“Chemical Engineering Equilibrium Separations” Lectures Oct 2012

In-Class Problem 2 benzene (17 mol%) toluene (66 mol%) m-xylene (17 mol%) F = 100 kmol/s sat’d liquid 1 atm DSTWU barPi star [bar] ComponentTbp oC80.1 oC123 oC Benzene Toluene m-Xylene

In-Class Problem 3

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Overview 9 AspenPlus: o Shortcut methods: DSTWU o Rigorous method: RADFRAC Efficiencies Introduction to multicomponent distillation (Chapter 9)

Homework Problem 10 benzene (17 mol%) toluene (66 mol%) m-xylene (17 mol%) F = 100 kmol/s sat’d liquid 1 atm X bz = 99 mol% X bz = 0.1 mol% DSTWU barPi star [bar] ComponentTbp oC80.1 oC123 oC Benzene Toluene m-Xylene

HWK Problem-molefrac specified 11

HWK Problem-molefrac specified 12

Overview 13 Review rigorous methods / RADFRAC Multicomponent systems: o Residue curves o DSTWU / RADFRAC o Rules of thumb Complex (Enhanced) distillation Column internals Batch distillation

14 Multicomponent Rigorous Methods Rigorous Methods: solution of stage by stage material balances, energy balances, and thermodynamic equilibrium equations.

AspenPlus: RADFRAC 15 Rigorous two- or three-phase fractionation for single columns. Models absorbers, strippers, reactive distillation, and so forth. RadFrac is a rigorous model for simulating all types of multistage vapor liquid fractionation operations. In addition to ordinary distillation, it can simulate: o absorption, reboiled absorption, stripping, reboiled stripping, extractive and azeotropic distillation

Rigorous Model 16

AspenPlus: RADFRAC 17 Rigorous two- or three-phase fractionation for single columns. Models absorbers, strippers, reactive distillation, and so forth. RadFrac is a rigorous model for simulating all types of multistage vapor liquid fractionation operations. In addition to ordinary distillation, it can simulate: o absorption, reboiled absorption, stripping, reboiled stripping, extractive and azeotropic distillation RadFrac is suitable for: o three phase systems, narrow boiling and wide boiling systems, systems exhibiting strong liquid phase nonideality RadFrac can detect and handle a free water phase or other second liquid phase anywhere in the column. You can decant free water from the condenser. RadFrac can handle solids on every stage. RadFrac can model columns where chemical reactions are occurring. Reactions can have fixed conversions, or they can be: o equilibrium, rate controlled, electrolytic RadFrac can model columns where two liquid phases exist and different chemical reactions occur in the two liquid phases. RadFrac can also model salt precipitation. RadFrac can operate in rating mode or design mode. With Aspen Rate-Based Distillation feature, RadFrac can perform rate-based distillation calculations (packed tower configurations).

Rating Mode 18

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Design Mode 21

Rigorous Model 22

Multicomponent Methods 23 AspenPlus (methanol, ethanol, 1-propanol): Component P* i (64.5 oC) Keys MeOH1.013 bar EtOH Propanol AspenPlus Txy

“Residue” From Batch Distillation 24 Seader & Henley (2006)

Residue Curve Map 25

Residue Curve Map 26

Residue Curve Map 27

DSTWU 28 Z i = 1/3 R = 1.2 * R min MeOH recovery (dist.) = 99.9% EtOH recovery (dist.) = 0.1%

RADFRAC 29 Z i = 1/3 R = 5.2 N = 63 N F = 31 D = 33 kmol/h F = 100 kmol/h

Residue Curve Map 30

Plot Wizard 31

N F = 21 32

Set up Scheme 2 (1 st column only) 33 Run DSTWU Run RADFRAC Check performance

Questions? 34