Thermodynamic Characteristics and Kinetic Mechanism of Bituminous Coal in Low-Oxygen Environments

Coal is a crucial energy source globally, but it poses environmental challenges due to high temperatures and harmful missions during combustion. This study investigates bituminous coal's oxidation combustion in low-oxygen environments using thermogravimetry and differential thermogravimetry tests. We explore the thermal behavior and kinetic properties of three coal samples during combustion. Our findings reveal that, as oxygen concentration decreases, the combined combustion index of the coal samples also decreases during the oxygen-absorption stage. Additionally, the apparent activation energy of coal increases with its conversion rate (temperature). We observe a shift in the reaction mechanism from three-dimensional dissipation mode to two-dimensional as the oxygen concentration decreases. Notably, the activation energy initially rises and then decreases with increasing conversion (temperature) during the pyrolysis combustion stage, with a shortened phase of increased activation energy at lower oxygen concentrations. Furthermore, the kinetic mechanism transitions from stochastic nucleation and growth to one-dimensional phase-boundary mode with decreasing oxygen concentration. These insights enhance our understanding of coal oxidation combustion in low-oxygen environments, contributing to strategies for mitigating coal spontaneous combustion.