Question:
A mixture of 100 kmoles of 30 mol% methanol, 30 mol% ethanol, and 50 mol% n-propanol is charged at a pressure of 120 kPa to a batch rectifier, consisting of a partial reboiler, a column containing the equivalent of 10 equilibrium stages, and a total condenser. After establishing a total-reflux condition, the column will begin a sequence of two operating steps, each for a duration of 15 hours at a distillate flow rate of 2 h o l h and a reflux ratio of 10. Thus, the two accumulated distillates will equal in moles that of the methanol and that of the ethanol in the feed. Neglect the liquid holdup in the condenser and the column. The column pressure drop is 8 kPa, with a pressure drop of 2 kPa through the condenser. Using a process-simulation program with the UNIFAC method for liquid-phase activity coefficients, determine the mole-fraction composition and amount in kmoles of each of the three cuts.