Improved Unit-Specific Event-Based Continuous-Time Model for Short-Term Scheduling of Continuous Processes:  Rigorous Treatment of Storage Requirements

The problem of short-term scheduling of multiproduct and multipurpose batch plants has received significant attention in the literature compared to the problem of short-term scheduling of continuous processes. In this paper, we present an improved model compared to the work of Ierapetritou and Floudas ( Ind. Eng. Chem. Res. 1998, 37, 4360) for short-term scheduling of continuous processes using unit-specific event-based continuous-time representation. The formulation is based on the state-task-network representation resulting in a mixed-integer linear programming model that accurately accounts for various storage requirements such as dedicated, finite, unlimited, and no intermediate storage policies. The formulation allows for unit-dependent variable processing rates, sequence-dependent changeovers, and with/without the option of bypassing of storage. Different variants of an industrial case study from a fast moving consumer goods manufacturing is presented to demonstrate the capability of the proposed model.