| In recent years,due to the influence of groundwater,surface water,grouting fire prevention measures and other factors,many large areas of water-soaked mined-out areas have been formed in some mining areas of our country,which makes a large number of coal soaked in water and air dry.However,there are still few studies on the spontaneous combustion and combustion characteristics of water-immersed coal at present.Therefore,this paper will start from the microscopic chemical structure,macroscopic spontaneous combustion and combustion characteristics of water-immersed coal to reveal the influence of water-immersion on low-rank coal.Firstly,the molecular structures of raw coal and water-soaked coal at room temperature are studied by Fourier transform infrared spectroscopy,and the effect of water immersion on the content percentage of different functional groups of coal is analyzed.The experimental results show that the content of aryl hydrocarbon groups in the coal body decreases after soaking,and the content of aliphatic hydrocarbon groups such as-CH3,-CH2-and oxygen-containing functional groups such as-OH increase to a certain extent,which accelerates the oxidation reaction rate of coal.In addition,compared with raw coal,the-CH3/-CH2-value of immersed coal increases,which reduces the stability of aliphatic hydrocarbon chain of coal.Secondly,the spontaneous characteristics of water-soaked coal in the low temperature oxidation process are analyzed by temperature-programmed experiment device,and the influence of water-soaked coal on the oxidation gas products and oxidation parameters is analyzed.The results show that the production amount and rate of CO and CO2,the oxygen consumption rate,the maximum and minimum heat release intensity of the water-soaked air-dried coal are higher than those in raw coal,and all of them decrease with the increase of the water-soaked duration in a certain range.On this basis,the change of apparent activation energy of water-soaked coal is studied in the accelerated heating stage,it can be seen that the apparent activation energy of water-soaked air-dried coal is lower than that of raw coal,and increases with the increase of the immersion duration.Then the spontaneous combustion characteristics of raw coal and water-soaked coal are studied by thermogravimetric analyzer,and the influence of water immersion on the characteristic temperature and thermal dynamics of coal is analyzed.The results show:compared with raw coal,the end temperature of low temperature oxidation stage T3 and ignition temperature point T4 of water-soaked coal advance to some extent,however,the maximum mass loss rate temperature point T5 does not show obvious regularity.In addition,compared with raw coal,the activation energy of water-soaked coal increases in the water evaporation stage,and decreases in the stage of thermal decomposition and weight gain by oxygen inhalation.Finally,the oxidation and combustion characteristics of raw coal and water-soaked coal are studied by conical calorimeter,and the influence of water-immersion on the heat release characteristics of coal in the combustion process is analyzed.The results show that the peak heat release rate of water-soaked coal is higher than that of raw coal,and decreases with the increase of water-immersion duration in a certain range.Figure 26 Table 19 Reference 80... |
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