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3.5 Summary—Objectives
In this chapter we introduced the idea of distillation columns and saw how to do external balances. At this
point you should be able to satisfy the following objectives:
1. Explain how a countercurrent distillation column physically works
2. Sketch and label the parts of a distillation system; explain the operation of each part and the flow
regime on the trays
3. Explain the difference between design and simulation problems; list the specifications for typical
problems
4. Write and solve external mass and energy balances for binary distillation systems
References
Biegler, L. T., I. E. Grossman, and A. W. Westerberg, Systematic Methods of Chemical Process
Design, Prentice Hall, Upper Saddle River, NJ, 1997.
Felder, R. M. and R. W. Rousseau, Elementary Principles of Chemical Processes, 3rd Updated ed.,
Wiley, New York, 2004.
Humphrey, J. L., and G. E. Keller II, Separation Process Technology, McGraw-Hill, New York,
1997.
Keller, G. E., II, “Separations: New Directions for an Old Field,” AIChE Monograph Series, 83
(17), 1987.
Homework
A. Discussion Problems
A1. Explain how a distillation column works.
A2. Without looking at the text, define the following:
a. Isothermal distillation
b. The four flow regimes in a staged distillation column
c. Reflux and reflux ratio
d. Boilup and boilup ratio
e. Rectifying (enriching) and stripping sections
f. Simulation and design problems
Check the text for definitions you did not know
A3. Explain the reasons a constant pressure distillation column is preferable to:
a. An isothermal distillation system.
b. A cascade of flash separators at constant temperature.
c. A cascade of flash separators at constant pressure.
A4. In a countercurrent distillation column at constant pressure, where is the temperature highest?
Where is it lowest?
A5. Develop your own key relations chart for this chapter. In one page or less draw sketches, write
equations, and include all key words you would want for solving problems.
A6. What type of specifications will lead to simultaneous solution of the mass and energy balances?
A7. Specifications for a distillation column cannot include all three flow rates F, D, and B. Why not?
