More Related Content
What's hot
What's hot (20)
Similar to design_fyp_slide.ppt
Similar to design_fyp_slide.ppt (20)
design_fyp_slide.ppt
- 1. Packed Distillation Column Design By Ahmad Firdaus KEK 110003 Group 4 1
- 2. Outline Introduction Chemical Engineering Design Mechanical Engineering Design Control and Safety Consideration Purchased Equipment Cost Conclusion 2
- 4. Overview Pyrolysis of palm kernel shell Activation of char Synthesis of methanol Separation of gas and methanol Separation of water and methanol Activated Carbon Methanol
- 6. Design Procedure for Packed Column 1) Select the type and size of packing 2) Determine the packing height required for the specified separation 3) Determine the column diameter to handle the liquid and vapour flow rates. 4) Select appropriate packing support, liquid distributor and redistributors. 6
- 7. 7 Preliminary selection Type of Distillation Column Type of Packing Packing Material Always chosen for small diameter columns (less than 0.6m). Preferable and will usually be cheaper for handling with corrosive materials. Suitable for handling foaming systems. Packed Distillation column
- 8. 8 Preliminary selection Type of Distillation Column Type of Packing Packing Material Availability of data and references for design purpose Random packing is more cheaper in term of cost - Easy transport and storage - Cost of packing material per cubic meter is significantly lower Random Packing
- 9. Preliminary selection Type of Distillation Column Type of Packing Packing Material 9 Pall Ring Metal Availability data for design purpose. High capacity with good liquid and gas distributions. Easily wettable due to its structure. Available in various type of material.
- 10. 10 Estimation and Theories Packing Height Column Diameter
- 11. 11 Empirical correlation published by Erbar and Maddox to estimate number of stages. Use of concept of height equivalent to a theoretical plate (HETP) to convert the number of theoretical stages required to a packing height. Estimation and Theories Packing Height Column Diameter
- 12. 12 The diameter of a packed column is determined by its cross-sectional area. The column cross-sectional area and diameter for the selected pressure drop is determined from the generalised pressure-drop correlation. Estimation and Theories Packing Height Column Diameter
- 13. Summary of Chemical Engineering Design 13 Design Parameters Number of stages 6 Reflux ratio 0.1502 Percentage of flooding 81.64 % Column diameter 0.3622 m Packing height 3.79 m Height of column 7.33 m Pressure drop 0.028 bar Internal Fittings Liquid distributor Weir raiser pan distributor Liquid re-distributor Wall wiper liquid re-distributor Packing support Gas injection packing support
- 15. Material of Construction Material Carbon Steel Stainless Steel Spec. No/Grade SA-285/A SA-240/304L SA-240/316L Max. Use Temperature (°C) 482 649 454 Min. Tensile Strength (N/mm2) 310 485 485 Max. Allowable Stress (N/mm2) 94.3 115 115 Price ($/lb) 0.27 0.90 1.64 15 Lower cost compared to stainless steel. The operating temperature does not exceed maximum use temperature of carbon steel. The stress experienced by vessel does not exceed the maximum allowable stress.
- 16. Closure for Packed Column 16 Torispherical head Parameter Value Crown radius 362.25 mm Knuckle radius 28.98 mm Thickness of torispherical head 3.91 mm Height of torispherical head 70.76 mm Suitable for an operation lower than 10 bar. Lower cost compared to the ellipsoidal head and hemispherical head.
