Theory of Carbon Formation in Steam Reforming
Contents
1 Introduction
2 Underpinning Theory
2.1 Conceptualization
2.2 Reforming Reactions
2.3 Carbon Formation Chemistry
2.3.1 Natural Gas
2.3.2 Carbon Formation for Naphtha Feeds
2.3.3 Carbon Gasification
2.4 Heat Transfer
3 Causes
3.1 Effects of Carbon Formation
3.2 Types of Carbon
4 What are the Effects of Carbon Formation?
4.1 Why does Carbon Formation Get Worse?
4.1.1 So what is the Next Step?
4.2 Consequences of Carbon Formation
4.3 Why does Carbon Form where it does?
4.3.1 Effect on Process Gas Temperature
4.4 Why does Carbon Formation Propagate Down the Tube?
4.4.1 Effect on Radiation on the Fluegas Side
4.5 Why does Carbon Formation propagate Up the Tube?
5 How do we Prevent Carbon Formation
5.1 The Role of Potash
5.2 Inclusion of Pre-reformer
5.3 Primary Reformer Catalyst Parameters
5.3.1 Activity
5.3.2 Heat Transfer
5.3.3 Increased Steam to Carbon Ratio
6 Steam Out
6.1 Why does increasing the Steam to Carbon Ratio Not Work?
6.2 Why does reducing the Feed Rate not help?
6.3 Fundamental Principles of Steam Outs
TABLES
1 Heat Transfer Coefficients in a Typical Reformer
2 Typical Catalyst Loading Options
FIGURES
1 Hot Bands
2 Conceptual Pellet
3 Naphtha Carbon Formation
4 Heat Transfer within an Reformer
5 Types of Carbon Formation
6 Effect of Carbon on Nickel Crystallites
7 Absorption of Heat
8 Comparison of "Base Case" v Carbon Forming Tube
9 Carbon Formation Vicious Circle
10 Temperature Profiles
11 Carbon Pinch Point
12 Carbon Formation
13 Effect on Process Gas Temperature
14 How does Carbon Propagate into an Unaffected Zone?
15 Movement of the Carbon Forming Region
16 Effect of Hot Bands on Radiative Heat Transfer
17 Effect of Potash on Carbon Formation
18 Application of a Pre-reformer
19 Effect of Activity on Carbon Formation
Look at two main types
Explain mechanisms
Explain prevention of cracking
Three main types
1 Carbon cracking
2 Boudouard carbon formation
3 CO reduction
VULCAN Series VSG-Z101 Primary Reforming
Initial Catalyst Reduction
Activating (reducing) the catalyst involves changing the nickel oxide to nickel, represented by:
NiO + H2 <==========> Ni + H2O
Natural gas is typically used as the hydrogen source. When it is, the catalyst reduction and putting the reformer on-line are accompanied in the same step.
Introduction and Theoretical Aspects
Catalyst Reduction and Start-up
Normal Operation and Troubleshooting
Shutdown and Catalyst Discharge
Nickel Carbonyl Hazard
Modern Methanation Catalyst Requirements
Getting the Most Out of Your Refinery Hydrogen PlantGerard B. Hawkins
Getting the Most Out of Your Refinery Hydrogen Plant
Contents
Summary
1 Introduction
2 "On-purpose" Hydrogen Production
3 Operational Aspects
4 Uprating Options on the Steam Reformer
4.1 Steam Reforming Catalysts and Tube Metallurgy
4.2 Oxygen-blown Secondary Reformer
4.3 Pre-reforming
4.4 Post-reforming
5 Downstream Units
6 Summary of Uprating Options
7 Conclusions
Introduction
Catalyst breakage is a well known phenomena that occurs during operation and transients such as reformer trips, whether this be due to,
• Normal in service breakage,
• Breakage due to carbon formation/removal,
• Breakage due to steam condensation or carry over,
• Breakage during a trip.
The effect of catalyst breakage can be observed in a number of ways,
• Hot bands,
• Speckling and giraffe necking,
• Catalyst breakage and settling.
Look at two main types
Explain mechanisms
Explain prevention of cracking
Three main types
1 Carbon cracking
2 Boudouard carbon formation
3 CO reduction
VULCAN Series VSG-Z101 Primary Reforming
Initial Catalyst Reduction
Activating (reducing) the catalyst involves changing the nickel oxide to nickel, represented by:
NiO + H2 <==========> Ni + H2O
Natural gas is typically used as the hydrogen source. When it is, the catalyst reduction and putting the reformer on-line are accompanied in the same step.
Introduction and Theoretical Aspects
Catalyst Reduction and Start-up
Normal Operation and Troubleshooting
Shutdown and Catalyst Discharge
Nickel Carbonyl Hazard
Modern Methanation Catalyst Requirements
Getting the Most Out of Your Refinery Hydrogen PlantGerard B. Hawkins
Getting the Most Out of Your Refinery Hydrogen Plant
Contents
Summary
1 Introduction
2 "On-purpose" Hydrogen Production
3 Operational Aspects
4 Uprating Options on the Steam Reformer
4.1 Steam Reforming Catalysts and Tube Metallurgy
4.2 Oxygen-blown Secondary Reformer
4.3 Pre-reforming
4.4 Post-reforming
5 Downstream Units
6 Summary of Uprating Options
7 Conclusions
Introduction
Catalyst breakage is a well known phenomena that occurs during operation and transients such as reformer trips, whether this be due to,
• Normal in service breakage,
• Breakage due to carbon formation/removal,
• Breakage due to steam condensation or carry over,
• Breakage during a trip.
The effect of catalyst breakage can be observed in a number of ways,
• Hot bands,
• Speckling and giraffe necking,
• Catalyst breakage and settling.
Introduction High temperature shift Catalysts
Low temperature shift catalysts
Catalyst storage, handling, charging and discharging
Health and safety precautions
Reduction and start-up of high temperature shift catalysts
Operation of high temperature shift catalysts
Reduction and start-up of low temperature shift catalysts
Operation of low temperature shift catalysts
Reactor and Catalyst Design
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 CATALYST DESIGN
4.1 Equivalent Pellet Diameter
4.2 Voidage
4.3 Pellet Density
5 REACTOR DESIGN
6 CATALYST SUPPORT
6.1 Choice of Support
TABLES
1 CATALYST SUPPORT SHAPES
2 SECONDARY REFORMER SPREADSHEET
FIGURES
1 GRAPH OF EFFECTIVENESS v THIELE MODULUS
2 VARIATION OF COSTS WITH CATALYST SIZE
3 VARIATION OF COSTS WITH CATALYST BED VOIDAGE
4 VARIATION OF COSTS WITH VESSEL DIAMETER
Reformer Tube design principles
- Larsen Miller Plot
- Larsen Miller & Tube Design
- Design Margins - Stress Data Used
- Max Allowable & Design Temperature
- Tube Life
- Effect of Temperature on Life
- Material Types
HK40: 25 Cr / 20 Ni
HP Modified: 25 Cr / 35 Ni + Nb
Microalloy: 25 Cr / 35 Ni + Nb + Ti
- Alloy Developments
- Comparison of Alloys
Manufacturing Technology
- Welds
Failure mechanisms
- Failure Mechanisms - Creep
- Creep Propagation
- Common Failure Modes
- Uncommon Failure Modes
- Failure by Creep
- Creep Rupture - Cross Section
- Failure at Weld
Actions to Take if Tube Fails
- Pigtail Nipping
Inspection techniques
Classification of Problems
- Visual Examination
- Girth Measurement
- Ultrasonic Attenuation
- Radiography
Eddy Current Measurement
LOTIS Tube Inspection
LOTIS Compared to External Inspection
Equilibrium Effects
- Methane Steam
- Water Gas Shift
Relationship of Kp to Temperature
Relationship of WGS Kp to Temperature
Effect of Temperature on Methane Slip
Approach to Equilibrium
Reaction Path and Equilibrium
Effect of Pressure Increase
Operating Parameters
- Pressure
- Temperature
- Feed Rate
- Steam to Carbon
Effect of Exit Temperature Spread
Useful Tools
Calculating ATM
Steam Reformer Surveys - Techniques for Optimization of Primary Reformer Oper...Gerard B. Hawkins
Introduction
Background Radiation and Temperature Measurement
Reformer Survey Inputs
Other Troubleshooting Tools
Safety
Preparation
Onsite Data Collection
TWT Survey
Observation/Troubleshooting
Modelling and Analysis
Results/Outputs
Case Studies
Conclusions
Case Study 1
Case Study 2
Case Study 3
Conclusions
Purpose
Key to good performance
Problem Areas
Catalysts, heat shields and plant up-rates
Burner Guns
Development of High Intensity Ring Burner
Case Studies
Conclusions
Most modern ammonia processes are based on steam-reforming of natural gas or naphtha.
The 3 main technology suppliers are Uhde (Uhde/JM Partnership), Topsoe & KBR.
The process steps are very similar in all cases.
Other suppliers are Linde (LAC) & Ammonia Casale.
Catalytic Reactions in Catalytic Reforming
Catalytic Reforming Reactions
Sulfur Related Problems
Effects of Sulfur in Catalytic Reforming
Reactions in Catalytic Reforming
Catalytic Reforming Catalysts
Effect of Sulfur on Catalytic Reforming Catalysts
Catalytic Reformer Efficiency
VULCAN Sulfur Guards
VULCAN Sulfur Guards for Catalytic Reformers
VULCAN Guard Installation Protects Isomerization Catalysts
Liquid Phase vs Gas Phase: Relative Advantages
Liquid Phase Treating
Which active metal is best?
Thiophenes and Nickel Sulfur Guards
Sulfiding mechanisms with reduced metals
Thiophene adsorption on nickel
Advantages of Cu/Zn Over Nickel Sulfur Guards
Copper oxide vs Nickel
Nickel Sulfur Guards
Manganese Sulfur Guards
The Benefits and Disadvantages of Potash in Steam ReformingGerard B. Hawkins
Why do we include potash ?
What are the benefits ?
What are the disadvantages ?
Catalyst Deactivation
Carbon Deposition : Thermodynamics & Kinetics
Carbon formation margin
Reaction chemistry (Tube inlet)
Hydrocarbons undergo cracking reactions on hot surfaces at the tube inlet
Products of catalytic cracking reactions can form polymeric carbon
Introduction High temperature shift Catalysts
Low temperature shift catalysts
Catalyst storage, handling, charging and discharging
Health and safety precautions
Reduction and start-up of high temperature shift catalysts
Operation of high temperature shift catalysts
Reduction and start-up of low temperature shift catalysts
Operation of low temperature shift catalysts
Reactor and Catalyst Design
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 CATALYST DESIGN
4.1 Equivalent Pellet Diameter
4.2 Voidage
4.3 Pellet Density
5 REACTOR DESIGN
6 CATALYST SUPPORT
6.1 Choice of Support
TABLES
1 CATALYST SUPPORT SHAPES
2 SECONDARY REFORMER SPREADSHEET
FIGURES
1 GRAPH OF EFFECTIVENESS v THIELE MODULUS
2 VARIATION OF COSTS WITH CATALYST SIZE
3 VARIATION OF COSTS WITH CATALYST BED VOIDAGE
4 VARIATION OF COSTS WITH VESSEL DIAMETER
Reformer Tube design principles
- Larsen Miller Plot
- Larsen Miller & Tube Design
- Design Margins - Stress Data Used
- Max Allowable & Design Temperature
- Tube Life
- Effect of Temperature on Life
- Material Types
HK40: 25 Cr / 20 Ni
HP Modified: 25 Cr / 35 Ni + Nb
Microalloy: 25 Cr / 35 Ni + Nb + Ti
- Alloy Developments
- Comparison of Alloys
Manufacturing Technology
- Welds
Failure mechanisms
- Failure Mechanisms - Creep
- Creep Propagation
- Common Failure Modes
- Uncommon Failure Modes
- Failure by Creep
- Creep Rupture - Cross Section
- Failure at Weld
Actions to Take if Tube Fails
- Pigtail Nipping
Inspection techniques
Classification of Problems
- Visual Examination
- Girth Measurement
- Ultrasonic Attenuation
- Radiography
Eddy Current Measurement
LOTIS Tube Inspection
LOTIS Compared to External Inspection
Equilibrium Effects
- Methane Steam
- Water Gas Shift
Relationship of Kp to Temperature
Relationship of WGS Kp to Temperature
Effect of Temperature on Methane Slip
Approach to Equilibrium
Reaction Path and Equilibrium
Effect of Pressure Increase
Operating Parameters
- Pressure
- Temperature
- Feed Rate
- Steam to Carbon
Effect of Exit Temperature Spread
Useful Tools
Calculating ATM
Steam Reformer Surveys - Techniques for Optimization of Primary Reformer Oper...Gerard B. Hawkins
Introduction
Background Radiation and Temperature Measurement
Reformer Survey Inputs
Other Troubleshooting Tools
Safety
Preparation
Onsite Data Collection
TWT Survey
Observation/Troubleshooting
Modelling and Analysis
Results/Outputs
Case Studies
Conclusions
Case Study 1
Case Study 2
Case Study 3
Conclusions
Purpose
Key to good performance
Problem Areas
Catalysts, heat shields and plant up-rates
Burner Guns
Development of High Intensity Ring Burner
Case Studies
Conclusions
Most modern ammonia processes are based on steam-reforming of natural gas or naphtha.
