SHORT-CUT DESIGN PROCEDURE FOR BATCH DISTILLATIONS

This paper presents a short-cut procedure for the design of batch dist illations which is equivalent to the Fenske-Underwood-Gilliland proced ure for continuous distillations. Given a separation task, we propose computing the minimum number of stages and minimum reflux ratio requir ed to perform it by batch distillation. These parameters are quite dif ferent from the continuous N-min and R(min) parameters for the same se paration task, because of the difference in the form of the material b alances (steady state in continuous but integrated differential mass b alances in the batch case). We propose that they should be computed as the number of stages and reflux ratio required by hypothetical batch distillation columns that operate at total reflux or have an infinite number of stages, respectively. Then, it is shown that the performance of batch distillations does correlate in Gilliland coordinates constr ucted with these batch N-min and R(min). This produces a quite simple, straightforward method to do preliminary design of batch distillation s.