Experimental analysis on post-explosion residues for evaluating coal dust explosion severity and flame propagation behaviors

Coal dust explosion is a major threat to coal mine and other coal processing or utilizing industries. A deep investigation and accurate knowledge of coal dust explosion mechanism are still essential for the development of safety techniques for coal dust explosion prevention. In present work, the explosion severity of coal dust/air mixture, flame propagating properties, the characteristics of gas and solid residues had been studied. And, the correlations between the residues characteristics and explosion severity had been analyzed systematically. Results show that there is a linear relationship between explosion flame propagation speed (V-F) and dust concentration (C-dust). With the increasing of vitrinite reflectance (R-o,R-max), explosion pressure (P-m), explosion pressure rise rate (dP/dt)(m), explosion index (K-st) and flame propagation speed (V-F) are all presenting a first increasing and then decreasing trends. During coal dust explosion, much more solid fragments are produced by the thermal stress and blast shock impacts. Compared with raw coal dust, particle size dispersities of all residues are increased obviously. Chemical functional groups in the coal dust particles, such as aromatic C-H, aromatic C=C, aliphatic C-H bonds, and oxygen-containing functional groups, etc. are all involved in coal dust explosion process. Furthermore, aliphatic C-H and oxygen-containing matters may be the key factors influencing on the reactivity of dust explosion. For coal dust explosion under poor dust concentration conditions, the main gas components in the mixtures are CO2 product, residual oxygen and nitrogen gas in balance. The other combustible component (CO, CH4, C2H2, C2H4, C2H6 and C3H8) is almost undetectable. However, under dust-rich conditions, the combustible components would be increased sharply. The firstly detected combustible gases (CO, CH4, C2H2, C2H4, C2H6 and C3H8) can be used as the characteristic gases to determine the maximum explosion intensity of coal dust explosion.