The 3 main technology suppliers are Uhde (Uhde/JM Partnership), Topsoe & KBR.
The process steps are very similar in all cases.
Other suppliers are Linde (LAC) & Ammonia Casale.
Catalytic Reactions in Catalytic Reforming
Catalytic Reforming Reactions
Sulfur Related Problems
Effects of Sulfur in Catalytic Reforming
Reactions in Catalytic Reforming
Catalytic Reforming Catalysts
Effect of Sulfur on Catalytic Reforming Catalysts
Catalytic Reformer Efficiency
VULCAN Sulfur Guards
VULCAN Sulfur Guards for Catalytic Reformers
VULCAN Guard Installation Protects Isomerization Catalysts
Liquid Phase vs Gas Phase: Relative Advantages
Liquid Phase Treating
Which active metal is best?
Thiophenes and Nickel Sulfur Guards
Sulfiding mechanisms with reduced metals
Thiophene adsorption on nickel
Advantages of Cu/Zn Over Nickel Sulfur Guards
Copper oxide vs Nickel
Nickel Sulfur Guards
Manganese Sulfur Guards
The Benefits and Disadvantages of Potash in Steam ReformingGerard B. Hawkins
Why do we include potash ?
What are the benefits ?
What are the disadvantages ?
Catalyst Deactivation
Carbon Deposition : Thermodynamics & Kinetics
Carbon formation margin
Reaction chemistry (Tube inlet)
Hydrocarbons undergo cracking reactions on hot surfaces at the tube inlet
Products of catalytic cracking reactions can form polymeric carbon
Calculation of an Ammonia Plant Energy Consumption: Gerard B. Hawkins
Calculation of an Ammonia Plant Energy Consumption:
Case Study: #06023300
Plant Note Book Series: PNBS-0602
CONTENTS
0 SCOPE
1 CALCULATION OF NATURAL GAS PROCESS FEED CONSUMPTION
2 CALCULATION OF NATURAL GAS PROCESS FUEL CONSUMPTION
3 CALCULATION OF NATURAL GAS CONSUMPTION FOR PILOT BURNERS OF FLARES
4 CALCULATION OF DEMIN. WATER FROM DEMIN. UNIT
5 CALCULATION OF DEMIN. WATER TO PACKAGE BOILERS
6 CALCULATION OF MP STEAM EXPORT
7 CALCULATION OF LP STEAM IMPORT
8 DETERMINATION OF ELECTRIC POWER CONSUMPTION
9 DETERMINATION OF THE TOTAL ENERGY CONSUMPTION OF THE AMMONIA PLANT ISBL
10 ADJUSTMENT OF ELECTRIC POWER CONSUMPTION FOR TEST RUN CONDITIONS
11 CALCULATION OF AMMONIA SHARE IN MP STEAM CONSUMPTION IN UTILITIES
12 CALCULATION OF AMMONIA SHARE IN ELECTRIC POWER CONSUMPTION IN UTILITIES
13 DETERMINATION OF THE TOTAL ENERGY CONSUMPTION OF THE AMMONIA PLANT OSBL
14 DETERMINATION OF THE TOTAL ENERGY CONSUMPTION OF THE AMMONIA PLANT
Pressure Relief Systems Vol 2
Causes of Relief Situations
This Volume 2 is a guide to the qualitative identification of common causes of overpressure in process equipment. It cannot be exhaustive; the process engineer and relief systems team should look for any credible situation in addition to those given in this Part which could lead to a need for pressure relief (a relief situation).
Ammonia Plant Technology
Pre-Commissioning Best Practices
Piping and Vessels Flushing and Cleaning Procedure
CONTENTS
1 Scope
2 Aim/purpose
3 Responsibilities
4 Procedure
4.1 Main cleaning methods
4.1.1 Mechanical cleaning
4.1.2 Cleaning with air
4.1.3 Cleaning with steam (for steam networks only)
4.1.4 Cleaning with water
4.2 Choice of the cleaning method
4.3 Cleaning preparation
4.4 Protection of the devices included in the network
4.5 Protection of devices in the vicinity of the network
4.6 Water flushing procedure
4.6.1 Specific problems of water flushing
4.6.2 Preparation for water flushing
4.6.3 Performing a water flush
4.6.4 Cleanliness criteria
4.7 Air blowing procedure
4.7.1 Specific problems of air blowing
4.7.2 Preparation for air blowing
4.7.3 Performing air blowing
4.7.4 Cleanliness checks
4.8 Steam blowing procedure
4.8.1 Specific problems of steam blowing
4.8.2 Preparation for steam blowing
4.8.3 Performing steam blowing
4.8.4 Cleanliness checks
4.9 Chemical cleaning procedure
4.9.1 Specific problems of cleaning with a chemical solution
4.9.2 Preparation for chemical cleaning
4.9.3 Performing a chemical cleaning
4.9.4 Cleanliness criteria
4.10 Re-assembly - general guideline
4.11 Preservation of flushed piping
Ammonia Plant Technology
Pre-Commissioning Best Practices
GBHE-APT-0102
PICKLING & PASSIVATION
CONTENTS
1 PURPOSE OF THE WORK
2 CHEMICAL CONCEPT
3 TECHNICAL CONCEPT
4 WASTES & SAFETY CONCEPT
5 TARGET RESULTS
6 THE GENERAL CLEANING SEQUENCE MANAGEMENT
6.6.1 Pre-cleaning or “Physical Cleaning
6.6.2 Pre-rinsing
6.6.3 Chemical Cleaning
6.6.4 Critical Factors in Cleaning Success
6.6.5 Rinsing
6.6.6 Inspection and Re-Cleaning, if Necessary
7 Systems to be treated by Pickling/Passivation
GAS DISPERSION - A Definitive Guide to Accidental Releases of Heavy GasesGerard B. Hawkins
GAS DISPERSION - A Definitive Guide to Accidental Releases of Heavy Gases
This Process Safety Guide has been written with the aim of assisting process engineers, hazard analysts and environmental advisers in carrying out gas dispersion calculations. The Guide aims to provide assistance by:
• Improving awareness of the range of dispersion models available within GBHE, and providing guidance in choosing the most appropriate model for a particular application.
• Providing guidance to ensure that source terms and other model inputs are correctly specified, and the models are used within their range of applicability.
• Providing guidance to deal with particular topics in gas dispersion such as dense gas dispersion, complex terrain, and modeling the chemistry of oxides of nitrogen.
• Providing general background on air quality and dispersion modeling issues such as meteorology and air quality standards.
• Providing example calculations for real practical problems.
SCOPE
The gas dispersion guide contains the following Parts:
1 Fundamentals of meteorology.
2 Overview of air quality standards.
3 Comparison between different air quality models.
4 Designing a stack.
5 Dense gas dispersion.
6 Calculation of source terms.
7 Building wake effects.
8 Overview of the chemistry of the oxides of nitrogen.
9 Overview of the ADMS complex terrain module.
10 Overview of the ADMS deposition module.
11 ADMS examples.
12 Modeling odorous releases.
13 Bibliography of useful gas dispersion books and reports.
14 Glossary of gas dispersion modeling terms.
Appendix A : Modeling Wind Generation of Particulates.
APPENDIX B TABLE OF PROPERTY VALUES FOR SPECIFIC CHEMICALS
Pressure Relief Systems
BACKGROUND TO RELIEF SYSTEM DESIGN Vol.1 of 6
The Guide has been written to advise those involved in the design and engineering of pressure relief systems. It takes the user from the initial identification of potential causes of overpressure or under pressure through the process design of relief systems to the detailed mechanical design. "Hazard Studies" and quantitative hazards analysis are not described; these are seen as complementary activities. Typical users of the Guide will use some Parts in detail and others in overview.
Naphtha Steam Reforming Catalyst Reduction with MethanolGerard B. Hawkins
Procedure for Naphtha Steam Reforming Catalyst Reduction with Methanol
Scope
This procedure applies to the in situ reduction of VULCAN Series steam reforming catalysts using methanol cracking to form hydrogen over the catalyst in the steam reformer.
The procedure is likely to be applied to plants using only heavier feeds (e.g.: LPG and/or naphtha) and some combination of VULCAN Series catalysts.
Introduction
A small number of steam reforming plants do not have an available source of the commonly used reducing media (e.g.: hydrogen, hydrogen-rich off-gas, natural gas). These plants will usually operate on LPG and/or naphtha feed only where cracking of this hydrocarbon is not usually advised for reduction of the steam reforming catalyst ...
This Engineering Design Guide has several aims.
It is intended to take an experienced mechanical engineer through the steps necessary to specify a gear and to carry out an assessment of gears offered against a particular specification for pumps, fans and compressors driven by electric motors, steam turbines, combustion gas turbines or expanders. It is not part of this Engineering Design Guide to show how to decide that a gear is or is not necessary for a particular duty.
CONTENTS
1 SCOPE
2 PROPERTIES OF FLUID
2.1 General Properties of Sodium Hydroxide
2.2 Physical Properties of Sodium Hydroxide and its Solutions
2.3 Chemical Properties and uses of Sodium Hydroxide
2.4 Physiological effects of Sodium Hydroxide
2.5 Specifications of Commercial Caustic Soda Grades
3 CHOICE OF PUMP TYPE
3.1 Pump Duty
3.2 Pump Type
4 RECOMMENDED LINE DIAGRAMS
5 RECOMMENDED LAYOUT
6 CONSTRUCTION FEATURES
7 MATERIALS OF CONSTRUCTION
7.1 Nickel and Nickel Alloys
7.2 Austenitic Stainless Steel
7.3 Aluminium, Aluminium Alloys, etc.
7.4 Non-Metallic Materials
TABLES
1 PHYSICAL PROPERTIES (Solid Form)
2 PHYSICAL PROPERTIES (Solution Form)
3 CAUSTIC SODA GRADES
FIGURES
1.1 LINE DIAGRAM - HORIZONTAL GLANDED, GLANDLESS AND VERTICAL IN-LINE PUMPS
1.2 LINE DIAGRAM - VERTICAL SPINDLE CANTILEVER PUMPS
1.3 LINE DIAGRAM - SELF PRIMING PUMPS
1.4 LINE DIAGRAM - RECIPROCATING PLUNGER METERING PUMPS
1.5 LINE DIAGRAM - POSITIVE DISPLACEMENT DIAPHRAGM METERING PUMPS
1.6 WATER FLUSHING ARRANGEMENT FOR DOUBLE MECHANICAL SEAL
1.7 WATER FLUSH (QUENCH) ARRANGEMENT FOR SINGLE HARD FACED (CARBIDE) SEAL AND BACK-UP LIP SEAL
2 PHASE DIAGRAM OF NaOH-H2O
3 VISCOSITY OF AQUEOUS CAUSTIC SODA SOLUTIONS
4 VAPOR PRESSURE OF AQUEOUS CAUSTIC SODA SOLUTIONS
5 ENTHALPY CONCENTRATION FOR AQUEOUS CAUSTIC SODA SOLUTIONS
6 SPECIFIC GRAVITY FOR AQUEOUS CAUSTIC SODA SOLUTIONS
7 DILUTION OF CAUSTIC SODA LIQUOR
8 THERMAL CONDUCTIVITY OF AQUEOUS CAUSTIC SODA SOLUTIONS
9 SPECIFIC HEAT OF CAUSTIC SODA SOLUTIONS
10 BOILING POINTS OF STRONG CAUSTIC SODA SOLUTIONS AT REDUCED PRESSURE
11 COMMENCEMENT OF FREEZING OF CAUSTIC SODA SOLUTIONS (0 - 52% W/W)
12 TEMPERATURES ATTAINED ON DISSOLUTION OF ANHYDROUS CAUSTIC SODA
13 HEAT OF SOLUTION FOR ANHYDROUS CAUSTIC SODA
14 SOLUBILITY OF SODIUM CHLORIDE IN CAUSTIC SODA SOLUTIONS
15 DENSITY - CONCENTRATION TABLES FOR CAUSTIC SODA SOLUTIONS AT 600 F (15.5 0 C)
16 MATERIAL SELECTION CHART FOR CAUSTIC SODA HANDLING
Naphtha Steam Reforming Catalyst Reduction by NH3 CrackingGerard B. Hawkins
Procedure for Naphtha Steam Reforming Catalyst Reduction by NH3 Cracking
Scope
This procedure applies to the in situ reduction of VULCAN Series steam reforming catalysts using ammonia cracking to form hydrogen over the catalyst in the steam reformer. This procedure covers plants with a dry gas circulation loop for reduction. The procedure is likely to be applied to plants using only heavier feeds (e.g.: LPG and/or naphtha) and some combination of VULCAN Series catalysts.
