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 $3\mathrm{.}07$ bara. The distillate composition is shown in Table $1$ and the

external reflux ratio is $2\mathrm{.}5.$

Table $1.$ Distillate composition

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.

b$.$ Calculate the distillate temperature $($K$).$

$[5$ marks$]$

An air cooler is proposed to be usec

suitability for this operation?

sess the

$[5$ marks$]$

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

the pressure is $3\mathrm{.}07$ 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$]$

Question $2[30$ marks$]$

A tray distillation column fractionates a mixture of n$-$hexane, $n-$heptane, and $n-$octane. The

liquid leaving the last tray $($lowermost tray$)$ is introduced to a reboiler which operates at $413$

$K$ and $3\mathrm{.}07$ bara. The composition of the liquid entering the reboiler is shown in Table $2$

Table $2.$ Composition of liquid entering reboiler.

a$.$ Calculate the boil$-$up ratio of this operation.

column.

c$.$ There is a suggestion from a newly joined process

maintaing the pressure and feed composition the same.

$[10$ marks$]$

Specific instructions:

For all questions, please use the following constants for Antoine equations:

Note that SVP is the saturated vapor pressure $(mmHg),T$ is the temperature $(K)$ and $1$

bara $=750\mathrm{.}062mmHg$

Relevant assumptions are mentioned in the questions but if there is missing information,

you should state and use reasonable assumptions in your calculations.