Page 195 - Separation process engineering

A2. For this McCabe-Thiele diagram answer the following questions.
a. (1) The actual feed tray is?

(2) The mole fraction MVC in the feed is?

(3) The vapor composition on the feed tray is?
(4) The liquid composition on the feed tray is?
b. Is the feed a superheated vapor feed, saturated vapor feed, two-phase feed, saturated liquid

feed, or subcooled liquid feed?
c. Is the temperature at stage 7 higher, lower, or the same as at stage 1?

A3. Suppose that constant mass overflow is valid instead of CMO. Explain how to carry out the
Lewis and McCabe-Thiele procedures in this case.

A4. Drawing the McCabe-Thiele graph as y MVC vs. x MVC is traditional but not necessary. Repeat
Example 4-3, but plot y vs. x . Note the differences in the diagram. Do you expect to get the
w
w
same answer?
A5. For distillation at CMO, show the flow profiles schematically (plot L and V vs. stage location)
j
j
for
a. Subcooled liquid feed

b. Two-phase feed
c. Superheated vapor feed

A6. A distillation column is operating under a vacuum. The column has 18 stages with the feed at
stage 9, a partial reboiler, and a partial condenser. The pressure drop per stage is 1.0 mm Hg. The
pressure of the condenser is controlled at 100 mm Hg. The pressure of the reboiler is: a. higher
than 100 mm Hg, b. 100 mm Hg, c. lower than 100 mm Hg.
A7. What is the effect of column pressure on distillation? To explore this consider pressure’s effect

on the reboiler and condenser temperatures, the volumetric flow rates inside the column, and the