Introduction
A small number of steam reforming plants do not have an available source of the commonly used reducing media (e.g.: hydrogen, hydrogen-rich off-gas, natural gas). These plants will usually operate on LPG and/or naphtha feed only where cracking of this hydrocarbon is not usually advised for reduction of the steam reforming catalyst. In such circumstances, the plant may be designed to use the installed steam reforming catalyst to crack ammonia to provide hydrogen for the reformer catalyst reduction....
GE / Texaco Gasifier Feed to a Lurgi Methanol Plant and its Effect on Methano...Gerard B. Hawkins
GE / Texaco Gasifier Feed to a Lurgi Methanol Plant and its Effect on Methanol Production
CONTENTS
0 Methanol Synthesis Introduction
1 Executive Summary
2 Design Basis
2.1.1 Train I Design Basis
2.1.2 Train II Design Basis
2.1.3 Train III Design Basis
2.2 Design Philosophy
2.2.1 Operability Review
2.3 Assumptions
2.4 Train IV Flowsheet
2.4.1 CO2 Removal
3 Discussion
3.1 Natural Gas Consumption Figures
3.1.1 Base Case
3.1.2 Case 1 – Coal Gasification in Service
3.1.3 Case 2 – Coal Gasification in Service – No CO2 Export
3.2 Methanol Production Figures
3.2.1 Base Case
3.2.2 Case 1 – Coal Gasification in Service
3.2.3 Case 2 – Coal Gasification in Service – No CO2 Export
3.3 85% Natural Gas Availability
3.4 100% Natural Gas Availability
3.5 CO2 Emissions
3.5.1 Base Case
3.5.2 Case 1 – Coal Gasification in Service
3.5.3 Case 2 – Coal Gasification in Service – No CO2 Export
3.6 Specific Consumption Figures
3.6.1 Base Case
3.6.2 Case 1 – Coal Gasification and CO2 Import
3.6.3 Case 2 – Coal Gasification and No CO2 Import
3.7 Train IV Synthesis Gas Composition
4 Further Work
5 Conclusion
APPENDIX
Important Stream Data – Material Balance Stream Data
Texaco Gasifier with HP Steam Raising Boiler
CHARACTERISTICS OF COAL
Material Balance Considerations
Methanation catalysts are almost always manufactured and transported in the oxidized form, and therefore they must be reduced in the reactor to give nickel metal in order to make them active. The reduction is usually carried out in process gas and occurs by the two reactions:
Debottlenecking Claus Sulfur Recovery Units: An Investigation of the applicat...Gerard B. Hawkins
Debottlenecking Claus Sulfur Recovery Units: An Investigation of the application of Zinc Titanates
1 Executive Summary
2 Claus Process
2.1 Partial Combustion Claus
2.2 Split Flow Claus
2.3 Sulfur Recycle Claus
3 Zinc Titanates
4 Application of Zinc Titanate to Debottleneck Partial Combustion Claus by 10%
4.1 Process
4.2 ASPEN Modeling Results
4.3 Cost of Zinc Titanate Bed Installation
4.3.1 Basis of Costing
4.3.2 Zinc Titanate Beds
4.3.3 Regen Cooler
4.3.4 Blowers
4.3.5 Results
4.4 Alternative Debottlenecking Technology for Partial Combustion Claus
4.5 Cost of 10% Debottlenecking Using COPE Process
5 Debottlenecking Claus Split Flow System by 10% with Zinc Titanates
6 Debottlenecking Claus Sulfur Recycle System With Zinc Titanate
7 Effect of Zinc Titanate Debottlenecking on Existing Tail; Gas Treatment Systems
7.1 Selectox
7.2 SuperClaus99
7.3 Superclaus 99.5
7.4 SCOT Process
7.5 Zinc Titanate as a Claus Tail Gas Treatment
7.6 H2S Removal Efficiency With Zinc Titanate
8 Effects on COS and CS2 Formation
9 Questions for further Investigation
FIGURES
Figure 1 Claus Unit and TGCU
Figure 2 Claus Process
Figure 3 Typical Claus Sulfur Recovery Unit
Figure 4 Two-Stage Claus SRU
Figure 5 The Super Claus Process
Figure 6 SCOT
Figure 7 SCOT/BSR-MDEA (or clone) TGCU
REFERENCES: PATENTS
US4333855_PROMOTED_ZINC_TITANATE_CATALYTIC_AGENT
US4394297_ZINC_TITANATE_CATALYST
US6338794B1_DESULFURIZATION_ZINC_TITANATE_SORBENTS
Pumps for Hydrocarbon Service
1 SCOPE
2 HYDROCARBON PROPERTIES
2.1 General
2.2 Pure Hydrocarbons
2.3 Associated Compounds
2.4 Crude Oil
2.5 Toxicology
2.6 Cavitation
2.7 Velocity of Sound
3 FLAMMABILITY HAZARDS
3.1 General
3.2 Definitions
3.3 The Electrical Area Classification
4 CHOICE OF PUMP TYPE
5 LINE DIAGRAM (PROCESS)
6 LAYOUT
7 SHAFT SEALS
7.1 Selection
7.2 Engineering of Seals
8 CONSTRUCTION FEATURES
8.1 General
8.2 Effects of Low Density
9 MATERIALS OF CONSTRUCTION
9.1 Process Wetted Parts
9.2 Mechanical Components
9.3 Non Metallic’s
APPENDIX A - BARNARD & WEIR SEAL THEORY FIGURES
1 VAPOR PRESSURE OF HYDROCARBONS
2 VAPOR PRESSURE OF LIGHT HYDROCARBONS
3 VAPOR PRESSURE OF GASOLINES
4 SPECIFIC HEAT OF HYDROCARBON LIQUIDS
5 SPECIFIC GRAVITY OF OLEFINE, DI OLEFINES AND PARAFFINS
6 SPECIFIC GRAVITY OF AROMATICS
7 VISCOSITY - TEMPERATURE CHART FOR PARAFFINS, AROMATICS
AND PETROLEUM FRACTIONS
8 VISCOSITY - TEMPERATURE CHART FOR MINERAL LUBRICATING
OILS
TABLES
1 PURE HYDROCARBON PROPERTIES
2A CRUDE OILS PROPERTIES
2B NINIAN: PROPERTIES OF CRUDE OIL, NAPHTHAS AND KEROSENE
2C NINIAN: PROPERTIES OF GAS OILS AND RESIDUES
3 PURE HYROCARBON FLAMMABILITY PROPERTIES
BIBLIOGRAPHY
Reactor Arrangement for Continuous Vapor Phase ChlorinationGerard B. Hawkins
Reactor Arrangement for Continuous Vapor Phase Chlorination
CONTENTS
1 BACKGROUND
2 REACTOR
3 CHEMICAL SYSTEM
4 PROCESS CHEMISTRY
5 KINETICS EXPERIMENTS AND MODELING
6 INTERPRETATION OF KINETICS INFORMATION
7 OPERATING CONDITIONS AND REACTOR DESIGN
8 REACTOR STABILITY AND CONTROL
FIGURES
1 POSTULATED REACTION PATHS FOR PROGRESSIVE CHLORINATION OF B-PICOLINE 3
2 CHLORINATION OF b-PICOLINE: MODEL PREDICTIONS OF PRODUCT DISTRIBUTION IN FULLY-MIXED REACTOR
3 TWO-STAGE REACTOR: RATE OF CHLORINATION OF b-PICOLINE
DOCUMENTS REFERRED TO IN THIS PROCESS ENGINEERING GUIDE
METHANOL PLANT - SHALE GAS FEED PRETREATMENT
CASE STUDY #091406
Case Background
A Methanol plant operator would like to examine the technical feasibility of using Shale Gas as a feedstock to their Methanol plant.
The first step in the Methanol production process is gas pretreatment. The purpose of gas pretreatment is to make the gas suitable for the downstream processes. There are two groups of compounds that are usually present in natural gas and that should be removed during pretreatment—the associate NGL and the sulfur-containing compounds. Some natural gas reservoirs may also have other trace components that must be removed, but these are not discussed here.
This case study examines the impact of CO2 (Carbon Dioxide) on the pre-treatment section design, performance and efficiency of ACME Methanol Plant’ feed gas pre-treatment section.
Case 1: Normal Shale Gas
Case 2: “Bad Gas”
Case 3: Low CO2
Case 4: High CO2
Methanol Casale Advanced Reactor Concept (ARC) Converter Retrofit CASE STUDY #10231406
For older methanol plants, efficiency is worse than for a modern plant
• To maximize profit we must improve either
– Plant efficiency
– Plant production rate
This case study highlights the revamp of a Middle Eastern Methanol Plant ARC converter with part IMC internals, to improve efficiency and production; with no CO2 addition to the Synloop, and with CO2 addition to the Synloop.
- 250 TPD CO2
- 500 TPD CO2
SYNGAS CONDITIONING UNIT FEASIBILITY CASE STUDY: COAL-TO-LIQUIDSGerard B. Hawkins
SYNGAS CONDITIONING UNIT FEASIBILITY CASE STUDY: COAL-TO-LIQUIDS
Case Study: #0953616GB/H
HT SHIFT REACTOR CATALYST SPECIFICATION
Process Specification
This process duty specification refers to a Syngas Conditioning Unit which utilizes HT Shift reaction technology on a slip stream of raw gas to produce a recombined gas stream with a H2:CO ratio of 1.57:1. This is an important consideration as the Shift reactor is not required to minimize CO at outlet, and this specification refers to the expected performance that can be achieved in a single stage reactor scheme.
The Syngas Conditioning Unit is part of a proposed coal-to-liquids complex in which synthesis gas is produced by gasification of coal for downstream processing in a Fischer Tropsch reactor and Hydrocracker unit.
