A mixture of $i-C_4,n-C_4,i-C_5,n-C_5$ and $n-C_6$ is to be separated in a distillation column. The

recovery of $n-C_4$ in the distillate is $98$mol$\%$ and the recovery of $i-C_5$ in the bottom product

is also $98\%.$ The feed temperature is $T_F=90C$ and the feed pressure is $6$ bar.

Data:

Identify the key components and find the top and bottom product compositions $(4$ marks$)$

a$.$ Estimate the relative volatilities based on the feed conditions $(6$ marks$)$

b$.$ What is the feed liquid fraction? $(6$ marks$)$

c$.$ Find $N_{\text{m}\text{i}\text{n}}$ from Fenske equation $(6$ marks$)$

d$.$ Find $R_{\text{m}\text{i}\text{n}}$ from the Underwood equation $(6$ marks$)$

e$.$ If the actual reflux is $R=1\mathrm{.}25R_{\text{m}\text{i}\text{n}},$ Use the Gilliland chart and find the number stages

are needed for this separation. $(6$ marks$)$

f$.$ Determine the optimal feed stage $(6$ marks$)$