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.

Study on the effect of Ce-Cu doping on Mn/γ-Al2O3 catalyst for selective catalytic reduction in NO with NH3.

A series of Mn/γ-Al2O3, Mn-Cu/γ-Al2O3, Mn-Ce/γ-Al2O3 and Mn-Ce-Cu/γ-Al2O3 catalysts were prepared by equal volume impregnation. The denitrification effects of the different catalysts were studied by activity measurement, X-ray diffraction, Brunauer, Emmett, and Teller surface area tests, Scanning electron microscopy, H2-temperature programmed reduction and Fourier-transform infrared spectroscopy. The experimental results show that Ce and Cu are added to a Mn/γ-Al2O3 catalyst as bimetallic additives, which weakens the interaction between Mn and the carrier, improves the dispersion of MnOx on the surface of the carrier, improves the specific surface area of the catalyst, and improves the reducibility. Mn-Ce-Cu/γ-Al2O3 catalyst reaches a maximum conversion of 92% at 202 °C. Also, the addition of the auxiliary metals promotes the reaction mechanism to a certain extent, and the addition of Ce especially promotes the conversion of NO-NO2, which is conducive to the production of intermediate products that promote the NH3-SCR reaction.

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

The high growth in the use of underground diesel vehicles has led to a large number of exhaust pollutants, especially particulate matter (PM), which is a serious threat to the lives and health of underground personnel. In this paper, based on numerical simulations and field measurements, the temporal and spatial distribution of PM in the exhaust of two vehicles and the impact on the health of underground personnel was analyzed. The results showed that in both conditions, the airflow velocity between two vehicles showed a zonal distribution, and there was an airflow vortex in the chamber under the interaction of the wind. When the vehicles were running in the same direction into the wind, PM with a concentration range of 15.79-26.32 mg/m3 could reach the height of the human respiratory belt and was mainly distributed on the east side of the roadway. Therefore, underground personnel should avoid approaching the right area of the vehicle body. In addition, PM concentration around the driver position of the vehicle was still higher than the human contact limit, so the drivers of the vehicle would need personal protection. When the vehicles were running in the same direction with the wind, compared with the airflow inlet side, the amount of PM on the airflow outlet side increased more obviously with time, especially for PM with a concentration range of 21.05-31.58 mg/m3. Also, partial PM flowed into the chamber with the airflow, such that personnel should avoid being located on the downwind side of the vehicle, and personnel in the chamber should also have personal protection.

Carboxymethyl cellulose sodium gel: A modified material used to suppress coal dust pollution.

To reduce the environmental pollution caused by coal dust, a new type of dust inhibitor with a wide application range, high efficiency, and production simplicity was synthesized by modifying sodium carboxymethylcellulose (CMC-Na) with acrylamide (AM). Through molecular dynamics simulations and experiments, the surfactant composition and concentration were optimized. The experimental results showed that the graft copolymer of CMC-Na and AM (CMC-Na-co-AM) had more pores on the microscopic surface and a unique fiber network structure, which greatly increased its contact area with coal dust. After 14 h of drying at 60 °C, coal samples that were sprayed with the dust suppression agent retained >50% of the water in the spray, which was 9 times greater than the water retention of coal samples sprayed with just water. Additionally, the ability of the dust suppression agent to resist wind erosion was 6 times that of water. The CMC-Na-co-AM dust suppression agent showed that it could effectively inhibit the spread of coal dust under strong winds, offering a solution to the problem of coal dust pollution in coal production and storage.

Green surfactant-modified TiO2 nanoparticles doped with La-Cr bimetal for NOx removal.

