Computer evaluation of distillation processes with parallel streams

Abstract

Mathematical models and iterative methods are developed for simulating alternative multicomponent distillation processes with parallel flow streams (vapour and liquid streams) in order to study the variation of separating effects. In the parastillation process, the uprising vapour stream is divided into two equal parts at the bottom of the distillation column and the whole amount of the falling liquid is stage-by-stage alternatively contacted with both parts of the vapour. In the metastillation process, the falling liquid is separated into two equal parts at the top of the column, while the whole amount of the uprising vapour is stage-by-stage alternatively contacted with both liquids flows (Fig.1). According to our previous study [6], the parastillation process results in smaller column with less investment or operating cost than distillation. In this study the metastillation process is investigated and it is found that the required theoretical number of stages increases roughly by 50 %. However, the following liquid and vapour patterns on the trays, as specified by Lewis [5], can change significantly the stage efficiency as well as the economics of the alternative processes.