(141h) A Resource-Task Network Approach For Optimal Scheduling And Heat Integration In Multipurpose Batch Plants

Because of the production of high value added products, the application of batch processes becomes more and more important. Since the batch operation often needs massive energy, possibly exothermic or heat absorption, the suitable adjustment of operation order may dramatically reduce the demand energy by heat exchanging. The integration between scheduling with heat-integration is thus an important issue in the optimization model. Over the past two decades, a considerable number of studies have been made on scheduling of batch plants. Many of them were developed in general formulation. In this article, we will extend the resource-task network, a global event-based formulation proposed by Castro et al., for simultaneously considering optimal scheduling and the possibility of heat integration in multipurpose batch plants. Although the formulation is capable in dealing with continuous processes, the main goal of this article is focus on the heat-integration of batch processes since a great deal of effort has been made at continuous processes and only few attempts have so far been made at batch chemical processes. In considering with the heat-integration, there are two methods available to be applied: the direct heat integration and the indirect heat integration. In the direct case, we arrange exothermic/heat absorption tasks at the same time point; whereas the indirect case involves the use of the heat transfer medium (HTM) to make the energy stores up temporarily. Obviously, the direct heat exchange is the prior consideration due to its high energy efficiency and lower the cost of hardware. Moreover, in multipurpose batch scheduling, it is straightforward to apply a flexible set of unit allocation that increase the change of direct heat exchange. Two examples from the literature (Majozi, 2006) will be supplied to demonstrate the proposed formulation.

Reference: Castro, P. M., A. P. Barbosa-Povoa, A. Henrique, and Q.N. Augusto, ?Simple Continuous-Time Formulation for Short-Term Scheduling of Batch and Continuous Processes ,? Ind. Eng. Chem. Res, 43 105-118 (2004) Majozi, T. ?Heat integration of multipurpose batch plants using a continuous-time framework,? Applied Thermal Engineering, 26, 1369-1377 (2006)