Study On Migration And Transformation Mechanism Of Reactive Silicon Tetrachloride Leakage

With the rapid development of the national economy,it becomes inseparable from various chemical substances in production and life of human beings.On the other hand,the hazardous effect caused by dangerous chemicals are more prominent.A hazardous chemical leak accident often causes huge casualties and economic losses.And reactive hazardous chemicals will react with substances in the atmosphere to generate new toxic substances,resulting in more complicated evolution and dangerous consequences.Their dispersion and conversion will be affected by ambient temperature and humidity,wind speed and direction,atmospheric stability,and the state of the release source,making it more difficult to predict and identify.Silicon tetrachloride is the main by-product of the polysilicon industry,which is highly corrosive,strong irritating,volatile,and easily deliquescent to produce toxic corrosive fumes.If silicon tetrachloride leaks,it will react with water vapor in the air to form hydrogen chloride and silicic acid,forming a heavy gas cloud,which is seriously harmful.It is of great significance to study the law of dispersion and migration of reactive silicon tetrachloride in the atmosphere,quickly and effectively predicting the dispersion area and analyze its harmful consequences to guide emergency response,reduce environmental and social risks,and ensure the healthy development of photovoltaic industry.In this thesis,the migration and transformation mechanism of the reactive chemical silicon tetrachloride is studied.The experimental scheme of on-site leakage diffusion is designed to simulate the accident of liquid pool formed after the leakage of silicon tetrachloride.The environmental data including HC1 concentration,temperature and humidity of the leakage site are obtained,and the behavior and dispersion of cloud formed after leakage of silicon tetrachloride are analyzed.The distribution law of HCl concentration are deeply explored.An abnormal phenomenon is found that after the HCl concentration decreases below the safe concentration on the first day,it would increase by more than 300 ppm in the early morning of next day.It is found that the downwind HC1 concentration peak and the relative humidity are negatively correlated.The higher the humidity,the smaller the HCl concentration peak is.In summer,the high temperature will promote the reaction,and the peak of HCl concentration in the downwind is higher than that in spring,and the peak time is shorter than that in spring.Furthermore,this thesis uses the terahertz imaging system to observe and analyze the reaction profile of silicon tetrachloride with water vapor and water.Two kinds of experiments of direct contact and indirect contact between silicon tetrachloride and water are designed,and the evolution of reflectivity with time during the reaction process is obtained.It is indicated that the reaction between silicon tetrachloride and water is mainly affected by the amount of water.The more the water,the more severe the reaction is,and the reaction is mainly concentrated on one side of the water.The closer the water is,the more severe the chemical reaction and the more solids is produced.This thesis fills the blank of the domestic silicon tetrachloride field leakage experiment.The research results provide a scientific basis for the subsequent theoretical study of reactive material diffusion and migration,pollution prevention and control,and emergency treatment and control of hazardous chemicals accidents.