Separation system synthesis of fractional crystallisation processes with heat integration

Abstract

A methodology is presented for the synthesis of fractional crystallisation process with heat integration. The methodology is based on the construction of three networks. The first network is based on the identification of feasible thermodynamic states. Using equilbrium data for a candidate set of potential operation point temperatures, a network flow model is constructed to represent the set of potential separation flowsheet structures that can result. The second network is used to represent the variety of tasks that can be performed at each multiple saturation point. Multiple saturation nodes can be used for different tasks depending on the characteristic of the input and output streams. These tasks include cooling crystallisation, evaporative crystallisation, reactive crystallisation, dissolution, and leaching, This multiple task condition for each equilibrium state is modelled using disjunctive programming and then converted into mixed integer programming. Heat integration is included using a heat exchanger network which can be regarded as a transshipment problem. The method is illustrated through the design of a salt separation example.