FEASIBILITY AND SEPARATION SEQUENCING IN MULTICOMPONENT BATCH DISTILLATION

Batch distillation of azeotropic mixtures usually produces azeotropes. Various techniques such as pressure swing or extractive distillation are currently available to break azeotropes in continuous columns. We describe methods to break azeotropes using a homogeneous entrainer in a conventional or inverted batch column. We show that the use of an inverted configuration is essential to break minimum boiling azeotropes. The entrainer selection is determined from an analysis of the batch distillation regions in the limit of a large number of stages and large reflux ratio or large reboil ratio. Several possible schemes for breaking binary azeotropes are described. We find that most ternary azeotropes can be broken into pure components and binary azeotropes using only an appropriate choice of the initial feed. We finally describe how to obtain a feasible sequence to separate an azeotropic mixture of methyl acetate, methanol, ethyl acetate and ethanol, and present some sequence alternatives.