the desired setpoint. Turn on and set the feed flowrate to the desired setpoint by adjusting the pump speed, and close the top water vent. 4. Allow the interface to form between the top mesh and the top left nozzle. 5. Small adjustments should be made in order to keep the interface constant. Shut down procedure 1. Turn off all inlet flowrates on the right control panel. 2. Shut off the stirrer on the right control panel. 50
  • PRODUCTION OF 300,000 METRIC TON MTBE PER YEAR 3. Open the top water in vent valve. 4. Open the bottom centre black valve to drain the column. 3.3.2.4 Heat Exchanger Start up Procedure When putting a heat exchanger in operation, open the vent connections and slowly start to circulate the cold medium only. Be sure that the entire cold side of the exchanger is completely flooded before closing its vents. The hot medium should then be gradually introduced until all passages are filled with fluid. Then close the hot side vents and slowly bring the unit up to its operating temperature. Shut down Procedure When heat exchanger is required to be shutdown, the hot fluid should be turned off first. If it is necessary to stop the circulation of the cold fluid, the hot medium should also be stopped by by-passing the heat exchanger. 3.4 EMERGENCY RESPONSE PLAN (ERP) It is expected that every person who working in this plant will act responsibly in any Department of Emergency. ERP procedures were state in Appendix: Safety. In most cases, the observer of an emergency is faced with decision to leave the scene to summon help or stay and provide help. The basic rule is as follows. “Unless we are sure that we are not putting ourselves in any danger and we know we can make a difference, summon help. 3.4.1 Emergency Response Procedures General Procedures 51
  • PRODUCTION OF 300,000 METRIC TON MTBE PER YEAR When alarm system is activated whether by break glass or by smoke detector, the alarm that is siren sound will be triggered throughout plant. The following general procedures should be followed if there is no immediate emergency in your area. • Do not panic and stay alert: Stay calm and be alert and ready to response to any emergency according to the Plant Emergency Organization Programmed. The shift manager should go to the security guard to identify the location of the alarm. • Access the situation around your area : Look around and ensure that your immediate area is not in danger or affected by the emergency. Stop all contractors from working immediately. • Wait for instruction from Supervisor/Shift Manager : Do no evacuate from one’s post unless one is immediate danger or when instructed by one’s supervisor or the shift manager. • Avoid using the telephone : Do not use the telephone unless it is absolutely necessary, as the telephone lines must be reserved for calling emergency services. All incidents resulting in injuries, property damage and/ or productions loss shall be investigated and reported for within 24 hours. Corrective action to prevent the recurrence of the incident shall be initiated 48 hours. 3.4.2 • Evacuation Procedures: Exit building via the stairways : It takes time to the person familiarize with evacuation routes in advance. The maps showing the location of all emergency exits and extinguishers are posted on all floors. • Assist the injured when possible : Do not move the seriously injured unless there is danger of further injury. If it is necessary to leave someone in the building, try to leave him in a relatively secure place (example, the stairwell is one of the safer places to be in fire). After someone has been evacuated the building, find the proper officials and report the location and condition of persons who need assistance. • Designed persons are responsible for clearing the production floors and offices : 52
  • PRODUCTION OF 300,000 METRIC TON MTBE PER YEAR Efforts to clear the production floor and offices should be limited to 5 minutes. As the areas are cleared, all doors should be closed. • Once outside the building : Keep at least 50 feet away from the building to avoid danger from falling glass, example “Evacuate to the Emergency Assembly Area “. • Do not re – enter the building until safety officer or fire personnel have been determined that it is safe. 3.4.3 • Fires: If the fire alarm sounds or a fire broke out in the plant, turn off any electrical equipment that been operating and evacuate the building immediately. Close all doors to help prevent fires from spreading. Exit via stairwells. • Call 994 to give location and extent of fire and notify the management to report the fire : State if there are any special circumstances, such as the presence of dangerous chemicals. • Don’t attempt to fight a fire unless we have been trained in fire extinguisher use and the fire is very small : When fighting a fire, always position ourselves between the exit and the fire to ensure an escape route. IF THE FIRE CANNOT BE CONTAINED, GET OUT QUICKLY! 3.4.4 • Explosion, Line Rupture or Serious Leak Do the following if possible. 1. Turn the “Emergency Stop” switch to “Off” position 2. Isolate the effected area of the limit. Block in high-pressure source as required accomplishing this. 3. Complete the shut down 3.4.5 • Other Emergencies : Injuries : 53
  • PRODUCTION OF 300,000 METRIC TON MTBE PER YEAR For life – threatening emergencies, CALL 991 for medical aid and for transportation to hospital and at same time notify the management as listed on the Notification Lists. For less serious injuries or illness, first aid can be obtained at the nearest clinic. Report all injuries to the management. • Equipment failures : Any equipment failures, which may harm or injured the workers, should be reported to the Production Supervisors or the management for further action to be taken. 3.5 PLANT LAYOUT The process units and ancillary buildings should be laid out to give the most economical flow of material and personnel around the site. Hazardous process must be located at a safe distance from other buildings. Consideration must be also being given to the future expansion of the site. The ancillary buildings and services required on site, in addition to the main processing units (building) will include: (Coulson and Richardson’s 1999) 1. Storage for raw materials and products; tank farms and warehouses 2. Maintenance workshop 3. Stores, for maintenance and operating supplies 4. Laboratories for process control 5. Fire stations and other emergency services 6. Utilities: steam boilers, compressed air, power generation, refrigeration, transformer stations. 7. Effluent disposal plant 8. Offices for general administration 9. Canteens and other amenity buildings, such as medical centres 10. Car parks Normally, the process units will be sited first and arranged to give a smooth flow of materials through various processing steps, from raw material to final product storage. It is normally spaced at least 30 apart and for hazardous processes, the greater spacing may be needed. Then, the principal ancillary buildings to be located and arranged in order to minimize the time spent by the personnel in travelling between the buildings. The administration offices and 54
