Question 1 [50 marks]

A tray distillation column is used to separate a multicomponent mixture of propane, n-butane,

n-pentane, and n-hexane. Vapor leaving the first tray (uppermost tray) is then fed to a partial

condenser which operates at 3.07 bara. The distillate composition is shown in Table 1 and the

external reflux ratio is 2.5.

Table 1. Distillate composition

Component

n-propane

n-butane

n-pentane

n-hexane

Composition (mol basis)

0.05

0.75

0.12

0.08

a. Sketch a schematic diagram for the process clearly showing the flow of vapor and

liquid entering and leaving the column first tray (uppermost tray) and condenser.

[5 marks]

[10 marks]

b. Calculate the distillate temperature (K).

c. An air cooler is proposed to be used as the condenser. Can you please assess the

suitability for this operation?

[5 marks]

d. Estimate the temperature of the column first tray (uppermost tray) (K). Assume that

the pressure is 3.07 bara.

[20 marks]

e. Determine the vapor composition leaving the second tray (second uppermost tray)

and state reasonable assumption(s) for your calculation.

[10 marks]