Determination of Coal Spontaneous Combustion Zone in Overlaying Multilayer Goaf and Its Control Technology of Thickened Slurry

In order to study the law of coal spontaneous combustion and prevention methods in the overlying multilayer goaf, this study combined the situation of 378 working face and overlying multilayer goaf in Anyuan Coal Mine and determined the coal spontaneous combustion zone in the overlying multilayer goaf by overlaying the oxidation zones divided by wind velocity and oxygen concentration, and verified it. Subsequently, a new type of thickened slurry was prepared based on sodium alginate, carboxymethyl cellulose, loess, and water as the main raw materials, and a thickened slurry fire prevention technique suitable for overlying multilayer goaf was proposed. The research results indicated that the coal spontaneous combustion zone was located near the 3117 return air roadway and the 378 return air roadway in 378 working face, as well as the upper part of 3117 return air roadway in 372 (4) goaf. When the water-soil ratio was 8:1 and thickener concentration was 0.3%, the suspension performance of the thickened slurry was better. At this point, the corresponding yield stress was the smallest and the flow ability was better. Through the used of fixed-point grouting and regional sealing of a thickened slurry fire prevention technique, it was found that the CO concentration gradually decreased to zero in the 372 (4) goaf. The oxygen concentration significantly decreased and the pressure difference remained stable in the sealing wall in the return air roadway. The outlet water temperature were below 25 degrees C all boreholes.