China has abundant coal seam gas resources. The main combustible component of coal seam gas is methane, which is the second largest greenhouse gas after carbon dioxide. There is a large quantity of coal mine methane emissions in China caused by the energy activities. Therefore, utilization and mitigation of coal mine methane especially for the low concentration methane (LCM) have great significance to the "dual carbon" target of Chinese coal mines. Generally, Porous-Media Combustion (PMC) is a new type of combustion technology, which is suitable to the low concentration methane due to the enhanced heat exchanges caused by the porous media. In present work, coal mine low concentration methane combustion in porous media were studied and the effects of pores density, inlet velocity and wall heat losses, as well as the flashback and blow-off limits, the uniformity of temperature distributions were analyzed considering the external and internal heat recirculation by experimental and numerical method. And, a local thermal non-equilibrium (LTNE) model was established using modified effective thermal conductivity of the porous media based on the volume average theory (VAT). Results show that, for the foam ceramics media, the blow-off limit would be increase with the pores density of foam ceramics under relative higher methane concentration conditions. However, under ultralow methane concentration conditions, there is no significant effects of pores density on the blow-off limits. Compared with honeycomb porous media, foam ceramic performs a broader stable combustion range. With the enhanced external heat recirculation by dual-channel porous medium combustor, the preheating process of the inlet gas would be greatly shortened and the uniformity of temperature distributions are improved, that is helpful to the combustion stabilities.

Coal mine low concentration methane, Porous media combustion, Stability, Heat Recirculation, Temperature distributions