Separation Power ◾  21
from the overhead vapor stream. The separation power for a
distillation column is associated with the energy consumption,
that is, steam and cooling water per pound of feed.
Exercises
3.1 What is the key impurity separation power for a benzene and toluene binary distillation with 1% benzene in
the bottoms and 98% benzene in the distillate?
3.2 What is the minimum number of theoretical stages
required for a C 3 splitter to separate propylene from
propane if the geometric mean relative volatility
between the top and bottom is 1.12, and the desired
separation is 99.5% propylene in the distillate and 1%
propylene in the bottoms?
3.3 If a desired ethanol–water separation by distillation
requires a minimum of 17 theoretical stages at total
reflux, how many theoretical stages would be recommended for a first-pass design of a plant column using
a computer simulation?
References
1. Komori, T., and Ohe, S., Vapor-liquid equilibrium data for
the system: Cyclohexane-n-heptane at atmospheric pressure,
Kagaku Kogaku Ronbunshu, 16, 384, 1990.
2. Fenske, M. R., Fractionation of straight run Pennsylvania gasoline, Ind. Eng. Chem., 24, 482, 1932.