Dynamic control analysis of intensified extractive distillation process with vapor recompression

This paper explores the dynamic control of a complex multivarlable interacting extractive distillation process with vapor recompression by taking the separation of acetone and methanol using water as separating agent. Results show that the effectiveness of conventional single-end temperature control structure with holding the solvent-to-feed and reflux-to-distillate ratios constant is poor owing to the large product offsets, and a series of improved control structures with composition controller(s) are developed and assessed by inserting the large throughput and feed composition perturbations. In the configuration of composition control loops, there are two crucial issues needed to be solved: one is that which of distillate impurities (methanol and solvent) should be controlled; another is the correspondingly paired manipulated variable (whether solvent-to-feed ratio or reflux ratio). Results illustrate that the effective product quality control is achieved for facing large (20%) disturbances in throughput and feed composition when the distillate methanol and water impurities are controlled by manipulating the solvent-to-feed and reflux-to-distillate ratios for extractive column, while another alternative is infeasible due to the failure of the tuning of the composition controller. And the control scheme with dual-impurity control strategy works better than that with single purity control option in terms of transient product peaks and settling time whether for handling throughput or feed composition disturbances.