Experimental Study On The Effect Of Pore Structure Of Coal With Different Particle Sizes On Spontaneous Combustion Characteristics

There are many natural disasters associated with the production and processing of coal,among which mine fires caused by spontaneous combustion of coal are one of the major disasters threatening the safe production of coal mines.In the composition of China’s mineral resources,the largest proportion of low metamorphic coal species is high,among which lignite,as the main form of low-rank coal species,accounts for a relatively large proportion of the total proven coal reserves in China.Therefore,it is of great practical importance to investigate the effect of lignite particle size on spontaneous combustion characteristics.In order to investigate the effect of particle size on the spontaneous combustion characteristics,six coal samples with different particle sizes were selected from Yannan coal mine in Inner Mongolia,and the specific surface area,pore volume and pore size distribution of the coal samples with different particle sizes were obtained by liquid nitrogen adsorption tests,and the surface morphological characteristics of the coal samples with different particle sizes were obtained by scanning electron microscopy.The surface morphology of coal samples with different particle sizes was obtained by SEM.The results show that the pores of the coal samples are mainly mesopores,and the specific surface area and pore volume are mainly provided by mesopores and macropores,with the total specific surface area gradually increasing as the particle size of the coal samples decreases.The inter-particle pore volume of the coal sample is related to its particle size.Overall,as the particle size decreases,the inter-particle pore volume of the coal sample tends to increase and then decrease.The CO and CO₂ production rates of the coal samples showed a trend of increasing and then decreasing with decreasing particle size,and the overall temperature rise rate gradually increased with decreasing particle size,and the effect of particle size on the oxygen consumption rate of the coal samples was not consistent at different oxidation stages.The strongest spontaneous combustion tendency was 0.5mm coal sample.The correlation between the spontaneous combustion characteristics and the pore structure of the coal samples was found to be closely related to the pore structure.The oxygen consumption rate of coal samples in the slow oxidation stage was mainly related to the volume of mesopores and macropores,and in the rapid oxidation stage was mainly related to the specific surface area of coal samples;the temperature rise rate of coal samples in the slow oxidation stage was mainly related to the volume of connected pores,and in the rapid oxidation stage,the temperature rise rate of coal samples was mainly related to the specific surface area of micropores;the tendency of spontaneous combustion of coal samples was mainly related to the specific surface area of internal micropores and the volume of connected pores between coal particles.In the rapid oxidation stage,the temperature rise rate of coal samples was mainly related to the specific surface area of micro-pores;the propensity of spontaneous combustion of coal samples was mainly related to the internal specific surface area of micro-pores and the volume of inter-connecting pores.