Heat integration and cyclic scheduling of multipurpose batch plants using three index unit-specific event based model

Process scheduling with a long time horizon always leads to large problem size, which is challenging to solve for global optimal solutions. The problem complexity further increases with the inclusion of additional tasks such as heat integration, water integration, material transfers and shared storage. Cyclic scheduling can be a potential option to handle the long time horizon scheduling problems. In this work, a novel unified three index unit-specific event-based mathematical formulation is presented for cyclic scheduling of multipurpose batch plants. The unified framework reduces to a simple case in the absence of cyclic scheduling. The task extending to the next cycle is integrated with the short term scheduling constraints using the active task concept. Further, the framework is also extended for simultaneous cyclic scheduling and heat integration of multipurpose batch plants. The computational performance of the unified framework is evaluated with benchmark examples taken from the literature.