“Chemical Engineering Equilibrium Separations” Lectures 15

1. “Chemical Engineering Equilibrium Separations” Lectures 15 22-31 Oct 2012

2. In-Class Problem benzene (17 mol%) toluene (66 mol%) m-xylene (17 mol%) DSTWU F = 100 kmol/s sat’d liquid 1 atm

3. In-Class Problem

4. In-Class Problem

5. In-Class Problem

6. In-Class Problem

7. In-Class Problem

8. In-Class Problem

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

10. Homework Problem benzene (17 mol%) toluene (66 mol%) m-xylene (17 mol%) Xbz = 99 mol% DSTWU F = 100 kmol/s sat’d liquid 1 atm Xbz = 0.1 mol%

11. HWK Problem-molefrac specified

12. HWK Problem-molefrac specified

13. Overview • Review rigorous methods / RADFRAC • Multicomponent systems: • Residue curves • DSTWU / RADFRAC • 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.

15. AspenPlus: RADFRAC 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: • absorption, reboiled absorption, stripping, reboiled stripping, extractive and azeotropic distillation

16. Rigorous Model

17. AspenPlus: RADFRAC 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: • absorption, reboiled absorption, stripping, reboiled stripping, extractive and azeotropic distillation • RadFrac is suitable for: • 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 secondliquidphase anywhere in the column. You can decant free water from the condenser. • RadFraccan handle solids on every stage. • RadFrac can model columns where chemical reactions are occurring. Reactions can have fixed conversions, or they can be: • 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).

18. Rating Mode

21. Design Mode

22. Rigorous Model

23. Multicomponent Methods AspenPlus (methanol, ethanol, 1-propanol): AspenPlusTxy

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

25. Residue Curve Map

26. Residue Curve Map

27. Residue Curve Map

28. DSTWU Zi= 1/3 MeOH recovery (dist.) = 99.9% EtOH recovery (dist.) = 0.1% R=1.2* Rmin

29. RADFRAC Zi= 1/3 F= 100 kmol/h R=5.2 N=63 NF=31 D=33 kmol/h

30. Residue Curve Map

31. Plot Wizard

32. NF = 21

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

34. Questions?