Study on the influence of immersion degree on coal spontaneous combustion characteristics

In the process of coal mining, groundwater flows into the crack of coal seam and coal body is soaked by different degrees of water.In order to study the natural characteristics of coal with different degrees of immersion, the coal samples of 0250 coal seam in Tangshan Mine are made by immersion, and the coal samples with different immersion degrees are tested by temperature-programmed, low-temperature liquid nitrogen adsorption and Fourier infrared spectroscopy.It is known from the experiment that with the increase of immersion degree, the specific surface area decreases, the proportion of macropores increases, oxygen consumption rate and CO, CO₂ production rate increase; the contents of aliphatic hydrocarbon groups decreased while the contents of aromatic hydrocarbons and oxygen-containing functional groups increase.The experimental results show that immersion leads to the transformation of small pores into large pores, and the connection between pores and cracks is enhanced, which leads to the increase of the contact area between coal and oxygen, which is conducive to the physical adsorption of oxygen.Soaking promotes the formation of peroxide complex, which is beneficial to the chemical adsorption of oxygen.With the increase of immersion, the content of hydroxyl (—OH)increases, and the oxidation characteristics of coal are more obvious in low temperature oxidation stage, and the content of carbonyl (C=O)and carboxyl (—COOH)increases, leading to the increase of oxygen consumption, oxygen consumption rate and CO and CO₂ production rate in coal oxidation combustion stage.Soaking promotes the mutual transformation of functional groups in coal.