Development of a novel wind-assisted centralized spraying dedusting device for dust suppression in a fully mechanized mining face

Numerical simulation for spray spatial distribution of swirl nozzle and its target dustfall area prediction

The droplet breakup and distribution of the internal flow field and external spray field of a nozzle were obtained under different pressures. The thickness of the liquid film increased with pressure as a quadratic function. The maximum value of 0.281 mm at 2 MPa decreased to 0.172 mm at 10 MPa, equivalent to 38.8% decrease. The MATLAB was used to obtain the particle size distribution characteristics of the droplets under different pressures. At 2 MPa, droplet breakup dominated the axial interval [0-700 mm]. With the increase of pressure, D50 distribution as a whole continues to decrease, 2-6 MPa change, the particle size reduction is larger, every increase of 2 MPa reduced by about 15%. 6-10 MPa change, the particle size reduction is smaller, every increase of 2 MPa reduced by about 8%. A model to predict the optimal dust reduction areas under varying pressures was developed. The prediction results indicate that at pressures of 5 MPa and 9 MPa, the target dust removal areas were [344 mm, 710 mm] and [424 mm, 942 mm] along the axial direction, respectively.

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.

Critical assessment of the effectiveness of different dust control measures in a granite quarry

The exposure to respirable crystalline silica found in granite dust presents significant health hazards to quarry workers and nearby communities, including silicosis and various respiratory ailments. This study evaluates the efficacy of various pollution control measures implemented in granite quarries. It aimed to provide a comprehensive critical assessment of the effectiveness of various dust control measures, considering their mechanisms, impact on air quality, and implications for worker health and community welfare. The strategy involved compiling and systematically analysing existing research articles, literature, and industry reports. The investigation identified three primary categories of measures: engineering controls, water-based suppression methods, and technological solutions. The study highlighted the significance of environmental impact and sustainability factors in selecting measures. These factors include water and energy consumption, production of secondary pollutants, long-term ecological effects, regulatory compliance, and cost-effectiveness. Operators and policymakers should utilize integrated, context-specific, inventive, and interdisciplinary strategies to efficiently control particle emissions from granite quarrying.

Experimental study on ratio optimization and application of improved bonded dust suppressant based on wetting effect

Traditional bonded dust suppressants have high viscosity, insufficient fluidity and poor permeability problems, which is adverse to the formation of a continuous and stable solidified layer of dust suppressant solution on the surface of a dust pile. Gemini surfactant has efficient wetting performance and environmental protection performance, it is introduced as a wetting component to improve the flow and penetration performance of bonded dust suppressant solution, polymer absorbent resin (SAP) and sodium carboxymethyl starch (CMS) were selected as the main components of dust suppressant. A proportioning optimization model was constructed based on response surface methodology (RSM), and the concentration of each dust suppression component was selected as the independent variable, water loss rate, moisture retention rate, wind erosion rate and solution viscosity were chosen as the dependent variables in this model. The optimal formulation of the improved bonded dust suppressant was obtained by analyzing the laboratory experiments and field tests data. The results show that the effective time (≥15d) of the newly developed dust suppressant is 45 times longer than that of pure water (≈1/3d), and 1.875 times longer than that of the comparative dust suppressant (8d), the comprehensive cost is 27.36% lower than that of the similar dust suppressant product for mining enterprises.Implications: This paper presents the research idea of optimizing the bonded dust suppressant based on the improvement of wetting performance. And the paper used response surface method to obtain a wetting and bonding composite dust suppressant formulation. The field test shows that the dust suppressant has good dust suppression performance and economic benefits. This study laid the foundation for the development of new and efficient dust suppressants, and had important theoretical and application values for reducing dust environmental hazards and preventing occupational diseases.

