Experimental Study On The Changes Of Oxygen In Coal During Coal Heating Process

Fire caused by spontaneous combustion of coal is one of the major disasters of coal production, transport and storage processes. Scholars have done a lot of research on mechanism of coal spontaneous combustion for a long time. The mechanism of coal and oxygen is the main reason of the coal spontaneous combustion which has also been recognized by the vast majority of scholars. For coal oxygen compound mechanism research, this paper mainly studies on physical adsorption of coal and oxygen in contact, the macro characteristics of oxygen consumption and gas output in the process of coal spontaneous combustion and the oxidation temperature microscopic properties of functional groups in the process of structure change in order to reveal the physical adsorption, chemical adsorption and chemical reaction of coal and oxygen in the process of coal spontaneous combustion.Use coal spontaneous combustion tendency measuring instrument to determine physical oxygen absorption of nine kinds of coal samples with different metamorphic degree at the temperature of 30 ℃。The experimental results show that, with the increase of the degree of metamorphism, the physical oxygen absorption of coal decreases and then increases. The physical oxygen absorption of coal sample is shown as a whole in the temperature rising process of 30 ~ 105 ℃. Use the method of equal volume replacement to distinguish the existence state of oxygen in the coal porosity: free state and physical adsorption state. The influencing factors were analyzed by experiment.The temperature rise test of the coal preparation was carried out by using the programmed heating system, and the other gases produced by the gas chromatograph were analyzed, the results showed that: with the increase of temperature, the amount of oxygen consumption, CO2 production and CO production increased with the increase of temperature. The overall performance of oxygen consumption of different ranks of coal is: lignite> bituminous>anthracite. The overall performance of amount of CO2 generated is: lignite> bituminous> anthracite. When the temperature is below 130 ℃, the concentration of CO increased with the increase of temperature, the amount of CO formation was not significantly related to the degree of metamorphism of coal. When the temperature is higher than 130 ℃ the production of CO :lignite>bituminous>anthracite.The coal sample was scanned by an in situ Fourier transform infrared spectroscopy system consisting of a Fourier transform infrared spectrometer and an in situ reaction cell. It can be found by analyzing the different metamorphic degree of coal in the infrared spectrum that the content of the coal molecular structure of functional groups from big to small are: oxygen-containing functional groups, aliphatic hydrocarbon, hydroxyl, aromatic hydrocarbon. By using the Fourier transform infrared spectrometer, in situ reaction cell and the temperature rising device, the experiment of different coal samples was carried out and the experimental results show that in the process of coal sample oxidation, the content of carboxyl group increases with the increase of temperature, which decreases and then increases; The lower the degree of metamorphism of coal, the greater the decrease of hydroxyl group in the initial stage of oxidation heating up. This phenomenon shows that the reaction activity of hydroxyl group is large, and there is a large amount of hydroxyl group in the initial stage of oxidation heating up; In the process of low temperature oxidation of coal samples, the structure of the aromatic nucleus in the coal macromolecular structure is relatively stable, and almost does not participate in the oxidation reaction process.