A novel heat integrated double extractive divided-wall column avoiding vapor recompression system in water purification from petrochemical

Abstract

The chemical plant produces wastewater with tetrahydrofuran (THF), methanol, and water, which form two energy-intensive binary azeotropes. With this aim, this research introduces a novel extractive divided-wall column (DWC) to efficiently separate water from the THF-methanol mixture. The study utilizes a combination of a solvent and steam, leading to the creation of a double extractive DWC (DEDWC) as the foundational model. A key innovation of this study is the recovery and reuse of waste heat from the column's top vapor through vapor recompression, which is used for further separation. While this method requires a significant initial compression ratio and, by extension, a considerable capital investment, the study introduces a heat integration system to mitigate these costs. This system raises the vapor temperature by combining it with the heated solvent (bottom product) and strategically employing intermediate steam-driven reboilers. This inventive method, known as the heat-integrated DEDWC (HiDEDWC), notably increases the vapor temperature by 15 K beyond the reboiler liquid. Impressively, HiDEDWC demonstrates a remarkable improvement in energy and cost efficiency over the standard DEDWC and the version with vapor recompression. Specifically, HiDEDWC achieves an impressive energy saving of 52.81% and reduces the total annual cost by 52.11% compared to DEDWC.