SYNTHESIS OF OPTIMAL HEAT-INDUCED SEPARATION NETWORKS

In this work we introduce the novel problem of synthesizing heat-induc ed separation networks (HISENs). The essence of HISEN synthesis is to reduce the concentration of a certain component in a number of rich (t ypically waste) streams from a set of supply compositions to a set of target compositions by using a number of heat-induced separators. A he at-induced separator is any indirect contact unit which employs an ene rgy-separating agent (ESA) to affect separation via phase change. Exam ples of these systems include condensation, crystallization, vaporizat ion and drying. By combining phase-equilibrium data with enthalpy bala nces, we develop pinch diagrams that can be used to determine the mini mum operating cost of the system. There are two distinctive characteri stics associated with the pinch diagrams for the HISENs. First, the lo cation of the pinch point is not restricted to the supply temperatures of streams. Second, heat-induced separators may straddle the pinch po int even for networks featuring the minimum cost of energy-separating agents. A systematic procedure is presented to address these character istics and to synthesize a cost effective network of heat-induced sepa rators. The problem is formulated as an optimization program. A soluti on procedure that is guaranteed to identify the global solution is dev ised to solve the problem. In addition, a slightly revised formulation is developed to incorporate the effect of stream bypass/mixing. Sever al case studies are tackled using the proposed procedures.