In the manufacture of absolute alcohol by fermentation, the product is separated and purified using several stages of distillation. In the first stage, a mixture of 5 mol% ethanol in water, with traces of acetaldehyde and fusel oil, is concentrated to 50 mol%. The concentration of alcohol in the wastewater is reduced to less than 0.1 mol%.
Design a sieve plate column to perform this separation, for a feed rate of 10,000 kg/hour. Treat the feed as a binary mixture of ethanol and water. Take the feed temperature as 20 °C. The column will operate at 1 atmosphere.
Determine:
a. The number of theoretical stages
b. An estimate of the stage efficiency
c. The number of actual stages needed
Design a suitable sieve plate for conditions below the feed point. Equilibrium data for the system ethanol-water, at 760 mmHg, mol fractions ethanol:
