Dust Control Efficiency Research Articles

Study on the influence of combined utilization of air-fog curtain on fully mechanized face

To address the ambiguous regulations for dust control and removal in the joint use of air curtain and fog curtain, this study developed a multi-field coupling model of airflow, dust, and droplets. By incorporating the spraying method into both traditional ventilation technology and air curtain technology, this study comparatively analyzed the dust control and removal efficiencies of these two methods under various ventilation conditions in tunnels. The spray experiment and simulated result indicated a maximum relative error of 19.9%. The simulation results demonstrated that the use of traditional ventilation technology resulted in significant dust contamination in the rear and top regions of the tunnel. Although the dust pollution was ameliorated when the pressure-suction ratio was 1.25, the dust control effect remained unsatisfactory, with the pollution distance extending 37.0m. After implementing air curtain technology, the airflow generated a spiral air curtain due to the wall attachment effect, effectively confining the majority of dust to the heading face area. When the axial flow ratio was 45%, the dust concentration at exceeding 13.0m from the heading face dropped to blow 1.0mg/m3, significantly reducing health risks for operators.

Investigate the optimum design of atomizing nozzles for coal dust suppression by using multifactor level response surface methodology

Mechanized coal extraction generates substantial dust, adversely affecting the physical and mental wellbeing of underground workers and degrading the operational environment. To address the limitations of traditional spray systems, which often suffer from poor atomization effects and limited ability to withstand wind interference, the innovative vortex atomizing nozzle has been developed specifically for dust suppression. This advanced solution was rigorously tested through detailed numerical simulations and comprehensive experimental investigations. These studies focused on examining the impact of critical parameters, including the velocity at the airflow director's exit, the angle of the exit hole, and its radius, on the efficacy of dust suppression. Findings highlighted the paramount importance of the airflow director's exit velocity in enhancing dust removal, with the exit hole's radius having the least impact. Optimal conditions for dust suppression were identified as an airflow director exit velocity of 20 m/s, an angle of 60°, and a radius of 0.6 mm. Field validations under these optimum parameters demonstrated unparalleled dust control efficiency, achieving a reduction in coal dust concentration exceeding 90 %. This apparatus offers a highly effective, user-friendly solution for comprehensive coal dust management across various mine locations.

Study of highly efficient control and dust removal system for double-tunnel boring processes in coal mines

To reduce coal dust pollution during double-tunnel boring processes in coal mines, an efficient control and dust removal system has been established and studied by combining theoretical analysis, experimental investigations, numerical simulations, and on-site measurements. The self-developed new spiral air curtain generator can quickly form multiple axial and radial dust control air curtains that cover the entire tunnel section. When combined with a wet-type dust removal fan, they form an efficient dust control and elimination system for double-tunnel boring in coal mines. The airflow and dust control effects of the highly efficient dust control and removal system, single press-in ventilation, and ventilation with dust removal fans were compared. The results show that with the proposed system, the dust concentrations in the boring tunnel and supporting tunnel can be controlled within 18 and 15 m distances from the working face, respectively. The dust control efficiency is increased by 82 % and 85 %, respectively. Hence, the dust concentrations in the coal mine are effectively reduced.

Research on the optimal parameters of wind curtain dust control technology based on multi factor disturbance conditions

For the current coal mining surface air curtain dust control technology to control the low efficiency of the problem of dust, numerical simulations were used to study the effects of three factors on dust control efficiency: air outlet width, air volume, and placement angle, to improve the effectiveness of its application. The results show that the air outlet width and the air volume have a significant effect on dust control efficiency, while the placement angle has less of an effect. As the air outlet width increases from 50 mm to 250 mm, the peak wind speed of the wind curtain gradually decreases and the dust removal efficiency first increases and then decreases. As the air volume increases from 30 m3/min to 150 m3/min, the peak wind speed of the wind curtain increases significantly and the dust control efficiency first increases and then decreases, changing significantly. As the angle of placement increases from 5° to 25°, the wind speed of the wind curtain essentially remains the same, and the dust removal efficiency increases slightly before decreasing. The optimum performance for the wind curtain in controlling dust is achieved when the air outlet width is 150 mm, the placement angle is 10°, and the air volume is 90 m3/min. Field tests show that applying this technology has resulted in a significant reduction in the dust concentration from 857.26 to 68.83 mg/m3 in the working area of the shearer driver, representing a dust control efficiency of 92%. This technology has greatly improved the working conditions in coal mining areas.

