Question

A distillation column is separating a feed that is 40 mol% methanol and 60% water. The two phase feed is 60% liquid. Distillate product should be 92% methanol and bottoms 4 mol%. A total reboiler and a total condenser are used and reflux is saturated. Operation is at atmospheric pressure with a reflux ratio of 0.9. Under these conditions, HG = 1.3 ft and HL = 0.8ft in both the stripping and enriching sections. Determine the required packing height in the enriching section.

0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 Methanol (methanol more volatile) 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Answer 1

The minimum number of stages is seen to be 6. The value is independent of the feed condition because at total reflux, there is no no feed. The temperature of the bottoms is 93.5oC. The temperature of the distillate is 64.7oC

One hundred lbmol/h of a mixture of 69 mol% methanol in water at 30oC and 1 atm is to be separated by distillation at the same pressure into a liquid distillate containing 98 mol% methanol and a bottoms liquid product containing 96 mol% water. The enthalpy of the feed mixture is 765 Btu/lbmol. Determine the minimum number of equilibrium stages, the temperatures of the distillate and the bottoms.