Integrated batch production planning and scheduling optimization considering processing time uncertainty

Planning and scheduling of a multipurpose batch chemical plant is always affected by uncertain factors, and one of them is the processing time of tasks. When the processing time deviates from its nominal value, the original production target calculated by the planning-layer model may be infeasible for the scheduling-layer model. To address this issue, an integrated model of planning and scheduling layers is proposed in this article. The integrated model is based on a rolling horizon with recently proposed production capacity constraints; while the scheduling-layer model is based on stochastic programming. Based on the comparison with different strategies in our case studies, we show that the proposed approach could achieve a reduction of approximately 46% in total cost and a higher demand satisfaction level.