異丙苯氣化反應器之安全分析

Safety Analysis of a Cumene Oxidation Reactor

雖然故障樹分析早已應用到核能及航太工業，在化工安全評估國外應用頗多，但國內應用並不普遍，原因乃在於絕大部分的化工製程的複雜與其獨特性，大型數學模式的付之闕如，耗時耗費的故障樹之建立以及製程上裝置、設備與儀器等故障數據的缺乏。故障樹分析概無疑問的是鑑定化學工廠危害性的一個有效工具，由此法可分析出那些是設計上的問題，那些是人為操作上的問題以及那些是設備保養的問題，因此它可避免過去僅憑經驗或較不科學的工程判斷所引起之缺失。唯故障樹分析仍舊是一種不連續的分析法，蓋設備元件不是處於正常就是處於故障；一個製程不是處於安全就是處於不安全的狀況。此種不連續的分析遺漏了一個重要的「時間」因素，有真實世界裡，一個製程常呈現變化多端的動態行為，設備元件一有異動（突然故障或逐漸變壞）便自然會引起與時間有關連的程序擾動，程序最終也許會迴歸至安全的操作狀況，雖然它不再是最適的操作狀況，誠然程序可能就此遷向不安全的不歸路，因果之間也許是很快的也可能是相當緩慢的；總之，程序擾動所造成的後果是有「時效性」 的。本文使用一種新的安全分析模式，就是結合故障樹分析與實際的動態模擬，姑稱之為事故動態模擬，並簡稱為FDM。比較傳統的故障樹分析可做定性上程序擾動之危害分析，其次藉FDM預測嚴重事故或頂端事件的時效性，以此方式針對異丙苯氧化反應器做安全評估。

Although fault tree analysis has been applied to nuclear, aerospace, and chemical industries for some time abroad, its application in the chemical process industry in Taiwan has been limited. The reasons for this lag are the complexity and uniqueness of most chemical plants, the limited availability of large mathematical process models, the time-consuming and costly process of generating a fault tree, and the limited availability of failure data for process equipment. Undoubtedly, fault tree analysis is an invaluable tool to make safety analysis more systematic and logical and less dependent on rules-of-thumb and arbitrary judgment in the design phases of processes. One major drawback of fault tree analysis is that it is discrete. A component is either in a normal or a failed state; a process is either in a safe or an unsafe condition. Analysis along these lines can be very valuable, but it leaves out the very important time factor. In reality, a process exhibits a wide range of dynamic behavior. A change (sudden failure or gradual deterioration) in a component will lead to a time-dependent change in the state of the process. The process may move toward safe conditions, which may or may not also be suitable operating conditions, or it may move toward unsafe conditions. It may move rapidly or it may move slowly. It does not shift from a safe state to an unsafe one instantaneously. The present study will combine fault tree analysis as well as a realistic dynamic modeling - fault-dynamic modeling to analyze a reactor for cumene oxidation. The more traditional fault tree analysis is used for hazard analysis for process upsets. Then, fault-dynamic modeling is employed to predict the time factor for runaway reactions.