Comparison of regular and inverted batch distillation

Abstract

Several alternative strategies have been suggested to increase the productivity of batch distillation. One is the use of inverted columns where the feed is charged to the condenser drum instead of to the reboiler as for regular columns. In the first part of this paper, optimal results in terms of minimum operating time for separations in a regular and an inverted batch column are presented. The differences in dynamic behaviour between the two columns are discussed. Intuitively, one may think that an inverted column is best for separations with large amounts of light component in the feed since, in this case, only a small amount of heavy component needs to be removed from the column. Surprisingly, the opposite is found: the inverted column is better in terms of less operating time when the light component is present in only small amounts and where a large amount of heavy component is removed from the column. In the second part of the paper inverted separations are discussed; i.e. removal of light component in a regular column vs removal of heavy component in an inverted column. Finally, a qualitative comparison between a regular column and an ideal inverted column, where the feed is in vapour phase, is presented.