Controlling Tangent Pinches in the Design of Distillation Columns for

1. Science Symposium 99’ Controlling Tangent Pinches in the Design of Distillation Columns for the separation of non-ideal mixtures Audi Okullo

2. Column distillation for non-ideal mixtures • Background Information on column distillation • and the Chemical and Physical concepts • Design and considerations • Graphical representation • Simulation and Analysis of Economics of design

3. The Concept of Design Inputs and out puts are Known Ideal mixture: approximate design and parameters using equation models non-ideal mixture: guess design and improve by successive simulation Steps Check feasibility Calculate minimum reflux r, (R/D) Calculate number of stages (N), Separation purities (99.5%) Energy requirements size of column

4. Example of Distillation Tower

5. Sections of a Distillation Tower

6. Tray Hydraulics: vapor & liquid flows

7. Operating Region for a Plate column

8. Internal liquid and vapor flows

9. Material Balances F = D + B FzF= DZD + BZB D = ZF-ZB B = ZD-ZF F ZD-ZB F ZD-ZB    Ideal mixture: i(T,P,x) = io (T,P) + RTln xi Non-ideal Mixture: il(T,P,x)=iol(T,P) + RTln xiyi Assume Constant Volatility and Molal Overflow

10. Graphical Solution of a stripping design Operating line

11. McCabe-Thiele showing a pinch

12. McCabe Thiele Diagrams Minimum stages Minimum reflux

13. Tangent Pinch controlling minimum reflux (Benzene-ethylenediamine )

14. Tangent pinch on a bifurcation diagram

15. Component Data

16. Column with recycle

17. Separation Profiles

18. Sensitivity Analysis

19. Two Columns with recycle

20. Sensitivity Analysis

21. Effects of Reflux Ratio on Costs

22. Economics Operating Costs ln P= 0.00365h-6.3967 Cstm= (31 ln P -214) PE + 482 Pc Total Annual Costs TAC= [2.43 Kcap + 0.19] Ccap + Cop

23. Acknowledgments Professor Mike Malone, UMass Chemical Engineering Dept. Advisor: Mary Campbell Professor: Sheila Browne Chemistry Department

24. Traditional process to produce methyl Acetate