- 17. Wall Thickness of Vessel 17 Thickness of wall Parameter Value Minimum thickness required 0.38 mm Wall thickness 3.55 mm Internal thickness of column 362.25 mm External thickness of column 369.36 mm
- 18. Base support 18 Skirt base support Parameter Value Height of skirt support 1.2 m Thickness 18 mm Material Carbon Steel Stress analysis Maximum tensile stress 16.40 N/mm2 Maximum compressive stress 17.94 N/mm2 Bending stress 17.00 N/mm2
- 19. Stress Analysis on Vessel Stress analysis Longitudinal stress 6.02 N/mm2 Circumferential stress 12.04 N/mm2 Direct stress 3.14 N/mm2 Bending stress 62.10 N/mm2 Maximum compressive stress 65.24 N/mm2 Critical buckling stress 192.60 N/mm2 19
- 21. 21
- 24. 24 Level control and Composition control
- 25. Hazard and Operability Study (HAZOP) 25 Project: Removal of Syngas from Methanol-Water Mixture Node: S-001 Page: 1 Node Description: Feed line Date: Drw No. Parameter Deviation Cause Consequence Action Flow No flow Full blockage in valves at feed line Feed accumulation in the piping leads to pipe burst (pressure building) Fit in the low level alarm Less flow Partial blockage of valve, partial failure of control valve FV-001, pipe fouling Drop in liquid level within the column Liquid level is controlled by flow controller LIC 002 (regulates bottom flow)More Flow Flow controller fault to detect the increased flowrate Rise in liquid level within the column Pressure Lower pressure Pipe leakage Separation operation in column is affected due to changed feed condition Assign maintenance team to perform proper and regular inspection on the pipeline Higher pressure Pressure regulatory valve failure Separation operation in column is affected, pressure build-up in column Fit in the high pressure alarm, install rupture disc at the column
- 26. HAZOP (continued)… 26 Project: Removal of Syngas from Methanol-Water Mixture Node: C-01 Page: 2 Node Description: Packed column Date: Drw No. Parameter Deviation Cause Consequence Action Level Lower level Lower feed flowrate none Liquid level is controlled by flow controller LIC 002 (regulates bottom flow) Higher level Level controller LIC-001 fault Liquid entrainment into the rising vapor due to turbulence in the liquid surface when maximum liquid level approach to the vapor nozzle Assign maintenance team to perform proper and regular inspection on the level controller. Install high level alarm. Pressure Lower pressure Leakage in pipeline, vessel Separation operation in column is affected Assign maintenance team to perform proper and regular inspection on the vessel and pipeline Higher pressure Pressure controller PIC-001 fault Overpressurized of vessel Install high pressure alarm.
- 27. HAZOP (continued)… 27 Project: Removal of Syngas from Methanol-Water Mixture Node: E-01, S-004 Page: 3 Node Description: Condenser, reflux Date: Drw No. Parameter Deviation Cause Consequence Action Pressure Higher pressure Failure of pressure controller PIC-001 as venting system Burst of vessel due to pressure build Install high pressure alarm system, pressure relief valve with additional rupture disc Temperature Higher temperature Failure coolant system Internal tubes overheated and may rupture Install high temperature alarm, backup cooling system Flow More flow Higher pump capacity Column flooding Install high flow alarm, regular inspection and maintenance on the pump
- 28. HAZOP (continued)… 28 Project: Removal of Syngas from Methanol-Water Mixture Node: E-02, S-007 Page: 4 Node Description: Reboiler, boilup Date: Drw No. Parameter Deviation Cause Consequence Action Pressure Higher pressure Valve on steam condensate line failure or blockage Burst on heating medium tube due to overpressurised Fit in high pressure alarm, bypass line, pressure relief valve Flow More flow Fault on flow controller FRC-002, valves Flooding to increased vapor flowrate within the column Install high flow alarm, regular inspection and maintenance
- 29. Costing 29
- 30. Purchased Equipment Cost The purchased cost estimation of packed column using correlating equations and factorial method is MYR 58, 752.3209 and MYR 35, 450.70 respectively. 30
- 31. Conclusion The design project has discussed the proper guidelines, steps, codes and standards that should be followed in order to have viable and feasible design of equipment which is being used in the real life industry. 31
- 32. Q & A Session 32
Editor's Notes
- To ensure the choice between a plate or packed column is feasible, the choice of selection should be based on complete assurance of costing for each design. But, this kind of approach will not always necessary or worth doing since the selection can be made based on the basis of strong references and experiences. The following are the justifications for the selection. Packing is always chosen for small diameter columns (less than 0.6m) where the installation of packing would be much easier for packing rather than plate1. 2) A packed column is preferable and will usually be cheaper for handling with corrosive materials compared to the equivalent plate column1. Such corrosive effect can occurred with the presence of CO2 with the presence of water vapor. CO also have corrosive effect although the effect is very low. 3) Packed column is suitable for handling foaming systems1. Foaming occurs when bubble rise to the surface of the liquid on a tray and do not coalesce. The effect of foaming will reduce separation efficiency causing contamination of the top and bottom products.
- Packing are divided into random, structured and grid packing by having their own characteristics. In process industry, the structured and random packing are more commonly used. Based on some references, it was decided that random packing is chosen due to availability of data and references for design purpose. In term of costing, random packing is more cheaper compared to structured packing due to easy transport and storage as well as the cost of packing material per cubic meter itself is significantly lower than that of structured packing1.
- The choice would usually be made between Pall rings, Berl or Intalox saddles for new column. The availability data for design purpose mostly found for Pall ring, Raschig ring and Berl saddle. Pall ring is selected due to its high capacity with good liquid and gas distributions. It was also more stronger than Intalox saddles and Berl saddles. It was stated that Intalox saddles and Berl saddles are easier to break in bed compared to Raschig ring (the earliest type of packing). The type of material for Pall ring can be selected among plastic, ceramic and metal. In term of costs, plastic and ceramic is preferred although their mechanical strength is weaker than metal type. A plastic material is not preferable when it is going to be operated within 50°F (10°C) due to its softening or deflection temperature which will change the characteristics of packing bed while the ceramic type tends to break5. A metal type of Pall ring is selected due to its high strength-to-weight ratio, easily wettable due to its structure and high resistance to fouling.
- Figure 11.44 correlates the liquid and vapour flow rates, system physical properties and packing characteristics, with the gas mass flow-rate per unit cross-sectional area; with lines of constant pressure drop as a parameter. Basically Figure 4 correlates the physical properties of stream, the flow rates of the liquid and vapor, packing factor and also the mass flow rate of gas per unit cross-sectional area of the column. Such correlations is expressed by the following equation
- Liquid distributor- since this weir type design can handle wider range of liquid flow rates. This type of liquid distributor also offer high resistance for fouling and suits with the design since it is suitable for diameter of column ranging from 200 to 1000 mm Liquid redistributor - The wall wiper liquid re-distributor is selected since it gives useful performance for smaller column diameter. This type of liquid re- distributor collects liquid from the wall of column and redistribute it into the centre of packing. Packing support - The packing support is used to support the weight of wet packing while allowing the passage of gas and liquid. A poor selection or design of packing support will cause a high pressure drop and a local flooding. The Gas Injection Packing Support Plate is selected since the design gives lower pressure drop and there is no tendency to flooding1. It is also being chosen since it is the common packing support used to support a bed of random packing and it is preferable for small column diameter ranging from 0.3 to 1.2 m
- The shell and head of tower are normally fabricated with carbon steel or low alloy steel plate.
- The required wall thickness of a segmented plate to be welded in a vessel to withstand with the design pressure with additional stresses caused the attachment of leg
- The stress due to pressure is known as the longitudinal and circumferential stress. The stress due to weight of the vessel with its contents is known as the direct stress. The bending stress is the resulting stress from the bending moment due to wind loads. Under condition where the vessel experienced maximum compressive stress (when vessel is not under pressure), the vessel may fail due to buckling stress (elastic instability). The stress analysis of a column should be carried out such that the value of maximum compressive stress does not greater than the value of critical buckling stress.
- Emphasize on best distillation control configuration using steady state relative gain array commonly used in the industry. LV configuration Control pressure by cooling Bottom level controlled by bottom flow reflux or boilup as independent variable used to control composition Better performance for one point composition control
- In most towers, the pressure is controlled through the heat removal in the condenser. The logic is as follows: On increasing pressure, the condensation rate in the condenser must be increased. This increases a major output term to the material balance around the vapor space. To increase the condensation rate, the rate of heat removal in the condenser must be increased. One method to achieve this venting process is to implement a control scheme in which a process control valve is placed on the vent line from the condenser. A pressure signal from the condenser is used to trigger the opening or closing of the vent line valve.
- Before a process is started up and periodically thereafter (typically every three to five years or whenever significant modifications are made), a detailed study must be made of the process to determine potential hazards and to correct them. There are several approved procedures, and an organization can opt to use an alternative procedure if it can be shown to be as effective. In fact, most of the chemical processing industry uses the HAZOP technique, which is described in Section 24.4. This technique is a modified brainstorming process in which potential hazards are identified, their consequences are determined, and an action to deal with the hazard is identified. The action to be taken is assigned by the HAZOP team. In this case, the action might be assigning the process engineer to investigate a backup pumping system. The team then goes on to the next possible deviation, until all reasonable deviations have been considered. The team does not solve the safety problem during the HAZOP; its job is to identify the problem and to assign its resolution to a specific person.