Study Questions for
“Separation Process Principles” by
J. D. Seader and Ernest J. Henley
Chapter 11
1. What is meant by enhanced distillation? When should it be considered?
2. What is the difference between extractive distillation and azeotropic distillation?
3. What is the difference between homogeneous and heterogeneous azeotropic distillation?
4. What are the two reasons for conducting reactive distillation?
5. Why do enhanced distillation calculations frequently fail?
Section 11.1:
6. Can vapor-liquid phase equilibria for a ternary mixture at a fixed pressure be represented on a triangular diagram? If so, why is it rarely done?
7. What do the curves on the triangular diagrams of Fig. 11.3 represent?
8. What is the direct sequence of distillation columns? What is the indirect sequence? Why would you expect the direct sequence to be favored?
9. What is a distillation boundary? Why is it important?
10. To what type of a distillation does a residue curve apply? What is a residue-curve map?
11. Is a residue curve computed from an algebraic or a differential equation? Does a residue curve follow the composition of the distillate or the residue?
12. Residue curves involve nodes. What is the difference between a stable and an unstable node? What is a saddle?
13. Can a residue-curve map be quickly approximated? How?
14. What is the number of possible types of curve maps?
16. Is a distillation curve computed from algebraic or differential equations? Under what conditions is a distillation curve identical to a residue curve?
17. Why do the arrows on a distillation-curve map point in directions opposite to a residue-curve map?
18. What is a region of feasible product compositions? How is it determined? Why is it important?
19. Under what conditions can a distillation boundary be crossed by a material balance line?
Section 11.2:
20. Under what conditions should extractive distillation be considered?
21. What are the characteristics of a desirable solvent for extractive distillation?
22. Can a binary azeotrope be separated by extractive distillation followed by ordinary distillation? Sketch a process flow diagram showing how this can be done?
23. In extractive distillation, why is a large concentration of solvent required in the liquid phase? Why doesn't the solvent enter the column at the top tray?
Section 11.3:
24. Under what conditions should salt distillation be considered? What is the effect of the salt?
25. What is the difference between salting in and salting out?
Section 11.4:
26. Under what conditions should pressure-swing distillation be considered for the separation of an azeotrope?
27. Why are two columns required for pressure-swing distillation?
28. Why is the recycle ratio an important factor in the design of a pressure-swing distillation system?
Section 11.5:
29. In azeotropic distillation, what is the entrainer?
31. What makes the application of a sequence involving just homogeneous azeotropic distillation and ordinary distillation difficult?
Section 11.6:
32. Why is heterogeneous azeotropic distillation a more feasible technique than homogeneous azeotropic distillation?
33. What is a decanter? How is it used in heterogeneous azeotropic distillation?
34. Should the formation of two liquid phases (phase splitting) be avoided in the top trays of a heterogeneous azeotropic distillation column?
35. What is the most common sequence for the use of heterogeneous azeotropic distillation?
36. What is meant by multiplicity? What kinds of multiplicity are there?
37. Why is it important to obtain all multiple solutions when they exist?
Section 11.7:
38. In reactive distillation, does the reaction preferably take place in the vapor or liquid phase? Can a homogeneous or solid catalyst be used?
39. What are the two major applications of reactive distillation?
40. When large liquid holdups are required to provide the necessary residence time for a reaction, what type of trays are preferred?
41. Can multiplicity occur in reactive distillation? If so, give an example.
Section 11.8:
42. What is the supercritical fluid region?
43. What happens to the solvent power of a compressed gas as it passes through the critical region? What happens to physical properties in the critical region?
44. What are the key characteristics of a desirable solvent for SCE?
45. Why is carbon dioxide frequently a desirable solvent?
46. What techniques can be used to recover CO2 when it is used as a solvent in SCE?
