QUESTION $4(20$ Marks$)$

A liquid mixture containing $40$ mol $\%-$hexane $(C_6{H}_{14})$ and $60$mol$\%-$heptane $(C_7{H}_{16})$ is fed

to a flash drum operating at $1520mmHg$ pressure. The feed rate is $100mo\frac{l}{s}.$ The mixture is

heated to $111C,$ and vapor and liquid products are removed continuously. The liquid stream

only contains $67\mathrm{.}4$ mol $\%C_7{H}_{16},$ and the rest is $C_6{H}_{14}.$ However, the products obtained did not

meet customer specifications. The customer requires $99$mol$\%C_6{H}_{14}$ in the vapor stream and

$99\mathrm{.}5$mol$\%C_7{H}_{16}$ in the bottom stream. To meet customer specifications, you will design a

distillation column and select an operating pressure of $1520mmHg.$

$($a$)$ Draw and label the process flow diagram completely, perform the degree of freedom

analysis, and calculate the total flow rates $(mo\frac{l}{s})$ of vapor and liquid of the flash drum

product streams.

$($b$)$ Prove that the temperature at the top and bottom of the distillation column is $93\mathrm{.}1C$

and $123\mathrm{.}7C,$ respectively. Show the equations involved clearly.

Given data:

Antoine equation: $\{$:$log10p^{*}(mmHg)=A-\frac{B}{TC}+C]$

Table $2$: Antoine Equation Constants for $n-$Hexane and $n-$Heptane