Improved Operational Policies for Batch Extractive Distillation Columns

Abstract

We and others (Hasebe et al., 1992; Meski et al., 1993; Davidyan et al., 1994) have previously developed insights into batch distillation when using a “middle vessel” batch column. We extended earlier work on reachable product regions for continuous columns to this and other batch column configurations. Our work also examined the use of a continuously flowing extractive agent to facilitate the separation of azeotropic mixtures. A middle vessel batch column has both an enriching and stripping section and thus both a distillate and bottoms product. In many ways it is just like a traditional continuous column, but we feed it by charging a middle tray having a very large holdup (a pot or still) with the initial feed. Our work compared running this column with running a batch rectifier for an azeotropic mixture when using an extractive agent. We showed that both are often able in theory to recover all of the distillate component in relatively pure form, with the middle vessel accomplishing this by “steering” t...