An efficient design method for binary, azeotropic, batch distillation columns

Abstract

Using rigorous models to simulate batch distillation involves the solution of many stiff differential equations. The dimensionality of the problem also increases with an increase in the number of plates and components, which imposes limitations on the use of rigorous models. Furthermore, problems in design, optimization, synthesis, and control involve iterative procedures, and considerable computational efforts would be required to solve them rigorously. As an alternative, the short-cut method (Diwekar and Madhavan, 1991a) provided reasonably accurate solutions without much computational effort. This method in the present form, however, cannot be applied to azeotropic systems because of the impassable barrier of the azeotropic point and needs to be modified. The azeotropic approximation proposed by Anderson and Doherty (1984) was used to modify the short-cut method for binary azeotropic systems. The modified algorithm presented here was tested extensively with a number of binary azeotropic systems for both constant reflux and variable reflux modes of operation, and the results were shown to compare well with the rigorous models. The method requires significantly less computational efforts and is very useful in analyzing feasible region of operation.