Ethanol is used in alcoholic beverages, for medical purposes but it is also the most important biofuel currently, most petrol cars in the UK use a blend of petrol with 10% ethanol. C₂H₅OH is produced from sugar cane and wood, and a step of the process is distillation.

Design a distillation column for separation of a mixture of ethanol and water of: flow rate F = 250 kmol/h with composition z = 14% ethanol. You want to separate it into water with 3% ethanol and ethanol with 25% water.

a) Find the flow rates of the distillate and the bottoms product.

b) Extract from Aspen the Txy and the xy phase diagram at p = 1 atm using the NRTL method. Find the operational temperatures in the reboiler and in the condenser.

c) Find the minimum number of theoretical stages N_min required for the specified separation.

What would be the value of N_min if the specifications were to split the feed into purified water with 2% ethanol and purified 98% ethanol? Why is this not working? What is the maximum possible separation?

d) Find the minimum reflux ratio R_min, and the respective reboil ratio for the specified separation.

What would R_min be if the distillate was specified at 82.5% ethanol? Where is the pinch point in this case?

e) Assume a reflux ratio of R = 1.3R_min and determine the respective reboil ratio R^B and the number N of theoretical stages. Determine the optimal location of the feed stage.

f) Simulate the distillation column with the parameters you chose in e), and check whether the values of R, N and R^F produce a separation that fulfils the stated specifications.

In Aspen, find the heat duty of the condenser and the reboiler.