Process flow scheduling as a resource-constrained project planning problem

We discuss a project scheduling model for batch scheduling in process industries like chemicals or food industry. The production of Various final products out of different raw materials is achieved by several successive chemical or physical transformation processes on different production stages, e.g. heating, filtration, or packaging. In batch mode production, a given quantity of a substance, called batch, is processed at each production level using multi-purpose equipment. The complexity of the batch scheduling problem is increased by constraints as finite intermediate storage, minimal and maximal time lags that have to be considered between different production steps, sequence dependent cleaning operations, alternative modes for individual production steps, campaign scheduling etc. The objective is to determine a start time and a mode for each production step such that all constraints of the problem are observed and a given goal function is minimized. After an analysis of the problem and objective functions relevant in praxis, we present a deterministic resource-constrained project scheduling model and basic concepts of a solution algorithm.