| Coal spontaneous combustion fire is one of the main disasters in the process of coal mining,storage and transportation.It not only wastes coal resources,produces a large amount of toxic and harmful gases,but also seriously endangers the life safety of underground personnel.Therefore,the scientific prevention and control of coal spontaneous combustion fires has always been an important topic in the safe and efficient mining of coal resources.Based on the fact that it is difficult to accurately detect the hidden high-temperature areas in goafs,old roadways,and enclosed areas,the use of pressure injection of inert gas to reduce oxygen in large areas and control leakage has become the main method for daily fire prevention in most mines.CO2 and N2 are widely used as typical inert gases,but N2 has disadvantages such as poor fire-fighting effect,easy dissipation,and high energy consumption.However,CO2 has the disadvantages of difficult transportation,clogging of pipelines,complicated process and high cost.How to develop strengths and avoid weaknesses and scientifically utilize CO2/N2 inerting fire-fighting technology is of great practical significance for the scientific prevention and control of coal spontaneous combustion hazards.In this paper,a series of experiments and simulation comparative studies on coal spontaneous combustion inerting performance are carried out around a single CO2/N2 injection and different proportions of CO2-N2 mixed gas,which provide theoretical basis and data support for further improving the application effect of coal mine inert gas fire-fighting technology.The result is as follows:The adsorption characteristics of CO2-N2 mixed gas under single CO2/N2 and different concentration ratios were studied by using adsorption characteristic experiments.Based on multi-factor analysis of variance,the difference of adsorption performance under each influencing factor was quantitatively analyzed,and it was obtained:under the same conditions,the adsorption performance of 30%N2+70%CO2 in four kinds of mixed inert gas to coal was the best,which was the same as that of 100%CO2.The adsorption performance of high metamorphic anthracite coal is better than that of bituminous coal and lignite;the adsorption performance decreases with the increase of temperature.The temperature-programmed experiment was used to compare and study the variation law of the characteristic parameters of the spontaneous combustion coal body by injecting a single CO2/N2 gas and different proportions of CO2-N2 mixed gas.In the process of inert gas,30%N2+70%CO2 has a better inhibitory effect on the spontaneous combustion and oxidation of high temperature coal than CO2,N2 and other proportions of inert gas;in the process of pressure injection of inert gas into the coal body with a dry cracking temperature of 120℃,30%N2+70%CO2 has better cooling and deoxidizing effects than CO2,N2 and other proportions of inert gas,but the CO concentration of 10%N2+90%CO2 changes more significantly.Comparing the inerting effect of the oxygen concentration and the width of the oxidation zone in the goaf from the position of the gas injection port,the pressure injection flow rate and the CO2-N2 mixed gas in different proportions,the reasonable position of the gas injection port and the pressure injection flow rate were determined,and obtained:The difference between the inerting effect of CO2-N2 mixed gas on spontaneous combustion of coal in goaf is not obvious,and the inerting effect of 30%N2+70%CO2 on the oxidation zone of goaf is slightly better than other proportions of mixed inert gas. |
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