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Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
Methanol Plant - Theory of Distillation
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Methanol Plant - Theory of Distillation

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Principles of Distillation …

Principles of Distillation
Distillation Theory
Flowsheet Description
Topping Column Details
Topping Column Operation
Refining Column Details
Refining Column Operation
Distillation Control
Distillation Problems

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  • 1. Methanol Plant Theory of Distillation Gerard B. Hawkins Managing Director, CEO
  • 2. Introduction  Principles of Distillation  Distillation Theory  Flowsheet Description  Topping Column Details  Topping Column Operation  Refining Column Details  Refining Column Operation  Distillation Control  Distillation Problems 2
  • 3. Principles of Distillation  The aim is to separate the product from any impurities • On a methanol plant this is the separation of methanol from Water, Alcohol's, Alkanes, etc.  This is achieved by • Adding heat to boil liquid and passing through a series of mixing zones  Here heat and mass transfer occurs 3
  • 4. Typical Crude Analysis 4  Ethanol  Acetone  Propanol's  Butanol's  Methyl Formate  Di Methyl Ether  Alkanes  + Dissolved CO2, CH4 300 ppm ~10 ppm 200 ppm 80 ppm 400 ppm 100 ppm 50-100 ppm Crude 10 ppm 20 ppm Refined Spec
  • 5. Methanol Specifications 5  Characteristics  Acetone  Ethanol  Acidity  Appearance  Hydrocarbons  Gravity  Minimum methanol  PFT  Water  Smell  Grade AA  20 ppm  10 ppm  n/a  Clear and no sediment  miscibillity test clear in 20 mins  793 kg/m3  98.5%  60 minutes  0.1%  No characteristic smell.
  • 6. Distillation Theory 6Heat 50 % A / 50 % B 60 % A 40 % B Heat 60 % A / 40 % B 70 % A 30 % B Heat 70 % A / 30 % B 80 % A 20 % B Cool Cool Cool
  • 7. Principles of Distillation Processes within a Column 7 Vapour Vapour Vapour Vapour Liquid Liquid Liquid Liquid Top Product Bottom Product Heat Cooling
  • 8. Distillation Column Schematic 8 Vapour Liquid Vapour Vapour Liquid Sieve Tray weir Down comer
  • 9. Distillation Theory 9 0 0.2 0.4 0.6 0.8 1 0 0.5 1 Mol frac. in Liq Molfrac.inVap.
  • 10. Effect of Reflux on No. of Stages 10 0 0.2 0.4 0.6 0.8 1 0 0.5 1 Mol frac. in Liq Molfrac.inVap. Due to Reflux Reduction in Reflux Feed Comp
  • 11. Distillation control 11 Feed Methanol Water 80 te/hr Methanol 20 te/hr Water 70 te/hr 100 % 30 te/hr 80 te/hr 100 % 10 te/hr Methanol 20 te/hr Water High Methanol • Control Mass Balance ! 20 te/hr Water
  • 12. GBHE Two Column Distillation Flowsheet 12 Vent Gases CO2 Meth Form DME acetone CO CH4 N2 Crude Methanol 80 % Methanol 20 % water + impurities Refined Methanol 99.99 % Fusel Oil Ethanol Propanol Butanol Bottoms Water Topping Column Refining Column Methanol Ethanol Water (Prop, Butan) 70°C 0.24 barg 125°C 1.29 barg 81°C 0.86 barg 80°C 0.64 barg 82°C 104°C 89°C 2.1 barg
  • 13. Topping Column Function  Remove Light Ends  Top product (vapour) • Di Methyl Ether • Methyl Formate • Acetone • Lower Hydrocarbons • Dissolved gasses (CO2 and CH4) • Low Alkanes <C10
  • 14. Topping Column Products  Bottom product • Methanol • Ethanol • Water • Trace quantities higher hydrocarbons  propanol  butanol 14
  • 15. Topping Column Flowsheet 15 Primary condenser Vent condenser Reflux drum Reboiler Feed Meth, Eth, water, Acetone DME MF To refining column Meth, Eth Water Light ends to fuel Acetone DME MF Topping columnFeed Preheater 70 °C 0.24 barg 84 °C 0.64 barg 67°C 45°C LIC LIC
  • 16. Topping Column Details  42 trays  Normal feed Tray 34 • Also feed points at trays 27, 31, 38  2 Reboilers duty, one typically heated by reformed gas the other by LP steam  Base level controlled by LIC  Varies flow to refining column 16
  • 17. Condensing System  2 condensers • Light ends column condenser  85% of vapour condensed • Vent Condenser  This is done to prevent re-absorption of lights ends into reflux 17 To Light Ends Reflux Drum Air To Vent condenser Vapour from Light ends column Light Ends Column Condenser 67 °C TIC
  • 18. Refining Column Function  To separate • Methanol • Ethanol • High Alcohol's • Water 18
  • 19. Typical Refining Column Feed Analysis  Methanol  Water  Ethanol  Propanol's  Butanol's  Higher Alkanes >C10  80 %  20 %  300 ppm  100 ppm  80 ppm  Trace Quantities
  • 20. Refining Column Products  Top product • Methanol 99.999 %  Bottom product • Water (typically < 10 ppm methanol)  Fusel Oil • Ethanol  Propanol, Butanol, higher alkanes >C10 • Methanol Product Loss
  • 21. Refining Column Flowsheet 21 ReboilerFeed Meth, Eth, water, Acetone DME MF Bottoms Water Heavy Ends column Feed Preheater 81 °C 0.86 barg 130 °C 1.8 barg LIC Condenser Reflux drum 81°C PIC LIC 89°C Product Methanol Fusel Oil Purge Liquid Purge
  • 22. Refining Column Details Typically 45-60 m high 72-93 trays Normal feed Tray 26 Also feed points at trays 29, 23, 20 2 Reboilers One heated by reformed gas One heated by steam (trim heater) Base level controlled by LIC Varies bottoms water flow to drain7
  • 23. Refining Column Reboiler Duty as Function of Ethanol in Crude 23 0 500 1,000 1,500 2,000 75 80 85 90 95 100 105 Ethanol in crude %designheatload Fixed recovery efficiency
  • 24. Refining Column Composition Profiles 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Theoretical Tray Methanol/WaterFraction Water Methanol Ethanol Top Bottom
  • 25. Distillation Column Problems Downcomer Flooding New level Downcomer Backing up Holes in Sieve Tray Downcomer Froth Symptoms - High PD, Poor Performance Cause - Liquid rate too high
  • 26. Problems With Trays Liquid Liquid Gas flow Froth Tray Weeping Jet Flooding Low vapour rate Liquid drips down Vapour rate too high Blows liquid on to tray above
  • 27. Effects of Various Components on Methanol Specification Tests Component Test Affected PFT Water Miscibility Odour Saturated hydrocarbon, None Yes - Unsaturated hydrocarbon, Large - - Saturated aldehyde Small - Yes unsaturated aldehyde V large - Yes Keytones None - Yes Ether None - - esters None - Yes Iron Carbonyl V large - - PFT = permanganate fading time
  • 28. 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 or damage resulting from reliance on this information. Freedom under Patent, Copyright and Designs cannot be assumed.

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