Leak detection and repair in refining and petrochemical plants

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This article briefly outlines the concept and hazards of pollutants released due to leaks in refining and chemical processing units in the petrochemical industry. It introduces LDAR technology for leak detection and repair, explains the importance of this technology, states that its implementation can reduce leakage rates and improve production efficiency, and discusses the development trends of LDAR technology. I. Pollutants leaked from refining and chemical processing units: During the period of increasing scale of such units and rapid development in factory production, the issue of leaks from refining and chemical processing equipment has become a major concern at present. In the refining production process, the main pollutants emitted are organic substances. They are characterized by numerous and relatively scattered emission points, as well as significant variations in emission concentration. In the petrochemical industry, leaks generally refer to the emission of volatile organic compounds (VOCs). The main reactants in photochemical reactions are volatile organic compounds (VOCs), which can react with NOx to produce strongly oxidizing intermediates such as PAN and O3. In cities, VOCs mainly originate from human emissions, with industrial sources being one of the primary sources of such emissions; among these, emissions from the petrochemical industry hold an absolutely crucial position. II. Hazards of Volatile Organic Compounds 　　 During the operation of refining equipment, uncontrolled emissions resulting from leaks in the equipment occur frequently, which can lead to processing losses, energy waste, environmental pollution, and even fires, explosions, and poisoning. VOCs are characterized by strong permeability, high lipophilicity, and low boiling points; most of their components are also toxic, and many VOC components have been identified as potential carcinogens and hazardous substances. One of the main causes of foul odors is also the uncontrolled emission of VOCs resulting from leaks in refining and processing facilities. III. The importance of implementing LDAR 　　 Due to poor sealing in components such as pumps, valves, and connections in refining units, some VOCs are emitted in an uncontrolled manner during the production process. Leakage emissions from pipeline components and storage tanks in the petrochemical industry account for approximately 76% of the total VOC emissions. 　　 In the early days, visual inspection and listening without any instrumental assistance were the main leak detection techniques. Later, these evolved into leak detection methods aided by soap films; ultimately, they developed into techniques utilizing portable detection instruments. Currently, China lacks a complete technical standard system for directly monitoring unorganized emissions resulting from leaks in refining and chemical processing equipment. As a result, it is impossible to achieve direct and effective real-time monitoring of VOC emissions caused by such leaks. 　　 Currently, the United States gives priority to LDAR (Leak Detection and Repair, a method designated by the EPA as Method 21), which uses infrared camera-assisted leak detection technology; it is currently the most effective method for detection and control, and has been incorporated into the U.S. Federal Code. This technology is an effective control measure for detecting volatile organic compounds through instruments; it directly inspects the pipeline components where leaks may occur, identifies such components in real time, marks and reports any leaks found, and carries out maintenance or replacement to reduce leak emissions. This technology has been widely cited and has become the standard for common monitoring methods today. IV. Benefits resulting from the implementation of LDAR Leakage from refining equipment, which mostly consists of VOCs and volatile hazardous air pollutants (VHAPs), has been shown to have adverse effects on the environment and human health. The U.S. EPA conducted a survey and evaluation of companies that have implemented LDAR. The results showed that after implementing LDAR, equipment leakage at oil refineries decreased by 63%, while VOC emissions from petrochemical companies were reduced by 56%. After the implementation of LDAR technology, leakage emissions can be significantly reduced, thereby improving production efficiency. This is evident in the following ways: 1. In petrochemical companies, most of the substances that are released through uncontrolled leaks are marketable materials. If such leaks are reduced, these products can be sold again as materials, **which reduces losses of products such as gasoline and other petroleum products ； 　　 2. HAPs are also part of the volatile organic compounds emitted in an unorganized manner; excessive emissions of these substances can be harmful to the health of equipment operators. Implementing LDAR can reduce the uncontrolled release of materials, and from the perspective of occupational health and safety, it enables an effective reduction in operators’ exposure to these harmful substances ； 　　 3. Uncontrolled leaks not only affect the employees of the company, but also have a negative impact on the residents living in the area surrounding the company, as well as on schools and other facilities in that vicinity, due to their long-term exposure to air filled with harmful pollutants. Implementing LDAR can effectively reduce the negative impact on the air quality of the surrounding environment ； 　　 4. Chemical processing equipment equipped with LDAR can effectively reduce the total amount of pollutants emitted, thereby lowering corporate costs ； 　　 5. Implementing LDAR measures to reduce the uncontrolled emissions from refining and chemical processing units can lower the compliance risks faced by enterprises, as well as the risks associated with excessive emissions such as financial losses and damage to reputation, thereby enhancing the brand value of these enterprises. V. Development Trends in Leak Detection and Repair 　　 At present, leak detection and repair of equipment have adopted a systematic, professional, and regulated approach in the United States. Since the implementation of LDAR, foreign refineries have achieved significant economic and social benefits, particularly in terms of environmental protection, energy conservation, and safe production. Research on leaks in our country began relatively early; after experiencing slow progress, it once again became a key focus in environmental protection following the issuance of the \"Guiding Opinions on Promoting Joint Prevention and Control of Air Pollution to Improve Regional Air Quality\". Therefore, the gradual achievement of standardization in regulations and specialization in technology is an inevitable trend in the development of leak detection and repair.