Safety Analysis Of Hydrogen Releases And Explosion Accident In A Skid-mounted Hydrogen Refueling Station

Environmental pollution and resource shortages have become increasingly serious due to the extensive use of fossil fuels.Hydrogen is one of the promising alternative fuels since hydrogen is clean,sustainable and abundant.However,hydrogen infrastructure is now insufficient for the commercialization of fuel cell vehicles,especially hydrogen refueling stations.Skid-mounted hydrogen refueling stations have the advantages of small footprint,short construction time and low cost,which can be more easily commercialized.The equipment of the skid-mounted hydrogen refueling station is placed in the container body which is semi-closed in operation.Hydrogen is flammable and explosion with a wide flammability range in the air.The leaked hydrogen can be easily ignited to harm the surrounding people and buildings.Therefore,the hydrogen releases and explosions should be studied for the skid-mounted hydrogen refueling station to understand the influence range and take prevention measures,which is of great significance for developing the construction standards and safety distance.This paper presented qualitative analysis,numerical simulations and prevention measures for skid-mounted hydrogen refueling stations based on the hydrogen refueling station safety designs.The Fault Tree Analysis was used to qualitatively study the hydrogen accident risk of skidmounted hydrogen refueling stations.The fault tree was established reasoning the accident causes and logics,which has 35 basic events and 23 logic gates.The Boolean operation obtained 918 minimum cut sets and 13 minimum path sets.Hence,there are 918 possible ways to cause accidents and 13 possible ways to prevent accidents.Finally,the structural importance of the basic events was analyzed.The results show that the two basic events "hydrogen detection device failure" and "hydrogen detection device not installed" have the greatest importance in causing accidents.The hydrogen releases and explosions were numerically modeled in a skid-mounted hydrogen refueling station for various conditions.The results show that the flammable cloud formed in the X direction has the longest spreading distance of 11.9 m.The hydrogen concentrations in the personnel operating area are lower than in other areas,but the flammable clouds still gather near the hydrogen storage tank and the ceiling.The explosive overpressure increases with the hydrogen molar concentration approaching the stoichiometric ratio.With the further increase of hydrogen concentration,the overpressure decreases but the flame range increases.Protective walls and explosion vents were used to reduce the explosion damage,The protective effects of the two prevention measures were modeled.The results show that the protective wall with a distance of 6 m can effectively protect the surrounding people and avoid the secondary overpressure injury of the container body.The explosion vents show consistent protection effect with the same vent area,which can reduce the inside overpressure by 50%.This work provides suggestions for the skid-mounted hydrogen refueling stations protective structural design.