Time (energy) requirements in closed batch distillation arrangements

Batch time (energy) requirements comparisons are provided for the separation of a ternary zeotropic mixture in three closed batch column configurations. Two multivessel column arrangements, with and without vapor bypass, and a regular batch column (rectifier) operated under the cyclic policy, were studied. First, the improvement achieved in the middle vessel dynamics by elimination of the vapor bypass is exhibited, through a base case study. The proposed modified multivessel column requires 30% less time than the conventional one, mostly studied in the literature. Next, the effect of the feed composition and product specification on the time requirements is discussed. The multivessel arrangements perform always better than the cyclic column, which requires from 35% 100% more time to perform a given separation. All results are based on dynamic simulations of the processes.