Control comparison of extractive distillation configurations for separating ethyl acetate-ethanol-water ternary mixture using ionic liquids as entrainer

摘要

The new extractive distillation configurations, which use ionic liquids (ILs) as entrainer to develop green processes, have attracted widespread attention among scholars. Design and comparison of different process control schemes can facilitate the application of new solvents in future continuous production. In this paper, three extractive distillation configurations, including conventional extractive distillation (CED), multistage solvent recovery (MSR), and thermally coupled extractive distillation (TCED), are selected from previous work. The separation system of ethyl acetate-ethanol-water ternary mixture is studied, and 1-butyl-3-methylimidazolium acetate is used as an efficient entrainer. In order to compare the dynamic characteristics, six proportional-integral control schemes are established to evaluate the plant-wide control performance of those arrangements. Then, the improved control schemes, which correspond to the three extractive distillation configurations, are selected to test the dynamic behavior under complex disturbance conditions. Integral absolute error and destroyed exergy are calculated to examine the robustness and energy efficiency of the system. The results show that the plant-wide dynamic responses of MSR process are satisfactory in terms of product purity, and the total destroyed exergy of CED process is relatively small during the operation period. There is an effective trade-off between controllability and energy efficiency, and the optimal control scheme should be determined based on actual conditions.