91Ó°ÊÓ

A feed consisting of \(62 \mathrm{~mol} \%\) para-dichlorobenzene in ortho- dichlorobenzene is to be separated by distillation at near atmospheric pressure into a distillate containing \(98 \mathrm{~mol} \%\) para isomer and bottoms containing \(96 \mathrm{~mol} \%\) ortho isomer. If a total condenser and partial reboiler are used, \(q=0.9\), average relative volatility \(=1.154\), and reflux/minimum reflux \(=1.15\), use the Fenske- Underwood-Gilliland procedure to estimate the number of theoretical stages required.

One hundred kilogram-moles per hour of an equimolar mixture of benzene \((\mathrm{B})\), toluene \((\mathrm{T}), n\)-hexane \(\left(\mathrm{C}_{6}\right)\), and \(n\)-heptane \(\left(\mathrm{C}_{7}\right)\) is to be extracted at \(150^{\circ} \mathrm{C}\) by \(300 \mathrm{kmol} / \mathrm{h}\) of diethylene glycol (DEG) in a countercurrent, liquid-liquid extractor having five equilibrium stages. Estimate the flow rates and compositions of the extract and raffinate streams by the group method. In mole-fraction units, the distribution coefficients for the hydrocarbon can be assumed essentially constant at the following values: $$ \begin{aligned} &\text { Component } \quad K_{D_{i}}=y(\text { solvent phase }) / x(\text { raffinate phase })\\\ &\begin{array}{cl} \mathrm{B} & 0.33 \\ \mathrm{~T} & 0.29 \\ \mathrm{C}_{6} & 0.050 \\ \mathrm{C}_{7} & 0.043 \end{array} \end{aligned} $$ For diethylene glycol, assume \(K_{D}=30\). [E.D. Oliver, Diffusional Separation Processes, John Wiley and Sons, New York, p. 432 (1966).]