Batch scheduling in process industries: an application of resource-constrained project scheduling

The paper deals with batch scheduling problems in process industries where final products arise from several successive chemical or physical transformations of raw materials using multi-purpose equipment. In batch production mode, the total requirements of intermediate and final products are partitioned into batches. The production start of a batch at a given level requires the availability of all input products. We consider the problem of scheduling the production of given batches such that the makespan is minimized. Constraints like minimum and maximum time lags between successive production levels, sequence-dependent facility setup times, finite intermediate storages, production breaks, and time-varying manpower contribute to the complexity of this problem. We propose a new solution approach using models and methods of resource-constrained project scheduling, which (approximately) solves problems of industrial size within a reasonable amount of time.