Short-Term Scheduling: New Mathematical Models vs Algorithmic Improvements

Department of Chemical Engineering, Princeton University Princeton, N.J. 08544 In this paper, a novel formulation is presented for the short-term scheduling of batch plants. The proposed formulation is based on a continuous time representation and results in a Mixed Integer Linear Programming (MILP) problem. In contrast to the previously published continuous-time scheduling formulations, the proposed approach leads to smaller and simpler mathematical models which exhibit fewer binary and continuous variables, have smaller integrality gaps, require fewer constraints, need fewer linear programming relaxations, and can be solved in significantly less CPU time. Several examples are presented that illustrate the effectiveness of the proposed formulation and comparisons with other approaches are provided.