The effects of thermal distillation on the performance of differential-contact distillation columns

Abstract

It is shown for a differential-contact distillation column that when there is net evaporation or net condensation within the column the height of a transfer unit should be lower than it is for adiabatic conditions. However, this improvement in efficiency, which is due to thermal distillation occurring in addition to contact distillation, is detected experimentally only for net condensation. It is also shown that, for the same reflux ratio at the top of the column, when there is thermal distillation fewer transfer units are needed, seemingly giving a further improvement in the performance. However, operating under the more realistic criterion of the same heat load per unit of throughput, implying a higher reflux ratio for adiabatic conditions, a column gives about the same separation whether there is thermal distillation or not.