  • PRODUCTION OF 300,000 METRIC TON MTBE PER YEAR laboratory should be located well away from potentially hazardous processes since a many people be in here. The control rooms normally are located adjacent to the process units but if it with the potentially hazardous processes has to be sited at safer distance. Besides that, the layout of the plant roads, pipe alleys and drains also must be considered to locate the main process units. Easy access roads will be needed to each building for construction and for operation and maintenance. The utilities buildings should be sited to give most economical run of pipes to and from the process units. Finally, the main storage areas should be placed between loading and unloading facilities and the process units they serve. Storage tanks containing hazardous materials should be sited at least 70 m (200 ft) from the site boundary. There are 7 principal factors to be considered : 1. Economic considerations: construction and operating costs. 2. The process requirements. 3. Convenience of operation. 4. Convenience of maintenance. 5. Safety. 6. Future expansion. 7. Modular construction. The MTBE site layout have shown in Figure 3.1. 55
  • PRODUCTION OF 300,000 METRIC TON MTBE PER YEAR Figure 3.1 Methyl tert-Butyl Ether (MTBE) Plan Layout U 56
  • PRODUCTION OF 300,000 METRIC TON MTBE PER YEAR Figure 3.2: Methyl tert-Butyl Ether (MTBE) Plant Evacuation Routes U Legand Evacuation Routes 57
  • PRODUCTION OF 300,000 METRIC TON MTBE PER YEAR Figure 3.3 PID before HAZOP 58
  • PRODUCTION OF 300,000 METRIC TON MTBE PER YEAR Figure 3.4 PID after HAZOP 59
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR REFERENCES Clarles A.Wentz, 1998. Safety, Health and Environmental Protection. United State of America:McGraw-Hill. R.K.Sinnot, 1999. Chemical Engineering Design. Coulson & Richardson’s Chemical Engineering 3rd Edition. Volume 6. Britain; Butterworth Heinemann. Robert H. Perry, Don W. Green, 1998 Perry’s Chemical Engineer’s Handbook, Seventh Edition, McGraw-Hill. http://www.sulfatreat.com/Documents/HTML/St/startup.html http://www.amberjet.com/IP/start_up.htm http://www.sulfatreat.com/Documents/PDF/SulfaTreat/ST-Start_Up_Procedure.pdf http://chem.engr.utc.edu/Webres/435F/Proc.htm http://www.eng.buffalo.edu/Courses/ce428/Distillation/procedure.htm http://users.rowan.edu/~savelski/uol/liqliq.html http://pharmaflo.com/heatexch/ 60
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR CHAPTER 4 ECONOMIC EVALUATION INTRODUCTION Economic evaluation is very important for a proposed plant. We have to be able to estimate and decide between alternative designs and for project evaluation. Chemical plants are built to make a profit an estimate of the investment required and the cost of production are needed before the profitability of a project can be assessed. The total investment needed for a project is the sum of the fixed and working capital. Fixed capital is the total cost of the plant ready for start up. It is the cost paid to the contractors. Working capital is the additional investment needed, over and above the fixed capital, to start the plant up and operate it to the point when income is earned. Most of the working capital is recovered at the end of the project. 61
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 4.1.1 The Specification Of Plant In this chapter, the costing of equipment which has been designed will be estimated and the feasibility of MTBE production will be evaluated by profitability analysis to make sure the project is economically attractive. There are some general assumptions to this chapter; i. The plant life span is fifteen years. ii. The currency exchange rate of US dollar to Ringgit Malaysia is fixed at 3.8 as fixed by Malaysian Government. iii. The price of raw materials, catalyst and product is fixed for the whole period of operation. Price of raw material : Isobutane - RM 0.8094 / kg : Methanol - RM 0.988 / kg Price of product : MTBE - RM 1.320 / kg : TBA - RM 1.035 / kg : DME - RM 0.655 / kg 62
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 4.1.2 Revenue From Sales i. MTBE = 37878.76 kg/h = 300000 tonne year Price: RM 1.320/kg = 37878 .76 kg 24 hr 365 day RM 1.320 × × × ×0.90 hr day year kg = ii. TBA = RM 394199710/yr 639.663 kg/h Price: RM 1.035/kg = 639 .663 kg 24 hr 365 day RM 1.035 × × × ×0.90 hr day year kg = iii. DME = RM 5219612/yr 1210.9868 kg/h Price: RM 0.655/kg = 1210 .9868 kg 24 hr 365 day RM 0.655 × × × ×0.90 hr day year kg = iv. Isobutane = RM 6253560/yr 13718.4558 kg/h Price: RM 0.8094/kg = 13718 .4558 kg 24 hr 365 day RM 0.8094 × × × ×0.90 hr day year kg = RM 87541714/yr v. n-butane = 157.412 kg/h Price: RM 0.35/kg = = Total revenue 157 .412 kg 24 hr 365 day RM 0.35 × × × ×0.90 hr day year kg RM 434363/yr = RM 493648959/yr 63
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 4.2 COST ESTIMATION 4.2.1 Capital cost estimation Capital cost estimates are essentially “paper and pencil” studies. The cost of making an estimate indicates the personnel hours required in order to complete the estimate. The capital needed to supply the necessary manufacturing and plant facilities is called the fixed capital investment (FC), while the additional investment needed for the plant operation (for plant start-up and operation to the point when income is earned) form the working capital (WC). Capital cost estimates for chemical process plants are often based on an estimate of the purchase cost of the major equipment items required for the process, the other costs being estimated as factors of the equipment cost. The accuracy of this type of estimate will depend on what stage the design has reached at the time estimate is made and on the reliability of the data available on equipment cost. The cost of the purchased equipment is used as the basis of the factorial method of cost estimation and must be determined as accurately as possible. It should preferably be based on recent prices paid for similar equipment. Calculation of total module cost and gross roots cost (based on table 4.2) CTC = CFC + CWC + CL Where, CTC = total capital cost CFC = fixed capital cost CWC = working capital cost CL = cost of land & other non-depreciable costs FP = Pressure factor to account for high pressure FM = Material factor to account for material of constructions CP = Purchase cost for base condition FBM = Bare module cost factor 64
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR CBM = Bare module equipment cost for base condition C°BM = Bare module equipment cost for actual condition Total Module Cost, CTM 1.18 (∑C°BM ) = 1.18 (3223841) = RM 3804132 x 3.8 = RM 14455703 = CTM + 0.35 ( ∑ CBM) = = Grass Root Cost, CGR = 14455703 + 0.35 (12659343) x 3.8 RM 31292629 Since, Grass Root Cost (CGR) is: CGR = CFC + CL Area for 1 lot of land = 200000 m2 The price of land is RM 60 per m2 CL = RM 12000000 CFC = CGR - CL = RM 31292629 - RM 12000000 = RM 19292629 Working capital is the additional investment needed over and above the fixed capital to start the plant up and operate it to the point when income is earned. Working capital cost = 5% of fixed capital costs CWC = 5% fixed capital cost (CFC) (Coulson & Richardson, = RM 964631 1990) Thus, Total capital cost (CTC) = CFC + CL + CWC = RM 19292629+ RM 12000000+ RM 964631 = RM 32257260 65
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 4.2.2 Manufacturing Cost Estimation The cost of associated with the day to day operation of a chemical plant must be estimated before the economic feasibility of a proposed process can be assessed. The equation below is used to evaluate the cost of manufacture: Cost of manufacture (COM) = Direct Manufacturing Cost (DMC) + Fixed Manufacturing Cost (FMC) + General Expenses (GE) COM = 0.304FCI + 2.73COL + 1.23(CUT + CWT + CRM) The cost of manufacturing (COM) can be determined when the following costs are known or can be estimated: 1. Fixed Capital Investment (FCI): (CTM or CGR) 2. Cost of Operating Labor (COL) 3. Cost of Utilities (CUT) 4. Cost of Waste Treatment (CWT) 5. Cost of Raw Material (CRM) 4.2.2.1 Cost of Operating Labor (COL) Table 4.1 Labor Cost No of Equipment type Heat exchangers Reactor Vessels Pumps Compressor Operators per shift per Operator per equipment 6 2 1 5 2 equipment 0.1 0.5 0.0 0.0 0.15 shift 0.6 1.0 0.0 0.0 0.3 66