DEACTIVATION OF METHANOL SYNTHESIS CATALYSTS
CONTENTS
1 INTRODUCTION
2 THERMAL SINTERING
3 CATALYST POISONING
4 REACTANT INDUCED DEACTIVATION
5 SUMMARY
TABLES
1 DEACTIVATION PROCESSES ON METHANOL SYNTHESIS CATALYSTS
2 MELTING POINT, HUTTIG AND TAMMANN TEMPERATURES OF COPPER, IRON AND NICKEL
3 SINTERING RATE CONSTANTS CALCULATED INLET AND OUTLET SIDE STREAM UNIT FOR VULCAN VSG-M101
4 COMPARISON BETWEEN CALCULATED S∞ AND DISCHARGED MEASUREMENTS ON VULCAN VSG-M101
5 EFFECT OF POSSIBLE CONTAMINANTS AND POISONS ON CU/ZNO/AL2O3 CATALYSTS FOR METHANOL SYNTHESIS
6 GUARD SCREENING TEST RESULTS ON METHANOL MICRO-REACTOR. EFFECT OF DEPOSITED METALS ON METHANOL ACTIVITY
FIGURES
1 THE HΫTTIG AND TAMMANN TEMPERATURES OF THE COMPONENTS OF A SYNTHESIS CATALYST
2 A SCHEMATIC REPRESENTATION OF TWO CATALYST SINTERING MECHANISMS
3 SIDE STREAM DATA FOR VULCAN VSG-M101. INLET TEMPERATURE 242 OC, PRESSURE 1500 PSI, GAS COMPOSITION 6% CO, 9.2% CO2, 66.9% H2, 2.5% N2 AND 15.4% CH4, SPACE VELOCITY 17,778 HR-1. MEAN OUTLET TEMPERATURE 280 OC
4 TEMPERATURE DEPENDENCE OF THE RATE OF SINTERING
5 MECHANISM OF SULFUR RETENTION
6 CORRELATION OF SULFUR CAPACITY WITH TOTAL SURFACE AREA
7 EFFECT OF DEPOSITED (NI+FE) PPM ON METHANOL SYNTHESIS CATALYST ACTIVITY
8 DISCHARGED (FE + NI) DEPOSITION LEVELS ON METHANOL SYNTHESIS PLANT SAMPLES
9 EPMA ANALYSIS OF DISCHARGED LABORATORY SAMPLE OF POISONED VULCAN VSG-M101
10 THE EFFECT OF CO2 ON SYNTHESIS CATALYST DEACTIVATION
REFERENCES
H - Acid Caustic Fusion Stage
CONTENTS
0 INTRODUCTION
1 DESIGN INFORMATION
1.1 Reactor Type
1.2 Temperature Range
1.3 Pressure Range
1.4 Chemical System
2 BACKGROUND
3 KINETICS AND MECHANISM
4 MAXIMUM YIELD AND IMPLICATIONS FOR REACTOR DESIGN
5 USE OF DESIGN MODEL FOR START-UP AND MANUFACTURING MONITORING
6 BIBLIOGRAPHY
FIGURES
1 FUSION MODEL OUTLINE MECHANISM AND KINETIC SCHEME
2 TEST RUN OPTIMIZATION OF HEATING TIME 3600 kg/h STEAM
Psychrometry
0 INTRODUCTION / PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 PSYCHROMETRIC CHARTS
5 EXAMPLE CALCULATION
6 CHARTS FOR SPECIFIC SYSTEMS
7 BIBLIOGRAPHY
FIGURES
1 GROSVENOR CHART (Humidity vs. Temperature)
FOR AIR-WATER VAPOR AT 1.0133 bar
2 MOLLIER CHART (Enthalpy vs. Humidity) FOR
NITROGEN-TOLUENE VAPOR AT 100 kPa
Data Sources For Calculating Chemical Reaction EquilibriaGerard B. Hawkins
Data Sources For Calculating Chemical Reaction Equilibria
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
4 BACKGROUND TO THEORY
5 BIBLIOGRAPHY
Integration of Special Purpose Reciprocating Compressors into a ProcessGerard B. Hawkins
1 SCOPE
2 CHOICE OF COMPRESSOR TYPE
2.1 Parameters
2.2 Preliminary Choice of Machine Type
2.3 Review of Other Types of Compressor
3 CHOICE OF NUMBER OF COMPRESSORS
3.1 Influence of Reliability Classification
3.2 Driver Considerations
3.3 Deterioration of Standby Machines
4 EFFECTS OF PROCESS GAS COMPOSITION
4.1 Particulate Contamination
4.2 Droplets in Suspension
4.3 Polymer Deposit
4.4 Molecular Weight Variation
4.5 Compressibility Variation
4.6 Gas Dryness
4.7 Gas Solution in Lubricating Oil for Cylinder and Gland
5 THROUGHPUT REGULATION
5.1 Inlet Line Throttle Valve
5.2 Inlet Line Cut-off Valve
5.3 Compressor Inlet Valve Lifter
5.4 Clearance Volume Variation
5.5 Speed Variation
5.6 Bypass
5.7 Hybrid Regulation Systems
6 PRINCIPAL FEATURES
6.1 Calculate Discharge Gas Temperature
6.2 Choice of Number of Stages
6.3 Configuration
6.4 Valve Operation Limit on Piston Speed
6.5 Limits for Mean Piston Speed
6.6 Estimation of Volumetric Efficiency
6.7 Estimation of Crankshaft Rotational Speed
6.8 Calculation of Piston Diameter
6.9 Choice of Number of Cylinders
7 DRIVER TYPE
7.1 Electric Motors
7.2 Steam Turbines
7.3 Special Drivers
8 VESSELS
APPENDICES
A RELIABILITY CLASSIFICATION
B CONDITIONS FOR LUBRICATED CYLINDERS AND GLANDS
C ESTIMATE OF LUBE OIL CONTAMINATION OF PROCESS GAS
D INFLUENCE OF GAS COMPOSITION AND MACHINE CONSTRUCTION
ON FILLED PTFE PISTON RING SEALS
E LIMITS ON GAS TEMPERATURES
FIGURES
1 SELECTION CHART
2 DESIGN SEQUENCE 1 - ESTIMATE NUMBER OF STAGES
3 DESIGN SEQUENCE 2 - ESTIMATE CYLINDER SIZES
In pyrolysis gasoline hydrogenation there is a tendency to form polymeric materials on and in the catalyst bed. These are formed by condensation of gums and diolefins at local areas in the reactor .........
(AGRU) ACID GAS SOUR SHIFT: CASE STUDY IN REFINERY GAS TREATMENTGerard B. Hawkins
(AGRU) ACID GAS SOUR SHIFT: CASE STUDY IN REFINERY GAS TREATMENT; Case Study: #0978766GB/H
CASE STUDY OVERVIEW
Syn Gas Sour Shift: Process Flow Diagram
AGR: Acid Gas to VULCAN SYSTEMS Sour Gas Shift
DESIGN BASIS:
ACID GAS REACTOR CATALYST SPECIFICATION
SOUR SHIFT CASE
SHIFT REACTOR CATALYST SPECIFICATIONS
COS REACTOR CATALYST SPECIFICATIONS
SWEET SHIFT CASE
SHIFT REACTOR CATALYST SPECIFICATIONS
PERFORMANCE SIMULATION RESULTS
SOUR SHIFT SECTION
1 Cases Considered
2 Catalyst Used
3 Client Requirements
4 Oxygen and Olefins
5 HCN
6 NH3
7 Arsine
8 Input Data Sour Shift Unit
9 Activity (PROPRIETARY)
10 Results
ADIABATIC SWEET SHIFT SECTION: HTS Reactor followed by LTS Reactor
1 Catalyst Used
2 Inlet Operating Temperature HTS Reactor
3 Feed Flow Rate, Inlet Operating Pressure and Feed Composition HTS Reactor
4 Inlet Operating Conditions LTS Reactor
5 Client Requirements
6 Results: Standard Case as Presented to the Client
7 Results: Inlet Operating Pressure HTS Reactor = 25.2 bara
8 Results: Addition of 100 kmol/h N2
COS HYDROLYSIS SECTION FOR SWEET SHIFT CASE
1 Total Feed Flow Rate, Feed Composition, Direction of Flow, Inlet Operating Temperature, Inlet Operating Pressure
2 Inlet H2S and COS Levels
3 Equilibrium H2S and COS Levels (COS Hydrolysis Reaction)
4 Client Requirements
5 Results
H2S REMOVAL SECTION AFTER AGR UNIT
(2 Absorbent Beds (VULCAN VSG-EZ200) in Lead/Lag Arrangement)
1 Total Feed Flow Rate, Feed Composition, Direction of Flow, Inlet Operating Temperature, Inlet Operating Pressure
2 Inlet H2S and COS Levels
3 Client Requirements (All Cases)
4 Results
ISOTHERMAL SWEET SHIFT SECTION: Alternative Approach
VULCAN Simulation Input Data
1 Enthalpy method
2 Cases considered
3 Feed stream data
4 Kinetics
5 Catalyst
6 Catalyst Activity relative to standard
7 Catalyst size and packing details
8 Catalyst pressure drop parameters
9 Catalyst Volume
10 Standard die-off rate
11 BFW Rate
12 Vapor fraction
13 Steam Temperature
14 Steam Pressure
15 Boiling Model
16 Volumetric UA
Isothermal Shift Simulations Results
APPENDIX
Characteristics of Acid Gas Removal Technologies
Conference for Catalysis Webinar 2021: "The Key Role of Catalysts and Adsorb...Dr. Meritxell Vila
Energy transition is a challenge for refineries and petrochemical plants. In this sense, the role of catalysts and adsorbents will be crucial in three areas:
New schemes of refineries: crude oil to chemicals (COTC)
Production of biofuels
Production of green hydrogen
This presentation was done at Catalysis Webinar 2021, the 24th March.
