Study On Methane-Coal Dust Compound Explosion And Its Suppression By Ultra-Fine Water Mist

Compared with a single component explosion,coal mine gas-coal dust explosion has a more complicated mechanism and more serious losses.Due to its good fire-extinguishing properties,ultra-fine water mist can exert both physical and chemical suppression effects in an explosion.It has been considered as an explosion suppressant with good application prospects.However,the research of ultra-fine water mist on gas-dust compound explosions it is still in its infancy.This paper conducts experimental research on the characteristics of methane-coal dust compound explosion and the suppression of ultra-fine water mist,analyzes the influence of coal dust and water mist on the intensity of compound explosion,and focuses on the interaction process of coal dust,water mist and explosion flame.On this basis,the critical water mist concentration of methane-coal dust compound explosion was determined.The main work and conclusions are as following:(1)A visual explosion experiment platform was built.Including airtight visual explosion pipeline,a gas distribution system,powder spraying system,water mist generation system,ignition system and control and data acquisition system.The pressure response during the explosion process is collected by the pressure sensor,and the dynamic evolution process of flame is recorded by high-speed camera.(2)Research on the characteristics of methane-coal dust compound explosion has been carried out.After ignition,methane appears as a red flame,volatile matter burns as a yellow flame on the surface of coal dust,and the combustion of solid coke appears as a bright white flame.In the later stage of the explosion,three forms a layered stable flame and spread to the top of the pipe.With the increase of coal dust concentration and the decrease of coal dust particle size,the time when the bright white flame appears in the composite system is earlier,and a stable layered flame structure is formed earlier.In the explosion parameters,the explosion overpressure and pressure rise rate first increase and then decrease with the increase of coal dust concentration,which is approximately a quadratic function relationship with the coal dust concentration;it decreases with the increase of the coal dust particle size,which is similar to the coal dust particle size A linear relationship.The flame propagation speed increases first and then decreases with the increase of coal dust concentration,and decreases with the increase of coal dust particle size.In this experiment,when the coal dust concentration is 500g/m3 and the coal dust particle size is 25.17?m,the explosion risk is the highest.(3)Research on the suppression of methane-coal dust compound explosion by ultra-fine water mist.After the application of ultra-fine water mist,the time from ignition to pressure rise of the methane-coal dust compound explosion was significantly extended.The ultra-fine water mist causes the composite system to have a point flame,and experience four development stages: point flame,local strong development flame,continuous matte flame and stable layered flame;the increase of water mist concentration will delay the point flame to stable layered flame.During the development process,suppressing the point flame to develop into a strong local development flame is the key to suppressing the explosive boost behavior.(4)As the concentration of ultra-fine water mist increases,the overall heat release rate of the methane-coal dust composite explosion has an increased correlation with the combustion rate of the flame front.The flame propagation speed decreases,resulting in a decrease in the rate of pressure rise,and because the coal dust does not completely participate in the combustion and its thermal desorption heat,the secondary accelerated pressure rise phenomenon disappears.(5)The critical explosion suppression water mist concentration of different coal dust concentration and particle size was measured,and the results showed that the critical explosion suppression water mist concentration increased with the increase of coal dust concentration,first increased and then decreased,and decreased with the increase of coal dust particle size.Under all experimental conditions,when the water mist concentration is 216.58 ml/m3,the explosion can be completely suppressed,which provides a reference for the selection of water mist concentration in actual production.