Page 238 - Separation process engineering
P. 238
1. Have two LNKs, an LK, and an HK
a. step off stages top down.
b. step off stages bottom up.
c. step off stages in either direction.
d. stage-by stage calculation probably will not work because of extreme convergence problems.
2. Have an LNK, an LK, an HK, and an HNK
a. step off stages top down.
b. step off stages bottom up.
c. step off stages in either direction.
d. stage-by stage calculation probably will not work because of extreme convergence problems.
3. Have an LK, an HK, and two HNKs
a. step off stages top down.
b. step off stages bottom up.
c. step off stages in either direction.
d. stage-by stage calculation probably will not work because of extreme convergence problems.
4. Have an LK, a sandwich component, and an HK
a. step off stages top down.
b. step off stages bottom up.
c. step off stages in either direction.
d. stage-by stage calculation probably will not work because of extreme convergence problems.
A15.e. Have an LK, a sandwich component, an HK, and an HNK
a. step off stages top down.
b. step off stages bottom up.
c. step off stages in either direction.
d. stage-by stage calculation probably will not work because of extreme convergence problems.
C. Derivations
C1. Derive Eq. (5-29).
D. Problems
*Answers to problems with an asterisk are at the back of the book.
D1. A distillation column with a total condenser and a partial reboiler is fed a mixture of alcohols.
The feed is 19 wt % methanol, 31 wt % ethanol, 27 wt % n-propanol, and 23 wt % n-butanol.
(Methanol is most volatile and n-butanol is least volatile.) The feed rate is 12,000 kg/h. We desire
a 97.8% recovery of ethanol in the distillate and a 99.4% recovery of n-propanol in the bottoms.
a. Estimate D and B and distillate and bottoms weight fractions.
b. List your assumptions, if any.
D2. What is the dew point of a vapor that is 30 mol% n-butane, 50 mol% n-pentane, and 20 mol% n-
hexane at p = 760 mm Hg? Use Raoult’s law to predict K values. Find vapor pressures from
Antoine’s equation,
