Chemical Engineering Research & Design, Vol.74, No.8, 863-871, 1996
Batch Distillation of Multicomponent Systems with Constant Relative Volatilities
A method is proposed for the shortcut simulation of multicomponent batch distillation operations. The method relies on the assumption that a given batch column can be approximated with one having an infinite number of stages, so that the Underwood equations developed for the design of continuous columns can be applied to evaluate the evolution of product compositions during the batch. The results obtained represent the limiting fractionation that can be obtained when the number of stages becomes large. A rigorous, computationally efficient model is also developed within the assumptions of constant relative volatilities, constant molal overflows, and negligible stage holdup. Three operating modes are considered : constant reflux ratio, constant composition of one component in the overhead product, and total reflux. Examples are presented showing that the shortcut model allows close approximation to the results given by the rigorous model. The computational demand of the shortcut model is very low, so that it can be profitably used as a tool for preliminary batch distillation process design, simulation, and optimization.