Investigation of energy-saving thermally coupled extractive distillation alternatives with different liquid side-stream for a quaternary azeotropic system

Abstract The acetone/methanol/butanone/tert-butanol system is a quaternary organic compound with multi-azeotropes and often appears in the chemical and petrochemical industries. In view of achieving its energy efficient separation, this article establishes seven alternative thermally coupled extractive distillation configurations by introducing one or more liquid side-streams into one regular four-column configuration with chlorobenzene as an entrainer. Furthermore, the intensified configurations having multiple side-streams, multiple recycling-streams, and multiple solvent recovery sections features are optimized by a simulated annealing based systematic optimization method with the minimum total annual cost (TAC) as the target. Finally, a comprehensive assessment is made among all the configurations in terms of several metrics such as TAC, energy-saving, exergy loss and CO2 emissions. The results demonstrate that these intensified configurations can respectively reduce 5.32%-14.38% energy consumption, 3.91%-10.11% TAC and 5.65%-18.05% CO2 emissions as compared with the regular configuration. One of double-side-stream configuration is the optimal option while the only triple-side-stream configuration is the suboptimal one. Besides, the proposed optimization method for side-stream extractive distillation configurations shows high computational efficiency and good applicability and flexibility.