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Towers Waste Treatment 3 1 0.35 0.5 1.05 0.5 3.45 Since, a single operators works on the average 48 weeks (3 weeks time off for vacation and sick leave) a year, five 8-hour shifts a week. = 48 week 5 shift × Year week = 1 operator 240 shift Year Working days for MTBE plant is 7920 hour = 330 days = 330 days 3 operating × Year days = Operating shift per Year 990 operating shift Year Working days for MTBE plant is 7920 hour So, the number operator needed = = 990 operating shift Year 240 shift Year 4.125 operators Thus, Operating Labor = 4.125 operators x 3.45 operator per shift = 14.23 operator = 15 operator A mechanical engineers maximum wages per year (MIDA 2002) RM 60,000.00 Thus, Labor Cost (1996) = 15 x RM 60,000.00 = RM 900,000.00 67
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 4.2.2.2 Cost of Utilities (CUT) Yearly costs = flowrate x costs x period x steam factor Since, assuming the plants operating days per year = 330 days So, = no . of day ' s plant operates per year no . of days per year = Steam factor (SF) 330 = 0.90 365 1. Heater (E-100) Duty = 3109542 J s = 11 .16 G J h r From table 8.5 (W.R Wan Daud, Princip Reka bentuk Proses Kimia, 2002, page 285) cost of heater RM 19.6 / GJ. Thus , Yearly cost = (Q) (C steam) (t) = 11 .16 GJ 19 .6 hr day × RM × 24 ×365 ×0.90 hr GJ day yr = RM 1724515 2. Heater (E-101) Duty = 3423874 J s = 12 .24 G J hr From table 8.5 (W.R Wan Daud, Princip Reka bentuk Proses Kimia, 2002, page 285) cost of cooling water RM 0.6 / GJ. Thus , Yearly cost = (Q) (C steam) (t) = 12 .24 GJ 19 .6 hr day × RM × 24 ×365 ×0.90 hr GJ day yr = RM1891403 68
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 3. Compressor (C-100) Power (shaft) = 137.73kW Effeciency of drives, ξdr = 92.28% (refer to table 3.7) Appendix Electric Power, Pr = Power output ξdr = 137 .73 0.9228 = 149.25 kW Yearly cost 149 .25 kW × = 0.228 hr day ×24 ×365 ×0.90 kW h day yr = RM 268285 4. Cooler 1 (E-102) Duty = 4014590 K s = 14 .4 G hr J J From table 8.5 (W.R Wan Daud, Princip Reka bentuk Proses Kimia, 2002, page 285) cost of cooling water RM 0.6 / GJ. Thus , Yearly cost = (Q) (C steam) (t) = 14 .4 GJ 0.6 hr day × RM × 24 ×365 ×0.90 hr GJ day yr = RM 68118 5. Cooler 2 (E-103) Duty = 4204290 J s = 15 .12 G J hr From table 8.5 (W.R Wan Daud, Prinsip Reka bentuk Proses Kimia, 2002, page 285) cost of cooling water RM 0.6 / GJ. Thus , Yearly cost = (Q) (C steam) (t) = 15 .12 GJ 0.6 hr day × RM × 24 ×365 ×0.90 hr GJ day yr = RM71524 69
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 6. Cooler 3 (E-104) Duty = J s = 1.8 G J h r 503240 From table 8.5 (W.R Wan Daud, Princip Reka bentuk Proses Kimia, 2002, page 285) cost of cooling water RM 0.6 / GJ. Thus , Yearly cost = (Q) (C steam) (t) G J 0.6 hr day = 1.8 hr × RM GJ ×24 day ×365 yr ×0.90 = RM 8514 7. Cooler 4 (E-105) Duty = J s = 0.72 G J hr 240320 From table 8.5 (W.R Wan Daud, Princip Reka Bentuk Proses Kimia, 2002, page 285) cost of cooling water RM 0.6 / GJ. Thus , Yearly cost = (Q) (C steam) (t) = 0.72 GJ 0.6 hr day × RM × 24 ×365 ×0.90 hr GJ day yr = RM 3406 8. Pump 1(P100) Power (shaft) = 327.94kW Effeciency of drives, ξdr = 93.71% (refer to table 3.7) Appendix Electric Power, Pr = Power output ξdr = = Yearly cost 349 .95 kW × 327 .94 0.9371 349.95kW = 0.228 hr day × 24 ×365 ×0.90 kW h day yr = RM 629053 70
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 9. Pump 2(P101) Power (shaft) = 79.19kW Effeciency of drives, ξdr = 91.58% (refer to table 3.7) Appendix Electric Power, Pr = Power output ξdr = 79 .19 0.9158 = 86.47kW Yearly cost = 86 .47 kW × 0.228 hr day × 24 ×365 ×0.90 kW h day yr = RM 155434 10. Pump 3(P102) Power (shaft) = 22.85kW Effeciency of drives, ξdr = 86.93% (refer to table 3.7) Appendix Electric Power, Pr = Power output ξdr = = Yearly cost 22 .85 0.8693 26.29kW = 26 .29 kW × 0.228 hr day × 24 ×365 ×0.90 kW h day yr = RM 47258 11. Pump 4(P103) Power (shaft) = 685.64kW Effeciency of drives, ξdr = 95.37% (refer to table 3.7) Appendix Electric Power, Pr = Power output ξdr = 685 .64 0.9537 = 718.93kW 71
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Yearly cost 718 .93 kW × = 0.228 hr day × 24 ×365 ×0.90 kW h day yr = RM 1292314 12. Pump 5(P104) Power (shaft) = 322.75kW Effeciency of drives, ξdr = 93.67% (refer to table 3.7) Appendix Electric Power, Pr = Power output ξdr = = Yearly cost 344 .56 kW × 322 .75 0.9367 344.56kW = 0.228 hr day × 24 ×365 ×0.90 kWh day yr = RM 619366 Total cost of utilities (CUT) = RM 6779190 4.2.2.3Cost of Raw Material (CRM) 1. Isobutane = 39353 kg/h Price RM 0.8094/kg = = 2. Methanol 39353 kg 24 hr 365 day RM 0.8094 × × × ×0.90 hr day year kg RM 251123677/yr = 15462 kg/hr Price RM 0.988/kg (Chemical week, June 2003) = 15462 kg 24 hr 365 day RM 0.988 × × × ×0.90 hr day year kg = RM 120439579/yr 72
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 3. Catalyst (Alumina silica) = 95679 kg × RM 9.5 1 tonne × tonne 1000 kg = RM909 = RM 251123677/yr + RM 120439579/yr = RM 371563256/yr Total cost of catalyst (for 3 year) = RM 909 Total cost = RM 371564165 Total cost of raw material The estimation of total manufacturing cost (with catalyst): COM = 0.304FCI + 2.73COL + 1.23(CUT + CWT + CRM) COM = 0.304 (31292629) + 2.73 (900000) + 1.23 (6779190 + 371564165) COM = RM 477332286/yr The estimation of total manufacturing cost (without catalyst): COM = 0.304FCI + 2.73COL + 1.23(CUT + CWT + CRM) COM = 0.304 (31292629) + 2.73 (900000) + 1.23 (6779190 + 371563256) COM = RM 477331168/yr 73
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Table 4.2: Estimation Cost Of Purchased Equipment Equipment Capacity/Size Operating Pressure 0.0 barg Area =94.33m2 (floating head) Material Of Construction Carbon Steel Carbon Steel Tube-CS Shell-CS C100 W=137.73kW C101 W = 22.85kW E 100 Heat Exchanger E 101 Heat exchanger E 102 Heat Exchanger E 103 Heat Exchanger E 104 Heat Exchanger E 105 Heat Exchanger FP Tube- 9 barg Shell- 9 barg 1.0 1.0 Area =95.71m2 (floating head) Tube-CS Shell-CS Tube- 9 barg Shell- 9 barg Area =94.33m2 (floating head) Tube-CS Shell-CS Area =94.33m2 (floating head) FM FBM Cp CBM 2.2 16000 264000 3.0 3536676 10610028 1.0 1.0 3.2 3.2 15000 15000 48000 1.0 1.0 1.0 1.0 3.2 3.2 16000 16000 51200 Tube- 9 barg Shell- 9 barg 1.0 1.0 1.0 1.0 3.2 3.2 15000 15000 48000 Tube-CS Shell-CS Tube- 9 barg Shell- 9 barg 1.0 1.0 1.0 1.0 3.2 3.2 15000 15000 48000 Area =94.33m2 (floating head) Tube-CS Shell-CS Tube- 9 barg Shell- 9 barg 1.0 1.0 1.0 1.0 3.2 3.2 15000 15000 48000 Area =94.33m2 (floating head) Tube-CS Shell-CS Tube- 9 barg Shell- 9 barg 1.0 1.0 1.0 1.0 3.2 3.2 15000 15000 Co BM 48000 0.1 barg 74
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Table 4.2: Estimation Cost Of Purchased Equipment Equipment Capacity/Size P100 W = 327.94kW P101 P102 W = 79.19kW W = 22.85kW Material Of Construction Cass Steel Cass Steel Cass Steel Operating Pressure 3.5 barg 0.1 barg 0.0 barg P103 W = 685.64kW Cass Steel 1.50 barg P104 W = 322.75kW Cass Steel 0.0 barg R100 R101 T100 Sieve tray T101 T102 Sieve tray V100 Total D = 6.512 H = 18m D = 1.814m H = 4m D = 0.765 m H = 10.85 11 trays D = 1.01 m H =9 m D = 0.765 m H = 10.85 11 trays Stainless Steel 1.75 barg Carbon Steel 1.0 barg Stainless Steel Stainless Steel Stainless Steel Stainless Steel 3.5 barg 1.75 barg 3.5 barg FP FM FBM Cp 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.3 1.0 1.0 1.0 1.2 1.0 1.8 1.0 1.8 1.0 1.8 1.0 1.8 1.0 1.8 1.0 4.0 1.0 1.0 1.0 4.0 1.0 4.518 3.31 4.518 3.31 4.518 3.31 4.518 3.31 4.518 3.31 11.5 4.2 4.2 4.2 11 4 2.0 1.0 2.0 1.2 11 4 2.0 1.0 36881 1.2 1.0 1.2 1.0 4.0 1.0 4.0 1.0 CBM Co BM 333257 244152 8571 77448 56740 1429 12912 9460 52276 472366 346067 36593 330654 121123 200000 840000 230000 19000 79800 79800 40000 440000 160000 294 9702 5821 17000 178000 68000 40000 440000 160000 294 9702 5821 7131 12659343 3223841 75
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 4.3 PROFITABILITY ANALYSIS Profitability is used as the general term for the measure of the amount of profit that can be obtained from a given situation. Profitability therefore, is the common denominator for all business activities. The feasibility of MTBE production in Malaysia is evaluated by profitability analysis. The profitability of the project will be the largest factor that makes a project economically attractive. To this stage, almost all the design and cost information required for the profitability analysis were obtained. Based on the information available, the best methods assessing the profitability of alternatives are based on projections of the cash flows during the project file. A proposed capital investment / project and its associated expenditures can be recovered by revenue (or savings) over time in addition to a return on the capital that is sufficiently attractive in view of the risks involved of the potential alternatives uses. There are 5 common methods in performing engineering economic analysis: 1) Present Worth (PW) 2) Future Worth (FW) 3) Annual Worth (AW) 4) Internal Rate Of Return (IRR) 5) Benefits / Cost Ratio (B/C) 4.3.1 Discounted Cash Flow The economic feasibility of this plant is evaluated using the Discounted Cash Flow Analysis (DCF), which is the most frequently used method of economic evaluation in the chemical industry. This method measures the profitability of the project taking into account the time value of money. From this method, the internal rate of return (IRR) of the project can be determined which indicates the feasibility of the project. The value of IRR is calculated using the information obtained in the sections. 76
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Table 4.3: Annual Cash Flow Before Tax Year Gross Income (RM) Annual Expenses (RM) 1 0 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 15 2 493648959 493648959 493648959 493648959 493648959 493648959 493648959 493648959 493648959 493648959 493648959 493648959 493648959 493648959 493648959 Investment & Salvage Value (RM) 3 -19292629 -964631 -12000000 -477332286 -477331168 -477331168 -477332286 -477331168 -477331168 -477332286 -477331168 -477331168 -477332286 -477331168 -477331168 -477332286 -477331168 -477331168 Estimated salvage value 1929262.9 = 10%CFC = 0.1 x RM 19292629 = Before Tax Cash Flow (RM) (4)= (1)+(2)+(3) -19292629 -964631 -12000000 16316673 16317791 16317791 16316673 16317791 16317791 16316673 16317791 16317791 16316673 16317791 16317791 16316673 16317791 16317791 1929262.9 (Coulson & Richardson, 1990) RM 1929262.9 77
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Table 4.4 : Annual Cash Flow After Tax Taxes rate at 38% is chosen referring to reference from MIDA Year Gross Income (RM) 1 0 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 15 15 Expenses (RM) 2 Investment & Salvage Value (RM) Taxable Income (RM) Taxes (RM) Taxes rates = 38% After Tax Cash Flow (RM) (5)=(1)+(2)(4) (6)=(5)*0.38 2756916.69 4724764.84 3374280.81 2409649.36 1722831.77 1720902.50 1722831.77 860451.25 0 0 0 0 0 0 0 3 Depreciation Cost Basis * MACRS Rates 4 13559756.32 11593026.16 12943510.19 13907023.64 14594959.23 14596888.49 14593841.23 15457339.75 16317791 16316673 16317791 16317791 16316673 16317791 16317791 1929262.9 5152707.4 4405349.94 4918533.871 5284668.982 5546084.508 5546817.627 5545659.668 5873789.104 6200760.58 6200335.74 6200760.58 6200760.58 6200335.74 6200760.58 6200760.58 733119.902 (7)=(1)+(2)+ (3)-(6) -19292629 -964631 -12000000 11163965.6 11912441.06 11399257.13 11032004.02 10771706.49 10770973.37 10771013.33 10444001.9 10117030.42 10116337.26 10117030.42 10117030.42 10116337.26 10117030.42 10117030.42 1929262.9 12964631 -19292629 -964631 -12000000 493648959 493648959 493648959 493648959 493648959 493648959 493648959 493648959 493648959 493648959 493648959 493648959 493648959 493648959 493648959 -477332286 -477331168 -477331168 -477332286 -477331168 -477331168 -477332286 -477331168 -477331168 -477332286 -477331168 -477331168 -477332286 -477331168 -477331168 1929262.9 12964631 Cumulative Cash Flow (RM) -32257260 -21093294.4 -9180853.34 2218403.789 13250407.81 24022114.3 34793087.67 45564101 56008102.9 66125133.32 76241470.58 86358501 96475531.42 106591868.7 116708899.1 126825929.5 128755192.4 141719823.4 78
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 4.3.2 Net Present Value 4.3.2.1 Present Worth MARR is the rate set by an organization to designate the lowest level that makes an investment acceptable. For a risky investment, MARR should be set higher. However, for public purpose (government, public utility), MARR is lower. For this proposed plant, MARR that has been selected is 15%. By using present worth, we can determine either this proposed plant is profitable and acceptable or not. Table 4.4 shows the value of present worth by using 15%, therefore this proposed plant is profitable because the value of PW is > 0. PW when MARR = 15% Table 4.5: Present Worth Value Year 0 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 15 PW After Tax Cash Flow (RM) -19292629 -964631 -12000000 11163965.6 11912441.06 11399257.13 11032004.02 10771706.49 10770973.37 10771013.33 10444001.9 10117030.42 10116337.26 10117030.42 10117030.42 10116337.26 10117030.42 10117030.42 13697750.9 MARR = 15% 0.86957 0.75614 0.65752 0.57175 0.49718 0.43233 0.37594 0.3269 0.28426 0.24718 0.21494 0.18691 0.16253 0.14133 0.12289 0.12289 Present Worth (PW), (RM) -19292629 -964631 -12000000 9707849.57 9007473.18 7495239.55 6307548.3 5355477.03 4656614.92 4049254.75 3414144.22 2875867.07 2500556.24 2174554.52 1890974.16 1644208.29 1429839.91 1243281.87 1683316.61 33178940.2 MARR = 15% PW = RM 33178940.2 This project is attractive and acceptable because PW > 0 79
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 4.3.3 Cumulative Cash Flow Diagram For The Evaluation Of A New Project Table 4.6: After Tax Cumulative Cash Flow Year 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 15 After Tax Cash Flow (RM) -32257260 11163965.6 11912441.06 11399257.13 11032004.02 10771706.49 10770973.37 10771013.33 10444001.9 10117030.42 10116337.26 10117030.42 10117030.42 10116337.26 10117030.42 10117030.42 13697750.9 Cumulative Cash Flow -32257260 -21093294.4 -9180853.34 2218403.789 13250407.81 24022114.3 34793087.67 45564101 56008102.9 66125133.32 76241470.58 86358501 96475531.42 106591868.7 116708899.1 126825929.5 140523680.4 Cumulative Cash Flow vs Year 150000000 125000000 100000000 Cumulative 75000000 Cash Flow 50000000 25000000 (RM) 0 -25000000 0 -50000000 2 4 6 8 10 12 14 16 Year Figure 4.1: Cumulative Cash Flow (RM) Versus Year 4.3.4 Rate Of Return (ROR) 4.3.4.1 Internal Rate Of Return 80
