| In recent years, fire and explosion accidents occur from time to time from various industries throughout the country, especially the chemical industry.In its production process, there are many risk factors, such as fire, explosion, toxic gas leakage, that has not only brought tremendous harm,to the safety and health of people but also caused serious environmental pollution.Environmental risk assessment as an important component of the environmental impact assessment, its narrow sense is to assess the possibility of the incident about the harmful substances to human health and in the ecosystem from this kind of project, moreover,the environmental risk reduction programs and countermeasures were proposed after the accident and the environmental impact.In this paper, a 600,000 t/a of ammonia production project as an example, it assessed the environmental risk from the chemical production and stockpiling .Ammonia industry is the basis of our country's important chemical industry, and provide many other important raw materials,after investigating the tache and the cause of the accident in ammonia production process,the text established influencing factors set, weight coefficient sets and evaluation sets.The various processes' weights in the production as well as various incidents factors' weights of each process were determined by AHP on the basis of statistical analyzing a great deal of research data.. A more reasonable weight coefficient is a basis for judging the project's environmental risks, and based on this,finally it established 2 fuzzy comprehensive evaluation model for ammonia production projects, and calculated the size of its environmental risks, and estimitted that the accident-happening probability is 7.96×10-6 times/a.Although the possibility of accidents about some chemical projects in the production process is small, but when the accidents happened , the impact would be extremely serious, the consequences would be disastrous.Therefor, it is not only need to identify environmental risk from chemical projects such as the size, also need to determine its consequences after the accident and the severity of the affected areas.In this ammonia production projects, the biggest risk comes from the leakage of liquid ammonia tank and fire,explosion accidents by calculation analysis.Once ammonia tank leakage, 10 minuts later, at downwind direction, the greatest diffusion distance is 933 m,but 612 m at cross-wind direction,when in the static wind conditions.In small wind conditions, the greatest diffusion distance is 538 m at downwind direction and 259 m at cross-wind direction.If the tank fired, thermal radiation hazards radius will reach 13.18 m,or if the explosion occurred, the blast caused the greatest damage radius will reach 90.01 m.These are potentially dangerous for the plant built structures, production facilities and staff.Through calculating, the health protection distance of this ammonia project is 1,700m. The risk value is 5.24×10-5 person/a, which is lower than the statistic value of the field. The accident risk level of this project is acceptable.Finally, the daily management measures of factory are putted forward, it effectively lower the possibility of the accident.In allusion to the occurrence of the accident,the text produced a chemical accident emergency construction project plans, and banish the potential cause of an accident in the bud.
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