| Coal spontaneous combustion fires are one of the major mine disasters that cause waste of resources and threaten safe production.Moisture in the air is one of the important factors that affect the process of coal spontaneous combustion.Affected by groundwater and rainfall,air humidity has multiple effects on the process of coal spontaneous combustion.By studying the influence of air with different relative humidity on coal spontaneous combustion,exploring how the moisture in the air affects the low-temperature oxidation process of coal is of great significance for improving the prevention and control of coal spontaneous combustion during coal production,transportation,storage and processing.This paper selects the Shendong long flame coal and the Ximeng lignite as the research objects.In order to analyze the spontaneous combustion characteristics of different original moisture-occurring coal bodies in air with different relative humidity,the original coal bodies are dried with nitrogen at 70oC and 110oC to prepare different forms of moisture content Analyze the results of low-temperature nitrogen adsorption,temperature-programmed oxidation,and thermal analysis,and establish gas-solid two-phase mass and energy balance equations on the basis of experimental data.Perform numerical simulations to explore the influence of air humidity on coal spontaneous combustion.The following conclusions:(1)After the lignite is supplied with moist air during the heating process,the moisture in the air will act on the lignite to promote the production of CO and CO2.In the slow oxidation stage,it will hinder the contact of oxygen with the coal and reduce the oxygen consumption rate;During the heating process of coal,the air humidity will also promote the production of CO and CO2,but its oxygen consumption rate will be affected by the air humidity,and there is a critical humidity,which makes the oxygen consumption rate the lowest.(2)The influence of air humidity on the heat and quality changes of lignite and long-flame coal will affect the original moisture of the coal.Between 70-110oC,lignite has a strong ability to adsorb moisture in the air,but a large amount of adsorbed moisture will increase its activation energy.The greater the humidity,the greater the increase in activation energy.The less the original moisture of lignite,the stronger the physical adsorption effect.The more heat it releases;the adsorption effect of long-flame coal on the moisture in the air is less than that of lignite,and its activation energy is lower than that of lignite,but the heat change of long-flame coal is still affected by the air humidity,which is proportional to the air humidity.After 110oC,moist air will promote lignite and long-flame coal,and directly participate in the coal-oxygen reaction process in gaseous form,increase the exothermic strength of coals,and promote the thermal decomposition of coal.(3)Through the establishment of gas and solid two-phase mass and energy balance equations,numerical simulation is used to further study the influence of water vapor adsorption on coal temperature and heat in coal in moist air.The heat of adsorption produced by moisture is an important factor affecting the rate of heat generation of coal.The heat generated in this part will increase the temperature of coal,and to a certain extent promote the self-heating oxidation process of coal.Before the heat dissipation rate exceeds the adsorption of moisture,it will affect the coal.The production of more heat plays a role in promoting,and there may be an optimal humidity ventilation rate,so that the moisture adsorption heat of the coal body in a certain period of time is greater than the heat dissipation rate of the coal body,which provides good heat storage conditions for the coal body and promotes The coal is further heated and oxidized,which generates more heat and may cause spontaneous combustion. |
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