Question A$1$

The effluent of a chlorination reaction is separated by distillation to recover

chloroethane $(C_2{H}_{5}Cl).$ The effluent, with a molar flow rate of $100kmol{h}^{-1},$ is fed

into the distillation column as a saturated liquid at the operating pressure of

$250a.$ The feed stream has the following composition:

The aim is to achieve $98\%$ recovery $($by moles$)$ of chloroethane in the bottoms

product and $95\%$ recovery of ethane $(C_2{H}_6)$ in the distillate. The vapor pressures

of the different components at the temperatures achieved at the top and bottom

of the column are given in the table above. Useful equations and correlations are

given on the following page.

$($a$)$ Determine the 'key components' and outline briefly the logic involved.

$($b$)$ Estimate the molar flow rates and compositions of the distillate and bottoms

products.

Hint: Assume at this point that no components heavier than the heavy key are in

the distillate and no components lighter than the light key are in the bottoms.

$($c$)$ Determine the relative volatility of all the components at the top and the

bottom of the column. Use the heavy key component as the reference

component. State the assumptions made in the derivations.

$($d$)$ Determine the minimum number of theoretical stages $N_{\text{m}\text{i}\text{n}}$ under total

reflux, and hence determine the actual molar flows and mole fractions of

the non$-$key components in the distillate and bottoms.

The effluent of a chlorination reaction is separated by distillation to recover

chloroethane $(C_2{H}_{5}Cl).$ The effluent, with a molar flow rate of $100kmol{h}^{-1},$ is fed

into the distillation column as a saturated liquid at the operating pressure of

$250$ psia. The feed stream has the following composition:

The aim is to achieve $98\%$ recovery $($by moles$)$ of chloroethane in the bottoms

product and $95\%$ recovery of ethane $(C_2{H}_6)$ in the distillate. The vapor pressures

of the different components at the temperatures achieved at the top and bottom

of the column are given in the table above. Useful equations and correlations are

given on the following page.

$($a$)$ Determine the 'key components' and outline briefly the logic involved.

$[3$ marks$]$

$($b$)$ Estimate the molar flow rates and compositions of the distillate and bottoms

products.

Hint: Assume at this point that no components heavier than the heavy key are in

the distillate and no components lighter than the light key are in the bottoms.

$[4$ marks$]$

$($c$)$ Determine the relative volatility of all the components at the top and the

bottom of the column. Use the heavy key component as the reference

component. State the assumptions made in the derivations.

$[3$ marks$]$

$($d$)$ Determine the minimum number of theoretical stages $N_{\text{m}\text{i}\text{n}}$ under total

reflux, and hence determine the actual molar flows and mole fractions of

the non$-$key components in the distillate and bottoms.

$[4$ marks$]$