On the design of multicomponent batch distillation columns

Abstract

This paper presents a mathematical programming approach to the optimal design of batch distillation columns. Both capital and operating cost contributions are taken into account. The column design parameters and operating policy are determined simultaneously. Treating the number of trays in the column as a decision parameter necessitates the introduction of a superstructure that encompasses all possible tray numbers between a lower and an upper bound. The mathematical formulation leads to a mixed integer dynamic optimisation problem which is solved using an outer approximation/augmented penalty algorithm comprising a continuous subproblem involving the optimisation of a column with a fixed number of trays and a master problem involving the solution of a small mixed integer linear programming (MILP) problem that determines the number of trays to be considered at the next iteration of the algorithm. The methodology presented is illustrated by its application to the design of a plant involving a sequence of two batch distillation columns.