Energy-saving investigation of pressure-swing distillation strengthening configurations for benzene/isobutanol binary azeotrope

Abstract

Benzene (PhH)/isobutanol (IBA) is one of untraditional binary azeotropes with opposite non-ideal behaviors under different pressure in the chemical industry. An untraditional pressure-swing distillation configuration (UPSD) can effectively separate this type of mixture, which is characterized by IBA being at the bottom of low-pressure column (LPC) and PhH being at the top of high-pressure column (HPC). According to this feature, two important methods to improve energy efficiency - vapor recompression (VRC) and internally heat-integrated distillation column (HIDiC) are applied to this configuration. Specifically, five variants are designed and optimized to minimize total annual cost (TAC). As compared to the UPSD configuration, the results show that two variants called VRC-UPSD and HIDiC-UPSD can respectively reduce energy costs by 74.26% and 69.74% and CO2 emission by 66.61% and 57.48%. Importantly, despite the use of expensive compressors in both configurations, TAC is reduced by 38.13% and 44.96%, respectively.