Study On The Inhibition Of Coal Spontaneous Combustion By Composite Inorganic Clay Fire Extinguishing Material With High Water Retention Properties

Coal has always been a critical component of our energy security strategy system,and changing the energy consumption structure dominated by coal in the short term is challenging.However,coal spontaneous combustion disaster in the process of coal mining seriously restricts the safe and efficient production of coal mines.The research and development and application of mine fire prevention materials is one of the main technical means to solve the coal spontaneous combustion disaster.At the moment,the use of various mine fire control materials has effectively reduced the frequency of coal spontaneous combustion disasters,but there are still certain flaws,such as remarkable single performance and a difficult preparation procedure.In this article,the resistance and fire-fighting performance of coal are investigated using composite inorganic clay type fire-fighting materials as the research object.Inorganic compounds are added to build composite inorganic materials based on the unique interlayer structure of sodium bentonite.The characteristics of the changed substances have been examined using X-ray diffraction（XRD）,scanning electron microscopy（SEM）,and thermogravimetric analysis.The results demonstrate that as compared to the original soil,the layer spacing of the inorganic components is increased by 20.4%.The surface of the material is smooth,dense and has good dispersion.At high temperature,the material loss is less than 15%.The viscosity of slurry mixed with water,water retention at room temperature and temperature,and filling rate of coal were studied.The results showed that the slurry with the ratio of water to material above 9:1had better fluidity,the slurry with the ratio of 12:1 had the best water retention,and the slurry with the ratio of 10:1 had the highest filling rate.By setting up a 0.5m×0.5m×0.5m grouting test platform in the laboratory and taking the water-material ratio grout in the selected range as the research object,the grouting diffusion test of grout in loose voids was carried out.The temperature contour map was made by Surfer software to analyze the diffusion pattern of grout.The empirical mathematical model of grout diffusion was derived according to the final diffusion radius.The results show that the complex correlation coefficient of the mathematical model R²=0.936,and there is a significant correlation among all factors,among which the grouting pressure has the greatest influence on grout diffusion,followed by the grout water-material ratio and void ratio.Through temperature programmed experiment,synchronous thermal analysis experiment and laboratory fire extinguishing experiment of small coal pile,the resistance and fire extinguishing performance of inorganic slurry were investigated comprehensively.The inhibition effect of grout and Mg Cl₂ solution with different ratio of water to material on coal samples was analyzed by comparing the release of the signature gas,the inhibition rate and the temperature at the crossing point.The influence law of grout on characteristic temperature and heat release of coal is analyzed.The results showed that all indexes of 10:1 and 12:1 grout were better than Mg Cl₂ solution.After grout treatment,each critical temperature of coal sample has varying degrees of delay,and the maximum heat release rate of coal sample after 10:1 grout treatment is reduced by 30.1%.In addition,the addition of grout also greatly increases the activation energy of coal sample in the water evaporation stage,making it more difficult to carry out the next stage of oxidation reaction.In the actual test of extinguishing small coal pile fire,the smoke produced by inorganic slurry is smaller and there is no coal slag spatter.The temperature of each monitoring point will drop rapidly,and the mud in the comparison group cannot be evenly cooled,and the duration of cooling is short.Combined with the properties of inorganic grout and its flame-retardant properties to coal samples,the fire prevention mechanism of the grout was discussed.The high water retention characteristics of composite inorganic materials can rapidly reduce the ambient temperature of coal body.The slurry with a certain viscosity can both diffuse in the coal body and stay on its surface for a long time,reducing the physical and chemical adsorption of oxygen by the coal body,and it is difficult for the wrapped and separated coal body to accumulate heat and reignite.The research expands the application field of clay materials in mine fire prevention and further enriches the system of mine fire prevention materials.There are 43 figures,11 tables and 99 references in this thesis.