Study of dust pollution control effect based on orthogonal test and CFD numerical simulations.

To control the diffusion of high concentrations of coal dust during tunnel boring and minimize the threat to the life and health of coal miners, theoretical analysis, numerical simulations, and field measurements were combined in this study. First, computational fluid dynamic simulation software was used to simulate the generation of dust particles and their transport pattern in the tunnel. Subsequently, an innovative orthogonal test was performed to study the effect of four ventilation parameters [the pressure airflow rate (Q), distance between the air duct center and heading face (LA), distance between the air duct center and tunnel floor (LB), and distance between the air duct center and nearest coal wall (LC)] on dust diffusion. According to the orthogonal test results, the optimal ventilation parameters for effective dust control are as follows: Q = 1400 m3/min, LA = 7 m, LB = 2.8 m, and LC = 1 m. The optimized set of ventilation parameters was applied to the Wangpo 3206 working face. The results show that dust diffusion in the tunnel was effectively controlled and that the air quality was sufficiently improved.

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.

CFD-based simulation study of dust transport law and air age in tunnel under different ventilation methods.

To solve the problem of high-concentration dust pollution in a bored tunnel, we conducted a simulation study on the dust transport law and air age of the wind flow in a bored tunnel under different ventilation methods. Air age was innovatively introduced as an index for evaluating tunnel air quality. The results show that dust pollution is serious under conditions of press-in ventilation, which is unfavorable to personnel operations. Following the installation of an on-board dust-removal fan, an effective dust-control air curtain forms in the tunnel, and the high-concentration dust is essentially controlled within the range of Z = 13 m from the working face. The dust concentration in the working area on the left side of the tunnel is CD < 200 mg/m3, and the dust-control effect is obvious. At the same time, the air age on both sides of the tunnel is reduced by 35.5% following the use of the on-board dust-removal fan. Taking into account dust control by ventilation and dust removal by fan, spraying dust reduction measures are added, and we developed automated wind-mist synergistic wet high-frequency oscillation dust-capturing technology for tunnel boring. This could effectively improve the problem of high levels of coal dust pollution in tunnels.

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.

Numerically simulated behavior of diesel particulate matter emitted by hydraulic support transporters.

WC55-Y hydraulic support transporters allow an efficient transport of support equipment in fully mechanized mining faces. However, the diesel particulate matter (DPM) emitted by these transporters seriously pollutes the air environment along mine roadways, endangering the health of coal mine workers. In this paper, we simulated the diffusion dispersion of DPM during the functioning of a WC55-Y hydraulic support transporter (emitting high amounts of exhaust pollutants) by computational fluid dynamics, identifying high DPM concentration zones. While the transporter was driven along a coal auxiliary transportation roadway, the diffusion-dispersion characteristics of DPM changed: DPM reached a long horizontal diffusion distance and a high concentration. We found that to avoid the inhalation of DPM and reduce its potential harm, coal mine workers should keep a distance of at least 21.27 m from the hydraulic support transporter while the vehicle runs along the roadway. Moreover, according to our simulation, the operators responsible for disassembling the hydraulic support transporter should wear protective equipment with good filterability while unloading it. Overall, the findings of this study can be applied to outline new work practice guidelines and design new optimum auxiliary ventilation for reducing underground miner exposure to DPM.

Study on dust-gas coupling pollution law and selection of optimal purification distance of air duct during tunneling process.

During the excavation of high gas mine, gas and dust often exist at the same time. In order to ensure that the gas concentration remains within a safe range and minimize the risk of workers' pneumoconiosis, we simulated the interaction mechanism of airflow, gas, and dust, explored the pollution law of gas and dust, and obtained the optimal purification distance (Lp) by the CFD method. The reliability of the numerical simulation was verified by field measurements. Firstly, the properties of the gas and dust affected the structure of the airflow field. At the same time, the change in the airflow field affected the concentration distributions of the gas and dust. During the diffusion process, some high-risk regions in which the gas or dust concentrations exceeded 0.80% or 200 mg/m3, respectively, were discovered. Moreover, we have found that the airflow velocity in the top region of the tunnel and at the intersection corner between the cutting face and tunnel wall was the main factor affecting the purification effects. When Lp = 5-8 m, the gas concentration remained below 0.50%. When Lp = 6 m, the dust concentration reached a minimum of 287.5 mg/m3. Therefore, the optimal purification distance was determined to be 6 m; in which case, the gas and dust concentrations decreased by 32.84% and 47.02%, respectively.

Prediction of dispersion behavior of typical exhaust pollutants from hydraulic support transporters based on numerical simulation.

