A continuous distillation unit, consisting of a perforated-tray column together with a partial reboiler and a total condenser, is to be designed to operate at atmospheric pressure to separate ethanol and water. The feed, which is introduced into the column as liquid at its bubble point, contains 20 mol% alcohol. The distillate is to contain 85 mol% alcohol, and the alcohol recovery is to be 97%.

(a) What is the molar concentration of the bottoms?

(b) What is the minimum value of:

(1) The reflux ratio L/V?

(2) The reflux ratio L/D?

(3) The boilup ratio V/B from the reboiler?

(c) What is the minimum number of theoretical stages and the corresponding number of actual plates if the overall plate efficiency is 55%?

(d) If the reflux ratio L/Vused is 0.80, how many actual plates will be required?

Vapor-liquid equilibrium for ethanol-water at 1 atm in terms of mole fractions of ethanolare

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т, "с т, "с У 0.0190 0.1700 95.50 0.3273 0.5826 81.50 0.0721 0.3891 89.00 0.3965 0.6122 80.70 86.70 0.0966 0.4375 0.5079 0.6564 79.80 0.1238 0.4704 85.30 0.5198 0.6599 79.70 0.1661 0.5089 84.10 0.5732 0.6841 79.30 0.5445 0.2337 82.70 0.6763 0.7385 78.74 0.2608 0.5580 82.30 78.41 0.7472 0.7815 0.8943 0.8943 78.15