以純對苯二甲酸製造程序風險危害分析之研究

Study on Hazards Analysis and Risk Assessment of the PTA Manufacturing Processes

本研究對象為某石化廠，產品為純對苯二甲酸（Purified Terephthalic Acid, PTA），該廠製程中使用及產生高壓氣體，符合到丙類危險性工作場所之標準，將利用危險及可操作性分析方法（Hazard and operability study, HazOp）和保護層分析（Layer of protection analysis, LOPA）方法評估製程危害，及利用失誤樹（Fault Tree analysis, FTA）分析反應器爆炸主因。製程區經初步危害分析為風險危害等級最高，所以在製程區選定6大區域分析，HazOp共有25個節點及偵測或防護措施共55項；其中嚴重度為5共5項，進一步使用LOPA計算各獨立保護層失效概率，有效掌握改善前及改善後風險等級，經由新加措施，風險降低後都能達到可接受風險；再利用FTA分析反應器爆炸原因，原因為反應器攪拌器低轉速危害失誤率為6.13×10-11，觸媒進料低流速造成危害失誤率為1.44×10- 11，藉由FTA找出反應器爆炸主因，訂定降低失誤率方法及有效降低庫存及購買成本。經由HazOp、LOPA及FTA風險評估工具分析，人員巡檢能直接改善風險與預知危害，分析製程危害改善須從製程操作、製程參數、防護措施及導入智慧巡檢系統著手，智慧化巡檢採用近距離無線通訊（Near Field Communication, NFC）行動科技方案，將紙本抄錶傳化成電子化，將廠內60個紙本表格轉換成300個電子表單，安裝在平板電腦分配給操作人員使用，並在製程區佈署NFC感應點位。讓操作人員查看操作數據並直接用平板電腦輸入讀值，數據上傳到公司的雲端資料庫分析。如果有異常，提前做預防措施，降低風險。藉由本研究能提供其他國內石化廠或化工廠為參考，依循本研究方法來檢視自己企業內風險評估工具及製程風險量化數據，來檢討企業內相關降低風險措施。 This study takes a petrochemical plant in Taiwan as the subject. The petrochemical plant produces Purified Terephthalic Acid (PTA) and the high-pressure gases used and produced during the production have been categorized as Class C dangerous work place. This study applies both the Hazard and operability study (HazOp) and the Layer of Protection Analysis (LOPA) to evaluate the process hazard and performs the Fault Tree Analysis (FTA) to evaluate the main causes of reactor explosion. Assuming the process scenario as the explosion risk, the HazOp selects 6 major zones for analysis. A total of 55 items have been analyzed including 25 knots and detective or preventive measures; among them, five items have been ranked Level 5 severity. LOPA is further applied to calculate the failure probability of each independent protection layer in order to effectively control the risks after the improvement. With the application of new measures, the risks have been reduced to acceptable level. FTA is applied to analyze the causes of reactor explosion and finds the error rates due to low speed of stirred tank reactor and catalyst feeding are 6.13×10-11 and 1.44×10-11 respectively. Finding the main reasons for reactor explosion with the application of FTA, the results help to reduce the error rate, inventory and purchase costs. With the risk assessment tools such as HazOp, LOPA and FTA, patrol personnel can reduce risks and prevent damages directly. Process Hazard Analysis improvement begins with process operation, process parameter, protective measure and the implementation of smart patrolling system. The smart patrolling system adopts the Near Field Communication (NFC) mobile technology program to replace manual meter reader. A total of 300 paper forms in the factory are converted into 60 electronic forms. The smart patrolling system is installed on the personal digital assistant(PDA) of meter readers. With NFC beacons installed on site, the readers can read and input the data through their PDAs. The data will be uploaded to the cloud database of the company. In case of abnormality, the system will send an immediate warning for immediate repair, and take preventive measures in advance to reduce the risk. This study aims to serve as a reference for other domestic petrochemical or chemical plants to examine their quantitative data of risk assessment tool and process risk as well as to examine the internal risk reduction measures of the enterprise.