Time requirements for heteroazeotropic distillation in batch columns

Abstract

Batch time requirements are provided for the separation of ternary heterogeneous azeotropic mixtures into three pure products in closed batch column configurations. The separations are performed in hybrid processes where distillation is combined with decantation for completing the separation task. Two multivessel column configurations, with and without vapour bypass, and a rectifier column, are compared in terms of time requirements. Three common classes of azeotropic systems were studied, classified under Serafimov’s topological classes 1.0–2, 1.0–1a and 2.0–2b. The multivessel configurations were found to perform always better than the rectifier column, which requires from 29 to 88% more time in order to perform a given separation. The elimination of the vapour bypass in the multivessel column is either impractical or it has a negligible effect on the batch time requirements. Thus, the conventional multivessel-decanter hybrid, with the vapour stream bypassing the middle vessel, is proposed as the best candidate for heteroazeotropic mixtures.