Cost-effective new environmental catalysts play a crucial role in purifying NOx from exhaust gas of coal mine diesel vehicle. A new, environmentally friendly catalyst with high catalytic activity and good redox properties was prepared by a microwave-assisted sol-gel method using TiO2 nanoparticles as a catalyst, which were doped with La and Cr, and adding the surfactant dimethyldiallylammonium chloride (DMDAAC) as an organic modifier. The morphological characteristics, crystalline structure, functional groups, and elemental types of the catalyst were characterized, and the properties of the catalyst, such as redox ability and catalytic activity, were examined with H2-temperature-programmed reduction experiments and activity tests. The results showed that the addition of surfactant suppressed the growth of particle size, increased the specific surface area, and improved the redox ability and catalytic activity of the catalyst. I hope to reduce the pollution of NOx to environment and achieve efficient cleaner production.

Vehicle Interaction Behavior Prediction with Self-Attention.

The structured road is a scene with high interaction between vehicles, but due to the high uncertainty of behavior, the prediction of vehicle interaction behavior is still a challenge. This prediction is significant for controlling the ego-vehicle. We propose an interaction behavior prediction model based on vehicle cluster (VC) by self-attention (VC-Attention) to improve the prediction performance. Firstly, a five-vehicle based cluster structure is designed to extract the interactive features between ego-vehicle and target vehicle, such as Deceleration Rate to Avoid a Crash (DRAC) and the lane gap. In addition, the proposed model utilizes the sliding window algorithm to extract VC behavior information. Then the temporal characteristics of the three interactive features mentioned above will be caught by two layers of self-attention encoder with six heads respectively. Finally, target vehicle's future behavior will be predicted by a sub-network consists of a fully connected layer and SoftMax module. The experimental results show that this method has achieved accuracy, precision, recall, and F1 score of more than 92% and time to event of 2.9 s on a Next Generation Simulation (NGSIM) dataset. It accurately predicts the interactive behaviors in class-imbalance prediction and adapts to various driving scenarios.

Study of the microscopic mechanism of lauryl glucoside wetting coal dust: Environmental pollution prevention and control.

Molecular dynamics simulation combined with experimental methods were used to investigate the adsorption and wetting process of 25 lauryl glucoside (APG-12) molecules on coal molecules and in turn study the dust suppression mechanism by APG-12 at the molecular level. Through wetting experiments, our preliminary findings showed that APG-12 does have a certain wetting effect on coal dust. According to density functional theory in molecular dynamics simulations, the electrostatic potential and surface charge of the APG-12 and coal molecular models were analyzed to identify their nucleophilic and electrophilic regions, and illustrate the hydrogen bond adsorption mechanism. The dynamics simulation results showed that APG-12 molecules can be easily adsorbed on the surface of coal molecules and then adsorb water molecules around them under the action of hydrogen bonds. This was consistent with the results of an analysis of the system's radial distribution function and the relative concentration distribution of each component in the Z-axis direction. The results are in good agreement with the experimental results from scanning electron microscopy and energy dispersive spectrometer analysis. These data provide further evidence that APG-12 can clearly improve the wettability and suppression of coal dust, which is of great importance for controlling coal dust pollution.

Behavior of the particulate matter (PM) emitted by trackless rubber-tyred vehicle (TRTV) at an idle speed under different movement conditions and ventilation optimization.

The particulate matter (PM) emitted by a trackless rubber-tyred vehicle (TRTV) in coal mines can seriously threaten the health and safety of the exposed workers underground. In this paper, in order to effectively reduce the PM concentration and improve the underground working environment, a combination of numerical simulations and field measurements was adopted to study the migration distribution of the PM emitted by a TRTV at an idle speed for 60 s under different movement conditions, and the dilution effects of the ventilation rate on the PM. The results showed that under different movement conditions, the PM mainly moved along the floor of the roadway, but upward diffusion trends were shown overall, which meant that the chambers are in high-risk areas. Field measurements were then performed under the two conditions to verify the effectiveness of the simulations. Furthermore, the dilution effects of the increased ventilation rate on the PM were analyzed. It was concluded that the optimal dilution ventilation rate under condition 1 was 4600m3/min, and that under condition 2 was 2800m3/min. Accordingly, the driver of the TRTV should try to move forward when entering the chamber.