An MILP formulation for optimal scheduling of multi-product batch plant with a heuristic approach

A scheduling model for the single-stage, multi-product batch plant with parallel units based on a heuristic approach is developed. The model uses the continuous time representation mode and considers the constraints of the release times and due dates of tasks as well as the ready times of units. A heuristic approach is developed to predefine the processing sequence of tasks, which can reduce the model size and improve the solution performance of the scheduling model. The model is formulated as a mixed integer linear programming problem, where a kind of binary variables is used to represent the assignment of tasks and units. The model not only involves fewer binary variables than the models in the literatures but also can be used to optimize two kinds of objective functions. Several illustrative examples demonstrate the feasibility and validity of the proposed model. Comparisons of the solution results between the presented model and the models in the literatures show that the presented model has more advantages.