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 percent ethanol in water, with traces of acetaldehyde and fusel oil, is concentrated to 50 mol percent. The concentration of alcohol in the waste water is reduced to less than 0.1 mol percent.

Design a sieve plate column to perform this separation, for a feed rate of 10,000 kg/h. 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:

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liquid phase vapor phase boiling point C 0.019 0.072 0.124 0.234 0.327 0.508 0.573 0.676 0.747 0.894 0.170 0.389 0.470 0.545 0.583 0.656 0.684 0.739 0.782 0.894 95.5 89.0 85.3 82.7 81.5 79.8 79.3 78.7 78.4 78.2