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR In theory, the Minimum Attractive Rate of Return (MARR) is chosen higher than the rate expected from the bank or some safe investment that involved minimal investment risk. The MARR for after taxes is selected at 15%. (Analysis, and Design of Chemical Processes) IRR is a method that produces an annual rate of profit, or return, resulting from an investment and compared with the MARR. In determining the internal rate of return, trial and error has been done based on the MARR that mentioned before. By trial and error, the IRR for this plant has been found as 34.94%. Table 4.7: Present Value (RM) when i = 30% and i = 40% Year 0 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 15 PW After Tax Cash Flow (RM) -19292629 -964631 -12000000 11163965.6 11912441.06 11399257.13 11032004.02 10771706.49 10770973.37 10771013.33 10444001.9 10117030.42 10116337.26 10117030.42 10117030.42 10116337.26 10117030.42 10117030.42 13697750.9 i = 30% 0.76923 0.59172 0.45517 0.35013 0.26933 0.20718 0.15937 0.12259 0.0943 0.07254 0.0558 0.04292 0.03302 0.0254 0.01954 0.01954 Present Value (RM) i = 40% -19292629 -964631 -12000000 8587657.26 7048829.62 5188599.87 3862635.57 2901143.71 2231530.26 1716576.39 1280330.19 954035.969 733839.105 564530.297 434222.946 334041.456 256972.573 197686.774 267654.053 4303026.05 0.71129 0.5102 0.36443 0.26031 0.18593 0.13281 0.09486 0.06776 0.0484 0.03457 0.02469 0.01764 0.0126 0.009 0.00643 0.00643 Present Value (RM) -19292629 -964631 -12000000 7940817.092 6077727.429 4154231.275 2871740.966 2002783.388 1430492.974 1021738.325 707685.5685 489664.2723 349721.7791 249789.4811 178464.4166 127465.8495 91053.27378 65052.5056 88076.5383 -4410754.867 By interpolation, IRR value is 34.94% when P is at 0 value. IRR (34.94%) > MARR (15%). This project is profitable and acceptable. 4.3.5 Sensitivity Analysis A sensitivity analysis is a way of examining the effects of uncertainties in the forecasts on the viability of a project. AW = PW (A/P, 15%, 15) 81
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR = 33178940.2 (0.17102) = RM 5674262.32 FW = PW (F/P, 15%, 15) = 33178940.2 (8.13706) = RM 269979027.1 Table 4.8: Future Worth (RM) when MARR = 15% Year 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 15 After Tax Cash Flow (RM) -32257260 11163965.6 11912441.06 11399257.13 11032004.02 10771706.49 10770973.37 10771013.33 10444001.9 10117030.42 10116337.26 10117030.42 10117030.42 10116337.26 10117030.42 10117030.42 13697750.9 MARR = 15% 8.13706 7.07571 6.15279 5.35025 4.65239 4.04556 3.51788 3.05902 2.66002 2.31306 2.01136 1.74901 1.52088 1.3225 1.15 - FW 4.3.6 Future Worth (FW), (RM) -262479260.1 78992983.04 73294748.23 60988875.45 51325185.17 43577584.92 37890991.81 32948745.2 27781253.92 23401298.38 20347596.11 17694787.37 15386789.23 13378856.03 11634584.98 10117030.42 13697750.9 269979801.1 Payback Period The payback period analysis is a more simplistic method of calculating the economic feasibility of a project. This method determines the period in number of years required for the project to recover back the initial capital investment of the plant. In using this method, the assumptions stated above such as below still applies: 1) The plant life is taken as 15 years. 2) The annual net profit of the plant is taken as constant. 3) The class life or recovery period is 7 years. 4) The working capital is taken as 5% of the total fixed capital cost. 4.3.6.1 Simple Payback Period Table 4.9 : Simple Payback Period 82
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Year 0 1 2 After Tax Cash Flow -32257260 16316673 16317791 Cumulative Cash Flow -32257260 -15940587 377204 By interpolation, Table 4.10 : The Interpolation Simple Payback Period Cumulative Cash Flow -15940587 0 377204 Year 1 1.97 2 Therefore, MTBE plant can have payback period with: Payback period = (1 + 0.97) years = 1 years 12 month ≈ 2 years 4.3.6.2 Discounted Payback Period Normally, the interest in Malaysia standardized for chemical plant. By referring to Hong Leong Bank, the interest is 15% and use as a basis for discounted payback period. Table 4.11 : Discounted Payback Period Year Annual Cash Flow After Tax 0 1 2 3 -32257260 16316673 16317791 16317791 Cumulative Cash Flow Cumulative Cash Flow After Tax -32257260 -15940587 -2013884.05 14001824.34 -18331675.05 -2315966.658 16102097.99 By interpolation, Table 4.12 : The Interpolation Discounted Payback Period Cumulative Cash Flow -2315966.658 0 16102097.99 Year 2 2.03 3 Therefore, MTBE plant can have payback period with: = 2 + (0.03) years 83
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR = 2 year 1 month 4.4 CONCLUSION Based on this chapter, the economic evaluation of MTBE plant are made through study in all aspect including feasibility study, process synthesis and flow sheeting and designed of major equipment. From the cash flow analysis, the payback period for the MTBE plant is about 2 years. Furthermore, it should be stated that the present work is primarily illustrated based on the method of engineering economic analysis of chemical processes. PW is positive value so the project is attractive and acceptable same as when IRR is bigger than MARR. By estimate the value of PW, FW and AW by using relationship between PW and FW the answer of FW same with estimate direct from CFAT. REFERENCES 84
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Perry R.H and Green, Don, “Perry’s Chemical Engineer’s Handbook”, 7th Edition, McGraw-Hill Book Company, Singapore, 1984. Sinnott, R. K., Coulson & Richardson, “Chemical Engineering Volume 6, Chemical Engineering Design”, Butterworth Heinemann, 1999. Peters, max Stone, “Plant Design and Economics for Chemical Engineers”, 2nd Edition, McGraw-Hill Chemical Engineering Series, 1968. 85
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR CHAPTER 5 PROCESS INTEGRATION AND PINCH TECHNOLOGY 5.1 INTRODUCTION Process integration can lead to a substantial reduction in the energy requirements of a process. One of the most successful and generally useful techniques is that developed by Bodo Linnhoff and other workers: pinch technology. The term derives from the fact that in a plot of the system temperatures versus the heat transferred, a pinch usually occurs between the hot stream and cold stream curves. It has been shown that the pinch represents a distinct thermodynamic break in the system and that, for minimum energy requirements, heat should not be transferred across the pinch, Linhoff and Townsend (1982) (Ref: Coulson & Richardson’s vol. 6) 5.2 PINCH TECHNOLOGY There are four streams to consider the problem of integrating the utilization of energy. Two hot streams which require cooling and two cold streams that have to be heated. Each streams starts from a source temperature Ts, and is to be heated or cooled to a target temperature, Tt. The heat capacity of each stream is shown as CP. CP is given by: CP = mCp (5.1) Where, m = mass flow rate, kg/s Cp = average specific heat capacity between Ts and Tt, (KJ/kgoC) Table 5.1: Shows the process data for each stream. 86
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Heat Stream number Type 1 2 3 4 Heat capacity Cp(KW/ oC) 3.2 1.3 2 4 HOT HOT COLD COLD Ts(oC) Tt (oC) 180 150 20 75 50 30 140 135 Load (KW) 416 156 240 240 The heat load shown in the table is the total heat required to heat or cools the stream from the source to target temperature. The stream are shown diagrammatically below, Stream 1 180°C CP = 3.2 kW/°C 50°C Stream 2 150°C CP = 1.3kW/°C 30°C Stream 3 20°C CP = 2 kW/°C 140°C Stream 4 75°C CP = 4 kW/°C 135°C Figure 5.1: 5.3 Diagrammatically representation of process stream THE PROBLEM TABLE METHOD The problem table is a numerical method for determining the pinch temperature and the minimum utility requirements. Firstly, it needs to convert the actual stream temperature Tact into the interval temperatures Tint. Hot streams Tint = Tact – (ΔTmin/2) Cold streams Tint = Tact – (ΔTmin/2) The minimum temperature difference taken from composite curve as, ΔTmin = 10 oC 87
