A Study For Screening Major Leakage Accidents In Risk Assessment Of Environment

During the rapid development process of chemical industry in China, in order to meet the requirements of circular economy and the development of industry chain, the construction of comprehensive chemical enterprise is increasing day by day. Several kinds of chemical products are produced by one project. The relative technology is complex, the raw and auxiliary material is diversified and the number of risk unit is increased. Also, the correspondent risk grade of enterprise environment is improved. In addition, accidents in some large-scale enterprises in chemical industry happened frequently in recent years. All these factors create coordination conflicts between enterprise development and the surrounding environment. At the same time,environmental management departments propose stricter requirements for environmental risk evaluation of newly established chemical project. The past depth and qualitative analysis of environmental risk evaluation are not accord with the present requirement of environmental risk management. Therefore, during the process of the risk evaluation strictly according to the Guidelines, it is found that there are several risk units in one comprehensive chemical project.Those risk units are the major objects for evaluation but they it’s difficult to screen them out. In the early stage of risk evaluation of project environment, quantitative analysis of numerous environmental risk accidents of the project is conducted. Severe accidents of the project are sorted out. The evaluation objects are decided in an objective manner. All these are significant for project environmental risk evaluation and risk management. Taking leakage accidents in chemical projects as the object, on the basis of project risk recognition, probability calculation, consequence calculations, risk calculation and screening methods for major accidents in ARAMIS construction system, accurate and scientific determination of the objects of project risk evaluation is realized.For probability calculation of accidents, it is proposed that probability statistics sheet of the occurrence of leakage accidents which are approved by public literature can be used to launch simplified calculation the original probability value obtained by checking the sheet through the ratio of on-line quantity and critical quantity of actual working conditions without hazardous substances. Thus, complex steps of using fault tree to analyze probability calculation can be left out; for accident consequences calculation, by using the Risk System, a risk evaluation system developed by Huan’an Technology, the radius of median lethal concentration range of hazardous substances obtained by forecast is treated as the accident consequence; aiming at the quantitative calculation of accident risk value, the concept of risk index is proposed. Taking the product of probability and consequence calculated by theory as the risk index of accidents, risk ranking of each accident is conducted according to the risk index; it is proposed that the average risk index should be used as the scale to finally screen out the major accidents, which are used as objects of risk evaluation, in the project. The environmental risk value of risk accident in the project is systematically quantified with three indexes including accident occurrence probability,consequence and risk index. Thus, the most dependable accidents in the project can be scientifically screened out no matter there are major hazard sources or not. Scientific basis for further gradation and evaluation of environmental risk, the proposing of risk prevention measuresand risk management and control is provided. By specific cases, application computation is conducted to verify the theory. In order to verify the reasonability of the computation, risk evaluation of each accident in the case is conducted according to the requirements of Guidelines and the risk value of accidents is calculated. In accordance with the risk value ranking, it is found that the theoretical result is the same as the computation. Thus, the theory is proved to be feasible.