Novel energy saving strategy for separating acetic acid – water in extractive distillation with N-methyl acetamide as entrainer

Abstract

The design of homogeneous extractive distillation for acetic acid (AA) dehydration with N-methyl acetamide (NMA) as entrainer was investigated. It belongs to the classification of 0.0-1. The main challenge is that NMA and AA will lead to another pinch point, probably leading to energy cost and total annual cost (TAC) increase. Through analyzing thermodynamic insight, we have proposed a new strategy: low recycling entrainer purity for the extractive distillation of class 0.0-1 with no univolatility line existing. The strategy could save energy cost by avoiding the approach of the pinch point between AA and NMA. We have run sequence iterative optimization method for the process optimization. The total eleven variables are optimized. Results show that energy consumption and TAC are reduced by 50.6% and 52.1%, respectively. The results also reveal that a suitable shift of the feed tray locations improves the efficiency of the separation, even when less entrainer is used.