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Hot a nd Cold Com posite curve s 350 Temperature o C 300 250 200 Hot Stre am s 150 Cold Stre am s 100 50 0 1 2 3 4 2 Enthalpy,1 0kW Figure 5.2: Hot and cold streams composite curves Table 5.2: Interval Temperature for ΔTmin = 10oC Actual Temp. oC Stream Interval Temp. oC 1 180 50 175 45 3 150 30 145 25 9 20 140 25 145 10 75 135 80 140 The heat balance for the streams falling within each temperature interval: For the nth interval: ΔHn = (∑CPc - ∑CPh) (ΔTn) = net heat required in the nth interval (5.2) Where, ΔHn ∑CPc = sum of the heat capacities of all the cold streams in interval ∑CPh = sum of the heat capacities of all the hot streams in the interval ΔTn = interval temperature difference=(Tn-1-Tn) 88
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 175 Interval 1: 145 1 Interval 2: 4 140 2 Interval 3: 80 Interval 4: 45 Interval 5: 3 25 Figure 5.3: Table 5.3: Intervals and streams Ranked order of interval temperature Rank,oC Interval, ΔTn oC Stream in interval 145 30 -1 140 5 4-(2+1) 80 60 (3+4)-(1+2) 45 35 3-(1+2) 25 20 (3-2) 175 Cascading the heat from one interval to the next implies that the temperature difference is such that the heat can be transferred between the hot and cold streams. A negative value in the column indicates the temperature gradient is in the wrong direction and that the exchange is not thermodynamically possible. Table 5.4: Problem Table ∑CPc - ∑CPh Interval o Tint, C o n ΔT ,C (Kw/oC) ΔHn (KW) surplus/deficit 89
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 175 1 145 30 -3.2 -96 S 2 140 5 0.5 2.5 D 3 80 60 2.1 126 D 4 45 35 -2.0 -87.5 S 5 25 20 1.0 14 D Interval temperature Rank oC 175oC 0kW 145oC -96kW 96 kW -96 kW 128.5 kW 140oC 2.5 kW 93.5 kW 2.5 kW 126 kW 80oC 126 kW -32.5 kW 126 kW 0 kW 45oC -87.5 kW 55 kW -87.5 kW 87.5 kW 25oC 14 kW -41 kW 14 kW 73.5 kW 32.5 kW Figure 5.4 Heat Cascade From figure 5.4: pinch occurs at interval temperature 80oC At the pinch, hot stream = 80 + 5 = 85 oC = 80 – 5 = 75oC (5.3) Cold stream (5.4) 5.4 THE HEAT EXCHANGER NETWORK The grid representation of the stream is shown in Figure 5 CP 90
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR (KW/ oC) o o 85 C75 C 180oC 50 oC 3.2 1 150 oC 30 oC 1.3 2 140 oC 20 oC 2.0 3 135 oC 75 oC 4.0 4 Figure 5.5 Grid for 4 stream problem For maximum energy recovery (minimum utility consumption) the best performance is obtained if no cooling is used above the pinch. This means the hot streams above the pinch should be brought it the pinch temperature solely by exchange with the cold streams. THE NETWORK DESIGN ABOVE THE PINCH CP hot ≤ CP cold Applying this condition at the pinch, stream 1 can be matched with stream 4, but not with 3. Matching streams 1 and 4 and transferring the full amount of heat required to bring stream 1 to the pinch temperature gives; ΔHex = CP (T pinch - Ts) = 304 kW (5.5) This will also satisfy the heat load required to bring stream 4 to its target temperature. 91
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Stream 2 can be matched with stream 3, whilst satisfying the heat capacity restriction. Transferring the full amount to bring stream 3 to the pinch temperature: ΔHex = CP (T pinch- Ts) = 97.5 kW The heat required to bring stream 3 to its target temperature, from the pinch temperature, is: ΔH = 2.0(140-75) = 130 kW So a heater will have to be included to provide the remaining heat load: ΔHhot = 130-97.5 kW = 32.5 kW (5.6) THE NETWORK DESIGN BELOW THE PINCH Stream 1 is matched with stream 3 transferring the full amount to bring stream 1 to its target temperature; transferring: ΔHex = 3.2(85-50) = 112 kW Stream 3 requires more heat to bring it to pinch temperature; amount needed: ΔH = 2.0(75-20)-85kW = 25 kW So transferring 25 kW will raise the temperature from the source temperature to: 20+ 25/2 =32.5 kW and gives a stream temperature difference on the outlet side of the exchanger of: 85-32.5 = 52.5 kW So the minimum temperature difference condition, 10oC will not be violet by this match. Stream 2 will need further cooling to bring its to its target temperature, so a cooler must be included; cooling required. ΔHcold = = 1.3 (85-50)-25 73.5 kW 92
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR The proposed network for maximum energy recovery is shown in Figure 5.5 B 1 2 C A D A D B C 3 4 Figure 5.6 Proposed heat exchanger network 5.5 MINIMUM NUMBER OF EXCHANGERS The network shown in figure 5.5 was designed to give the maximum heat recovery, and therefore give the minimum consumption, and cost of the hot and cold utilities. In figure 5.5 it is clear that there is scope for reducing the number of exchangers. Exchanger D can be deleted and the heat loads of the cooler and heater increased to bring stream 2 and 3 to their target temperatures. Heat would across the pinch and the consumption of the utilities would be increased For complex networks a more general expression is needed to determine the number of exchangers: Zmin = N’ +L’ – S (5.7) Where L’= the number of internal loops present in the network S= the number of independence branches (subsets) that exist in the network N= the number of streams including the utilities 93
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR In a final design, there are 3 exchangers, rather than 4 before the process integration and pinch technology, with the minimum heating and cooling loads, 32.5 kW and 73.5 kW, respectively, match those predicted from the problem table, compare with the loads for heating and cooling before process integration: 416 kW and 240 kW. 94
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR CHAPTER 6 WASTE TREATMENT 6.1 INTRODUCTION Pollution is something that should be taken into serious consideration in any petrochemical plant especially the MTBE plant. Pollution, no matter what kind of the pollution is has serious negative effects not only to human beings, but also to animals, plants and to the environment. Therefore, it is the responsibility of each individual to ensure that their activities are not harmful to the environment. This includes activities and works involved in designing a plant. Waste from any petrochemical plant should be treated according to the local and international standards before being released to the environment. In the MTBE plant, the wastes are only the in liquid form and gas form. The liquid will be treated in the wastewater treatment plant. The hydrogen gas leaving the reactor is sent to a gas cylinder which it is then sold to interested company at market price. The treatment processes and systems employed by the MTBE plant is the typical processes and systems based on Howard S. Peavy, Donald R. Rowe, George Tchobanoglous; Environmental Engineering, McGraw-Hill, 1985 and David H. F. Liu, Bela G. Liptak, Wastewater Treatment, Lewis Publishers, 1999. 6.2 WASTEWATER TREATMENT 95
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Wastewater treatment is a must in any plant. The wastewater from plant cannot be channeled into the sewage system without being treated. The wastewater from the MTBE plant may contains a small amount of the feed and product and a small quantity of by-products such as butene, TBA and dimethylether. According to the site location selected, the wastewater from the plant is to be treated and should comply with Standard B which is shown Table 6.1. In the design of the wastewater treatment plant for the production of MTBE, the COD value used is based of the COD value of wastewater from other plants that are in operation. The COD value of 3000 mg/l will be used for design purposes. The design of the plant consists of preliminary, primary and secondary treatment where each treatment unit chosen is based on the characteristics of the influent to be treated. Before being treated, all the wastewater is channeled to the holding tank. It is then ferried for screening and the next process is the primary settling tank. The effluent leaving this tank is sent to the active sludge reactor. After that, it will be sent to the secondary settling tank. Finally, the effluent undergoes adsorption by activated carbon before leaving the wastewater treatment plant. 6.2.1 Denitrification Process (Chemical Treatment) 96
