Influence study of coal dust composition on the lower explosion limit of hybrid mixture of gas and coal dust

The combined explosion of gas and coal dust is one of the main forms of explosion disasters in coal mines.Studying the lower limit change law of the gas/coal dust composite explosion is an indispensable condition for effective prevention of coal mine explosion disasters.In order to study the effect of coal dust composition on the lower explosion limit of hybrid mixture of gas/coal dust，two different components of coal dust (bituminous coal and anthracite coal) were selected.According to EN 14034 standard，the minimum explosion concentration of the two kinds of coal dust，lower explosion limit of methane and the lower explosion limit of methane and coal dust mixtures were measured by using a 10 kJ chemical ignitor in a standard 20 L spherical explosion container.The results show that the minimum explosion concentration of bituminous coal is 50 g/m3，and that of anthracite is 70 g/m3respectively，and the lower explosion limit of methane is 4%.When 1%、2%、3% and 4% was injected into coal dust，the minimum explosion concentration of bituminous coal were reduced to 40 g/m3，20 g/m3，5 g/m3and 0 g/m3 respectively，and the minimum explosive concentration of anthracite coal were reduced to 50 g/m3，20 g/m3，5 g/m3 and 0 g/m3 respectively.According to the measured results listed above，the lower explosion limits of hybrid mixtures of the two kinds of coal dust and gas were measured in a 20 L spherical explosive device.Based on the measured results，the effects of coal dust components on the lower explosion limit of hybrid mixture of gas and coal dust were analyzed.Simultaneously，the applicability of three different models (Le Chatelier，Bartknecht，Jiang) for predicting the lower explosion limit of hybrid mixture to gas/coal dust mixtures was discussed.It is shown that the minimum explosion concentration of the two types of coal dust decreases with the increase of gas concentration，but the coal dust with low volatile content decreases more，that is，the effect of gas on the minimum explosion concentration of low volatile coal dust is more significant.The predicted value of the Jiang model is far from the actual measured value； the predicted value of the Le Chatelier model is higher than the actual measured value，and the error increases with the increase of gas concentration； the Bartknecht model is relatively applicable，and more suitable for low-volatile gas/coal dust composite system.