Study on moisture infiltration process and wetting exothermic properties of pre-oxidized coal

CHAO Jiangkun; WEI Tao; SHEN Ling; HAN Xuefeng; PAN Rongkun; HU Daimin

doi:10.13347/j.cnki.mkaq.20241633

Abstract：In order to investigate the moisture infiltration process of pre-oxidized coal,the wetting exothermic properties and the in-fluence on oxidation and heat accumulation capacity of the coal body,the moisture infiltration process of pre-oxidized coal,the pore permeability properties,the wetting heat,and the evolution law of the functional groups have been analyzed by the low-field coal-rock nuclear magnetic resonance apparatus,the C600 high-precision microcalorimeter,and the Fourier infrared spectroscopy.The experimental results show that the water signal content of coal samples show a stable linear increase during water immersion,but the increase trend of pre-oxidized coal is much larger than that of the original coal,after 60 min water immersion,the relative water con-tent of adsorption pores of the original coal and the coals treated with pre-oxidation temperatures of 40,60,80,and 100℃reach 94.8%,95.7%,97.7%,99.6%,and 99.8%,respectively,under the same water immersion time,the relative water content of the ad-sorption pores of the pre-oxidized coal increases more,and the adsorption performance is stronger.The overall proportion of medi-um and large pores in the pre-oxidized coal decrease,the development of micropores leads to an increase in the proportion of trans-ition pores,the porosity increases from 15.9%to 32.3%,and the permeability enlarges by about 50 times,which enhances the oxy-gen adsorption and seepage capacity.The aromaticity and the degree of aromatic core condensation of the coal body under pre-oxida-tion show an increasing trend,and the hydrocarbon potential shows a decreasing trend.The proportion of hydrophilic groups such as hydroxyl group and carbonyl group in coal body increase,and the proportion of hydrophobic groups such as aromatic hydrocarbons decreases,which leads to the enhancement of the coal water affinity,and the two-phase wetting heat of coal and water increases from 6.3 J/g to 25.7 J/g,and the difference of exothermic intensity before and after the wetting heat is obvious,and the exothermic intens-ity is enhanced obviously by the heat accumulation after wetting,and the loose and porous nature of the coal body is further embod-ied and oxidation and heat accumulation capacity of the coal body is enhanced.Under the joint influence of pre-oxidation and wet-ting,the risk of coal spontaneous combustion increases,and the higher the pre-oxidation temperature is,the greater the risk is.