Coupled diffusion law of windflow-gas-dust in tunnel energy extraction processes and the location of optimal pollution control exhaust duct

Coal resources play an important role in the world's energy development. China's coal consumption in 2022 was as high as 88.41 EJ. However, the process of energy extraction generates dust and gas, which is a serious threat to efficient production and workers' health. More than 7000 new cases of pneumoconiosis are diagnosed in China each year. To improve this situation, numerical simulation experiments were used to obtain the coupling diffusion law of airflow-gas-dust during tunnel excavation under long-pressure short-extraction ventilation and to determine the optimal distance of the exhaust duct from the working face (LE) for the purpose of cleaner production. Our experimental results demonstrated that the spatial and temporal evolution of gas-dust coupling largely depends on the distribution of the airflow field. By comparing the concentration distribution of gas and dust at different distances from the working face, the average gas concentration in the tunnels was found to be low (0.249 %) when LE=4m. Furthermore, the average dust concentration in the tunnel was the lowest (242.5 mg/m3) and therefore the least harmful to workers. The optimal exhaust duct distance was LE=4m, which not only reduces the environmental pollution in a tunnel but also ensures the occupational health of workers. [Display omitted] •Pollutant diffusion pattern under mixed ventilation was studied.•The concentration of the gas field in this case has a step distribution.•Variation of dust concentration in the work area was studied.•The optimal location for a tunnel's dust-gas control duct was determined.