DESIGN OF VENT GAS COLLECTION AND DESTRUCTION SYSTEMS Gerard B. Hawkins
DESIGN OF VENT GAS COLLECTION AND DESTRUCTION SYSTEMS
CONTENTS
1 INTRODUCTION
1.1 Purpose
1.2 Scope of this Guide
1.3 Use of the Guide
2 ENVIRONMENTAL ISSUES
2.1 Principal Concerns
2.2 Mechanisms for Ozone Formation
2.3 Photochemical Ozone Creation Potential
2.4 Health and Environmental Effects
2.5 Air Quality Standards for Ground Level Concentrations of Ozone, Targets for Reduction of VOC Discharges and Statutory Discharge Limits
3 VENTS REDUCTION PHILOSOPHY
3.1 Reduction at Source
3.2 End-of-pipe Treatment
4 METHODOLOGY FOR COLLECTION & ASSESSMENT OF PROCESS FLOW DATA
4.1 General
4.2 Identification of Vent Sources
4.3 Characterization of Vents
4.4 Quantification of Process Vent Flows
4.5 Component Flammability Data Collection
4.6 Identification of Operating Scenarios
4.7 Quantification of Flammability Characteristics for Combined Vents
4.8 Identification, Quantification and Assessment of Possibility of Air Ingress Routes
4.9 Tabulation of Data
4.10 Hazard Study and Risk Assessment
4.11 Note on Aqueous / Organic Wastes
4.12 Complexity of Systems
4.13 Summary
5 SAFE DESIGN OF VENT COLLECTION HEADER SYSTEMS
5.1 General
5.2 Process Design of Vent Headers
5.3 Liquid in Vent Headers
5.4 Materials of Construction
5.5 Static Electricity Hazard
5.6 Diversion Systems
5.7 Snuffing Systems
6 SAFE DESIGN OF THERMAL OXIDISERS
6.1 Introduction
6.2 Design Basis
6.3 Types of High Temperature Thermal Oxidizer
6.4 Refractories
6.5 Flue Gas Treatment
6.6 Control and Safety Systems
6.7 Project Program
6.8 Commissioning
6.9 Operational and Maintenance Management
APPENDICES
A GLOSSARY
B FLAMMABILITY
C EXAMPLE PROFORMA
D REFERENCES
DOCUMENTS REFERRED TO IN THIS PROCESS GUIDE
TABLE
1 PHOTOCHEMICAL OZONE CREATION POTENTIAL REFERENCED
TO ETHYLENE AS UNITY
FIGURES
1 SCHEMATIC OF TYPICAL VENT COLLECTION AND THERMAL OXIDIZER SYSTEM
2 TYPICAL KNOCK-OUT POT WITH LUTED DRAIN
3 SCHEMATIC OF DIVERSION SYSTEM
4 CONVENTIONAL VERTICAL THERMAL OXIDIZER
5 CONVENTIONAL OXIDIZER WITH INTEGRAL WATER SPARGER
6 THERMAL OXIDIZER WITH STAGED AIR INJECTION
7 DOWN-FIRED UNIT WITH WATER BATH QUENCH
8 FLAMELESS THERMAL OXIDATION UNIT
9 THERMAL OXIDIZER WITH REGENERATIVE HEAT RECOVERY
10 TYPICAL PROJECT PROGRAM
11 TYPICAL FLAMMABILITY DIAGRAM
12 EFFECT OF DILUTION WITH AIR
13 EFFECT OF DILUTION WITH AIR ON 100 Rm³ OF FLAMMABLE GAS
PRACTICAL GUIDE ON THE SELECTION OF PROCESS TECHNOLOGY FOR THE TREATMENT OF A...Gerard B. Hawkins
PRACTICAL GUIDE ON THE SELECTION OF PROCESS TECHNOLOGY FOR THE TREATMENT OF AQUEOUS ORGANIC EFFLUENT STREAMS
CONTENTS
0 INTRODUCTION/PURPOSE
1 SCOPE
2 FIELD OF APPLICATION
3 DEFINITIONS
3.1 IPU
3.2 AOS
3.3 BODs
3.4 COD
3.5 TOC
3.6 Toxicity
3.7 Refractory Organics/Hard COD
3.8 Heavy Metals
3.9 EA
3.10 Biological Treatment Terms
3.11 BATNEEC
3.12 BPEO
3.13 EQS/LV
3.14 IPC
3.15 VOC
3.16 F/M Ratio
3.17 MLSS
3.18 MLVSS
4 DESIGN/ECONOMIC GUIDELINES
5 EUROPEAN LEGISLATION
5.1 General
5.2 Integrated Pollution Control (IPC)
5.3 Best Available Techniques Not Entailing Excessive Costs (BATNEEC)
5.4 Best Practicable Environmental Option (BPEO)
5.5 Environmental Quality Standards(EQS)
6 IPU EXIT CONCENTRATION
7 SITE/LOCAL REQUIREMENTS
8 PROCESS SELECTION PROCEDURE
8.1 Waste Minimization Techniques (WMT)
8.2 AOS Stream Definition
8.3 Technical Check List
8.4 Preliminary Selection of Suitable Technologies
8.5 Process Sequences
8.6 Economic Evaluation
8.7 Process Selection
APPENDICES
A DIRECTIVE 76/464/EEC - LIST 1
B DIRECTIVE 76/464/EEC - LIST 2
C THE EUROPEAN COMMISSION PRIORITY CANDIDATE LIST
D THE UK RED LIST
E CURRENT VALUES FOR EUROPEAN COMMUNITY ENVIRONMENTAL QUALITY STANDARDS AND CORRESPONDING LIMIT VALUES
F ESTABLISHED TECHNOLOGIES
G EMERGING TECHNOLOGY
H PROPRIETARY/LESS COMMON TECHNOLOGIES
J COMPARATIVE COST DATA
PRACTICAL GUIDE ON THE REDUCTION OF DISCHARGES TO ATMOSPHERE OF VOLATILE ORGA...Gerard B. Hawkins
PRACTICAL GUIDE ON THE REDUCTION OF DISCHARGES TO ATMOSPHERE OF VOLATILE ORGANIC COMPOUNDS (VOCs)
FOREWORD
CONTENTS
1 INTRODUCTION
2 THE NEED FOR VOC CONTROL
3 CONTROL AT SOURCE
3.1 Choice or Solvent
3.2 Venting Arrangements
3.3 Nitrogen Blanketing
3.4 Pump Versus Pneumatic Transfer
3.5 Batch Charging
3.6 Reduction of Volumetric Flow
3.7 Stock Tank Design
4 DISCHARGE MEASUREMENT
4.1 By Inference or Calculation
4.2 Flow Monitoring Equipment
4.3 Analytical Instruments
4.4 Vent Emissions Database
5 ABATEMENT TECHNOLOGY
5.1 Available Options
5.2 Selection of Preferred Option
5.3 Condensation
5.4 Adsorption
5.5 Absorption
5.6 Thermal Incineration
5.7 Catalytic Oxidation
5.8 Biological Filtration
5.9 Combinations of Process technologies
5.10 Processes Under Development
6 GLOSSARY OF TERMS
7 REFERENCES
Appendix 1. Photochemical Ozone Creation Potentials
Appendix 2. Examples of Adsorption Preliminary Calculations
Appendix 3. Example of Thermal Incineration Heat and Mass Balance
Appendix 4. Cost Correlations
EMERGENCY ISOLATION OF CHEMICAL PLANTS
CONTENTS
1 Introduction
2 When should Emergency Isolation Valves be Installed
3 Emergency Isolation Valves and Associated Equipment
3.1 Installations on existing plant
3.2 Actuators
3.3 Power to close or power to open
3.4 The need for testing
3.5 Hand operated Emergency Valves
3.6 The need to stop pumps in an emergency
3.7 Location of Operating Buttons
3.8 Use of control valves for Isolation
4 Detection of Leaks and Fires
5 Precautions during Maintenance
6 Training Operators to use Emergency Isolation Valves
7 Emergency Isolation when no remotely operated valve is available
References
Glossary
Appendix I Some Fires or Serious Escapes of Flammable Gases or Liquids that could have been controlled by Emergency Isolation Valves
Appendix II Some typical Installations
Amine Gas Treating Unit - Best Practices - Troubleshooting Guide Gerard B. Hawkins
Amine Gas Treating Unit Best Practices - Troubleshooting Guide for H2S/CO2 Amine Systems
Contents
Process Capabilities for gas treating process
Typical Amine Treating
Typical Amine System Improvements
Primary Equipment Overview
Inlet Gas Knockout
Absorber
Three Phase Flash Tank
Lean/Rich Heat Exchanger
Regenerator
Filtration
Amine Reclaimer
Operating Difficulties Overview
Foaming
Failure to Meet Gas Specification
Solvent Losses
Corrosion
Typical Amine System Improvements
Degradation of Amines and Alkanolamines during Sour Gas Treating
APPENDIX
Best Practices - Troubleshooting Guide
Burner Design, Operation and Maintenance on Ammonia PlantsGerard B. Hawkins
Burner Design, Operation and Maintenance on Ammonia Plants
Brief History
Reformer Burner Types/Design
Types of Reformers
Combustion Characteristics
Excess Air/Heater Efficiency
Maintenance, Good Practice
Low Nox Equipment
Summary
Catalyst Catastrophes in Syngas Production - II
Contents
Review of incidents by reactor
Primary reforming
Secondary reforming
HTS
LTS
Methanator
Reactor loading
Support media
Some general comments on alternative actions when a plant gets into abnormal operation
Catalyst Catastrophes in Syngas Production - I
The Hazards
Review incidents by reactor
Purification….
Through the various unit operations to
Ammonia synthesis
Nickel Carbonyl
Pre-reduced catalysts
Discharging catalysts
Conclusion
Integration of Special Purpose Centrifugal Pumps into a ProcessGerard B. Hawkins
Integration of Special Purpose Centrifugal Pumps into a Process
CONTENTS
1 SCOPE
2 PRELIMINARY CHOICE OF PUMP
SECTION A - INLET CONDITIONS
Al Calculation of Basic Nett Positive Suction Head (NPSH)
A2 Correction to Basic NPSH for Temperature Rise at Pump Inlet
A3 Correction to Basic NPSH for Acceleration Head
A4 Calculation of Available NPSH
A5 Correction to NPSH for Fluid Properties
A6 Calculation of Suction Specific Speed
A7 Priming
A8 Submergence
SECTION B – FLOW / HEAD RATING SEQUENCE
B1 Calculation of Static Head
B2 Calculation of Margins for Control
B3 Calculation of Q-H Duty
B4 Stability and Parallel Operation
B5 Corrections to Q-H Duty for Fluid Properties
B6 Guide to Pump Type and Speed
SECTION C – DRIVER POWER RATING
C1 Estimation of Pump Efficiency
C2 Calculation of Absorbed Power
C3 Calculation of Driver Power Rating
C4 Preliminary Power Ratings of Electric Motors
C5 Starting Conditions for Electric Motors
C6 Reverse Flow and Reverse Rotation
SECTION D - CASING PRESSURE RATING
D1 Calculation of Maximum Inlet Pressure
D2 Calculation of Differential Pressure
D3 Pressure Waves
D4 Pressure due to Liquid Thermal Expansion
D5 Casing Hydrostatic Test Pressure
SECTION E – SEALING CONSIDERATIONS
E1 Preliminary Choice of Seal
E2 Fluid Attributes
E3 Definition of Flushing Arrangements
APPENDICES
A RELIABILITY CLASSIFICATION
B SYMBOLS AND PREFERRED UNITS
DOCUMENTS REFERRED TO IN THIS ENGINEERING DESIGN GUIDE
Amines
Stereochemistry, Reaction Mechanisms, Catalysis, Production Processes and Applications
Contents
Historical perspective
Background
(MMA, DMA and TMA)
Stereochemistry and Structure
Reaction Mechanisms and Thermodynamics
CATALYSTS FOR AMINATION
Non-Zeolitic Catalysts for Amination
Mordinite (MOR) Catalysts for Amination
Zeolite Catalysts for Amination
Amines Production
Amines: Markets and Applications
Gas Separation
Conventional Amines Treating System
Amine System for Gas Sweetening
APPENDIX
Structures
Ethyleneamines Production
The Art of the Pitch: WordPress Relationships and SalesLaura Byrne
Clients don’t know what they don’t know. What web solutions are right for them? How does WordPress come into the picture? How do you make sure you understand scope and timeline? What do you do if sometime changes?
All these questions and more will be explored as we talk about matching clients’ needs with what your agency offers without pulling teeth or pulling your hair out. Practical tips, and strategies for successful relationship building that leads to closing the deal.
Key Trends Shaping the Future of Infrastructure.pdfCheryl Hung
Keynote at DIGIT West Expo, Glasgow on 29 May 2024.
Cheryl Hung, ochery.com
Sr Director, Infrastructure Ecosystem, Arm.
The key trends across hardware, cloud and open-source; exploring how these areas are likely to mature and develop over the short and long-term, and then considering how organisations can position themselves to adapt and thrive.
LF Energy Webinar: Electrical Grid Modelling and Simulation Through PowSyBl -...DanBrown980551
Do you want to learn how to model and simulate an electrical network from scratch in under an hour?
Then welcome to this PowSyBl workshop, hosted by Rte, the French Transmission System Operator (TSO)!
During the webinar, you will discover the PowSyBl ecosystem as well as handle and study an electrical network through an interactive Python notebook.
PowSyBl is an open source project hosted by LF Energy, which offers a comprehensive set of features for electrical grid modelling and simulation. Among other advanced features, PowSyBl provides:
- A fully editable and extendable library for grid component modelling;
- Visualization tools to display your network;
- Grid simulation tools, such as power flows, security analyses (with or without remedial actions) and sensitivity analyses;
The framework is mostly written in Java, with a Python binding so that Python developers can access PowSyBl functionalities as well.
What you will learn during the webinar:
- For beginners: discover PowSyBl's functionalities through a quick general presentation and the notebook, without needing any expert coding skills;
- For advanced developers: master the skills to efficiently apply PowSyBl functionalities to your real-world scenarios.
PHP Frameworks: I want to break free (IPC Berlin 2024)Ralf Eggert
In this presentation, we examine the challenges and limitations of relying too heavily on PHP frameworks in web development. We discuss the history of PHP and its frameworks to understand how this dependence has evolved. The focus will be on providing concrete tips and strategies to reduce reliance on these frameworks, based on real-world examples and practical considerations. The goal is to equip developers with the skills and knowledge to create more flexible and future-proof web applications. We'll explore the importance of maintaining autonomy in a rapidly changing tech landscape and how to make informed decisions in PHP development.
This talk is aimed at encouraging a more independent approach to using PHP frameworks, moving towards a more flexible and future-proof approach to PHP development.
Builder.ai Founder Sachin Dev Duggal's Strategic Approach to Create an Innova...Ramesh Iyer
In today's fast-changing business world, Companies that adapt and embrace new ideas often need help to keep up with the competition. However, fostering a culture of innovation takes much work. It takes vision, leadership and willingness to take risks in the right proportion. Sachin Dev Duggal, co-founder of Builder.ai, has perfected the art of this balance, creating a company culture where creativity and growth are nurtured at each stage.
State of ICS and IoT Cyber Threat Landscape Report 2024 previewPrayukth K V
The IoT and OT threat landscape report has been prepared by the Threat Research Team at Sectrio using data from Sectrio, cyber threat intelligence farming facilities spread across over 85 cities around the world. In addition, Sectrio also runs AI-based advanced threat and payload engagement facilities that serve as sinks to attract and engage sophisticated threat actors, and newer malware including new variants and latent threats that are at an earlier stage of development.
