Chinese Journal of Chemical Engineering ›› 2020, Vol. 28 ›› Issue (8): 2121-2130.doi: 10.1016/j.cjche.2020.05.018

• Process Systems Engineering and Process Safety • Previous Articles     Next Articles

Systematic exploration of the applicability of the idiomatic vapor balance rule to distillation column consolidation

Shuo Zhang1, Yifan Sun1, Yiqing Luo1,2, Hongzhe Hou1, Xigang Yuan1,2,3   

  1. 1 School of Chemical Engineering and Technology, Tianjin University, Tianjin 300350, China;
    2 Chemical Engineering Research Center, Tianjin University, Tianjin 300350, China;
    3 State Key Laboratory of Chemical Engineering, Tianjin University, Tianjin 300350, China
  • Received:2020-03-02 Revised:2020-05-08 Online:2020-08-28 Published:2020-09-19
  • Contact: Yiqing Luo

Abstract: For N-component distillation (N ≥ 3), consolidation between different column sections is an inevitable manipulation when synthesizing complex distillation configurations. In the consolidation, the idiomatic vapor balance (IVB) rule, in which the larger vapor flowrate in the two columns before consolidation will be chosen as the balanced vapor flowrate at the consolidation point, has been widely used. However, the applicability of the IVB rule has not been verified, which is of essential importance to the accuracy of the distillation configuration synthesis. In the present study, the applicability of the IVB rule to distillation column consolidation was systematically explored by rigorous method for the first time. First, the separation of ideal and non-ideal three-component mixtures with variable compositions was studied, and the optimized configurations before and after consolidation were determined by a rigorous method. The results indicated that for the separation of an ideal mixture, the IVB rule was applicable for the whole composition range, while for the separation of a non-ideal mixture, the IVB rule was only applicable for very limited composition range. Finally, two cases of synthesizing distillation configurations for the separation of non-ideal mixtures were studied to verify the remarkable deviations the IVB rule may cause. The results indicated that the applicability of the shortcut method using the IVB rule to the distillation configuration synthesis depended on the composition of the non-ideal mixture, and a remarkable error might result and the truly optimal configuration might be missed if the IVB rule is applied to a non-ideal mixture.

Key words: Distillation configuration, Column consolidation, Vapor flowrate balance, Rigorous optimization