Experimental Study on Mark Gas Determination of Spontaneous Combustion of Oil-immersed Coal

The coal seam roof is rich in crude oil in northern Shanxi Province. During the mining process, the crude oil in the roof is immersed in residual coal in the gob. In order to analyze the influence of crude oil immersion on spontaneous combustion of coal, the temperature programmed and oxidation tests of raw coal and coal samples with different oil content ratios of 2%, 5% and 10% were carried out. The gas output characteristics were analyzed. The coal spontaneous combustion prediction index is selected, and the critical temperature is determined. The results show that the gas produced by coal samples adding with different oil ratios has the characteristic of sectioning at 30 ℃ to 190 ℃, the crude oil occupies porosity, retards the progress of coal-oxygen reaction, and the higher the oil ratio, the more obvious delaying effect. In the late stage of vigorous oxidation（150 ℃ to 190 ℃）, the gas production difference of different oil ratios is much larger at the same temperature. With the increase of oxidation temperature, the oxidation difference becomes larger and larger. In the case of crude oil in unknown, it is not conducive to predict spontaneous combustion of coal oxidation stage, therefore, the combined ratio index forecasting method is adopted, the method can reduce the influence of oil immersion on coal spontaneous combustion prediction and improve the sensitivity and accuracy of prediction. Finally, according to the degree of oil content, the prediction of spontaneous combustion of oil-immersed coal is classified.