The latest edition of the OT/ICS and IoT security Threat Landscape Report 2024 also covers:
State of global ICS asset and network exposure
Sectoral targets and attacks as well as the cost of ransom
Global APT activity, AI usage, actor and tactic profiles, and implications
Rise in volumes of AI-powered cyberattacks
Major cyber events in 2024
Malware and malicious payload trends
Cyberattack types and targets
Vulnerability exploit attempts on CVEs
Attacks on counties – USA
Expansion of bot farms – how, where, and why
In-depth analysis of the cyber threat landscape across North America, South America, Europe, APAC, and the Middle East
Why are attacks on smart factories rising?
Cyber risk predictions
Axis of attacks – Europe
Systemic attacks in the Middle East
Download the full report from here:
https://sectrio.com/resources/ot-threat-landscape-reports/sectrio-releases-ot-ics-and-iot-security-threat-landscape-report-2024/
GDG Cloud Southlake #33: Boule & Rebala: Effective AppSec in SDLC using Deplo...James Anderson
Effective Application Security in Software Delivery lifecycle using Deployment Firewall and DBOM
The modern software delivery process (or the CI/CD process) includes many tools, distributed teams, open-source code, and cloud platforms. Constant focus on speed to release software to market, along with the traditional slow and manual security checks has caused gaps in continuous security as an important piece in the software supply chain. Today organizations feel more susceptible to external and internal cyber threats due to the vast attack surface in their applications supply chain and the lack of end-to-end governance and risk management.
The software team must secure its software delivery process to avoid vulnerability and security breaches. This needs to be achieved with existing tool chains and without extensive rework of the delivery processes. This talk will present strategies and techniques for providing visibility into the true risk of the existing vulnerabilities, preventing the introduction of security issues in the software, resolving vulnerabilities in production environments quickly, and capturing the deployment bill of materials (DBOM).
Speakers:
Bob Boule
Robert Boule is a technology enthusiast with PASSION for technology and making things work along with a knack for helping others understand how things work. He comes with around 20 years of solution engineering experience in application security, software continuous delivery, and SaaS platforms. He is known for his dynamic presentations in CI/CD and application security integrated in software delivery lifecycle.
Gopinath Rebala
Gopinath Rebala is the CTO of OpsMx, where he has overall responsibility for the machine learning and data processing architectures for Secure Software Delivery. Gopi also has a strong connection with our customers, leading design and architecture for strategic implementations. Gopi is a frequent speaker and well-known leader in continuous delivery and integrating security into software delivery.
"Impact of front-end architecture on development cost", Viktor TurskyiFwdays
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Theory of Carbon Formation in Steam Reforming
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GBH Enterprises, Ltd.
Theory of Carbon
Formation in Steam
Reforming
Process Information Disclaimer
Information contained in this publication or as otherwise supplied to Users is
believed to be accurate and correct at time of going to press, and is given in
good faith, but it is for the User to satisfy itself of the suitability of the Product for
its own particular purpose. GBHE gives no warranty as to the fitness of the
Product for any particular purpose and any implied warranty or condition
(statutory or otherwise) is excluded except to the extent that exclusion is
prevented by law. GBHE accepts no liability for loss, damage or personnel injury
caused or resulting from reliance on this information. Freedom under Patent,
Copyright and Designs cannot be assumed.
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Contents
1 Introduction
2 Underpinning Theory
2.1 Conceptualization
2.2 Reforming Reactions
2.3 Carbon Formation Chemistry
2.3.1 Natural Gas
2.3.2 Carbon Formation for Naphtha Feeds
2.3.3 Carbon Gasification
2.4 Heat Transfer
3 Causes
3.1 Effects of Carbon Formation
3.2 Types of Carbon
4 What are the Effects of Carbon Formation?
4.1 Why does Carbon Formation Get Worse?
4.1.1 So what is the Next Step?
4.2 Consequences of Carbon Formation
4.3 Why does Carbon Form where it does?
4.3.1 Effect on Process Gas Temperature
4.4 Why does Carbon Formation Propagate Down the Tube?
4.4.1 Effect on Radiation on the Fluegas Side
4.5 Why does Carbon Formation propagate Up the Tube?
5 How do we Prevent Carbon Formation
5.1 The Role of Potash
5.2 Inclusion of Pre-reformer
5.3 Primary Reformer Catalyst Parameters
5.3.1 Activity
5.3.2 Heat Transfer
5.3.3 Increased Steam to Carbon Ratio
6 Steam Out
6.1 Why does increasing the Steam to Carbon Ratio Not Work?
6.2 Why does reducing the Feed Rate not help?
6.3 Fundamental Principles of Steam Outs
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TABLES
1 Heat Transfer Coefficients in a Typical Reformer
2 Typical Catalyst Loading Options
FIGURES
1 Hot Bands
2 Conceptual Pellet
3 Naphtha Carbon Formation
4 Heat Transfer within an Reformer
5 Types of Carbon Formation
6 Effect of Carbon on Nickel Crystallites
7 Absorption of Heat
8 Comparison of "Base Case" v Carbon Forming Tube
9 Carbon Formation Vicious Circle
10 Temperature Profiles
11 Carbon Pinch Point
12 Carbon Formation
13 Effect on Process Gas Temperature
14 How does Carbon Propagate into an Unaffected Zone?
15 Movement of the Carbon Forming Region
16 Effect of Hot Bands on Radiative Heat Transfer
17 Effect of Potash on Carbon Formation
18 Application of a Pre-reformer
19 Effect of Activity on Carbon Formation
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Theory of Carbon Formation
1 Introduction
Carbon formation is a major problem for many operators of steam methane
reformers, most typically reformers of the Top Fired design. This document will
discuss the reasons why carbon formation occurs, how it develops and what can
be done to eliminate carbon formation.
The questions that hopefully will be answered are,
• How does carbon form?
• What are the causes of carbon formation?
• What are the effects of carbon formation?
• Why does carbon formation get worse?
• Why does carbon form where it does?
• Why does carbon formation propagate down the tube?
• Why does carbon formation propagate up the tube?
• How can carbon formation be prevented?
• Why does increasing the steam to carbon not remove carbon?
• Why does reducing the feed rate not remove carbon?
• How can we remove carbon?
If carbon is formed then eventually “hot bands” will be observed within the
reformer around one third of the way down the tube, or in the case of a bottom
fired design, one third up the tube. This is illustrated in the following picture,
Figure 1 – Hot Bands
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2 Underpinning Theory
The following sections will detail some of the underpinning theory behind carbon
formation, and as such will include details on,
• The conceptualization of the pellet,
• The reaction chemistry for both reforming and cracking reactions including
details on the reactions occurring with natural gas and naphtha as a
feedstock,
• The reaction chemistry for carbon gasification,
• Heat transfer
2.1 Conceptualization
For the purpose of this document, it is assumed that the reforming catalyst is a
pellet covered with nickel crystallites as shown below,
Figure 2 – Conceptual Pellet
The nickel crystallites in the “active” form are represented by the grey shapes
siting on the surface of the catalyst pellet. It is these crystallites that support the
reforming reaction.
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2.2 Reforming Reactions
The reforming reaction for methane can be described as,
CH4 + H2O CO + 3H2 Eqn 1
In parallel to this reaction is the water-gas shift reaction,
CO + H2O CO2 + H2 Eqn 2
And if these two reactions are combined, then the following reaction is the result,
CH4 + 2H2O CO2 + 4H2 Eqn 3
Clearly similar equations exist for the reforming of ethane, propane and butane,
C2H6 + 2H2O → 2CO + 5H2 Eqn 4
C3H8 + 3H2O → 3CO + 7H2 Eqn 5
C4H10 + 4H2O → 4CO + 9H2 Eqn 6
Or in the most general form,
CnH2m + nH2O nCO + (m+n)/2 H2 Eqn 7
The rate of methane steam reforming can be described by the following equation,
[ ] [ ]( )
[ ]4
TRΔE/4
CHPexpGSAAct
dt
CHd
×××∝ ×−
Eqn 8
Where,
• [CH4] is the methane concentration,
• t is time
• Act is the relative catalyst activity,
• GSA is the geometric surface area of the catalyst,
• ∆E is the activation energy for methane steam reforming,
• R is the universal gas constant,
• T is the temperature (in Kelvin),
• P[CH4] is the partial pressure of methane.
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Which can again be written in the more general form,
[ ] [ ]( )
[ ]2mn
TRΔE/2mn
HCPexpGSAAct
dt
HCd
×××∝ ×−
Eqn 9
2.3 Carbon Formation Reaction Chemistry
2.3.1 Natural Gas
Carbon can be formed by hydrocarbon cracking or CO disproportionation
(Boudouard reaction). In reformers for ammonia, hydrogen and methanol it is
hydrocarbon cracking that is the most likely to occur.
The simplistic reaction for the formation of carbon from methane can be written
as,
CH4 C + 2H2 Eqn 10
From this the reaction rate equation can be defined as,
[ ] ( )[ ]
[ ]4
TRΔE/4
4 CHPexp
dt
CHd
crackingCHofrate ×∝= ×−
Eqn 11
Where,
• [CH4] is the methane concentration,
• t is time
• ∆E is the activation energy for carbon cracking,
• R is the universal gas constant,
• T is the temperature (in Kelvin),
• P[CH4] is the partial pressure of methane.
The key issues to note are that,
• As the pressure rises, the rate of carbon formation increases,
• As the concentration of methane rises, the rate of carbon formation also
rises; this is really only true if the concentration of inerts (CO2 and N2 is
reduced); see below for the effect of increasing the higher hydrocarbon
content of the feed gas whilst reducing the methane content,
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• The rate of carbon formation rises with temperature; this is the classic
Arrehnius equation.
• When the hydrogen partial pressure is high enough the cracking reaction
will stop/reverse
Carbon forms in the region one third down the tube because at this point the
temperature is high enough for cracking reactions to proceed at a fast rate.
Carbon will form at this point if the hydrogen partial pressure from reforming is
not yet high enough to prevent the reactions from an equilibrium viewpoint.
Similarly for higher hydrocarbon, the following carbon cracking equations can be
written,
C2H6 → C2 + 3H2 Eqn 12
C3H8 → C3 + 4H2 Eqn 13
C4H10 → C4 + 5H2 Eqn 14
Which can be summarized as a general equation that says,
CnH2m → nC + mH2 Eqn 15
And in turn this can be translated into a reaction rate equation,
[ ] ( )[ ]
[ ]2mn
TRΔE/2mn
2mn HCPexp
dt
HCd
crackingHCofrate ×∝= ×−
Eqn 16
2.3.2 Carbon Formation for Naphtha Feeds
Naphtha feeds due to the inherent high carbon to hydrogen ratio and the fact that
conversion of long chain alkanes require that the hydrocarbons are first cracked
(before being reformed) mean that the carbon formation potential is greater than
for natural gas. The cracking process produces olefins which can then be
reformed to carbon oxides and hydrogen, however, in parallel to this there is also
the polymerization of these olefins to form carbon. Heavy hydrocarbons can also
thermally crack to produce carbon directly. These competing reactions are
illustrated below,
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Figure 3 – Naphtha Carbon Formation
2.3.3 Carbon Gasification
The above sections detail the various carbon forming reactions that can occur
with the various hydrocarbon feeds seen on steam reformers. There is, however,
a reverse reaction that removes carbon from the reforming catalyst and that is
the reaction of carbon with steam.
C + H2O CO + H2 Eqn 17
This is the carbon gasification reaction. Gasification can also occur with the
reaction of carbon with carbon dioxide as detailed below,
C + CO2 2CO Eqn 18
These reactions operate in tandem with the carbon lay down reactions and
provided that the total carbon removal reaction rate is faster than the lay down
rates of reaction, then there will be no net carbon laydown. It should be noted
that both these reactions are reversible and therefore, if the operating conditions
are suitable, carbon can be formed from these two reactions.
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2.4 Heat Transfer
Although the activity of the installed catalyst is important in determining the
reaction rate within a primary reformer, a second parameter, heat transfer is just
as important and in the case of reformers that are on the carbon pinch point
[q.v.], the heat transfer is even more important. This is because the hottest point
inside the tube is the tube inside wall. Within a primary reformer, the most
important heat transfer mechanism is radiation; however, within the tube
convection and conduction are also important.
