Experiment And Numerical Simulation On Suppression Of Methane Explosion By Ultrafine Water Mist Cooperated With Methane-oxidi Zing Bacteria And Inorganic Salts

In recent years,combustible gas explosion is an urgent problem to be solved in safety production accidents,resulting in serious property losses and casualties.As an environment-friendly and efficient explosion inhibitor,ultrafine water mist is widely used in fire extinguishing and explosion suppression.As an environment-friendly strain,methane oxidizing bacteria are used to degrade methane gas in coal mines.The traditional single medium has poor effect on inhibiting methane explosion.Ultrafine water mist combined with methane oxidizing bacteria and inorganic salts can improve the explosion suppression effect,play the role of physical cooling and reducing the harm of methane explosion.Based on the visual semi closed small experimental platform designed and built by ourselves,the experiments of methane oxidizing bacteria degrading methane and the experiments of ultrafine water mist cooperating with methane oxidizing bacteria and inorganic salts inhibiting methane explosion were carried out respectively.The effects of ultrafine water mist and ultrafine water mist combined with methane oxidizing bacteria and inorganic salts（0.7 m L,2.1 m L,3.5 m L,4.9 m L and 6.3 m L）on 9.5%methane explosion were compared under the condition of secondary degradation,and the effects of ultrafine water mist combined with methane oxidizing bacteria and inorganic salts（5 m L,7.5 m L,10 m L and 12.5 m L）on 9.5%methane explosion under different degradation time and times.The best working condition of inhibiting methane explosion is determined.The mechanism of methane explosion is analyzed by CHEMKIN software,the sensitivity analysis and reaction path analysis of methane explosion are carried out,and the mechanism of inhibiting methane explosion is revealed.The conclusions are as follows:For one-time spraying water mist,when the degradation time is the same,the more water mist,the better explosion suppression effect.When the amount of water mist is the same,the longer the degradation time,the better the explosion suppression effect.For secondary spraying water mist,when the amount of water mist is the same,the explosion suppression effect of first degradation and then inhibition is better than that of one-time spraying water mist and direct ignition.The reason is that one-time spraying water mist mainly plays the role of biodegradation of methane oxidizing bacteria,and secondary spraying water mist mainly plays the role of physicochemical synergistic explosion suppression of ultrafine water mist containing inorganic salt.Methane oxidizing bacteria have good degradation effect on methane gas.The longer the degradation time is,the better the effect is.The best degradation effect is achieved at 10 h.Under the conditions of 10 h degradation time and 12.5 m L water mist amount of ultrafine water mist combined with methane oxidizing bacteria and inorganic salts,the peak flame velocity is 4 m·s^-1,which is 83.3%lower than that of 9.5%pure methane explosion.Under the same water mist amount,pure water ultrafine water mist and ultrafine water mist containing inorganic salt,the peak flame velocity is 7 m·s^-1 and 8 m·s^-1,respectively,which is reduced by 70.8%and 66.7%.Pure methane burns as a blue flame with a lighter color.The color of methane explosion flame added with explosion inhibitor is yellow.Under the condition of ultrafine water mist,the flame color of methane explosion is yellow,while when the water mist amount of ultra-fine water mist reaches 12.5 m L,the flame color becomes dark yellow.When inorganic salts are added to the ultrafine water mist,the methane explosion flame is brighter than that under the condition of ultra-fine water mist.Based on CHEMKIN library,the intermediate products,free radicals and end products of methane explosion can be obtained,and the sensitivity analysis and reaction path analysis can be carried out.Methane and air are mixed and burned at the front edge of the flame to form a diffusion flame.The flame temperature increases rapidly at the moment of explosion,and the chemical reaction is the most intense at the maximum temperature of2220 k.The explosion suppression mechanism is clarified:OH is the key free radical to inhibit methane explosion and flame propagation,while the intermediate products CH₃,CH₂O,CO and H₂ mainly affect the concentration of OH free radical and reaction rate in the reaction process.