OPTIMAL SYNTHESIS OF MULTIPRODUCT BATCH PLANTS WITH CYCLIC SCHEDULING AND INVENTORY CONSIDERATIONS

This paper addresses the problem of determining the optimal configuration and cyclic operation of batch plants in which all the products require the same processing sequence. In particular, the problem consists in determining the following items: number, type, and size of equipment, as well as their allocation to one or multiple tasks and possible parallel operation; location and size of intermediate storage vessels; the length of the production cycle including the sequence of production of the products; levels of product inventories. The objective is to maximize the net present value. The major complication of this design problem lies in the many trade-offs that are involved, as for instance the merging of tasks versus its impact on the schedule, and length of production cycle versus inventory levels. By using a novel representation for cyclic schedules and exact linearization schemes, it is shown that this problem can be formulated as a mixed-integer linear programming problem and solved rigorously to global optimality. An efficient computational scheme is proposed for this purpose. Several example problems are presented to illustrate the capability of this method.