Research On Risk Assessment And Disaster Simulation Of Urban Natural Gas Gate Stations

In recent years,natural gas industry in China has got expansion and became the strategic position of energy system,which plays an important role in safeguarding energy spply and energy security,protecting the ecological environment and improving the energy structure.City gas distribution station,connecting the long gas transportation line and the urban gas distribution pipeline network,plays an important role in city natural gas distribution pipeline system.In a safe,stable and efficient operation condition,city gas distribution station will be conductive to natural gas transportation.Once an accident occurs,it may cause casualties,economic losses and extremely negative social effects.The thesis studies the potential risks in the process of operation of city gas distribution station and the consequences of accidents the potential risks may lead to,which plays a critical role in reducing accidents,improving the ability to predict the accidents and minimizing the loss caused by the accidents.At first,this thesis identifies the hazard of city gas distribution station.According to different functions,city gas distribution station is divided into 8 blocks according to different functions which are pipeline pig zone,dust removed and filtration zone,regulating pressure zone,measUre zone,odorizing zone,vent and swage zone,station controlling system zone and pipeline zone.Fault trees of different zones have been built to guide the fuzzy comprehensive evaluation.Characteristic quantity of safety grade,AHP and expert scoring method have been sed to quantify the failure probability of city gas distribution station.Besides,an event tree which describes the consequences of pipeline leak has been built to calculate the severity of city gas contribution station.The consequences are deflagration,fire ball/jet fire,vapor cloud explosion,flash fire,suffocation and atmospheric pollution.As gas leakage is the basis for the simulation of accidents effects,a calculation model which matches the actual leakage has been built.The model takes pressure as dynamic,time as step size.Besides,CFD commercial software has been used to analyze the diffusion range of the gas leakage.In the thesis,comprehensive models and codes of harm have been used to simulate the consequences of gas leakage in city gas contribution station.The Thornton model with high credibility has been used to calculate the radiation released by jet fire.Besides,the harm range has been simulated by the model used for gas pipeline leak.What's more,TNT equivalent model has been used to calculate the scope of the damage caused by vapor cloud explosion.