This is key since any improvement in the heat transfer properties of the catalyst
will lead to a reduction in carbon formation potential. This is illustrated in the
figure below,
Figure 4 – Heat Transfer within an Reformer
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3 Causes
There are a number of causes of carbon formation; these include,
• Insufficient catalyst activity, either due to significant poisoning or the
catalyst is at the end of life,
• Operation at excessively low steam to carbon ratios, either during a
transient such as a start up or shut down or during normal operation due
increases in higher hydrocarbon content of the feed gas or incorrect steam
to carbon ratios,
• Poor catalyst heat transfer properties leading to high inside tube wall and
process gas temperatures,
• Condensation of liquid feeds in low points or dead legs upstream of the
reformer which is transferred to the steam methane reformer during start up
or when switching between available feed options,
• Hot spots formed due to either poor catalyst loading (e.g.: formation of
bridges) or zones of severe breakage (e.g.: crushing of catalyst during
excessively fast shut downs) which in there is low gas flow leading to hot
spots.
• Localized flame impingement either due to poor burner maintenance,
fluegas recirculation etc which leads to a localised hot spot. This is a
particular issue if the plant is operating at low rate.
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3.1 Effects of Carbon Formation
3.2 Types of Carbon
The following figure illustrates the two types of carbon formation,
Figure 5 – Types of Carbon Formation
• Graphitic – this is a hard layer of carbon that forms on the surface of the
catalyst and prevents the process gas from accessing the active nickel
sites. This type of carbon formation is usually generated from the thermal
cracking of hydrocarbons.
• Polymeric carbon – this is generated in the pore structure of the pellet and
does to some extent block off some of the active sites. A more serious
effect is that this carbon exerts a stress on the pellet and can if severe
enough lead to pellet breakage and associated pressure drop rise.
Alternatively, this form of carbon can lead to cracking of the pellets but the
pellets can remain intact with the carbon acting as a binder. Subsequent
steaming removes this carbon and it is at this stage that the pressure drop
rises significantly. Also, when polymeric carbon is gasified, the sudden
volume expansion can over stress the pellet and lead to pellet breakage,
usually giving the pellets a pock marked effect. This type of carbon is
usually generated from olefin polymerization.
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Whisker carbon – this is formed from the Boudouard reaction.
The carbon lifts a crystal of nickel off the catalyst support and grows as a
whisker from behind the nickel crystal. This is a similar mechanism to metal
dusting and can have the similar effect of spalling off the outer layer of a
catalyst particle.
4 What are the Effects of Carbon Formation?
Once some carbon has been formed, then a number of processes occur,
• Loss of Activity – Firstly, the carbon coats the nickel crystallites on the
surface and within a small element of the pellet (as illustrated below); this
leads to a loss of inherent activity since there is less nickel (since it is
covered in carbon and is therefore inaccessible to the process gas)
available to support the reforming reactions.
Figure 6 – Effect of Carbon on Nickel Crystallites
A consequence of this is that since there is no reaction but there is still heat
transfer to the process gas from the furnace side, the process gas
temperature rises.
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Since the outside tube wall temperature is directly related to the process
gas temperature, any increase in process gas temperature will result in an
increase in outside tube wall temperature. Since the process gas
temperature has increased, the rate of carbon lay down (equations 10 and
12 through 14) increases.
• Resistance to Flow – On a simplistic level, the carbon forms a layer over
the catalyst surface and therefore should not affect the resistance to flow
over the catalyst within that tube1
. However, once a significant amount of
carbon has been laid down in a tube, the resistance to flow increases; this
is not just because the flow area has been reduced (due to the blockage of
flow area due to carbon particles) but also the inherent friction has
increased (due to the roughness of the carbon particles).
Once the flow through a tube is reduced, then for a constant fluegas side
firing rate, the tube will still be receiving the same amount of heat (heat flux)
but there is less gas flow to receive this flow. Part of this additional heat will
be absorbed as heat of reaction, but a significant portion will increase the
process gas temperature as detailed in the following diagram,
Figure 7 – Absorption of Heat
1
Note that pressure drop is not mentioned here; the pressure drop during
normal operation across all tubes is the same, however, the resistance to
flow may vary between tubes. What does change is the flow rate through
tubes; a tube with a “relative” high resistance to flow will have a lower flow
than a tube with a “relative” low resistance to flow.
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Once carbon formation starts to occur, as more of the heat supplied to the
tubes is converted to sensible heat (i.e.: a temperature rise of the process
gas), this causes a rise in process gas temperature. Since the tube wall
outside temperature increases, the typical hot spots as observed will occur.
It should be noted that this additional resistance to flow through the affected
tubes will cause a re-distribution of flow of process gas throughout the
reformer. In the early stages of carbon formation, it is typical that only a few
tubes are affected (with the exception of carbon formation due to low steam
to carbon ratio or a large amount of heavy hydrocarbons), the flow
redistribution is relatively small.
• Heat Transfer Resistance – The carbon coats the surface of the pellets
(and in the worst case can also form between the pellets) and this increases
the heat transfer resistance. This increase in heat transfer resistance
means that the heat is not supplied as quickly (to provide the required heat
of reaction), the rate of reaction will drop. Why is this, well consider the
following heat transfer coefficients2
from a “typical” reformer,
Table 1 – Heat Transfer Coefficients in a Typical Reformer
Location Relative Heat Transfer
Coefficient
Units W/(m2
.K)
Fluegas 210
Tube Outside Laminar Layer 160
Tube Wall 2700
Tube Inside Laminar Layer 1200
Bed 100
So what does this mean? Well the “furnace side” and “outside tube laminar
layer” represent the greatest resistance to heat transfer (by this it is meant that
they have the lowest heat transfer coefficient). However, as carbon is laid down,
the “inside laminar layer” and the “bed” heat transfer coefficient will be reduced.
This will in turn reduce the overall heat transfer coefficient, as defined by,
2
From here on referred to as “htc”.
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bitwotfg0 h
1
h
1
h
1
h
1
h
1
U
1
++++= Eqn 19
Where,
Uo is the overall heat transfer coefficient,
hfg is the furnace side heat transfer coefficient,
hot is the outside tube laminar layer heat transfer coefficient,
hw is the wall heat transfer coefficient,
hit is inside wall heat transfer coefficient,
hb is the bed heat transfer coefficient.
This can be rewritten as,
bitwotfg h
1
h
1
h
1
h
1
h
1
++++
=
1
Uo Eqn 20
As can be seen any decrease in the “inside tube wall” or “bed” heat transfer
coefficient will result in a decrease in the overall heat transfer coefficient.
One minor point is that although carbon formation will reduce the flow rate
through the tube, there is also an effect on the heat transfer coefficient. In terms
of the flow through the tube, there are two effects; the first is that the capacity for
sensible heat is reduced since this is defined by,
ΔTCmQ psensible ××= Eqn 21
Where,
Qsensible is the sensible heat load transferred to the process gas,
m is the mass flow of gas through the tube,
Cp is the specific heat capacity of the gas,
∆T is the resultant rise in temperature.
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The second effect is that as the flowrate through a tube is reduced, there is less
reactants to be reformed and therefore there is less heat that can be absorb as
heat if reaction – this is defined as follows,
[ ]
dt
H2Cd
ΔHΔHr mn
N
1
rn ×= ∑ Eqn 22
Where,
∆Hr is the total heat of reaction,
∆Hrn is the heat of reaction for a hydrocarbon which has the formulae CnH2m,
N is the largest hydrocarbon in the feed,
t is time.
4.1 Why does Carbon Formation Get Worse?
There are a number of reasons why carbon formation always gets worse with
time (this is a summary of the effects detailed above),
• Loss of activity – As the catalyst activity is reduced (due to the coating of
the active nickel sites), the process gas temperature will rise and this
means that the reaction rate of carbon formation increases as per equation
16 above. That is to say the temperature dependent part of the reaction
rate equation increases and therefore so does the overall reaction rate.
• Flow resistance – Since the flow through an affected tube is decreased
due to the resistance generated by the carbon already formed, this leads to
increased process gas temperatures which in turn leads to an increase in
the rate of carbon formation (see equation 16).
• Heat transfer resistance – As the overall heat transfer coefficient is
reduced, the process gas temperature rises, thereby increasing the rate of
carbon formation.
It could be assumed that the reduction in reforming and consequent increase in
methane (and alkane) concentration in the next part of the tube would (as per
equation 16) lead to an increase in the rate of reforming, this is unfortunately not
the case. Furthermore, since the process gas temperature is higher once carbon
formation starts, it again could be assumed that the rate of reforming reaction
would increase; again this is not the case. Why is this?
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Well the reasons are complex but in summary,
• As the alkane content of the feed gas increases, the carbon formation
reaction rate increases faster than the reforming reaction rate for that
alkane. This is dictated by the thermodynamics of the cracking and
reforming reactions.
• The activation energy of the carbon forming reactions is greater than for the
reforming reactions and so in broad terms, the reforming reactions should
be more selective than the carbon forming reactions.
However, as the process gas temperature is increased due to carbon lay
down, the relative selectivity is changed marginally in favor of the carbon
forming reactions.
In real terms, this means that the rate of carbon forming reactions increases
faster than the increase in reforming reactions and therefore on a relative
basis, the carbon forming reactions will be preferred over the reforming
reactions.
It should be noted that the rate of reforming reactions during the initial
phases of carbon formation is still orders of magnitude greater than the rate
of carbon forming reactions.
In summary the result of carbon formation can be illustrated by the following
figure which considers a small element of the tube (highlighted in orange),
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Figure 8 – Comparison of “Base Case” v Carbon Forming Tube
It should be noted that “Base Case” and “Base” refers to the situation where
there is no carbon formation (the left hand figure). The with carbon formation
case is named “With Carbon Formation”. Text in red highlights the key changes
that will occur when carbon formation sets in.
4.1.1 So what is the Next Step?
In summary, all of the above effects of carbon formation have two consequences,
• The process gas temperature increases (due to the loss of activity,
reduction in flow through the effected tube and the reduction in heat
transfer) and as defined by equation 16, this will increase the rate of carbon
deposition,
• Since there is less reforming (due to the reduction in activity), there is an
increased concentration of alkanes which means that the rate of carbon
formation increases.
Both of these factors cause an increased rate of carbon formation which then in
turn causes,
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• An further reduction in catalyst activity and hence less reforming, so higher
temperatures and more hydrocarbon slippage down the tube,
• An increased resistance to flow, so that the flowrate through an effected
tube is reduced and hence the process gas temperature increases,
• A reduction in the heat transfer coefficient which raises the outside tube wall
temperature.
These then all cause the rate of carbon formation to increase and a vicious circle
is form as highlighted below,
Figure 9 - Carbon Formation Vicious Circle
It is also important feature of the two factors noted above that the rate of carbon
formation will always increase as the catalyst ages (it should also be noted that
as the catalyst ages, the activity drops due to the sintering of the nickel
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4.2 Consequences of Carbon Formation
The main consequence of carbon formation is an increase in process gas
temperature. Since the outside tube wall temperature is inherently linked to the
process gas temperature (due to the heat transfer coefficient of the tube wall and
inside laminar layer), any increase in the process gas temperature will lead to an
increase in the outside tube wall temperature. As is well known, reformer tubes
operate in the creep regime, and therefore any increase in tube wall temperature
will increase the rate of creep. Since the rate of creep defines the expected tube
life, any increase in the rate of creep will reduce the tube life.
For instance, hot banded tubes are between 30-50°C hotter than a tube that is
not affected. As is known, a 20°C rise in tube wall temperature will reduce the
tube life, hot bands will typically reduce the tube life by between 33-75%; i.e.:
rather than achieving 100,000 hours (12 years) life, the expected life will range
between 25,000 and 66,000 hours (3 and 5.5 years respectively).
A second effect is that the resistance to flow through the tube is increased and
therefore there will be less flow through the tube. This is not a major problem if
only a few tubes become hot since the majority of tubes will accept the additional
flow and there will be little overall pressure drop increase across the reformer.
However, if all the reformer tubes are affected by hot banding, then a pressure
drop rise will be observed.
4.3 Why does Carbon Form where it does?
This question can be translated as “Why does carbon form one third of the way
down the tube?”
As we have seen in equation 16, there are two key factors when carbon will start
to form; these are the hydrocarbon content and the process gas temperature.
