HEAT INTEGRATION FOR BATCH PROCESSES Part 1: Process Scheduling Based on Cascade Analysis

A systematic mathematical formulation is presented in this paper for the scheduling of some batch processes operated cyclically, involving the policy of no intermediate storage, but with heat integration. The formulation is based on cascade analysis and leads to an MINLP model. Extensive heat recovery from batch processes including the case of multiple stream matching can be accommodated by this model. An optimal schedule is found under the condition that heat is recovered in the mode of countercurrent exchange, but other types of heat exchange may be introduced after rescheduling. Because of the computing difficulties for solving the MINLP model, some problem preprocessing methods for reducing the size of the model as well as several simplified solving strategies are proposed. These simplified solving strategies require the solution of an MILP model or a series of LP models. The proposed problem preprocessing methods and solving strategies are demonstrated by examples.