Batch Extractive Distillation with Light Entrainer

Abstract

Use of a light entrainer in batch extractive distillation is justified when the mixture boils at a high temperature, or when an appropriate heavy or intermediate entrainer cannot be found. Feasibility of batch extractive distillation with light entrainer for separating minimum and maximum boiling azeotropes and close boiling mixtures is studied in this article. Our test mixtures are: ethanol/water (minimum boiling azeotrope) with methanol, water/ethylene diamine (maximum boiling azeotrope) with methanol, and chlorobenzene/ethylbenzene (close boiling mixture) with 4-methylheptane. Feasibility, operating steps, limiting entrainer flows, limiting reflux ratios, and limiting number of theoretical stages are determined by parametric study on profiles maps, and verified by rigorous simulation. The effects of reflux ratio, feed ratio, feed stage, number of stages, and thermodynamic state of the entrainer are also examined. It can be established, as a result, that processes separating either minimum or maximum boiling azeotropes, or close boiling mixtures, in batch extractive distillation using a light entrainer are feasible.