Study on microstructural changes and characteristics of low temperature oxidation of middle and high rank coal by microwave thermal radiation

To study the effect of microwave thermal radiation on coal structure and features of spontaneous combustion, lean coal (SM) from Shenyang Hongyang No. 2 Mine and anthracite (WYM) from Ordos were used. The experiments involved low-temperature nitrogen adsorption, thermal analysis, Fourier transform infrared (FTIR) testing, and closed oxygen consumption. Results showed that microwave radiation altered the coal's porous architecture, enhancing surface area per unit mass, porosity volume, and peak adsorption capacity. Higher radiation power led to earlier characteristic point temperatures and increased active groups. The rates of oxygen consumption, CO production, and oxidation intensity all exhibited exponential growth. Under 20.9% oxygen and 200–800W radiation, SM and WYM's oxidative heat release intensity was 1.44–3.73 and 1.15–4.13 times higher than raw coal, respectively. This increased spontaneous combustion tendency offers a theoretical foundation for coal fire prevention in mining and gas extraction. Theoretical guidance is offered regarding coal combustion control. This is particularly relevant to post-microwave radiation conditions within mining environments.