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR To remove methanol in the waste water, we use the denitrification process in our plant waste treatment. In the denitrification process, nitrate is reduced to nitrogen gas by the same facultative, heterotrophic bacteria involved in the oxidization of carbonaceous material. For reduction to occur the dissolved oxygen level must be at or near zero and a carbon supply must be available to the bacteria. Because low carbon content is required for the previous nitrification step, carbon must be added before denitrification can proceed. A small amount of primary effluent, bypassed around secondary and nitrification reactors, can be used to supply the carbon. However, the unnitrified compounds in this water will be unaffected by the denitrification process and will appear in the effluent. When essentially complete nitrogen removal is required, an external source of carbon containing no nitrogen will be required. The most commonly used external carbon source is methanol, CH3OH. When methanol is added, the denitrification reaction is: NO3- + 5 CH3OH 6 1 5 7 N2 + CO2+ H2O +OH2 6 6 Theoretically, each milligram per liter of nitrate should require 1.9 mg/L of methanol. Under treatment plant conditions, however about 3.0 mg/L of methanol is required for each milligram per litre of nitrate, making this process an expensive one. 97
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Table 6.1 Parameter Limits for Wastewater and Effluent Under the Environmental Quality Act 1974. PARAMETER Temperature pH BOD5 at 20oC COD Suspended solid Mercury Cadmium Chromium Hexavalent Arsenic Cyanide Lead Copper Manganese Nickel Tin Zinc Boron Iron Phenol Free Chlorine Sulfide Oil and grease UNIT o C mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l mg/l STANDARD A 40 6.0-9.0 20 50 50 0.005 0.01 0.05 0.05 0.05 0.10 0.20 0.20 0.20 0.20 1.0 1.0 1.0 0.001 1.0 0.5 None STANDARD B 40 5.5-9.0 50 100 100 0.05 0.02 0.05 0.10 0.10 0.5 1.0 1.0 1.0 1.0 1.0 4.0 5.0 1.0 2.0 0.5 10 * Both standards could be used and acceptable, but only one is chosen, Standard B for the wastewater treatment for the MTBE plant. 6.3 WASTEWATER TREATMENT PLANT DESIGN The design of the wastewater treatment plant consists of the holding tank, the design of the screening device, then the design of the settling tank, the design of the primary and secondary sedimentation tanks, and lastly the design for the activated sludge process. 98
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR The next step is the sludge treatment which consists of the sludge thickening by centrifugation, condensation by using heat treatment and lastly dehydration by using vacuum filter. Since the gas produced only hydrogen and no other gases, so the gas needs no treatment. The hydrogen gas produced is stored to be sold to interested companies like MOX Sdn. Bhd.. 6.3.1 Design of Holding Tank The purpose of the holding tank is to hold and accumulate the wastewater before it undergoes further treatment. The design of the holding tank is as follows: m 3 24 hr × hr day Volume of wastewater per day = 1.5642 = Wastewater flow rate 37 .54 = 37.54 m3 m3 d ay By taking into consideration the depth of the holding tank as 3 m, and the ratio of the length to the width as 3:1, the dimensions of the holding tank are as follows: Depth of holding tank = 3.0 m Width of holding tank = 3.0 m Length of holding tank = 9.0 m Volume of holding tank = 81.0 m3 This means that the holding time is about two days (81m3/37.54m3) and it is acceptable. 6.3.2 Design of Screening Device In the preliminary treatment of the wastewater, the treatment chosen is by using screening. Fine screens made of woven-wire cloth are used. The screen is used to remove small particles which might be in the wastewater. A screen with small sized openings is chosen because the wastewater does not contain large particles. The head loss is calculated by using the following equation: 99
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 1 Q  hL =   C( 2g )  A  2 (6.1) Where hL = head loss, m C = waste constant for screen = 0.6 for clean screen (Metcalf & Eddy, 1979) g = gravity, ms-2 Q = Flow through screen, m3s-1 A = Effective opening area for submerged screen, m2 = take as 9m2 Thus, h L = 1 0.6 ×2 ×9.81 2  4.345 x10 −4      9   h L = 1.9799 ×10 −10 m 6.3.3 Design of Settling Tank For the wastewater treatment, sulfide precipitation treatment is used to remove heavy metals from the wastewater. The precipitant used is sodium sulfide, which will react with the metal ions and will form non-soluble sulfide metal. However, extra care is required in this process to avoid sulfide poisoning. Pretreatment which involves the increasing of the pH of the wastewater is required to minimize the release of hydrogen sulfide gas. The design of the settling tank is as follows: Take holding time = 15 minutes (standard holding time) Average flow rate = 1.5642 Holding time = 15 minutes = 0.25 hr = Average flow rate = 1.5642 = 0.391 m 3 Tank volume m3 hr × Holding time m3 × 0.25 hr hr 100
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR By taking the depth as L=0.8m, and using a square tank, = V L = Length of tank 0.391 0.8 = 6.3.4 0.70 m Design of Primary and Secondary Sedimentation Tank Primary sedimentation is a unit operation designed to concentrate and remove suspended organic solids from the wastewater. The secondary sedimentation tank is designed as a unit operation for the activated sludge process. The design for the sedimentation tanks are as follows: Take holding time = 2 hr Average flow rate = 1.5642 Holding time = 2 hr Tank Volume = Average flow rate = 1.5642 = 3.1284 m 3 m3 hr × Holding time m3 × 2hr hr By taking the depth as L=2m, 2× V L 2× 3.1284 2 = 6.3.5 = = Length of tank 2.50 m Design for Activated Sludge Process The activated sludge process is a treatment process that involves the production of a living or active microorganism which is used to stabilize the waste aerobically. A completely mixed reactor is used in this process. This reactor is used as it is suitable for general wastewater treatment and it has a high efficiency (85-95%) to reduce high COD or BOD. This process involves a completely mixed reactor followed by a secondary sedimentation tank. Part of the sludge from the secondary 101
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR sedimentation tank is recycled to the influent reactor. The design for the reactor is as follows: m3 hr Average flow rate = 1.5642 Holding time = 3 hr Tank Volume = Average flow rate = 1.5642 = 4.693 m 3 × Holding time m3 ×3hr hr By taking the depth as L=2m, V L 4.69 2 = 6.3.6 = = Length of tank 1.53 m Oxygen Demand and Aerator COD (kg/day) = Influent COD = 3 = 11 .6 2 2 × wastewater flow rate kg m3 ×37 .54 m3 day kg day By assuming that 1kg COD requires 1kg of oxygen, thus 112.62 kg/day COD requires 112.62 kg O2/day. The aerator used is a mechanical aerator with an oxygen transfer rate of 1.8 kg O2/day. Power needed = Oxygen needed per hour O2 needed per hour / O2 transfer rate = 112 .62 = 4.69 kg 1day × day 24 hr kg hr 102
