Numerical study on temporal and spatial distribution of particulate matter under multi-vehicle working conditions

Dust distribution characteristics of the breathing zone in the walkway area of fully-mechanized mining face: a case study

To understand the dust distribution characteristics of fully mechanized mining faces, this study utilized the gravimetric method to sample dust in the walkway area during the coal cutting process of the shearer, followed by testing and analysis of the dust samples. The research findings reveal that the pollution level in the walkway area significantly surpasses coal mine safety regulations. There is no significant correlation between variations in dust concentration and dust quantity at different locations, with the region within 6 m behind the shearer exhibiting the highest dust quantity. The rate of change in respirable dust quantity is notably lower than that of non-respirable dust quantity. In all areas except those corresponding to the shearer, the number of dust particles within the range of 0 to 10 μm exceeds 90%. Additionally, dust particles on the mining face have smooth surfaces but are predominantly elongated in shape. These findings underscore the current inadequacies in effectively controlling dust in walkway areas. Therefore, there is a pressing need to implement more technological measures to control dust in these areas, with a specific emphasis on reducing the quantity of respirable dust, rather than solely focusing on variations in dust concentration.

Study of spatiotemporal evolution of coupled airflow-gas-dust multi-field diffusion at low-gas tunnel

The increasing level of mechanization in coal mining means more dust and gas are generated during excavation operations in tunnels. The high concentrations of dust and gas severely affect production efficiency and the physical and mental health of workers. Here, Ansys Fluent simulations were performed to derive the spatiotemporal evolution of coupled airflow-dust-gas diffusion in a low-gas excavation face. The aim was to optimize pollution control by determining the optimal duct distance, L, from the working face in the excavation tunnel. Our results showed that the airflow field affects the coupled diffusion and transport of dust and gas. According to a comparison of the effects of different duct distances from the working face, when L = 6 m, the average dust concentration in the tunnel is low (257.6 mg/m3), and the average gas concentration in the tunnel is 0.28 %, which does not exceed the safety limit. Accordingly, the optimal distance of the duct for pollution control is 6 m. The results of field measurements supported the validity of the simulation. Our findings can be used to improve the air quality in tunnels, thereby keeping miners safe and the working area clean.

Suspension characteristics of the coal-quartz dust mixture in the working environment during the fully mechanized mining process

Dust exposures during mining activity can result in lung diseases such as coal workers' pneumoconiosis (CWP) and silicosis, and it is closely related to quartz dust. In the present study, coal-quartz dust mixture were investigated considering the particle size and the specific constituents. Multiple numerical techniques, including computational fluid dynamics and discrete element method (CFD-DEM), hard sphere model, and direct Monte Carlo simulation (DSMC), were presented, and the dust diffusion processes were investigated. According to the validation of the numerical method, the suspension characteristics of the polydisperse mixed dust were analyzed in detail. The results show that PM10 responds quickly, has a large diffusion range, and is easily affected by the reflux. The particle size increases gradually from top to bottom. When the air velocity is low, the percentage of coal dust in the breathing zone tends to be 50%. The results provide theoretical guidance for the comprehensive prevention of the mixed dust in underground coal mines.

Analysis of the dust-methane two-phase coupling blowdown effect at different air duct positions in an excavation anchor synchronous tunnel

Bolter miners are being increasingly used. Unfortunately, this mining technology causes a considerable amount of air pollution (especially by methane and dust) during excavation. In this study, the multiphase coupling field of airflow-dust-methane for different distances between the pressure air outlet and the working face (Lp) was simulated by using the FLUENT software. The migration law of pollutants in the multiphase coupling field was analyzed, and the distance parameters between the pressure air outlet and the working face were optimized. Finally, the simulation results were verified based on the field measurement results. We found that the blowdown effect was more obvious when 14 m ≤ Lp < 16 m compared with other conditions. The peak value of dust concentration within this distance range was the smallest (44.4% lower than the highest peak value, which was verified when Lp = 18 m), while the methane concentration was < 0.6%. A high-concentration area (where methane concentration > 0.75%), identified near the walking part of the bolter miner, was 13 m shorter than the largest (when Lp = 18 m). Therefore, we determined that the optimal blowdown distance would be 14 m ≤ Lp < 16 m. Within this range, the dust removal and methane dilution effects are optimal, effectively improving the tunnel air quality and providing a safe and clean environment for mine workers.

Numerical simulation study on atomization rule and dust removal effect of surface-active dust suppressants

Spray dust reduction is a common dust control process in coal mines. However, the actual efficiency of spray dust reduction in a coal mine is low due to poor coal wettability. We select four surfactants that can greatly improve the surface activity of a dust suppressant solution. The wettability of the surfactant solution on coal dust is investigated in terms of two aspects: surface tension and contact angle. The effects of the type of surface-active dust suppressant and its concentration in the spray solution on the wetting of the coal dust and curing effects were analyzed. Numerical simulations were used to simulate spray atomization and to deduce how different types and concentrations of dust suppressant solutions affect the spray. The technical approach of the spray dust reduction method was further optimized by comprehensive analysis and numerical simulations, which could provide guidance for the application of spray dust reduction in coal mines.