一自來水廠的氯氣洩漏風險分析與危害控制

Abstract

氯在常溫、常壓下呈現成黃綠色的氣體，對呼吸系統有強烈刺激性，且具有毒性與腐蝕特性，在製程上如有操作或管理不當，極易產生中毒之危害並對生態環境造成影響。在國內自來水廠普遍使用氯氣作為殺菌藥劑，為防止發生氯氣洩漏災害，有必要透過危害評估方法探究其危害性，並採取有效的製程安全管理以降低洩漏災害。 本研究內容以台灣北部地區某自來水廠曾經於製程中發生加氯系統氯氣外洩為主，從氯筒入廠、搬運、儲存、加氯、更換、維修、緊急應變等，探討發生氯氣外洩因素。首先針對加氯系統實施初步危害鑑別，以分析氯氣洩漏後之風險。之後施以風險評估之定性分析方法「危害與可操作性分析(HAZOP)」，將所得之潛在危害加以風險分級管理，並刪除無明顯危害或重複之原因後，再使用風險評估之定量分析方法「失誤樹分析(FTA)」，計算出洩漏事故之機率。最後針對HAZOP分析所得的風險分級與FTA分析所計算之結果，加以整理且研議因應與改善之道，並追蹤評量改善後之危害控制績效，期能減少或避免氯外洩災害之發生與擴大，確保人員與設備的安全並減少淨水製程對環境的衝擊。

Under standard temperature and pressure conditons, chlorine exists in yellowish green gas form. It has suffocating odor which irritates the respiratory system, and is poisonous and corrosive. Without proper care in operation and management, it will pose serious intoxication hazard and environmental impacts. In Taiwan, chlorine is commonly used as a disinfectant. To avoid the potential danger of chlorine leakage, it is necessary to conduct a thorough study through an assessment method and to implement a standard safety management procedure to reduce its impact. This study deals with an incident of a chlorine leakage during the water-purifying process in one of the water supply companies in northern Taiwan. Focusing on the transportation, storage, injection, maintenance and emergency response of chlorine storage barrel, this study investigates the factors that trigger the leakage. The danger in the chlorine injection system evaluated first to analyze its risk once a leakage takes place. Later, the Hazard and Operability Analysis (HAZOP) is incorporated and the outcome is used to categorize its potential danger. After removing insignificant and redundant factors, the possibility of a leakage is calculated through the Fault Tree Analysis, FTA. Finally, the results of risk categorization by HAZOP and and the possibility of the leakage by FTA are integrated to develop methods to reduce the possibility of leakage and avoid its impact. The risk control performance is further evaluated after the improvement in operation and management. This study hopes to reduce or avoid the possible chlorine leakage, and ensure the safety of personnel and equipment, and minimize the environmental impacts of the water-purifying process.