Patterns of composition change in multicomponent batch distillation

Abstract

A simple dynamic model has been developed to study the behavior of multicomponent batch distillation. The distillate compositions obtained for ideal mixtures behave in accord with intuition since the fractions contain the individual pure components in order of increasing boiling point. Azeotropic mixtures are more complex and counter-intuitive, in some cases displaying non-adjacent distillate fractions which have the same composition. The general behavior of ternary azeotropic batch distillation is described in simple terms based on the nature of the distillate and still composition changes in the phase plane. At large reflux ratio and number of stages, the sequence of distillate fractions generated from any initial composition in the still can be found with little or no computational effort.