Abstract:
Against the backdrop of the deepening “dual carbon” goals and global strengthening of methane control, achieving near-zero emissions of coal mine methane has become an urgent task for the green transition of China’s energy industry. Currently, ultra-low-concentration ventilation air methane, which accounts for the vast majority of total coal mine methane emissions and has a concentration below 0.3%, remains an international technological challenge for large-scale, efficient utilization because of its excessively low methane concentration and the fact that the heat released from oxidation is insufficient to sustain autothermal operation of the system. To systematically break through the technical barriers to the safe, efficient conversion, and large-scale utilization of ultra-low-concentration gas, a comprehensive review is conducted on the technological developments in coal mine methane utilization over the past 15 years. It focuses on analyzing the current status and limitations of regenerative thermal oxidation (RTO) technology in handling ultra-low-concentration gas and addresses core issues such as improving methane conversion efficiency and reducing the system’s autothermal balance concentration. Four breakthrough technological pathways are systematically proposed: solid-fuel blending for heat supplementation, catalytic oxidation, coal-water slurry syngas heat supplementation, and dielectrophoretic enrichment. The mechanisms, key parameters, and economic characteristics of each pathway are elucidated. The results indicate that blending micron-sized coal powder can effectively increase system temperature and methane conversion rate, but requires prevention of ash deposition and channel blockage; the ignition temperature of non-noble metal catalysts decreases significantly after doping with elements such as Sr, though their catalytic activity still requires optimization; coal-water slurry syngas supplementation offers advantages of efficient heat compensation and clean operation, demonstrating strong engineering applicability; dielectrophoretic enrichment provides a novel approach for the physical concentration of ultra-low-concentration gas. Building on this, a systematic technology roadmap is constructed for the full-concentration hierarchical utilization and emission reduction of coal mine methane under the “dual carbon” goals. It clarifies that multi-dimensional collaborative innovation encompassing “concentration enhancement, heat supplementation, catalysis, and system optimization” is required to extend the applicable lower concentration limit of gas oxidation technology to the realm of ventilation air methane. This will promote the realization of “full-concentration, large-scale, high-value” utilization of coal mine methane, providing crucial technical support for methane emission reduction and energy structure transition in China’s coal mining sector.