We wish to separate a mixture of 60 mol% ethanol and 40 mol% n -propanol in a distillation column with a partial reboiler and a total condenser.

We wish to separate a mixture of 60 mol% ethanol and 40 mol% n-propanol in a distillation column with a partial reboiler and a total condenser. The feed rate is 1000 kmol/h, and feed is a saturated vapour. We desire a distillate product of 99 mol% ethanol and a bottoms product that is 0.8 mol% ethanol. Reflux is saturated liquid and CMO can be used. Equilibrium data can be approximated with an average relative volatility of 2.1 (ethanol is more volatile).

a) Use Underwood equations to find the minimum reflux ratio (Rmin).

b) Use Gilliland correlation to estimate the total number of stages for R = 1.05 x Rmin.

c) Determine the optimum feed stage location for R = 1.05 x Rmin.