A systematic review of the effectiveness of dust control measures adopted to reduce workplace exposure

The recent increase in silicosis cases in several countries casts doubt on dust control practices and their effectiveness in preventing respirable crystalline silica (RCS) exposure. Apart from silicosis, RCS may lead to other illnesses, health-related quality of life losses for workers and their families, and economic losses for companies. Thus, this systematic literature review examined the effectiveness of interventions employed to prevent exposure to RCS and increase the use of dust control measures. The review used keywords related to dust control interventions to search seven databases. Search results were screened and extracted for synthesis. The narrative synthesis showed the extent of research investment in China. In several designs and combinations, the interventions utilized water, surfactant, foam, and air currents to reduce dust exposure. These interventions offer varying degrees of dust control effectiveness against RCS and respirable dust. Although evidence indicates that interventions significantly decrease dust concentration levels, the control measures in place may not effectively prevent workplace overexposure to RCS. The review found that education and training interventions are employed to improve dust controls and respiratory protective equipment (RPE) use. Also, marketing strategies promote the use of RPE. These interventions can increase the frequency of use of RPE and the adoption of best practice dust control measures. Interventions increase knowledge, awareness, and attitudes about RPE usage and generate positive perceptions while reducing misconceptions. However, the benefits obtained from an intervention may diminish after its implementation, indicating that the interventions may not continually motivate workers to adopt control measures or use RPE.

Wetting behavior during impacting bituminous coal surface for dust suppression droplets of fatty alcohol polyoxyethylene ether

The wetting behavior of droplets during impacting coal surface widely exists in the dust control process. Understanding the effect of surfactants on the diffusion of water droplets on coal surface is critical. To study the effect of fatty alcohol polyoxyethylene ether (AEO) on the dynamic wetting behavior of droplets on bituminous coal surface, a high-speed camera is used to record the impact process of ultrapure water droplets and three different molecular weight AEO solution droplets. A dynamic evaluation index, dimensionless spreading coefficient ([Formula: see text]), is used to evaluate the dynamic wetting process. The research results show that maximum dimensionless spreading coefficient ([Formula: see text]) of AEO-3, AEO-6, and AEO-9 droplets is greater than that of ultrapure water droplets. With the increase of impact velocity, the [Formula: see text] increases, but the required time decreases. Moderately increasing the impact velocity is conducive to promoting the spreading of droplets on the coal surface. Below the critical micelle concentration (CMC), the concentration of AEO droplets is positively correlated with the [Formula: see text] and the required time. When the polymerization degree increases, the Reynolds number ([Formula: see text]) and Weber number ([Formula: see text]) of droplets decrease, and the [Formula: see text] decreases. AEO can effectively enhance the spreading of droplets on the coal surface, but the increase in polymerization degree can inhibit this process. Viscous force hinders droplet spreading during droplet interaction with the coal surface, and surface tension promotes droplet retraction. Under the experimental conditions of this paper ([Formula: see text], [Formula: see text]), there is a power exponential relationship between [Formula: see text] and [Formula: see text].

Spreading Behavior and Wetting Characteristics of Anionic Surfactant Droplets Impacting Bituminous Coal

Spraying water-based materials on the coal surface is a common means of coal dust suppression. There are obvious dynamic wetting behaviors during droplets impacting coal. To explore the spreading behavior and wetting characteristics of anionic surfactant droplets on bituminous coal, three anionic surfactants, which are sodium dodecyl sulfate (SDS), sodium dodecyl sulfonate (SDDS), and sodium dodecyl benzene sulfonate (SDBS), were used for the droplet impact experiment and molecular dynamics (MD) simulation. The results show that the addition of anionic surfactants can promote the wetting behavior of the droplet, and the difference between the head group and the tail group of the surfactant molecules can affect the wettability of the droplet. The dimensionless spreading coefficient shows the rule of SDBS > SDS > SDDS. When the concentration does not reach critical micelle concentration (CMC), the surface tension decreases and the dimensionless spreading coefficient of droplets increases with the increase of concentration. When the droplet concentration reaches the CMC, surface tension is no longer an effective indicator to evaluate the wettability of droplets. The dimensionless spreading coefficient can effectively evaluate the macroscopic spreading wetting behavior of droplets, and it is better than the surface tension. MD simulation results show that the interaction between anionic surfactants and coal molecules can affect the adsorption behavior, and the interaction energy and adhesion work are shown as the rule of SDBS < SDS < SDDS. The results of MD simulation and the impact experiment show that the intermolecular adsorption behavior has a significant influence on the spreading process. The results of MD simulation further explain the results of the droplet impact experiment.

