Study On The Effect Of Physical And Chemical Properties Of Powders On Their Gas Explosion Suppression Performance

China is rich in coal resources,but most of the mines are high gas or outburst mines.Gas explosion is one of the most serious disasters in coal production,which seriously threatens the lives of miners and the safety of national property.Automatic powder spraying system is the most commonly used active explosion suppression device,which can effectively suppress the gas explosion.The explosion suppression powder is an important part of the automatic powder spraying system,and its explosion suppression performance directly determines whether the system can suppress the explosion quickly and effectively.Therefore,it is significance to improve the performance of the explosion suppression powder to improve the efficiency of the automatic powder injection system for gas explosion suppression.In order to provide theoretical support for the development of new efficient explosion suppression powder and the improvement of existing explosion suppression powder,the influence of physical and chemical properties such as particle size,pore diameter,functional group and composition of explosion suppression powder on its gas explosion suppression characteristics is studied,and the relationship between them is clarified.The research work is mainly divided into the following four parts:(1)In order to study the influence of size effect on the performance of explosion suppression powder,the difference of gas explosion suppression effect of silica powder with average particle size of 19.8?m,13.7?m and 3.52?m was tested and analyzed.The heat absorption effect of silica with different particle size in the explosion system was simulated and analyzed.The explosion inhibition caused by size effect was further clarified.The results show that the explosion suppression effect of the silica increases with the decrease of its particle size.With the decrease of particle size of the powder,its specific surface area and heat absorption capacity becomes larger and stronger,so its gas explosion suppression capacity becomes stronger.(2)In order to obtain the influence of pore size on the gas explosion suppression characteristics of porous explosion suppression materials,three kinds of zeolite powders with approximate particle size and median pore size of 0.83nm,1.61nm and2.42nm were selected.The results show that the explosion suppression performance of zeolite powder increases with the increase of pore size.After adding a certain amount of zeolite powder,the pressure of gas explosion decreased by 49.9%,66.9%and 79.7%respectively,and the flame propagation speed decreased by 39.3%,67%and 78.9%.When the concentration of zeolite powder with a median pore diameter of 2.42 nm reaches 0.2 g/L,the gas explosion has a long induction period,and the front of the explosion flame is damaged,and a part of the flame close to the pipe wall starts to extinguish.(3)In order to study the effect of different functional groups on the explosion suppression performance of the powder,amino-silica powder and fluoro-silica powder were successfully prepared by the dopamine self polymerization and the perfluorodecyltriethoxysilane hydrolysis.The synergistic effect of surface functional group modification on gas explosion suppression was studied.The results show that the function group modification can effectively improve the gas explosion suppression effect of silica powder,and the amino-silica powder has better explosion suppression performance.With the suppression of Amino-silica powder and fluoro-silica powder,the pressure of gas explosion decreased by 57.2%and 45.8%,and the flame propagation speed decreased by 55.3%and 42.3%,respectively.Compared with the silica powder,the explosion pressure and the flame propagation with amino-silica powder decreased by 30.5%and 40.8%,and the explosion pressure and the flame propagation with the fluoro-silica decreased by 16.2%and 20.7%.The transition states of H·and amino group,fluorine group and methane were calculated by molecular dynamics,and it was found that the reaction of free radicals H·with methane requires the highest energy.Therefore,the free radical H·will preferentially react with amino group and fluorine group.Amino and fluorine groups can consume the free radical H·generated in the explosion and interrupt the chain reaction of the gas explosion.(4)Hydrotalcite which is a new type of gas explosion suppression powder was prepared by coprecipitation method.The gas explosion suppression characteristics of the hydrotalcite were experimentally studied,and its gas explosion suppression mechanism was analyzed and discussed.The results show that the hydrotalcite powder has excellent gas explosion suppression performance.With the hydrotalcite powder,the gas explosion pressure decreased by 77.7%,and the flame propagation speed decreased by 66.3%.The explosion suppression performance of the hydrotalcite powder is much better than that of Mg(OH)₂ and Al(OH)₃.The hydrotalcite powder not only has the similar heat absorption characteristics of Mg(OH)₂ powder and Al(OH)₂ powder,but also releases CO₂ gas during the pyrolysis process,which can reduce the concentration of methane and oxygen.