石油化學工業，簡稱石化工業(petrochemical industry)，以石油或天然氣為主要原料，經過化學反應，加工生產出各種化工產品的行業，屬於連續性生產模式。在石化工業中，有許多化學特性以及特殊生產限制會影響生產排程的表現與可行性，另外在實務上，石化工業可能因為管線堵塞，零件故障，化學反應不佳…等眾多原因導致產線停擺，且突發的故障無法預期，維修時間變異也較大，如維修時間會隨管線堵塞程度而有所差異，且在石化工業中的保養策略為一年一次並由公司決定為年底進行保養，在這一年中，產線若突然停擺，則採取緊急維修(reactive maintenance, RM)的策略，在維修保養結束或故障維修結束後需重排排程，因此對於制定石化工業的預防保養(preventive maintenance, PM)計畫建議以及開發一個有效率的生產排程是需要的。
本研究根據石化產業中工程經驗參考檔案開發三種啟發式演算法產生可行的化工廠生產排程，工程經驗參考檔案記錄石化工廠的生產特性與限制，而熔融指數在化工廠中表示加工時的流動性，因此熔融指數在化工廠排程中為主要參考的項目，在考慮化工廠目標以及限制的情況下，有三個關鍵生產議題為滿足客戶交期需求, 減少產能損失，增加生產良率。接著制訂四種石化工業保養策略，模擬隨機故障發生並使用三種啟發式演算法重排排程，目標為考慮保養維修成本，與產能損失下最小化總成本，並維持產線生產穩定(與換線換模次數有關)，最終根據此多目標問題給出預防維修保養與使用的啟發式演算法建議。

Petrochemical industry refers to the industry that uses petroleum or natural gas as the main raw materials, chemical reaction, to process and produce a variety of chemical products through chemical reactions and belongs to the continuous production. In the petrochemical industry, there are many chemical characteristics and special production constraints that affect the performance and feasibility of production scheduling. In addition, the maintenance strategy in the petrochemical industry is once a year and the company decides to carry out maintenance at the end of the year, if the production line suddenly stops, the reactive maintenance (RM) will be carried out at the other time. However, after the maintenance or RM is completed, the schedule is required to be reschedule. Therefore, this study aims to find preventive maintenance (PM) plan for the petrochemical industry and propose scheduling algorithms to generate the feasible schedule based on engineering experience reference files which records the production characteristics and constraints of petrochemical plants. Melt Flow Index (MFI) represents fluidity which the main reference item in petrochemical factory scheduling. There are three critical production issues, meet customer delivery requirements, reduce capacity loss, and increase production yields. Then formulate four maintenance strategies, simulate the occurrence of random failures and use three heuristic algorithms to reschedule. The goal is to minimize the total cost (i.e. PM cost, RM cost, and cost of capacity loss) and maintain the stability of the production line (depending on the transitional products). Finally, recommend the combination of PM strategy and proposed heuristic algorithm based on this multi-objective problem.

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