Investigations of the effects of two typical jet crushing methods on the atomization and dust reduction performance of nozzles

Single-fluid nozzles and dual-fluid nozzles are the two typical jet crushing methods used in spray dust reduction. To distinguish the atomization mechanism of single-fluid and dual-fluid nozzles and improve dust control efficiency at the coal mining faces, the atomization characteristics and dust reduction performance of the two nozzles were quantitatively compared. Results of experiments show that, as water supply pressure increased, the atomization angle of the swirl pressure nozzle reaches a maximum of 62° at 6 MPa and then decreases, but its droplet size shows an opposite trend with a minimum of 41.7 μm. The water supply pressure helps to improve the droplet size and the atomization angle of the internal mixing air–liquid nozzle, while the air supply pressure has a suppressive effect for them. When the water supply pressure is 0.2 MPa and the air supply pressure reaches 0.4 MPa, the nozzle obtains the smallest droplet size which is 10% smaller than the swirl pressure nozzle. Combined with the dust reduction experimental results, when the water consumption at the working surface is not limited, using the swirl pressure nozzle will achieve a better dust reduction effect. However, the internal mixing air–liquid nozzle can achieve better and more economical dust reduction performance in working environments where water consumption is limited.

Effects of surfactant adsorption on the surface functional group contents and polymerization properties of coal dust

In order to better explain the wetting and polymerization mechanism between surfactant and coal dust, the effects of surfactant adsorption on the surface physicochemical properties of coal dust were investigated based on the infrared spectroscopy, zeta and dust control efficiency experiments. The results showed that compared with nonionic surfactant, anionic surfactant was more easily adsorbed on coal dust surface, while the combination of anionic-nonionic surfactants made surfactant molecules more easily adsorbed on the surface of coal dust, especially compound surfactant (B+D). With the surfactant adsorption increased, the hydrophobic functional group content and absolute potential value of coal dust decreased. For example, the surface potential and hydrophilic functional group content of coal dust adsorbing the compound surfactant (B+D) was enhanced by 43.92%, 165.7% than that of single surfactant (B). Additionally, it was verified that surfactant adsorption capacity could not be used as a critical factor to optimize surfactants applied to enhance the solution wettability. In field tests, the developed compound surfactant (B+D) enhanced respirable dust and total dust control efficiencies by 41.86% and 40.16%, respectively, compared to that of water spray. This study was conducive to choose surfactants to improve coal dust control performance of the aqueous solution.

Research on airborne air curtain dust control technology and air volume optimization

The mechanization ratio of coal mining faces has reached more than 90%. However, the coal dust pollution in the fully mechanized mining operation is still an urgent problem to be solved, especially in the working area of the shearer driver. Therefore, an airborne air curtain dust control technology is proposed. The air current migration and dust pollution diffusion in a working face under various air volumes were studied using CFD numerical simulation technology. It was found that two high-speed air curtains form at the shearer driver’s operating position, while a trapezoidal full-section clean air chamber formed at the sidewalk, which could effectively block the dust engendered by the coal cutting drum. The air curtain with 90 m3/min air volume has the best dust control effect in this area, and the diffusion distance of high concentration dust is reduced by 90 m. After applying this technology in the field, the dust concentration in the shearer driver’s working area was reduced to 79.23 mg/m3, and the dust control efficiency was 83%. It is proved that the technology can reduce the dust concentration in the whole tunnel, especially at the shearer driver operating point. This work provides valuable information for dust prevention and control in a working face.

