Batch processes are economically desirable when small amounts of high value added products are made using similar production paths. It is very important even though continuous operation is prevalent and desirable in many chemical processes. Batch process scheduling conforms to needs for a number of environmental demands, that is, an increased kind of product, shortage of due date, ultimate utilization of unit etc. Batch scheduling involves scheduling the order in which a variety of products is subject to equipment and other constraints. A number of units may exist that need to be utilized to optimally process different products in a required sequence.
However, there is no algorithm that can be applied to the real chemical processes composed of batch processes, continuous processes and various storage units. On-line scheduling systems are also required to handle the situations such as cleaning, equipment failure, and additional product requirements. It is very important for the computation time to be short when the old schedules should be replaced with a new one. Therefore, the shorter computation time becomes a major concern and the scheduling systems for chemical process plants are required to obtain allowable solutions. In this work, an algorithm that can be applied to real chemical process plants is developed.
Heuristic methods to solve simple flowshop problems can find their uses in chemical process plants. Several heuristic methods have been evaluated and the local search method has been selected due to its computational efficiency and robustness in finding optimal or near optimal solutions. The local search method has been applied to scheduling problems in a real chemical process plant and it has been found to significantly reduce inventory level in a chemical process plant. Therefore, a scheduling program based on the local search method has been developed for an increased efficiency of chemical process plants.
Batch process는 비슷한 장치를 사용하여 고부가가치 제품을 소량생산할 때 유리한 장점을 지닌다. 아직도 대부분의 화학공정은 연속공정으로 이루어져 있으며 Scheduling은 회분공정에 먼저 적용되었다.
Batch process scheduling은 다품종생산, 납기단축, 그리고 장치의 활용 극대화 등의 환경변화에 부응하여왔다. 지금까지는 간단한 공정구조때문에 회분공정중에서도 특히 flowshop문제에 더 많은 관심을 가져왔으며, 회분과 연속공정이 혼재된 실제공정의 스케쥴링 문제는 거의 다루지않아왔다.
그러나, 기업의 외부환경변화에 부응하기 위해서는 온라인 스케쥴링 시스템이 요구된다. 이러한 On-line Scheduling System은 빠른 계산속도와 제약조건을 만족하면서 더 좋은 성능의 해를 얻을 수 있어야한다.
따라서 본 연구에서는 실제 화학공정에 적용할 수 있는 scheduling 알고리즘을 선정, 실제공정에 적용하였다. 간단한 flowshop 문제를 풀 수 있는 경험적인 방법들이 실제 화학공정의 scheduling문제에 적용 가능하였고, 이러한 방법을 사용하여 재고량 감소등으로 기업의 국제경쟁력 강화에 도움을 줄 수 있을 것으로 기대된다.
