A distillation unit consists of a partial reboiler, a bubble-cap column, and a total condenser. The overall plate efficiency is 65%. The feed is a liquid mixture, at its bubble point, consisting of 50 mol% benzene in toluene. This liquid is fed to the optimal plate. The column is to produce a distillate containing 95 mol% benzene and a bottoms of 95 mol% toluene. Calculate for an operating pressure of 1 atm:

(a) Minimum reflux ratio (LID)min,

(b) Minimum number of actual plates to carry out the desired separation,

(c) Using a reflux ratio (LID) of 50% more than the minimum, the number of actual plates needed,

(d) The kilograms per hour of product and residue, if the feed is 907.3 kgh,

(e) The saturated steam at 273.7 kPa required in kilograms per hour for heat to the reboiler using enthalpy data below and any assumptions necessary, and

(f) A rigorous enthalpy balance on the reboiler, using the enthalpy data, tabulated below and assuming ideal solutions. Enthalpies in Btu/lbmol at reboiler temperature:

Vapor-liquid equilibrium data are given in Exercise7.13.

hL hy 18,130 21,830 benzene toluene 4,900 8,080