Design and control of an energy intensified side-stream extractive distillation for binary azeotropic separation of n-hexane and ethyl acetate

In this work, we explored, for the first time, the possibility of improving the performance of conventional extractive distillation (CED) for the separation of n-hexane and ethyl-acetate system using dimethylformamide (DMF) as solvent through retrofitting it to an energy-intensified side-stream extractive distillation (SSED). This is since the application of the energy-intensified processes have never been explored in any of the existing studies for the n-hexane and ethyl-acetate system using DMF as solvent. Prior to the investigation, we first bridged the gap of previous study (Ind. Eng. Chem. Res. 2018, 57, 32, 11050-11060) where using DMF was found to be more economical relative to using n-methyl-2-pyrrolidone (NMP) as solvent but previous study did not explicitly compared the environmental and dynamic performances of both processes. The environmental performance evaluated based on the CO2 emission revealed that using DMF is much more environmentally sustainable relative to that using NMP. Likewise, DMF also provides better dynamic performance by about 3 times, as indicated by the sum of integral absolute error (SIAE), when both processes are tested under +/- 10% feed flowrate and +/- 5% feed composition disturbances. Therefore, it is used as a base case for subsequent comparison against the retrofitted energy-intensified SSED. Relative to the base case, the proposed SSED reduces the energy consumption, TAC, and CO2 emission by 26%, 19%, and 26%, respectively, indicating its economic and environmental advantages. It additionally provides 4 times better dynamic performance as reflected by the SIAE and it generally provides a lower transient deviation and can maintain both products at their desired purities.