Correlation Between Microstructural Evolution of Wuhai Coal Spontaneous Combustion and Industrial Analysis Indicators

As coal mining operations in China reach greater depths, spontaneous combustion incidents are becoming increasingly frequent, posing a serious threat to safe coal extraction. To prevent spontaneous combustion, studying coal oxidation and spontaneous combustion processes by integrating thermodynamic and microstructural characteristics is crucial, as it provides the foundation for elucidating the underlying mechanisms. Twelve different coal samples from the Wuhai region were selected and studied using thermogravimetric-differential scanning calorimetry (TG-DSC), electron spin resonance (ESR), and Fourier transform infrared spectroscopy (FTIR) to systematically investigate free radical characteristics, functional group evolution, and oxidation kinetics during low-temperature oxidation, as well as their correlation with industrial indicators. With increasing temperature, free radical concentration continues to rise, line width gradually narrows, and the g-factor shows an overall downward trend, reflecting the coal’s aliphatic-to-aromatic structural transformation. The g-factor evolution correlates significantly with ash/fixed carbon (A/FC) and volatile matter/ash (V/A) ratios, indicating industrial analysis parameters can effectively characterize radical transformation pathways. No significant correlation was found between kinetic parameters (ignition point, apparent activation energy) and industrial indicators, showing macroscopic indicators alone cannot adequately reflect coal oxidation kinetics. Combined ESR and FTIR analysis reveals the coal undergoes phased low-temperature oxidation involving weak bond cleavage, oxygen-containing structure formation, and aromatic rearrangement. This study establishes a quantitative relationship between industrial analytical indicators and microstructural evolution, offering a new approach to predict coal low-temperature oxidation behavior using conventional indicators, and providing valuable guidance for coal spontaneous combustion prevention and control.