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR = 4.69  kg  day   1.8  hr  kg  = Thus, power needed     2.61 kW An aerator unit provides 10kW of power. Thus, one unit is sufficient to provide enough power for the activated sludge process. 6.4 SLUDGE TREATMENT In this wastewater treatment plant, sludge is formed in the primary and secondary sedimentation tank. This sludge needs to be treated and disposed. For the MTBE plant, the following operations are used for the sludge treatment system: i. Sludge thickening by centrifugation ii. Condensation by using heat treatment iii. Dehydration by using vacuum filter Wastes from the sludge treatment system, for example the filtrate from the vacuum filter, are sent to the influent treatment plant to undergo further treatment. Dehydrated sludge is sent to the sludge dump site. The flow chart for the sludge treatment is shown in Figure 6.1. Although the treatment is expensive, it is necessary for our plant. 103
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR S l udge P la nt C EN TR IFU G ATIO N TH IC K EN IN G H EA T TR E ATM EN T T o influ ent plant S l udge to dis pos al s ite SL U D G E STO R AG E D ehy dr ated s lud ge VAC U U M FIL TE R F iltrate to influen t pl an t Figure 6.1 The Sludge Treatment System 6.5 WASTE TREATMENT PLANT LAYOUT Generally, the layout of a waste treatment plant depends on the process requirements. The treatment plant covers an area of 800m2. The plant layout is shown in Figure 6.3. The waste treatment plant consists of the following units: 1. 1 holding tank 2. 1 primary sedimentation tank 3. 1 secondary sedimentation tank 4. 1 activated sludge reactor 5. 1 screening device 6. 1 power house 7. 4 pumps 8. 1 sludge store 9. Units in the sludge treatment process Table 6.2 Functions of Pumps in the Waste Treatment Plant Pump Function 104
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR 1 To pump sludge from the sedimentation tank to the sludge treatment tank. 2 To pump sludge from the secondary sedimentation tank to be recycled to the activated sludge reactor. 3 To pump sludge from the secondary sedimentation tank to the sludge treatment process. 4 To pump wastewater from the sludge treatment system to be recycled to the influent plant. U LEG END Pum p 1 1 S lu d g e f ro m p r im a ry s e d im e n t a t io n t a n k to b e t re a t e d 2 P R IM A R Y S E D IM E N T A T IO N T A N K S lu d g e f ro m s e c o n d a ry s e d im e n t a t io n t a n k to b e r e c y c le d 3 4 S lu d g e f ro m s e c o n d a ry s e d im e n t a t io n t a n k to b e t r e a te d W a s t e w a te r f r o m s lu d g e t r e a tm e n t s y s te m to in flu e n t p la n t F lo w S lu d g e F lo w S E T T L IN G T A N K W a ste w a te r F lo w POW ER HOUSE A E R A T IO N T A N K S C R E E N IN G D E V IC E 2 3 S LU D G E TR EA TM E N T PR O C E SS SECO NDARY S E D IM E N T A T IO N T A N K H O L D IN G T A N K 4 Figure 6.2 Waste Treatment Plant Layout 6.6 ABSORPTION TANK USING GRANULAR ACTIVATED CARBON 105
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR In the operation of absorption tank, granular activated carbon (GAC) is used which has a diameter between 0.1-2.0 mm. The contact system for GAC consists of cylindrical tanks, which contain a bed of the carbon material (refer the design given). The water is passed through the bed with sufficient residence time allowed for completion of the adsorption process. The system is operating in a fixed bed mode. Fixed bed systems are batch operations that are taken off the line when the adsorptive capacity of the carbon in used up. Although fixed granular carbon beds can be cleaned in a place with superheated steam, the most common practice is to remove the carbon for cleaning in a furnace. The regeneration process is essentially the same as the original activation process. The adsorbed organics are first burned at about 800 oC in the absence of oxygen. An oxidizing agent, usually stream, is then applied at slightly higher temperatures to remove the residue and reactivated carbon. 6.6.1 Analysis of the Absorption Process The adsorption process takes place in the three steps, macrotransport, microtransport and sorption. The quantities of adsorbate that can be taken up by an adsorbent are function of both the characteristics and concentration of adsorbate and the temperature. Generally, the amount of material absorbed is determined as a function of the concentration at a constant temperature and the resulting function is called an absorption isotherm. Equation that are often used to described the experimental isotherm data where developed by Freundlich by Langmuir and by Brunauer, Emmet and Teller (BET isotherm). Freundlich Isotherm Equation: x 1 = K f Ce n m Where x/m = amount adsorbate absorbed per unit weight of absorbent (activated carbon) Ce = equilibrium concentration of absorbed in solution after absorption K f , n = empirical constant 106
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR The constants in the Freundlich isotherm can be determined by plotting (x/m) versus C and making use of above equation rewritten as: 1 x log   = log K f + log Ce n m 6.6.2 Breakthrough Absorption Capacity In the field, the breakthrough adsorption capacity, ( x m )b , of the GAC in a full-scale column is some percentage of the theoretical absorption capacity found from the isotherm. The (x m )b of a single column can be assumed to be approximately 25 to 50 percent of the theoretical capacity ( x m ) o . Once ( x m )b is known, time to breakthrough can be calculated by solving the following equation for tb X C  t x    = b = Q Ci − b  b [8.34 lb Mgal .( mg L ) ] 2  Mc  m b M c  x Where   = field breakthrough adsorption capacity, lb/lb or g/g  m b X b = mass of organic material absorbed in the GAC column at breakthrough, lb or g M c = mass of carbon in the column, lb or g Q = flow rate, Mgal/d Ci = influent organic concentration, mg/L Cb = breakthrough organic concentration, mg/L tb = time to breakthrough, day Equation above was developed assuming that Ci is constant and that the effluent concentration increases linearly with time from 0 to Cb value. The time breakthrough can be calculated using the rearranging equation above. From the test data by Freundlich adsorption isotherm plotted, 107
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR x 3.56 = 0.0015 Ce m x   = 0.0015(3.250)3.56  m 0 = 0.0996 mg/mg say 0.10 mg/mg = 0.10 Ib/Ib Determination of breakthrough time, tb = ( x / m) b M c Q (Ci − Cb / 2[8.34 Ib / Mgal .( mg / L)] Following condition apply: (x m )b =50 percent of ( x m ) o =o.5 (0.10 lb/lb) = 0.050 lb/lb Assuming from the data testing by Freundlich adsorption isotherm, 0 Surface area = 1 ft 2 = 0.929m2 M c = (10 ft 2 ) × ( 5.0 ft ) × 38 lb ft 3 = 1,900 lb Q = 5.0 gal ft 2 . min ×1440 min d ×10 ft 2 = 72000 gal d = 0.072 Mgal d Ci = 3.2 mg L Cb = 0.75 mg L the time to breakthrough is tb = ( x / m) b M c Q (Ci − Cb / 2[8.34 Ib / Mgal .( mg / L)] tb = 56 day Therefore, results from our study based on Freundlich adsorption isotherm the activated carbon in our design waste treatment column vessel can long lasting for 56 day. Therefore, our estimation is changing the activated carbon in the vessel waste treatment in every 56 day to make sure the efficiency capacity of adsorption carbon is in the maximum capacity. REFERENCES 108
  • PRODUCTION OF 300,000 METRIC TON OF MTBE PER YEAR Howard S. Peavy, Donald R. Rowe, George Tchobanoglous; Environmental Engineering, McGraw-Hill, 1985. David H. F. Liu, Bela G. Liptak, Wastewater Treatment, Lewis Publishers, 1999. 109