COMPARISON OF MATHEMATICAL PROGRAMMING AND PINCH-BASED TECHNIQUES FOR MASS EXCHANGE NETWORK SYNTHESIS

Abstract

In this paper two design techniques, based on mathematical programming, for the synthesis of mass exchange networks (MENs) are compared. Problems not generally dealt with in literature, and associated with these techniques, are highlighted. A method is presented for generating several feasible initial solutions to avoid accepting poor local solutions as final designs. Methods of handling the discontinuity of the Kremser equation used for determination of the number of stages are also discussed. In addition, a method of generating MINLP (mixed integer non-linear programming) solutions that feature integer stage-numbers is also presented. It is shown that insight-based superstructures assuming vertical mass transfer may fail to include the optimal structure of the MEN. An MINLP based design technique is selected for the solution of several MEN synthesis example problems. Our MINLP solutions are compared to the advanced pinch solutions taken from literature. Both simple and advanced capital costing functions are used for the estimation of the total annual cost (TAC) of the MENs.