Different extractive distillation processes for isopropanol dehydration using low transition temperature mixtures as entrainers

Abstract

Low transition temperature mixtures (LTTMs) are effective and environmental-friendly entrainers for extractive distillation. However, process intensification for the LTTMs extractive distillation process is less studied. This paper provides a techno-economic study for the separation of isopropanol and water by extractive distillation using ChCl/EG1:2 as entrainer. Firstly, the σ-profiles based on the COSMO-SAC model, the residue curve maps and univolatility lines are used to investigate the advantages of ChCl/EG1:2 over ethylene glycol. Then, the conventional extractive distillation (CED) system with EG or ChCl/EG1:2 entrainers are simulated and optimized by non-dominated sorting genetic algorithm-II (NSGA-II) method with targets of minimum total annual cost (TAC), minimum CO2 emissions and minimum global energy consumption (GEC). The TAC of the CED process using ChCl/EG1:2 as entrainer is reduced by 13.75% than that of the process using ethylene glycol as entrainer. Finally, in order to reduce energy consumption, the processes of extractive dividing wall column (EDWC) and the side-stream extractive distillation system (SED) with ChCl/EG1:2 as entrainer are simulated and optimized. The results show that the EDWC with ChCl/EG1:2 can save 23.83% of TAC, 23.43% of CO2 emissions and 22.66% of GEC compared with the CED process using EG as entrainer.