Research on environmental dust pollution: ventilation and dust space-time evolution law of a fully mechanized mining face with 7-m mining height

To investigate the influence of dust produced by multi-dust sources at a fully mechanized mining face with a large mining height on the safety conditions in a coal mine, the No. 22305 fully mechanized mining face of the Bulianta coal mine was considered as the research object in this study, and the space-time evolution of dust was analyzed with computational fluid dynamics (CFD). The wind flow simulation results show that the distribution law of wind flow is mainly affected by the structure of the roadway, and the speed and direction of the wind flow change greatly while passing by corners and through large-scale equipment. The dust generation and pollution diffusion laws with respect to time and space were investigated based on simulations of dust production due to 5-s, 30-s, and 60-s coal cutting, continuous coal cutting, and hydraulic support shifting. The space-time evolution law under different dust-producing times shows the transportation and diffusion procedure of dust under the wind flow; the dust-generated via coal mining and shifting were superposed on the downwind side and a 36-m-long dust belt was formed, which filled the coal mining space; the dust concentration in the breathing zone 120 m downwind the front drum had a dust concentration higher than 1700 mg/m³, this was the crucial dust-proof area, and effective dust reduction methods should be addressed.

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.

Experimental Investigation of the Basic Characteristics and Wettability of Oil Shale Dust

To investigate the influence of basic characteristics of oil shale dust on wet dust removal, oil shales (Longkou oil shales Y₁, Y₂S₂, and Y₂S₁ and Fushun oil shale) with different oil contents, brown coal (M₁), and bituminous coal (M) were selected from a typical mining area in China to test their physiochemical parameters. Their proximate component, chemical structures, surface morphology, and mineral contents were determined. The sedimentation experiments of oil shale dust and coal dust were implemented using three anionic surfactants (AOS, SDS, and SDBS) and a nonionic surfactant (AEO-9), and the wettability of oil shale dust was analyzed and compared with that of coal dust. The experimental results indicate that the moisture content, volatile content, fixed carbon content, and content of oxygen-containing functional groups of oil shale are higher than those of the coal sample; otherwise, contents of ash, SiO₂, aliphatic hydrocarbon, and aromatic hydrocarbon are lower. It can be found that oil shale has semiclosed pores, poor connectivity, a small pore size, a large specific surface area, and a rougher surface, which will lead to poorer wettability of oil shale. The wettability of oil shale can be improved by adding surfactants but is still weaker than that of the coal samples. Anionic surfactants are better than nonionic surfactants in improving the wetting performance. Among them, AOS shows strong wetting ability to oil shale dust. The research results of this paper have an important practical significance for analyzing the wettability of oil shale and controlling oil shale dust.

Experimental Research and Numerical Simulation of Ejector Precipitator in a Fully Mechanized Mining Face

