Spatiotemporal evolution patterns of compound dust sources and dust control and removal technology in main washing workshop of a coal preparation plant

Existing studies on dust evolution patterns mostly focus on a single dust source or a local dust-producing area, and lack systematic analysis of the formation process of dust agglomerates, diffusion paths and the evolution patterns of high-concentration areas under the combined action of multiple devices, multiple windows and multiple dust sources in the complex main washing workshop of a coal preparation plant. To address this problem, taking the main washing workshop of the coal preparation plant of Gongwusu Coal Mine of CHN Energy (Wuhai) Energy Co., Ltd. as the research object, an equal-scale, full-size three-dimensional geometric model was established. The spatiotemporal evolution patterns of compound dust sources under the combined action of dust input from a belt roadway and local dust in the centrifuge area were studied by computational fluid dynamics and a discrete phase model. Numerical simulation results showed that: ① after the airflow in the belt roadway entered the workshop, a high-speed airflow zone was formed through side-wall windows, carrying the belt-roadway dust into the main washing workshop. Wind velocity distributions at different heights above the floor were significantly different in the main washing workshop, and the lower-height region had a lower wind velocity, which caused dust particles to settle easily, while the local wind velocity at 1.5 m above the floor increased, which was conducive to dust diffusion. ② With continuous dust input, the belt-roadway dust diffused toward the centrifuge and worker operating areas along the running direction of the belt conveyor, and the externally input dust combined with local dust in the centrifuge area to form compound dust pollution in multiple areas. ③ The average dust mass concentration in the breathing zone continuously increased with dust diffusion time, indicating that the dust exposure risk in the workers' breathing zone had a clear cumulative characteristic. Based on the numerical simulation results, a composite dust control and removal technology of "air-washing dust removal in the belt roadway + soft-curtain sealing of the centrifuge" was proposed: air-washing dust removal was used to reduce dust input at the source in the belt roadway, and soft-curtain sealing was used to reduce local dust diffusion in the centrifuge area. Field application results showed that after the composite dust control and removal technology was adopted, dust concentrations in the worker operating area, at the tail of the scraper conveyor, in the mixing tank, and near the belt conveyor decreased from 87.7, 84.5, 76.3 and 123.2 mg/m³ to 9.5, 5.1, 4.3 and 5.5 mg/m³, respectively, and the average dust reduction rate reached 93.3%.