Integration of Production Planning and Scheduling in the Chemical Industry
Maravelias, Christos T.
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To remain competitive in today’s environment, chemical companies must adopt an integrated view across all their operations and use advanced planning methods to achieve enterprise-wide optimality. At the production level, it is necessary to simultaneously consider medium-term (planning) and short-term (scheduling) decisions. Despite recent advances in computer hardware and optimization software, current methods are insufficient to address real-world instances of this integrated problem. Three approaches to this integrated problem are discussed. First, a novel formulation for the “generalized” lot-sizing problem is presented. This formulation accounts for process characteristics that are common in the chemical industry but are not addressed by existing approaches. Second, a number of theoretical results for discrete-time formulations are developed, enabling us to formulate problems that can be solved very effectively. Third, we present how detailed scheduling models can be used off-line to obtain an approximation of feasible production levels and an underestimation of production cost. Finally, we present how these methods can be used to address large-scale integrated planning-scheduling problems.