Energy-saving heat integrated extraction-azeotropic distillation for separating isobutanol-ethanol-water

In the production of isobutyl alcohol by hydroxyl synthesis process, a large number of industrial effluent rich in isobutyl alcohol and ethanol would be produced, and the direct discharge could cause double harm to resources and environment. Therefore, it has important economic and environmental value to develop efficient and energy saving separation methods to realize the recovery of high value-added chemicals. Based on the conventional four column extractive distillation scheme (CED), this paper developed a more energy-saving extractive-azeotropic distillation alternative (EAD), which reduced energy consumption and TAC by 16.14% and 22.25%. Then, the steam recompression and variable pressure heat exchange were introduced to complete the heat integration strengthening design (HI1-EAD, HI2-EAD), which saves 54.32% and 54.36% energy consumption respectively. In order to further improve the energy efficiency, the dividing wall column distillation strengthening configuration (EADWC) was embedded into the EAD scheme. Compared with the CED scheme, TAC of the EADWC scheme and its heat integration configuration (HI-EADWC) decreased by 23.21% and 36.90%, respectively. However, the high bottom temperature of the main column leads to a significant increase in the duty and equipment investment, which makes the HI-EADWC scheme not show enough attraction. Through comprehensive evaluation, the HI2-EAD alternative presents more application potential.