For continuous distillation of a binary mixture of constant relative volatility, Fenske equation (6-58) can be used to estimate the minimum number of equilibrium stages required for the given separation, \(N_{\min }\).

Data From Equation 6-58:-

Use the Fenske equation to estimate \(N_{\min }\) for distillation of the benzene-toluene mixture of Example 6.4. Assume that, for this system at 1 atm, the relative volatility is constant at \(\alpha=2.5\).

Data From Example 6.4:-

A trayed tower operating at 1 atm is to be designed to continuously distill 200 kmol/h (55.6 mol/s) of a binary mixture of 60 mol% benzene, 40 mol% toluene. A liquid distillate and a liquid bottoms product of 95 mol% and 5 mol% benzene, respectively, are to be produced. Before entering the column, the feed—originally at 298 K—is flash-vaporized at 1 atm to produce an equimolal vapor–liquid mixture (VF/F = LF/F = 0.5). A reflux ratio 30% above the minimum is specified. Calculate:

(a) quantity of the products;

(b) minimum number of theoretical stages, Nmin;

(c) minimum reflux ratio;

(d) number of equilibrium stages and the optimal location of the feed stage for the reflux ratio specified; and

(e) thermal load of the condenser, reboiler, and feed preheater.

Transcribed Image Text:

XA,N-1 XA,W (6-58) = aNaR XB,N-1 XB,W