An Analysis of Some Unit-Specific Event-Based Models for the Short-Term Scheduling of Noncontinuous Processes

Abstract

Several event-based formulations for scheduling noncontinuous processes have been reported in the past decade. In fact, some unit-specific event-based models have proved more efficient than other models on several literature problems. Recently, Janak and Floudas [Comput. Chem. Eng. 2008, 32 (4−5), 913−955] and Shaik and Floudas [Ind. Eng. Chem. Res. 2009, 48 (6), 2947−2964] have shown that, without allowing tasks to occur over multiple events, some unit-specific event-based models may lead to suboptimal solutions. In this work, we present five examples, involving batch and semicontinuous processes, to study the performance of some recent variants of unit-specific event-based models. The first two examples involve batch plants with finite storage as a shared resource for which a recent unit-specific event-based model [Shaik, M. A.; Floudas, C. A. Comput. Chem. Eng. 2008, 32 (1−2), 260−274] gives trivial or suboptimal solutions, depending on the example and data. Our analysis confirms that assuming a single...