In order to effectively reduce the coal dust concentration in a fully mechanized mining face, this research used laboratory experiment, numerical simulation, and field test to conduct an in-depth exploration of the ejector precipitator installed at the low-level caving coal hydraulic support. Firstly, through the experimental platform in the laboratory, the dust removal effect of the nozzle with different structural parameters was tested, and the 3D particle dynamic analyzer was adopted to verify its atomization characteristics; then, the structural parameters corresponding to the nozzle in the best test results were obtained. Secondly, by using Fluent, the negative pressure flow field in the ejector barrel was numerically simulated. The results indicated that when the pressure of supply water was 12 MPa, the negative pressure value formed in the flow field was the lowest and the inspiratory velocity was the largest, which was conducive to dust removal. Finally, the tests of liquid–gas ratio and dust removal ratio were carried out in a fully mechanized mining face. The results showed that when the nozzle specification recommended by the experiment and the pressure of supply water recommended by the numerical simulation were used, the removal ratios of the total coal dust and the respirable coal dust were 89.5% and 91.0%, respectively, at the measuring point of the highest coal dust concentration. It indicates that the ejector precipitator has a good application effect in reducing the coal dust concentration in a fully mechanized mining face and improving the work environment of coal mine workers.

Effect of spraying on coal dust diffusion in a coal mine based on a numerical simulation

Aimed at effectively controlling coal dust pollution in the mining face of a coal mine, this study first conducted a theoretical analysis and then combined a spraying experiment and a numerical simulation to perform an in-depth examination of the atomizing characteristics and dust suppression performance of a coal cutter external spraying device. Based on the experimental spraying results, the optimal nozzle was determined to be a pressure round-mouth nozzle with an X-shaped core. The characteristics of the spray fields from nozzles of different calibers (1.6, 2.0 and 2.4 mm) at different spraying pressures (2, 4, 6 and 8 MPa) were then analyzed. It was found that the droplet concentration in the spray field increased with increasing spraying pressure and nozzle caliber. The droplet diameter was mainly dependent on the spraying pressure and varied more slowly with increased spraying pressure. At a spraying pressure of 8 MPa, the spray field formed could achieve effective dust suppression; specifically, the droplet concentration in the spray field was mostly more than 15 g/m³, and the droplet size was mainly distributed in the range of 30-100 μm. When using a 2.4 mm caliber nozzle, the dust concentration measured around the coal cutter operator was reduced to 87.21 mg/m³ under a spraying pressure of 8 MPa, suggesting adequate dust suppression.

Experimental Research on Heat Transfer and Strength Analysis of Backfill with Ice Grains in Deep Mines

In deep mines, two urgent problems are a high temperature thermal environment and solid waste. Filling the goaf with slurry mixed with ice grains is an effective way to solve these two problems simultaneously. The thermal property and mechanical property of the ice-added backfill have a great influence on the cooling effect in the deep mine. In this study, an experimental facility for measuring the temperature distribution of ice-added backfill slurry was established, and the temperature of backfill slurry with different proportions was measured. Then, the thermal properties of temperature distribution and cooling capacity and the mechanical property of uniaxial compressive strength of the backfill specimens were analyzed, and the results indicated the following: firstly, the cooling capacity of ice-added backfill specimens is negatively related with the slurry concentration C and is positively related with the ice-water ratio Ω; secondly, the strength of backfill specimens is affected by the slurry concentration C and ice-water ratio Ω by a contrary law compared to the cooling capacity; thirdly, ice-added backfill slurry with an ice-water ratio Ω of 1:1 has the best mechanical property after solidification. The effects of the slurry concentration and ice-water ratio on the thermal and mechanical properties were analyzed, and the results indicated that the optimum proportion of ice-added backfill slurry is a slurry concentration of 74% and an ice-water ratio of 1:1 in the present research range. This study is significant for the deep mine cooling method with ice-added backfill.

