| The 12 and 22 coal seams of the Bulianta Mine are both shallow coal seams.The surface fissures left during the mining of coal seams have become an important hidden danger of the oxidation of coal and natural ignition in the goaf.Surface water and air flow into the goaf through surface fissures,so that the coal remains immersed in water for a long time.The long-term exposure of residual coal in the goaf to oxygen also easily increases the risk of secondary oxidation.It is of great significance to study the oxidation characteristics and secondary oxidation characteristics of water immersion coal samples of 12 coal seams and 22 coal seams for the prevention of natural ignition of legacy coal.In this paper,low temperature oxidation experiments were performed on coal samples of 12 coal seams and 22 coal seams using a programmed heating device,and the differences in spontaneous combustion characteristics of coal samples with different water contents were obtained.In the low-temperature oxidation stage,the coal sample with a water content of 14.9%in the 12 coal seams is the most easily oxidized water immersion coal.Because its outlet oxygen concentration is the lowest.Its rate of oxygen consumption and the exothermic intensity are the highest.Both the critical temperature and the apparent activation energy are the lowest.The coal sample with a water content of 21.6%in the 22 coal seams is the most easily oxidized water immersion coal.Because its outlet oxygen concentration is the lowest.Its rate of oxygen consumption and the exothermic intensity are the highest.Both the critical temperature and the apparent activation energy are the lowest.In the study of the secondary oxidation of raw coal and the most easily oxidized water-immersed coal samples in the two coal seams,Among the three different degrees of pre-oxidation,the critical temperature and apparent activation energy of raw coal pre-oxidized to the 100? of 12 coal and 22 coal are the lowest,which is the most easily oxidized pre-oxidized coal sample.The critical temperature and apparent activation energy of the most easily oxidized water immersion coal pre-oxidized to the 60? of 12 coal and 22 coal are the lowest,which is the most easily oxidized pre-oxidized coal sample.Using Fourier transform infrared spectroscopy to study the molecular structure of 12 coal seams and 22 coal seams of raw coal and the most oxidizable water-soaked coal samples,it can be seen that the content of-CH2 and-CH3 functional groups in water immersion coal samples is slightly higher than that of raw coal,indicating that the water-immersion effect can promote the shedding of aliphatics,which is beneficial to the low-temperature oxidation of coal.The reduction rate of-CH2 and-CH3 functional groups and the growth rate of C=O functional groups were greater than those of raw coal,indicating that the reaction rate of low-temperature oxidation of the most oxidizable water immersion coal samples was higher than that of raw coal.The experimental results echo the phenomenon that the most oxidizable water immersion coal samples are larger than raw coal in the presence of CO and CO2 and other iconic gases during low-temperature oxidation,indicating that the danger of low-temperature oxidation and spontaneous combustion reactions of raw coal samples after immersion in water is greater than raw coal.Using TG-DSC thermal analysis technology,the thermodynamic research is performed on the raw coal and the most oxidizable water immersion coal samples of 12 coal and 22 coal seams and their most oxidizable pre-oxidized coal samples.The critical temperature,dry cracking temperature,mass maximum temperature,and activation energy during water evaporation and oxygen absorption weight gain phase of water immersion coal samples are lower than those of raw coal from two coal seams.The low-temperature oxidation stage has higher heat release and total heat release than raw coal.The water immersion coal samples are more susceptible to oxidation than raw coal,and are more dangerous for spontaneous combustion.The most easily oxidized pre-oxidized coal samples of raw coal and water-immersed coal samples are more susceptible to oxidative spontaneous combustion than raw coal.The critical temperature,dry cracking temperature,mass maximum temperature,and activation energy during water evaporation of pre-oxidized coal samples of immersion raw coal are lower than those of pre-oxidized coal samples of raw coal.And the low-temperature oxidation stage has higher heat release than raw coal.Water immersion coal samples are more susceptible to secondary oxidation than raw coal.Figure[48]table[15]reference[93]... |
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