Operational Design and Improvement of Conventional Batch Distillation and Middle-Vessel Batch Distillation

Abstract

Conventional batch distillation and middle-vessel batch distillation were studied for the separation of the ternary system of cyclohexane/n-heptane/toluene, which has low relative volatilities. The modified variable and constant reflux operations were applied in the conventional batch distillation. Two control structures were used: one of which was referred to as the composition control structure with a modified level-set point, and the other was referred to as the flowrate-limiting control structure. Thus, the middle-vessel batch distillation was able to simultaneously separate the components of the ternary mixture. Comparing the two control structures showed that the flowrate-limiting control structure was better than the composition control structure with a modified level-set point in terms of their applicability. Disturbances were introduced to assess the controllability of the flowrate-limiting control structure. The dynamic responses demonstrated that the control structure performed well. The results showed that the modified conventional batch distillation and middle-vessel batch distillation increased the purity of the separated components compared to previous studies.

Constant distillate composition of batch distillation column with variable reflux mode based on still pot concentration

“…Li et al [16] considered the ordinary BD and center vessel BD by modified variable and constant reflux operations in the traditional BD. For two control strategies one of which was mentioned the composition control strategy with an adjusted level-set point, and the other was mentioned the flowrate-restricting control strategy.…”