A new continuous-time state task network formulation for short term scheduling of multipurpose batch plants

A new continuous-time MILP model for the short-term scheduling of multipurpose batch plants is presented. The proposed model relies on the idea of the State Task Network (STN) and addresses the general problem of batch scheduling, accounting for resources other than equipment (utilities), variable batch sizes and processing times, various storage policies (UIS/FIS/NIS/ZW) and batch splitting/mixing. Compared to other general continuous STN formulations, the proposed model is more efficient. Compared to event-driven formulations, it often gives better solutions being equally fast. The application of the model is illustrated through an example problem.