| AlH3 has received widespread attention due to its excellent energy performance and hydrogen storage capacity,but there is a risk of dust explosion during its production,transportation,and storage.However,the existing research on the safety protection technology of AlH3 is not in-depth enough,and there is a lack of understanding of the venting characteristics of the AlH3 dust explosion.Therefore,this article took AlH3 dust as the research object and tested the explosion characteristics of AlH3 dust under airtight condition through the self-built dust cloud airtight pressure test platforms.On this basis,it explored the pressure and flame propagation laws of AlH3 dust explosion venting under the conditions of ductless venting and duct venting and evaluated the applicability of current dust explosion venting standards to the design of AlH3 dust explosion venting.The main conclusions are as follows:（1）In the airtight container,the lower explosion limit of AlH3 dust gradually decreased with the increase of ignition energy.When the ignition energy is 10 k J,the lower explosion limit was 30 g/m3.The explosion pressure and explosion pressure rise rate of AlH3 dust showed a trend of first increasing and then decreasing with the increase of mass concentration,reaching the maximum values of 1.15 MPa and 85.56 MPa/s at the optimal explosion concentration of750 g/m3,with an explosion index of 23.22 MPa·m/s.Compared to Al dust with similar particle sizes,AlH3 dust had a smaller lower explosion limit,stronger explosion pressure,and greater explosion index.（2）Explosion venting can effectively reduce the explosion pressure of AlH3 dust in containers.Compared to airtight conditions,the pressure peak and pressure rising rate peak both decreased in ductless venting containers,but the decreasing range decreased with the increase of mass concentration and brusting pressure.There were two types of ductless vent flames:single and multiple flames.Multiple flame types concentrate at higher mass concentrations.The maximum propagation distance and maximum propagation velocity of the vent flame front surface first increased,then decreased with the increase of mass concentration,and increased with the increase of opening pressure,reaching the maximum at 750 g/m3.（3）The duct venting pressure had a similar trend to that in ductless venting,and the presence of a venting duct will reduce the venting efficiency.At the same mass concentration and opening pressure,the peak venting pressure increased with the increase in the length of the venting duct,but the increasing range gradually decreased.The pressure on the venting duct depended on the pressure inside the container.As the distance from the venting port increased,the pressure on the venting duct decreased.Compared to ductless venting,the presence of a venting duct hindered the conditions for the formation of a secondary flame,and the occurrence of secondary flames was reduced.At the same time,due to the constraint effect of the venting duct,the flame front with duct venting propagated faster and farther than that without duct venting.（4）NFPA 68 and EN 14491 standards had adopted conservative estimates for the venting area and flame length for ductless venting.The NFPA 68 standard was more accurate in calculating the venting area,and the NFPA 68 standard and EN 14491 standard were closer to each other in predicting flame length.For duct venting,as the concentration increased,the NFPA 68 standard tended to be lower than the experimental value.The pressure prediction value in EN 14491 standard was linear with the duct length and deviates from the actual value when the venting duct was long.In comparison,referring to NFPA 68 standard and leaving sufficient safety margin for the design of AlH3 dust explosion venting is recommended. |
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