Microscale dispersion behaviors of dust particles during coal cutting at large-height mining face.

In order to ensure safe production and occupational health at a large-mining-height fully mechanized mining face in a coal mine, the present study firstly establishes an airflow-dust coupled model based on gas/solid two-phase flow equations and combines numerical simulation and field measurement for analyzing the dispersion pattern of dust particles with various sizes for different coal cutter locations. Results show that, due to the existence of drums, airflow deviates from the original direction and enters the footway. Driven by the airflow, dust particles enter the footway at different locations depending on coal cutter locations. The coal-cutting location (denoted as Prl ) and the location where dust particles enter the footway (denoted as Pdt ) are correlated as follows: Pdt (Prl ) = - 0.0007Prl 2  + 1.0343Prl  - 3.3536. When Prl  < 55 m, dust particles produced by the rear drum during coal cutting enter the footway earlier than those produced by the front drum, leading to the first and second dust concentration peaks in respiratory zones of footway. Dust suppression effects are assessed in these regions based on the first and second dust concentration peaks. Due to the superposition of the concentration fields associated with dust particles 2.5, 7, and 20 μm in diameter, dust concentration 25 m down the leeward side of the coal cutter can reach 1440 mg/m3 . The concentration of dust particles with a diameter of 40 μm drops steadily and approaches 0 at the return corner. The dust particles 80 μm in diameter are fully settled within 22 m down the leeward side of the coal cutter. A comparison with the field measurement indicates that the present simulation results are highly accurate. Graphical abstract.