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CBE 417 “Unit Operations”

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  1. CBE 417 “Unit Operations” Lecture: 3 7 Sep 2012

  2. Overview • Introduction • UO course overview • Equilibrium Stage separations • What are “Unit Operations” • Brief thermodynamics review • Binary flash with energy balance • Multicomponent flash

  3. Vapor Liquid Equilibrium (VLE) Vapor phase: good; liquid phase: good for HC or moderate – high pressures (compressible liquid phase) Typically used for liquid phase fugacity calculations Used for special cases (like gases dissolving into liquid phase) • Typical simplifications: • Ideal vapor phase • Ideal liquid phase Raoult’s Law

  4. Phase Equilibrium (Alternate Form VLE) Historically, when estimates were done by hand: • Seader & Henley (2006)

  5. Phase Equilibrium (Recommendations)

  6. Phase Equilibrium (Alternate Form VLE) Historically, when estimates were done by hand: Sometimes the K values are nearly composition independent “hand” techniques of design/solution have used DePriester Charts (hydrocarbons):

  7. DePriester Chart P = 2 bar T = 100 oC Isobutane others….

  8. DePriester(equation fit)

  9. Vapor Liquid Equilibrium (VLE) Vapor phase: good; liquid phase: good for HC or moderate – high pressures (compressible liquid phase) Typically used for liquid phase fugacity calculations Used for special cases (like gases dissolving into liquid phase) Equations of state models Activity coefficient models

  10. Equations of State Models

  11. Phase Equilibrium (Recommendations)

  12. Activity Coefficient Models

  13. Activity Coefficient Models

  14. Activity Coefficient Models

  15. Activity Coefficient Models

  16. CBE 417 “Unit Operations” Lecture: 4 10 Sep 2012

  17. Overview • Introduction • UO course overview • Equilibrium Stage separations • What are “Unit Operations” • Brief thermodynamics review • Binary flash with energy balance • Multicomponent flash

  18. Activity Coefficient Models

  19. Phase Equilibrium (Recommendations) Mixtures to model: • MeOH – water • EtOH– water • propanol – water • n-butanol– water • n-butane – n-pentane • benzene – toluene • acetic acid – propionic acid • CO2 – toluene (high P)

  20. Other Equilibrium Diagrams: P – T diagram

  21. PT Equilibrium Diagram: http://www.dlr.de/vt/en/Portaldata/29/Resources/dokumente/CO2GasphaseDiagrams_Goos_Riedel_Zhao_Blum2010_GHGT_webnew.pdf

  22. Other Equilibrium Diagrams: P = 1.013 bar T = various oC Benzene - Toluene Y vs X diagram T vs X or Temp vs Composition

  23. Other Equilibrium Diagrams:

  24. Y vs X Diagram (LLE)

  25. Effect of Pressure:

  26. Effect of Pressure: • Seader & Henley (2006)

  27. Other Equilibrium Diagrams:

  28. Overview • Brief thermodynamics review • Binary Flash with energy balance • Sequential solution • Simultaneous solution • Multicomponent Flash

  29. Binary Flash Overall mole balance mole balance on a mole balance on b equilibrium eqn for a mole balance on a

  30. Binary Flash Flash separation: Specify: Find: a = n-pentane b = n-hexane

  31. Binary Flash Overall mole balance mole balance on a mole balance on b equilibrium eqn for a mole balance on a

  32. Binary Flash Flash separation: Specify: Find: a = n-pentane b = n-hexane

  33. Binary Flash Graphical Solution: mole balance on a solve for ya “Operating Line”

  34. Binary Flash Graphical: Equilibrium curve y = x Solution! What if f is unknown, but T is known? Za Limits: f = 0 f = 1

  35. Binary Flash Energy Balance EB on CV:

  36. Other Equilibrium Diagrams:

  37. Alternative Thermodynamics Older (hand methods): Raoult’s law Relative Volatility (VLE): Aside (couple with MB)

  38. Separation Factor or Relative Volatility

  39. Effect of Pressure: • Seader & Henley (2006)

  40. Constant Relative Volatility?

  41. Alternative Thermodynamics Ki with multicomponent flash: Into MB: Sequential solution: suggestions p 35-37 (Rachford-Rice Eqn) Simultaneous solution technique: suggestions p 40-43

  42. Sizing Flash Drums

  43. Simulators Flash input: Sensitivity Analysis: Design Spec:

  44. Questions?