Dust distribution in open-pit mines based on monitoring data and fluent simulation

To understand the concentration and distribution of PM2.5 and PM10 in open-pit mines, a beta-ray particle monitor and some laser monitors were arranged in Haerwusu Surface Coal Mine (HSCM), Inner Mongolia, China. A fluent simulation was made to study the dust move in the pit and escape rate and time out of the pit. The main conclusions include (1) in HSCM, the concentration of PM10 changes with that of PM2.5, meeting the power function PM10 = 2.548 × PM2.5^0.993. The dust concentration around the working mining equipment is very high. For example, around a working drill, the PM2.5 can be up to 426 μg/m³, and around a working power shovel, the PM2.5 can be up to 352 μg/m³. (2) At the same time, the PM2.5 concentration is nearly equal throughout the pit, away from the operating equipment, with a confidence level of 95%. The mean dust concentration away from the equipment is 76.7 μg/m³ when this mining equipment is working. So, the number of monitors in the pit can be decreased without affecting the quality of dust monitoring, which means that the cost of monitoring can be cut down. (3) Base on Fluent simulation results, the average escape time of dust particles with different diameters is similar, but the maximum escape time decreases as the particle diameter increases, which means that most dust moves with the air swirl, but some smaller dust particles can hang in the pit for a longer time. Also, the escape rate decreases rapidly as the diameter of the dust increases. (4) Dust is rotated and diffused evenly in the pit under the action of the eddy current in the pit. Finally, when the dust is swirled to a higher level than that of the pit head, the dust can escape out of the pit.