Development of Environmental Friendly Dust Suppressant Based on the Modification of Soybean Protein Isolate

Aiming to further improve the dust suppression performance of the dust suppressant, the present study independently develops a new type of biodegradable environmentally-friendly dust suppressant. Specifically, the naturally occurring biodegradable soybean protein isolate (SPI) is selected as the main material, which is subject to an anionic surfactant, i.e., sodium dodecyl sulfonate (SDS) for modification with the presence of additives including carboxymethylcellulose sodium and methanesiliconic acid sodium. As a result, the SDS-SPI cementing dust suppressant is produced. The present study experimentally tests solutions with eight different dust suppressant concentrations under the same experimental condition, so as to evaluate their dust suppression performances. Key metrics considered include water retention capability, cementing power and dust suppression efficiency. The optimal concentration of dust suppressant solution is determined by collectively comparing these metrics. The experiments indicate that the optimal dust suppressant concentration is 3%, at which level the newly developed environmentally-friendly dust suppressant solution exhibits a decent dust suppression characteristic, with the water retention power reaching its peak level, and the corresponding viscosity being 12.96 mPa·s. This performance can generally meet the requirements imposed by coal mines. The peak efficiency of dust suppression can reach 92.13%. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) were used to analyze the dust suppression mechanism of the developed dust suppressant. It was observed that a dense hardened shell formed on the surface of the pulverized coal particles sprayed with the dust suppressant. There is strong cementation between coal dust particles, and the cementation effect is better. This can effectively inhibit the re-entrainment of coal dust and reduce environmental pollution.

Resilient Modulus—Physical Parameters Relationship of Improved Red Clay by Dynamic Tri-Axial Test

As one of the important parameters used in the analysis and design of subgrade, resilient modulus is directly related to the safety, economic and life time of subgrade structure. In this paper, the characteristics of resilient modulus of improved red clay at different additive content were studied through conducting laboratory repeated load tri-axial tests. The influence of stress state, moisture content, compactness, additive types, and content on resilient modulus were analyzed. In addition, the regression analysis of resilient modulus, was carried out referencing three existing prediction models. The results showed that the Andrei model can better fit the resilient modulus of red clay and have a higher determination coefficient. However, the Andrei model and other existing prediction models, reflect only the influence of stress state on resilient modulus, without considering the influence of moisture content, compactness and additive content. Therefore, based on the Andrei model, a comprehensive prediction model, which can reflect the influence of compactness, moisture content, additive content, and stress state on resilient modulus was introduced. Good agreement between the regression results and the measured ones demonstrated the integrative ability of the introduced model.

Behavior of Fiber-Reinforced and Lime-Stabilized Clayey Soil in Triaxial Tests

The beneficial role of combining fiber reinforcement with lime stabilization in altering soil behavior has been established in the literature. However, the coupling effect of their combination still remains unclear in terms of its magnitude and microscopic mechanism, especially for natural fibers with special microstructures. The objective of this study was to investigate the coupling effect of wheat straw fiber reinforcement and lime stabilization on the mechanical behavior of Hefei clayey soil. To achieve this, an experimental program including unconsolidated–undrained (UU) triaxial tests and SEM analysis was implemented. Static compaction test samples were prepared on untreated soil, fiber-reinforced soil, lime-stabilized soil, and lime-stabilized/fiber-reinforced soil at optimum moisture content with determining of the maximum dry density of the untreated soil. The lime was added in three different contents of 2%, 4%, and 6%, and 13 mm long wheat straw fiber slices with a cross section one-quarter that of the intact ones were mixed in at 0.2%, 0.4%, and 0.6% by dry weight of soil. Analysis of the derived results indicated that the addition of a small amount of wheat straw fibers into lime-stabilized soil improved the intensity of the strain-softening behavior associated with mere lime stabilization. The observed evidence that the shear strength increase brought by a combination of 0.4% fiber reinforcement and 4% lime stabilization was smaller than the summation of the shear strength increases brought by their presence alone in a sample demonstrated a coupling effect between fiber reinforcement and lime stabilization. This coupling effect was also detected in the comparisons of the secant modulus and failure pattern between the combined treatment and the individual treatments. These manifestations of the coupling effect were explained by a microscopic mechanism wherein the fiber reinforcing effect was made more effective by the ways in which lime chemically stabilized the soil and lime stabilization development was quickened by the water channels passing through the surfaces and honeycomb pores of the wheat straw fibers.