Optimization of reactive distillation processes using differential evolution strategies

Abstract

Many problems of process synthesis and design in chemical engineering can be modeled as mixed integer nonlinear programming (MINLP) problems. They include both the continuous (floating point) and integer variables. A common feature of this class of mathematical problems is the potential existence of nonconvexities due to a particular form of the objective function and/or the set of constraints. Owing to their combinatorial nature, these problems are considered to be difficult to solve. In the present study, a model based on an extension of conventional distillation is proposed for the synthesis of ethylene glycol using the nonequilibrium reactive distillation. The proposed model is simulated using the relaxation and homotopy-continuation methods. The differential evolution (DE) algorithm is applied to find the minimum total annualized cost of the nonequilibrium reactive distillation for the synthesis of ethylene glycol, which is a MINLP optimization problem.

The optimization is performed with nonideal vapor–liquid equilibrium using ten strategies of DE, considering synthesis reaction on all trays. The results show that the optimized objective function values are better than those reported in the literature, and mostly independent of the number of trays and of the reaction distribution. It is shown that the proposed homotopy-continuation method with DE strategy (DE/best/1/bin) is capable of providing optimized solutions which are close to the global optimum, and reveals its adequacy for the optimization of reactive distillation problems encountered in chemical engineering practice. Copyright © 2007 Curtin University of Technology and John Wiley & Sons, Ltd.