CFD modeling of optimal airflow rates for safe production in isolated mining faces with high methane concentration and coal spontaneous combustion

From the perspective of airflow rate adjustment for disaster prevention, controlling methane concentration and reducing spontaneous combustion zone in the goaf naturally contradict. Generally, an increased airflow rate is beneficial in reducing methane concentration but also increases the risk of coal spontaneous combustion. Coal pillars on both sides of an isolated mining face are broken to form air leakage passages, which connect its goaf and the two sides of the goafs to form triple goafs. Especially for triple goafs of the isolated mining faces with high methane concentration and coal spontaneous combustion tendencies, the lack of air leakage law and knowledge of the distribution of methane and oxygen concentrations makes disaster prevention and control difficult. To solve the above problem, this study adopts a computational fluid dynamics (CFD) modeling method to construct a physical model containing triple goafs and investigate the optimal airflow rates for safe produc-tion, with an isolated mining face in a mine in Guizhou taken as an object. Results show that the air leakage paths in the triple goafs of the isolated mining face mainly consist of "U-shaped" and "semi-U-shaped". The optimal airflow rates to maintain methane concentration at safety limits and to minimize the spontaneous combustion zone in the triple goafs are 1800 m3/min to 2000 m3/min. In consideration of economic efficiency and workload, the optimal installation spacing of the dynamic barriers is determined as 15.0 m-20.0 m. The study results provide scientific concepts and practical guidance for the prevention and control of methane and coal sponta-neous combustion hazards in triple goafs of isolated working faces.