Study on the effects of low-temperature oxidation on the thermal properties and microscopic parameters of bituminous coal

• Thermal properties of low-temperature oxidized coal. • Microstructural and pore changes in pre-oxidized coal. • Factors affecting thermal properties. • Correlation between thermal properties and key factors. The laser flash apparatus (LFA) and microscopic techniques were used to investigate the thermal properties and microstructural parameter of bituminous coal after low-temperature oxidation. The key factors influencing coal thermal properties and correlations were analyzed. The results indicate that as temperature increases, SHC and TC gradually increase, while TD decreases. With increasing oxidation temperature, TD, SHC, and TC exhibit a fluctuating upward trend. Meanwhile, d 002 , L a , and L c gradually rise, while the relative contents of aromatic and aliphatic structures show an overall downward trend. The contents of oxygen-containing functional groups and hydroxyl structures increase within a specific temperature range. When the oxidation temperature reaches 120 °C, significant changes occur in the functional group contents of the C and O spectra. As the oxidation temperature increases, the I D /I G exhibits a fluctuating decline, while the A D /A G and F D /F G initially decrease and then increase. The specific surface area and pore volume first increase and then decrease. The -C-O- functional group, V ad , and A ad are significantly correlated with TD, SHC, and TC, while the C-H shows a strong positive correlation with both TD and TC. These findings provide theoretical support for the study of the physicochemical properties and thermal characteristics of oxidized coal.