Research On Low-temperature Oxidation Characteristics Of Coal Based On Physical Factors

Coal plays a very important role in China's primary energy supply.In order to reveal the condition factors affecting coal oxidation at low temperature,a series of thermodynamic theory and experimental studies were carried out on the influence of three factors,coal particle size,air humidity and temperature,on coal oxidation at low temperature.The characteristics of coal surface pore structure were studied by nitrogen adsorption method,fractal dimension method,Barrett Joyner Halenda(BJH)and Brunauer Emmett Teller(BET)equation through industrial and element analysis,specific surface area and pore structure analysis.The results show that the coalification degree of Guizhou anthracite,Shaanxi long-flame coal,Xinjiang bituminous coal and Inner Mongolia lignite decreases successively,and the main pore volume is micropore and mesopore,and the pore structure surface is heterogeneous.The higher the degree of coalification,he larger the proportion of the corresponding micropore volume,the simpler the pore structure,and the rougher the surface morphology.At the same time,bituminous coal with particle size of 0.15?0.075 mm,0.075?0.053 mm,0.053?0.037 mm and 0.037?0.025 mm were selected to study the pore structure characteristics.The results show that the pore volume and specific surface area of bituminous coal with particle size of 0.075?0.053 mm are the largest,and the change of particle size does not affect the fractal characteristics of pore structure of bituminous coal.The oxygen adsorption capacity of lignite,long-flame coal,bituminous coal and anthracite was determined by using specific surface area and pore analyzer at room temperature when air humidity was 20?30?40?50?60?70 and 80% and particle size was 0.15?0.075 mm,0.075?0.053 mm,0.053?0.037 mm,0.037?0.025 mm,and temperature was 40?200?.The oxygen adsorption capacity of bituminous coal with particle size of 0.15?0.075 mm,0.075?0.053 mm,0.053?0.037 mm,0.037?0.025 mm was studied,and the effects of air humidity,particle size and temperature on the oxygen adsorption of coal were discussed.The results show that the oxygen adsorption capacity of lignite,long-flame coal,bituminous coal and anthracite increases first and then decreases with the increase of humidity,and the oxygen adsorption capacity reaches the maximum when the air humidity of coal samples is 45%,50%,55% and60%,respectively.At room temperature,the influence of particle size on coal oxygen absorption is more complex.With the decrease of particle size,the oxygen adsorption capacity of anthracite greatly and continuously decreases.The oxygen adsorption capacity of long-flame coal,lignite and bituminous coal increases rapidly in the range of 0.075?0.053 mm,and decreases slowly in the range of 0.053?0.025 mm.In addition,the study on the oxygen adsorption of bituminous coal with different particle sizes at heating temperature shows that the oxygen adsorption capacity of bituminous coal has two obvious stages in the range of 40?200?.The first stage is 40?100?,in which the coal and oxygen mainly undergo physical adsorption,and the oxygen adsorption capacity decreases slowly with the increase of temperature.In the second stage,the temperature is 100?200?,and the oxygen adsorption capacity of bituminous coal increases rapidly.The oxygen adsorption capacity is mainly reflected by the chemical adsorption of coal to oxygen.Based on the single scanning rate(Coats-Redfern integral method)thermal dynamic analysis method,the influence of air humidity at 20?30?40?50?60?70and 80% on the oxygen absorption and weight gain stage of bituminous coal was analyzed and studied.According to the apparent activation energy,when the air humidity is 20?30?40?50?60?70 and 80%,the activation energy is 136.35?137.97?347.79?127.44?121.74 and 123.14 k J/mol,respectively.In other words,when the air humidity is 50%,the activation energy of bituminous coal is the highest and it is the least susceptible to oxidation.