Mass exchange networks for waste minimization : a simultaneous approach : Process design

The synthesis problem of mass-exchange networks is addressed, where a number of process streams, rich in terms of certain components (typically pollutants) are integrated with lean process or utility streams in order to meet process specifications (e.g. environmental regulations) on their final compositions. A mathematical programming approach is adopted, based on a hyperstructure representation of the mass exchange network. The synthesis problem is then formulated as a mixed integer nonlinear programming optimization problem (MINLP), where both network operating and investment cost are optimized simultaneously. In contrast to all previously published work that simplifies the problem by assuming decomposition based on the concept of pinch, we treat the synthesis of mass exchange networks without decomposition. In the first part, the case of a single component is examined, whereas mass exchange in multiple components can be handled in a straightforward manner. In the second part the approach is applied to reactive mass exchange networks, where chemical sorption takes place. In the third part, the mass exchange hyperstructure is extended to include regeneration of the lean streams. A number of examples illustrate the applicability of the proposed approach to several problems of waste minimization and demonstrate the impact of simultaneously minimizing operating and investment cost