Selection of optimal structure of batch distillation system

The optimal structure of a batch distillation column is discussed from the viewpoint of energy conservation. In this paper, in addition to the ordinary and stripping batch distillation columns, many types of complex columns are taken into account. For example, in a complex column, the feed is supplied to the tank installed at the middle of the column, and the light and heavy components are withdrawn from the top and the bottom at the same time. Each complex column can be regarded as a combined system of batch distillation columns separating binary components. Thus, at first, by analyzing the differences among the ordinary, stripping, and total reflux batch distillation columns separating binary components, two heuristic rules with regard to the separation performance of the columns are derived. It becomes clear that, by using these heuristic rules, the candidates of the optimal structure can be limited to a few structures. For an example problem of separating four components, the optimal operating condition for every structure is determined, and it is verified that the proposed screening method is appropriate.