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

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

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

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

Phase Equilibrium (Recommendations)

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):

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

DePriester (equation fit)

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

Equations of State Models

Phase Equilibrium (Recommendations)

Activity Coefficient Models

Activity Coefficient Models

Activity Coefficient Models

Activity Coefficient Models

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

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

Activity Coefficient Models ^ = lambda

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)

Other Equilibrium Diagrams: P – T diagram

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

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

Other Equilibrium Diagrams:

Y vs X Diagram (LLE)

Effect of Pressure:

Effect of Pressure: Seader & Henley (2006)

Other Equilibrium Diagrams:

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

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

Binary Flash Flash separation: Specify: Find: a = n-pentane b = n-hexane Vfrac 0.471 V/F P 3.000 bar function -1.89E-08   Xa 0.394 Xb 0.606 Ya 0.619 Yb 0.381

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

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

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

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

Binary Flash Energy Balance EB on CV:

Other Equilibrium Diagrams:

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

Separation Factor or Relative Volatility

Effect of Pressure: Seader & Henley (2006)

Constant Relative Volatility?

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

Sizing Flash Drums

Simulators Flash input: Sensitivity Analysis: Design Spec:

Questions?