AUTOMATIC SYNTHESIS OF MASS-EXCHANGE NETWORKS WITH SINGLE-COMPONENT TARGETS

This paper addresses the problem of automatically synthesizing mass-exchange networks in which the mass of a single (key) component is exchanged between a set of rich streams and a set of lean streams. In the first part of this paper we present a two-stage synthesis procedure that employs one minimum allowable composition difference for all possible rich-lean stream pairs. In the first stage, a linear programming problem is solved to determine the minimum cost of mass-separating agents and to locate thermodynamic bottlenecks (pinch points) which restrict the exchange of mass between the rich and the lean streams. This formulation can also preclude (preassign) any specified forbidden (compulsory) matches between streams. In the second stage, a mixed-integer linear program is solved to yield minimum-utility cost networks in which the number of mass-exchanger units is minimized. In the second part of this paper we present a more general, yet computationally intensive, procedure that employs one minimum allowable composition difference for each possible rich-lean stream pair. These degrees of freedom are then used to minimize the annualized total cost of the network. An additional merit of the latter methodology is its potential as an improved approach for the synthesis of optimal heat-exchange networks. Several examples with industrial relevance are solved to demonstrate the usefulness of the notion of synthesizing mass-exchange networks and to illustrate the computational effectiveness of the proposed synthesis strategy. © 1990.