Analysis of a membrane/distillation column hydrid process

Abstract

Distillation of low relative volatility mixtures is highly energy intensive and can require tray numbers greater than 150. Two design methods for a hybrid process are given to minimize the tray number in a distillation column that contains a membrane unit: the minimum area method and the Smoker's equation method. The Smoker's equation method is used to study the effect of different membrane variables on the tray number. The optimal position of the membrane unit on the distillation column is close to the feed to the distillation column. The number of trays in the distillation column does not decrease indefinitely with an increase in the membrane surface area due to the decreased selectivity. Maximum reduction in tray number of the distillation column occurs when the ration of the membrane feed rate to the membrane area is close to 0.1 mol/m 2 s. An analytical expression for optimal placement of a membrane unit on a distillation column is given for a special case using the minimum area method. Finally, simulations were performed to prove that both methods are equally valid.