Separation of azeotropes in batch extractive stripper with intermediate entrainer

Abstract

Batch extractive distillation is an attractive technique for separating azeotropic mixtures (Steger et al 2005). These processes can be carried out in a batch rectifier, and in a stripping column, as well; but, unfortunately, the necessary feasibility studies of the latter one are still missing from the scientific communications. Here we present the first preliminary results on the feasibility of separating azeotropes with intermediate boiling entrainer in batch extractive stripper. The following mixtures are studied here: 1: methanol (MeOH)/toluene (TOL) (minimum boiling azeotrope) with triethylamine (Et3N) as intermediate boiling entrainer; 2: chloroform (CHCl3)/ethyl acetate (EtOAc) (maximum boiling azeotrope) with 2-chlorobutane (2ClBu) as intermediate boiling entrainer. Separation of the same mixtures with the same entrainers in rectifier have already been studied (Lelkes et al., 2002, Varga, 2003); thus, the results of the present feasibility study allow comparing the separation processes in a stripper or in a rectifier for the selected specified mixtures. Similar mixtures occure, in Rev et al., 2003. The mixture to be separated is charged to the reflux drum (the so-called vessel, or still vessel), of great hold-up capacity. Liquid entrainer is added to the stripping unit for enhancing the relative volatility of the mixture. The boiler at the bottom of the column serves as to evaporate the liquid. The product is removed from the bottom. The entrainer is either premixed to the charge (Solvent-enhanced Batch Stripping, SBS), or it can be continuously fed to the system (Batch Extractive Stripping, BES). The place of the continuous feeding can be the top vessel (BES-T), or some intermediate point in the column (BES-I).