Design and evaluation of energy-saving total distillation separation of N,N-Dimethylacetamide/acetic acid/water

Abstract

• Propose an evaluation index for the distillation process with multiple factors. • Propose three total distillation schemes for separating DMA/HAc/water. • Three heat integrated configurations further improve energy efficiency. Industrial wastewater containing N,N-Dimethylacetamide (DMA) and acetic acid (HAC) will be produced in the production of DMA by acetic acid method. The binary mixture of HAc and DMA has maximum-boiling azeotropic point, and the relative volatility of HAc and water is small. Therefore, high purity separation cannot be realized by traditional distillation. By analyzing the separation methods of binary mixture, three processes of extractive-pressure swing distillation, azeotropic-pressure swing distillation, and azeotropic-extractive distillation are proposed to separate DMA-HAc-water ternary mixtures. The heat integration enhancement configuration is completed according to the process characteristics. The results show that compared with the conventional processes, the TAC of the three heat integration processes is reduced by more than 25%, and the energy consumption is reduced by more than 40%. The process quality index (PQI), which integrates TAC, energy consumption, environment and thermodynamic efficiency, is proposed and applied to the evaluation of all processes. The results indicate that the heat integrated azeotropic-extractive distillation (HIAED) process shows more significant industrial application potential.