We investigated the impact of exhaust emissions from hydraulic support transporters on the air quality in roadways in mines. The dispersion distribution of diesel exhaust pollutants emitted by hydraulic support transporters was simulated with a dynamic mesh and computational fluid dynamics (CFD) simulations. More specifically, the dispersion and distribution of the main exhaust pollutants CO, HC, and NOx emitted by vehicles under the influence of the roadway wind flow were simulated with CFD simulations; in addition, the dispersion characteristics of exhaust pollutants from hydraulic support transporters during multiple driving phases in an alleyway (from transporting material, being unloaded at idle speed, to driving off without load) were predicted. The simulation results show that exhaust pollutants emitted by moving hydraulic support transporters can pollute the air in roadways and negatively affect the performance of gas monitoring devices in the roadway. Therefore, coal mining companies should optimize the ventilation design scheme to improve the air quality in roadways: they should increase the ventilation volume to dilute the emitted pollutants; in addition, the positions of underground gas monitoring devices should be adjusted to prevent interference from exhaust pollutants emitted by vehicles. This paper provides the theoretical basis and results of a preliminary investigation of the dispersion and transportation characteristics of exhaust pollutants emitted by vehicles in roadways. The results in this paper can serve as guidance for reducing the risk of occupational diseases.

Effects of press-in airflow rate and the distance between the pressure duct and the side wall on ventilation dust suppression performance in an excavating tunnel.

The efficiency of mine excavation has been significantly enhanced by continuing improvements in tunneling capabilities; however, this has also resulted in serious environmental pollution and greater safety risks for workers. To ensure safe production, the focus of this study is on the effect of varying the air pressure and the distance between the air pressure cylinder and the side wall settings on dust dispersion behavior and dust control in excavated tunnels. We also investigated temporal-spatial dust diffusion rules in tunnels by combining numerical simulation data with field measurement results. Through further analysis, when the pressure air volume and the exhaust air volume are both equal to 250 m3/min, the dust diffusion distance could be fitted as: [Formula: see text]. When the exhaust air volume is equal to 250 m3/min, dust control effects were improved as the pressure air volume decreased, becoming optimal when the pressure air volume dropped to 150 m3/min. Under these conditions, areas of high dust pollution were contained within 16 m of the cutting face, and the dust diffusion distance satisfied the formula: [Formula: see text]. When the pressure air volume is fixed, the change of the distance between the pressure air cylinder and the side wall has little effect on the dust diffusion. When the distance is 1.5 m, the dust control effect is the best, and the high dust pollution area is controlled within 14 m of the cutting surface. This alleviated dust pollution to a certain degree, thereby enhancing the air quality and ensuring safer production. This study provides a new understanding of the environmentally sustainable development of tunnels and is of great significance for clean production.

The control effect of 3D spiral wind-curtain generator on respirable dust pollution during tunnelling process.

The respirable dust pollution produced in the cutting process of tunnelling machine during tunnelling process is a serious threat to the health of workers. The key to solve this problem is to build an effective ventilation system in the tunnel. In this paper, experiments were designed and implemented to obtain the temporal-spatial evolution of respirable dust pollution before and after the 3D spiral wind-curtain generator was used for tunnel auxiliary ventilation, and the CFD method was used to supplement and visualize the experimental results. Before the 3D spiral wind-curtain generator was used, the respirable dust gradually diffused from the cutting face to other spaces of the tunnel, and finally presented a stable state with time. After using the 3D spiral wind-curtain generator for auxiliary ventilation, the dust diffusion speed in the tunnel was slower than before, and the dust concentration was lower than before. When adjusting the position of the generator and installing it 20m away from the cutting face, an effective dust control wind-curtain formed within the range of 3.5 ~ 6.5m away from the cutting face. With the increase of time, the dust is stably controlled within the space of 4.5m away from the cutting face, and then pumped away by the exhaust fan, so as to purify the tunnel environment and ensure the tunnel's cleanliness and safety and efficient excavation.

Behavior of diesel particulate matter transport from subsidiary transportation vehicle in mine.

The aim of this study was to investigate thoroughly the diffusion and distribution of diesel particulate matter (DPM) discharged from a mine subsidiary transportation vehicle to improve the air quality in tunnels by reducing exhaust pollution and to propose targeted prevention measures. More specifically, the diffusion of DPM from a WC40Y shield carrier during its travel was examined in depth with numerical simulations. The results show that, under the current ventilation conditions, the airflow in the tunnel was insufficient for diluting the DPM discharged from the shield carrier during starting, accelerated traveling, and turning; this can be effectively addressed by increasing the ventilation rate to 1.8 m/s. However, during high-velocity travel, the carrier was affected by the piston wind could not be diluted effectively by increasing ventilation rate. The velocity limit can lower the DPM concentration in the tunnel and alleviate DPM pollution from the shield carrier. To reduce DPM emissions, the travel velocity should be limited to 30 km/h. Summary: Determine the optimal airflow velocity in the tunnel that ensures that the discharged DPM is effectively diluted during the travel of the shield carrier.