Effect Of Flue Gas On Pulverized Coal-Methane Deflagration Flame Propagation Characteristics

The development of modern industry has made the application of powder technology more and more widespread,but the frequency of dust explosion disasters and the danger of accidents have also increased accordingly,causing serious production safety problems to human society.Because the process of dust explosion disaster is affected by many factors,the mechanism of action is extremely complicated,which brings trouble to the prevention and control of accidents.Therefore,carrying out relevant experiments on inerting explosion suppression technology is of great significance for revealing the mechanism of dust explosion disasters and improving existing explosion prevention and control technologies.In this paper,a pulverized coal-methane mixture is used as an experimental object,and a local gas layer loading device is designed.A 1.5m long visual vertical combustion pipeline is equipped with a fine thermocouple and a high-frequency pressure sensor.Combined with a high-speed camera system,different types and thickness of gas layers The pulverized coal-methane deflagration flame propagation behavior,flame temperature,flame propagation speed and deflagration pressure were compared and analyzed.The influence of local gas layer inerting on the deflagration flame propagation characteristics was studied,and the mechanism of smoke was revealed.The main conclusions are as follows:（1）When the gas layer is loaded,the impact of the air flow can slightly interfere with the flame shape,but the impact will not affect the trend of flame propagation and development as a whole.When the thickness of the gas layer is within 35 cm,the air flow impacts The effect of the effect on the flame is negligible.（2）The air layer can promote the spread and development of the flame.When the thickness of the gas layer loaded is in the range of 0-50cm,as the thickness of the air layer increases,the flames travel through the gas layer and reach the top of the pipe after reaching the range of the gas layer,and the overall flame brightness increases and the flame propagation speed becomes faster.The peak temperature and peak pressure rise.（3）Both the CO₂ gas layer and the smoke layer can inhibit the propagation and development of the deflagration flame,but the smoke layer has a better suppression effect.As the thickness of the suppression layer increases,the upward propagation distance of the flame gradually decreases after reaching the range of the gas layer,the flame brightness decreases,faults and local extinguishment become more apparent,the flame propagation speed becomes slower,and the peak temperature and peak pressure decrease.Under the experimental conditions,when the thickness of the CO₂ gas layer is 35cm,the flame cannot pass through the gas layer,and the phenomenon of rapid extinguishment occurs.However,when the gas layer is inerted,the ash concentration is positively related to its inhibitory effect.The smoke with an ash concentration of200g/m3The gas layer can completely suppress flame propagation at a thickness of 10cm.（4）The flue gas has a gas-solid two-phase composite inerting property,and its gas-phase composition can both dilute oxygen and play a competitive adsorption role,inerting the coal powder particles;solid-phase ash can greatly absorb the energy of the deflagration flame,and partly Pulverized coal particles are adsorbed to each other,which reduces the pyrolysis rate of the coal powder and blocks the combustion reaction of the coal powder.Therefore,the flue gas has a good inertization and explosion suppression effect.