Effects on environmental conditions and limiting parameters for spontaneous combustion of residual coal in underground goaf

Abstract

This study collected coal from the Meihuajing Coal Mine, Ningxia, China, and employed a temperature-programmed experimental setup to investigate the characteristics of coal spontaneous combustion (CSC) and determine the primary parameters influencing coal temperature in the goaf of this underground mine. The obtained results indicated that positive correlations existed between CO concentration, CO2 concentration, oxygen consumption rate, exothermic intensity, and coal temperature. Principal component analysis (PCA) was employed to examine the correlations of three limiting parameters—namely maximum air leakage intensity (Qmax), minimum oxygen volume fraction (Cmin), and minimum thickness of residual coal (Hmin)—with coal temperature (30–170 °C) during coal oxidation. The results of a PCA indicated that among these parameters, Qmax was most strongly correlated with coal temperature. In addition, gray correlation analysis (GCA) was adopted to examine the primary parameters influencing the occurrence of CSC during different stages. The results of GCA indicated that the primary parameter influencing the occurrence of CSC varied with the coal oxidation stage. At coal temperatures between 80 and 90 °C, Cmin and Hmin were the primary parameters influencing coal temperature. The correlation curves of Cmin and Hmin with respect to coal temperature fit well with the GaussMod model. The findings of this research provide a theoretical foundation for mitigating CSC in underground goafs.