Study On Prediction Of Coal Spontaneous Combustion In Mining Near-neighbored Coal Seams

Coal is main energy resource in China. It estimated that over 70% of energy consumpted in China is from coal. Both production and consumption of coal in China ranked No. 1 around the world. Nevertheless, spontaneous combustion of coal is very serious in China which greatly threatened coal safety production. Mining of near-neighbored coal seams is very common in coal enterprises. Large amount of connected cracks are formed during mining near-neighbored coal seams, which causes serious air leakage amoung coal seames, makes spontaneous combustion more easily to take place. The regulation of spontaneous combustion in mining near-neighbored coal seams is more complicated and harder to be predicted. The existing theory to partition spontaneous combustion danger zone is not applicable for partition spontaneous danger zone accurately. Prediction of spontaneous combustion by simulating the whole process of coal spontaneous combuston numerically takes large amount of calculation and is hard to be applied in real production. There is no theory available for predicting spontaneous combustion conveniently.Spontaneous combustion experiments are carried out to test parameters like oxygen consumption rate, CO and CO2 production rate as well as heat gerneration rate, according to which lower limit oxygen concentration, critic loose coal depth, and upper limit air leakage intensity of spontaneous combustion are deduced. The study set sound foundation for predicting spontaneous combustion of coal.Extention of caving zone is tested through drilling bores, and air penetration area is determined. And distribution of porosity in the gob is determined through theoretical analysis and investigating sinking hight in the ground of mined out area. In connecting with further laboratory studies, regulation of air permeability coefficient in the gob is obtained.A fairly complete coupled 3 dimension steady mathematical and physical model of seepage, diffusion and oxidation reaction is put forward to depict mass transfer in the gob during mining near-neighbored coal seams. The model is solved numerically to obtain distribution of air leakage strength and oxygen concentration in the gob of Shuangyashan coal field. The calculated results are compared with critical value of coal self-ignition to partition self-ignition danger zone and predict possible time of spontaneous combustion. The method supplied an approach for predicting coal spontaneous combustion in the gob of fully mechanized top coal long wall workface and during mining near-neighbored coal seams.The predicting results is proved reliable, accurate and can satisfy the demand of preventing and fathering spontaneous combustion in real producton.Mass transfer in the gob is simulated and"three zones"of coal spontaneous combustion is obtained on condition that injecting CO2 into the gob of different position and flux. Through these studies, an optimized carbon dioxide injecting port and flux is determined which is very meaningful for preventing and extinguishing gob fire through injecting inert gases. According to the above study, a coal seam fire is extinguished successfully by means of injecting fluidized carbon dioxide and gaind enormous economic effect.