Simultaneous Scheduling and Operational Optimization of Multiproduct, Cyclic Continuous Plants

Abstract

The problems of scheduling and optimization of operational conditions in multistage, multiproduct continuous plants with intermediate storage are simultaneously addressed. An MINLP model, called TSPFLOW, which is based on the TSP formulation for product sequencing, is proposed to schedule the operation of such plants. TSPFLOW yields a one-order-of-magnitude CPU time reduction as well as the solution of instances larger than those formerly reported (Pinto and Grossmann, 1994). Secondly, processing rates and yields are introduced as additional optimization variables in order to state the simultaneous problem of scheduling with operational optimization. Results show that trade-offs are very complex and that the development of a straightforward (rule of thumb) method to optimally schedule the operation is less effective than the proposed approach

A general framework for simultaneous cyclic scheduling and operational optimization of multiproduct continuous plants

“…The following are the assumptions for modeling the problem (Alle and Pinto, 2001a): A1) Every product must be processed in the same sequence at all stages (i.e., flowshop plant); A2) Intermediate inventory depends on the maximum level of material accumulated, as in Buzacott and Ozkarahan (1983). A3) Inventory cost of final products depends on the average amount of material to be stored, as in Sahinidis and Grossmann (1991).…”