Inherent safer, eco-friendly and energy saving vapor recompression assisted extractive dividing-wall column process for the separation of minimum-boiling azeotrope

Abstract

The vapor recompression (VRC) also called heat pump is widely used in the distillation to achieve energy saving. However, considering economic performance, high compression ratio impedes the application of VRC in the wide-boiling mixtures system such as extractive dividing-wall column (EDWC). In addition, the flammability of hydrocarbons as working fluids in VRC causes serious potential hazard especially for wide-boiling mixtures system. Hence, in this article, a systematic method is proposed to investigate vapor recompression assisted extractive dividing-wall column (EDWC-VRC) with multi-criteria assessment for the separation of dimethyl carbonate-methanol with heavy entrainer aniline as a case. Process preliminary analysis shows feed heater/vaporizer (feed preheating strategy) and intermediate reboiler can improve economic and inherent safety performance of VRC simultaneously. Especially for feed heater/vaporizer, the definition of minimum boiling azeotrope demonstrates that the application of vapor recompression between feed heater/vaporizer and condenser in EDWC is inherently attractive. Then, two novel configurations called EDWC-VRC integrating all feed preheating and heat integration (EDWC-VRC-AFPH-HI) and EDWC-VRC integrating two-feed preheating and intermediate reboiler (EDWC-VRC-TFPH-IR) are proposed and optimized to get optimal flowsheet. The economic and environmental results show that EDWC-VRC-AFPH-HI and EDWC-VRC-TFPH-IR are superior to original EDWC process in the open literature and EDWC-VRC with high compression ratio. Especially for EDWC-VRC-AFPH-HI with best performance, there are 12.42% TAC (five-year payback period) and 18.71% CO2 emission reduction and 20.78% energy saving than original EDWC process, respectively. Quantitative consequence assessment shows that EDWC-VRC-AFPH-HI and EDWC-VRC-TFPH-IR is inherent safer than EDWC-VRC with high compression ratio. We believe that integration of feed preheating strategy/intermediate reboiler with VRC can promote the application of VRC in the wide-boiling mixtures system.