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CBE 417 “Unit Operations” 1 Lecture: 3 7 Sep 2012
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Overview 2 Introduction UO course overview Equilibrium Stage separations What are “Unit Operations” Brief thermodynamics review Binary flash with energy balance Multicomponent flash
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Vapor Liquid Equilibrium (VLE) 3 Typical simplifications: Ideal vapor phase Ideal liquid phase
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Phase Equilibrium (Alternate Form VLE) 4 Historically, when estimates were done by hand: Seader & Henley (2006)
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Phase Equilibrium (Recommendations) 5
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Phase Equilibrium (Alternate Form VLE) 6 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):
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DePriester Chart 7 P = 2 bar T = 100 o C Isobutane others….
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DePriester (equation fit) 8
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Other Equilibrium Diagrams: 9 P = 1.013 bar T = various o C Benzene - Toluene
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Other Equilibrium Diagrams: 10
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Effect of Pressure: 11
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Effect of Pressure: 12 Seader & Henley (2006)
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Other Equilibrium Diagrams: 13
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Overview 14 Brief thermodynamics review Binary Flash with energy balance Sequential solution Simultaneous solution Multicomponent Flash
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Binary Flash 15 Overall mole balance mole balance on a mole balance on b equilibrium eqn for a mole balance on a
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Binary Flash 16 Flash separation: Specify: Find: a = n-pentane b = n-hexane Vfrac0.471 V/F P3.000bar functi on - 1.89E- 08 Xa0.394 Xb0.606 Ya0.619 Yb0.381
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Binary Flash 17 Overall mole balance mole balance on a mole balance on b equilibrium eqn for a mole balance on a
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Binary Flash 18 Flash separation: Specify: Find: a = n-pentane b = n-hexane
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Binary Flash 19 Graphical Solution: mole balance on a solve for y a “Operating Line”
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Binary Flash 20 Graphical: y = x Equilibrium curve Za Solution! What if f is unknown, but T is known? Limits: f = 0 f = 1
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Binary Flash Energy Balance 21 EB on CV:
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Other Equilibrium Diagrams: 22
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Alternative Thermodynamics 23 Older (hand methods): Relative Volatility (VLE): Raoult’s law Aside (couple with MB)
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Separation Factor or Relative Volatility 24
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Effect of Pressure: 25 Seader & Henley (2006)
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Constant Relative Volatility? 26
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Alternative Thermodynamics 27 K i with multicomponent flash: Sequential solution: suggestions p 35-37 (Rachford-Rice Eqn) Simultaneous solution technique: suggestions p 40-43 Into MB:
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Sizing Flash Drums 28
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Simulators 29 Flash input: Sensitivity Analysis: Design Spec:
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Questions? 30
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