Dynamic Optimization in the Design and Scheduling of Multiproduct Batch Plants

Abstract

Dynamic batch processing provides additional transient operating freedom, that can stretch the limits of profitability under strict market, facility, and time constraints. This paper incorporates dynamic processing conditions for products in a multiproduct batch plant, as opposed to fixing the process by recipes, in the broader context of equipment design, production planning, scheduling, and inventory considerations. The objective is a general function of fixed design costs, operating costs, production revenues, etc. Decisions include stage processing times for products, transient stage operating policies, continuous design parameters, production capacity, and production schedules. The infinite dimensional optimal control problem for each operation is solved using collocation over finite time elements (Cuthrell, J. E.; Biegler, L. T. Comp. Chem. Eng. 1989, 13, 49. Logsdon, J. S.; et al. Trans. Inst. Chem. Eng. 1990, 68A, 434). Scheduling, with its combinatorial complexity, is addressed in the scope of flowshop plants for specific transfer policies using the aggregated scheduling model in Birewar, D. B.; Grossmann, I. E. Ind. Eng. Chem. Res. 1989a, 28, 1333; Comp. Chem. Eng. 1989b, 13, 141.