The effect of both of these parameters is inter-linked; as the gas proceeds down
the tube, it is heated up and reforming reactions start to convert hydrocarbons to
carbon oxides and hydrogen. For carbon formation to occur, the process gas
temperature and hydrocarbon content must be sufficiently high that the rate of
carbon formation is greater than the rate of carbon gasification; i.e.: the net rate
of carbon formation is positive. In a top fired furnace, the conditions for forming
carbon (a high enough temperature and sufficient hydrocarbons) are co-incident
at around one third of the way down the tube.
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In terms of understanding this process, a comparison of the carbon formation
equilibrium line and the process gas temperature should be made as illustrated
below.
Figure 10 – Temperature Profiles
The key feature of this graph is that the two lines do not cross and there is a
positive difference between the two lines; this difference is called “the carbon
formation margin”. Some key conclusions can be drawn from this figure,
• Provided this margin is positive, the rate of carbon formation is less than the
rate of carbon gasification.
• If the margin is zero, then the process gas at this point can be described at
being at the “carbon pinch point”; that is to say the rate of carbon formation
is precisely matched by the rate of carbon gasification. This is illustrated in
the figure below,
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Figure 11 – Carbon Pinch Point
However, a small increase in the heavies in the feed, or a small increase in
the process gas temperature will mean that the balance is shifted to favor
carbon formation and hence carbon will be laid down. This is illustrated in
the following figure,
Figure 12 – Carbon Formation
As we can see, the change in heavies in the feed gas has moved the carbon
forming equilibrium line down such that it now crosses the process gas
temperature line.
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Furthermore, the margin is now negative and this indicates that there will be net
carbon formation. Furthermore, as the margin becomes more negative, the rate
of carbon formation increases and therefore more carbon will be laid down more
quickly.
4.3.1 Effect on Process Gas Temperature
As noted above, carbon formation will increase the process gas temperature due
to the loss of activity, reduction in heat transfer coefficient and flow through the
tube. The following figure illustrates the effect on the process gas temperature in
the affected zone,
Figure 13 – Effect on Process Gas Temperature
What does this mean – firstly, the small increase in process gas temperature
means that the carbon formation line and the process gas temperature line now
do cross and so we have a negative margin for carbon formation which means
that we now have net carbon formation.
We shall return to this concept in the next section which details why carbon
formation propagates down the tube.
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4.4 Why does Carbon Formation propagate Down the Tube?
When carbon formation starts, it is always observed to grow down the tube. In
order to understand this effect, consider the following illustration (see figure 8
above),
Figure 14 – How does Carbon Propagate into an Unaffected Zone ?
The gas leaving the affected zone is now at a higher temperature than if the tube
was unaffected (see figure 8) and has a high methane content; within the
unaffected element more heat is transferred from the flue gas thereby raising the
temperature even further.
Although there will be some reforming reaction within this unaffected element,
this is insufficient to reduce the process gas temperature and hydrocarbon
content of the process gas such that the carbon margin is positive. Since the
carbon formation margin is negative, carbon will start to form in this element.
This process is illustrated below,
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Figure 15 – Movement of the Carbon Forming Region
This process is then repeated down the tube so that the carbon forming region
grows down the tube; this is observed as an increase in the hot band on the tube.
This continues until the situation arises that the hydrocarbon content has been
reduced (by the reforming reaction and the cracking reaction) such that carbon
formation margin is again positive.
4.4.1 Effect on Radiation on the Fluegas Side
There is also a second order effect of carbon formation and the consequent
increase in outside tube wall temperature (observed as hot bands) in terms of the
radiative heat transfer on the fluegas side of the reformer.
As the outside tube temperature is increased, the rate of radiation emitted by the
tube increases; it should be noted that the rate of radiative heat transfer is
governed by the Stefan-Boltzman law which is,
)T(Tσ
dt
dQ 4
B
4
−×= Eqn 22
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Where,
Q is the radiative heat transferred
t is time
σ is the Stefan-Boltzmann constant
T is the outside tube wall temperature
TB is the fluegas bulk temperature
Although the fluegas temperature is much hotter than the outside tube wall
temperature, heat is still transferred in both directions. Since this is a 4th
power
relationship, a small increase in the outside tube wall temperature will lead to a
significant increase in the rate of heat transfer to the fluegas.
The fluegas will re-emit this heat back towards the tube, but some of this heat will
not return back to the element of the tube it came from, some will be transferred
to a higher portion (this will be discussed below) and some to a lower portion.
This is illustrated below,
Figure 16 – Effect of Hot Bands on Radiative Heat Transfer
As can be seen, the element of the tube below the affected zone will now receive
more radiation and therefore the outside tube wall temperature will increase.
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This will then lead to an increase in the inside tube wall temperature and
therefore the process gas temperature which as is illustrated above, may lead to
the carbon formation margin becoming negative hence leading to carbon
formation in this previously un-affected element.
This is a second mechanism for the progression of carbon formation down the
tube.
4.5 Why does Carbon Formation propagate Up the Tube?
It would initially seem impossible for carbon formation to propagate back up the
tube. However, as is illustrated in figure 16 above, the element of the tube above
an affected zone will receive more radiation than normal and therefore the
outside tube wall, inside tube wall and process gas temperature will rise.
Since it is implicit that as the zone below this unaffected zone is forming carbon,
then this unaffected zone must be close to forming carbon. Therefore, the small
temperature change that occurs will be sufficient to cause carbon formation in
this zone.
This will cause the outside tube wall temperature to rise and hence more
radiation will pass back to the fluegas and some of this will be re-emitted to the
zone above this one. Hence there is a mechanism for hot bands to propagate
back up the tube.
However, it is typical that the hot band will grow more than 5% upward. If hot
bands are observed above the 25% mark, then it is most likely to be due to
another effect (catalyst bridging which will lead to carbon formation) rather than
carbon formation growth.
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5 How do we Prevent Carbon Formation
5.1 The Role of Potash
One way of preventing the formation of carbon is to include a promoter in the
catalyst to help increase the rate of carbon gasification; one such promoter is
potash (others include lanthanum).
The way that potash helps is as illustrated below,
Figure 17 – Effect of Potash on Carbon Formation
Depending on the feedstock, there are a number of options for the inclusion of
potash within the reformer; the following table details some typical catalyst
loading options,
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Table 2 – Typical Catalyst Loading Options
Plant Conditions Loading
Light natural gas
Plant at design rate
High steam to carbon
100% Comp A or Comp B
Heavy natural gas
Plant above design rates
Feedgas composition changes
Low steam to carbon
40% Comp A over 60% Comp B or Comp C
LPG
Light Naphtha
30% Comp D over 20% Comp B over 50%
Comp D or Comp A
Heavy Naphtha 50% Comp D over 50% Comp C
In order to prevent the formation of carbon on heavier feeds, the level of potash
is increased from 0% (Comp A/C- series) to 2% (Comp C - series) to 7% (Comp
D - series).
Note: Comp = Proprietary Catalyst (Competitor Designation)
5.2 Inclusion of Pre-reformer
Installation of a pre-reformer allows for the conversion of all higher hydrocarbons
to methane, carbon dioxide and hydrogen. This effectively reduces the carbon
forming potential of a feed stock such that in the majority of cases, carbon
formation within the primary reformer can be eliminated.
The pre-reformer is a simple adiabatic bed with a highly active nickel bases
steam reforming catalyst. The application of a pre-reformer is illustrated below,
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Figure 18 – Application of a Pre-reformer
5.3 Primary Reformer Catalyst Parameters
Other than the addition of promoters to prevent carbon formation, there are two
catalyst parameters that can be altered to prevent carbon formation, activity and
the inherent heat transfer coefficient.
5.3.1 Activity
Increasing the catalyst activity, say for instance, by the use of a high surface area
catalyst, has a two fold effect,
• There is more reforming reaction higher up the tube which reduces the
process gas temperature due to the increased heat of reaction requirement.
• Also this reduces the hydrocarbon content of the process gas.
Both of these reduce the carbon potential of the process gas as illustrated below,
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Figure 19 - Effect of Activity on Carbon Potential
Again we see that the margin between the equilibrium line and the process gas
temperature line is increased when installing a highly active catalyst.
5.3.2 Heat Transfer
By improving the heat transfer characteristics of the reforming catalyst, for
instance making the pellet smaller, the rate of heat transfer from the fluegas side
to the process gas can be increased. Intuitively this would appear to increase
the process gas temperature thereby making the carbon forming potential worse,
however, since the reforming reaction with a primary reformer is heat transfer
limited, the additional heat transferred will increase the reaction rate such that the
carbon forming potential is reduced.
Furthermore, the additional reaction reduces the hydrocarbon content of the
process gas and this lifts the carbon forming equilibrium line away from the
process gas temperature.
The effect as exactly the same as for installing a highly active catalyst as
illustrated above.
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5.3.3 Increased Steam to Carbon Ratio
By increasing the steam to carbon ratio, two effects occur,
• The mass flow through the tubes increases and since the majority of the
additional steam does not react, this acts essentially as an inert and
therefore will reduce the process gas temperature such that carbon
formation is less likely. Furthermore, the inside tube wall heat transfer
coefficient is increased as the process gas velocity is increased which
reduces the outside tube wall temperature.
• Since there is a higher steam partial pressure, the rate of reforming
increases and therefore the concentration of higher hydrocarbons is
reduced which reduces the carbon forming potential of the process gas.
The effect as exactly the same as for installing a highly active catalyst as
illustrated above.
6 Steam Out
Once carbon has been laydown, then the only option to remove this carbon is to
conduct a steam out.
6.1 Why does increasing the Steam to Carbon Ratio Not Work?
Many people believe that increasing the steam to carbon ratio during normal
operation will remove carbon laid down on the reforming catalyst. Unfortunately
this is not true since,
• Once hot bands are observed (the normal method for identification that
carbon formation has occurred), the activity of the catalyst has already been
reduced. As such the rate of the reforming reaction is also reduced.
Increasing the steam rate will increase this rate of reaction such that the
hydrocarbon content of the gas is reduced. However, the activity
suppression reduces the reaction far more than the increase in steam to
carbon ratio causes. Therefore on balance, the reforming reaction rate is
still suppressed.
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• Increasing the steam to carbon ratio will also provide more driving force to
gasify the carbon already laid down. However, since there is less reforming
occurring, the hydrocarbon content of the process gas is raised and
therefore this increases the rate of carbon deposition. Again on balance,
the rate of carbon deposition is increased far more than the increase in the
rate of carbon gasification caused by the steam to carbon ratio increase.
It should be noted that if the steam to carbon is increased, carbon formation and
gasification will still occur. The key is whether sufficient additional steam has
been added such that the rate of gasification is increased such that the net
carbon formation rate is zero.
It should also be noted that increasing the steam to carbon ratio will not remove
any carbon that has already been laid down.
6.2 Why does reducing the Feed Rate not help?
Reducing the feed rate has exactly the same effect as increasing the steam to
carbon ratio (provided the total rate of steam is maintained), in that although this
will reduce the rate of carbon deposition, it will not eliminate it.
6.3 Fundamental Principles of Steam Outs
The key method to removing carbon is to conduct what is known as a “steam
out”. A steam out consists of operating the reformer at high temperature with no
feed gas being passed to the reformer whilst maximizing the steam rate to the
reformer. Under these conditions, carbon will be gasified and is therefore
removed from the surface and the pores of the catalyst.
When conducting a steam out, it is important that the process is monitored very
closely since the potential for a burn down of the reformer tubes is very high.
Under these conditions, the majority of the heat sink available during normal
operation (the reforming reactions) is not available and therefore small changes
in fuel rate can have a dramatic effect on tube wall temperatures. It is
recommended that regular visual inspections of the reformer tubes are
conducted. It is not sufficient to monitor the exit reformer header temperatures
since under these conditions; these will not give a true representation of what is
happening within the reformer.
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To ensure that a steam out has been effective, the effluent from the reformer
should be sampled and tested for carbon dioxide and methane; it is typical that
these will start off high and gradually reduces as more of the carbon is gasified.
Once the levels have dropped to an acceptable level, the feed can be introduced
back into the plant. It is also worth checking the reformer effluent and the
process condensate for hydrogen sulfide and sulfates / sulfites respectively. This
will identify whether sulfur was the root cause of the carbon formation.
In some cases, a steam out is not sufficiently aggressive enough to remove
carbon, and then an air burn may be required. It is important to note that it must
be possible for steam to be passed through the tubes at the same time as the air
or else there is no temperature control.