Risk Analysis And Control Strategy Study Of Tank Leakage Accident In LNG Receiving Station

As a clean and efficient energy source,natural gas is widely used.Natural gas is generally stored and transported in the form of liquefied natural gas.The liquefied natural gas receiving station has become the infrastructure for importing,storing and supplying liquefied natural gas,which is essential to guarantee the supply of natural gas.LNG has the characteristics of low temperature and deep cold,inflammable and explosive.Once leakage and fire and explosion accidents occur,it will cause serious property losses,casualties and environmental hazards.Therefore,conducting risk analysis on LNG receiving stations,studying the causes of leakage accidents,leakage diffusion rules,explosion accident impact and personnel evacuation,can prevent accidents,effectively predict the leakage and explosion process,and can rescue on-site accidents.Provide valuable data support for emergency evacuation,and provide important technical guarantees for the preparation of emergency plans and emergency command.The research content and conclusions of this paper are as follows:(1)In LNG receiving stations,a large amount of natural gas is transported,processed,and stored through various equipment.Due to the different locations of various equipment at LNG receiving stations,the amount of stored materials,and specific operating conditions,it is difficult to quantify the degree of danger.This paper uses RAST software to model dangerous equipment and quantitatively analyze the hazards of key equipment.The results show that LNG storage tanks have the highest frequency of accidents and serious consequences,followed by unloading arms.The most likely loss event caused by the failure of LNG storage tanks is leakage accidents.There are many types of factors that cause leakage accidents.The Bow-tie model is used to analyze the leakage accident to determine the basic events and possible consequences that caused the accident.In order to avoid the shortcomings of traditional risk analysis methods such as static and lack of pertinence,the fuzzy set theory is used to fuzzify basic events,and finally defuzzification obtains a more reasonable prior probability of basic events.The Bow-tie model is transformed into a Bayesian network,and the probability of basic events is updated to obtain the posterior probability,which more objectively describes the interaction between different events.Finally,a sensitivity analysis of the basic events is carried out,and it is determined that the LNG rollover is the main factor leading to the storage tank leakage accident,followed by the human factor,and the targeted measures are proposed.(2)Vapor cloud explosion accidents in recent years have shown that explosion accidents can produce unpredictable overpressure,which can lead to catastrophic accidents.Factors such as the location of the leak source,the volume and extent of the vapor cloud formed by the leak diffusion,the time of delayed ignition and the ignition location will all affect the evolution and intensity of the gas cloud explosion.Therefore,first use FLACS software to study the volume and range of vapor cloud formed by gas leakage and diffusion of natural gas under different influencing factors(leak rate,wind direction,wind speed,cofferdam height),and use the method of controlled variables to study the effect of single factor changes on leakage.The influence of the diffusion range,and the sensitivity analysis of the influencing factors,the degree of influence on the gas leakage diffusion range from large to small are leakage rate,cofferdam height,wind direction,and wind speed.Comparing the vapor cloud volume under different influencing factors,the changes in leakage rate and cofferdam height have a greater impact on the vapor cloud volume formed by gas diffusion,and the changes in wind speed and wind direction have less impact on the vapor cloud volume formed.The combination of influencing factors leading to the most serious accident scenarios was determined to provide data support for subsequent explosion accidents and personnel evacuation studies.(3)According to the most dangerous leakage accident scene,determine the vapor cloud volume and vapor cloud size,and analyze the impact of explosion accidents on buildings,equipment and personnel due to different delayed ignition times and different ignition positions.Use FLACS software to simulate explosion accidents,respectively ignite at different moments(120s,180 s,240s,300s),and study the overpressure range and intensity of explosions at two ignition positions in the storage tank area and the process area.The plant area is divided into four areas,and each area has a monitoring point to monitor the impact of overpressure generated by different ignition times and different ignition positions on buildings,equipment and personnel.The results show that as the delayed ignition time increases,the probability of damage also increases.In the same area,normal pressure equipment has a higher probability of damage,while high voltage equipment has a relatively low probability of damage.When 300 s ignition and explosion,the personnel in the storage tank area and the process area are at risk of death.Through the explosion simulation of the LNG receiving station and the analysis of the damage and impact of buildings,equipment and personnel,corresponding explosion prevention and control measures are proposed.(4)When an accident occurs,personnel will be affected by subjective and objective factors,resulting in uncertain behavior.The safety of personnel after an accident is the most important thing.Therefore,according to the scope of the leakage accident,the Pathfinder software was used to analyze the evacuation of personnel at LNG receiving stations,and explored the time required for the safe evacuation of personnel under different evacuation modes and different evacuation states.In the emergency evacuation mode,it is necessary to evacuate away from the dangerous area.Resulting in increased evacuation time.Through training and drills,the speed of personnel evacuation is increased,the response time of personnel is shortened,and it is more conducive to evacuation.Based on the analysis results,the corresponding prevention and control measures and countermeasure suggestions are put forward,which are extremely important to ensure the normal operation and safe production of LNG receiving stations.