Effect of bubble cutting on spray characteristics and dust control performance in the effervescent atomization

Effervescent atomization performance depends on the bubble size inside the mixing chamber, consequently influencing the spray dust control performance. This paper proposes an optimization of atomization quality and dust control performance by incorporating a bubble cutter in the atomizer mixing chamber. The effects of the bubble cutter aperture on spray characteristics and flow characteristics were experimentally investigated under different operating conditions. Experimental results showed that Sauter means diameter (SMD) decreases with increasing injection pressure and gas-liquid mass flow ratio (GLR). Furthermore, SMD initially increased and then decreased by reducing the aperture of the bubble cutter from 500 µm to 80 µm. In particular, high injection pressure (Pi =0.6 MPa) and low gas-liquid mass flow ratio (GLR=0.09) strengthened the effects of the bubble cutter aperture on SMD. Moreover, bubble cutter causes a contiguous concentrated droplet size distribution, but it has little effect on droplet velocity. Ultimately, the optimal bubble cutter aperture on the efficiency of respirable dust control efficiencies was theoretically calculated. The dust control efficiency is a maximum at the bubble cutter with an aperture of 230 µm for the effervescent atomizer in this paper. Spray dust control efficiency reaches 93.15 %, which effectively solves the problem of high dust concentration pollution in the mechanized working environment.

Dust control efficiency improvement

High dustiness of operating space in coal mines and active methane emission detains faster driving of coal production and weakens competitive ability of coal mines. From the physical research of inertia movement of rotation liquid drops, the mathematical model of the circulation in the gas environment is constructed to develop more effective dust catching techniques. It is proved that the equation of fluid whirl diffusion in motion of a liquid drop along a spiral line is identical to the equation of thermal conductivity with dispersion coefficient of liquid drop rotation energy. It is confirmed that circulation of liquid drops, both in super Stokes and Stokes flows, enlarges the relaxation time owing to reduction in aerodynamic drag factor of the gas environment, conditioned by the increase in the effective value of the Reynolds number with the increased rotational velocity of liquid drops. The averaging of the aerodynamic drag factors of liquid drop movement allows using the obtained formulas for calculating  hydraulic vortex coagulation in a wide range of the Reynolds number, 1 < Re < 104. For enhancing energy of high-head hydraulic dedusting, the mathematical model and technology of hydro-vortex dust collection are proposed. The similarity criteria and indicators of the hydro-vortex dust collection efficiency are obtained. The experiments prove that dedusting efficiency depends not on the fluid flow rate but on the energy of dynamic head of liquid drops and on their dispersion degree. The hydro-vortex dust collection technique allows enhancing the dust control efficiency up to 99 % owing to the increased rotational velocity of liquid drops.

Partially enclosed air curtain dust control technology to prevent pollution in a fully mechanized mining face

To mitigate the effect of coal dust on the health of workers and the work environment, a new type of partially enclosed air curtain device for dust control is proposed; its dust control effect was numerically simulated in this study. The results show that after the dust control air curtain device has been turned on, a partially enclosed dust control air chamber is formed in the shearer driver’s working area. Although the air chamber affects the air flow velocity and diffusion trajectory at the 1.4–2.0 m height in the coal mining area, it does not affect the safe operation of the entire tunnel ventilation system. Simultaneously, the air chamber prevents the dust generated at the dust source from entering the shearer driver’s working area; with a dust control efficiency of 61.8%, the quantity of dust is successfully reduced. The diffusion of particles to the downwind side reduces the diffusion distance of ultra-high-concentration dust by approximately 35 m. This technology effectively improves the working environment for coal mine operators (particularly for shearer drivers), reduces risks, and provides operators with a safe and clean production environment. Moreover, this technology can provide new ideas for dust prevention and control methods in other restricted spaces.

Suppression Effect of Waterborne Polymer on Soil Used for Backfilling at Construction Site

To improve the dust control efficiency of soil for backfilling at construction sites, a novel waterborne polymer was used as a dust suppressant, and the dust emission model was created to control the effect of a large-scale field. The results showed that the waterborne polymer could improve the water retention efficiency of soil for backfilling, and the average water content was 2.18 times that of the watered samples, significantly delaying water evaporation. The compressive strength of soil for backfilling reached 4.91 MPa and improved the wind erosion resistance of the consolidation layer, effectively resisting wind damage. At a construction site, the waterborne polymer was sprayed on soil for backfilling, and the concentration of PM10 was reduced by 67.41%, confirming the effectiveness for large-scale utilization.

Numerical simulation-based development and field application of trapezoidal air curtain

Air curtains have rectangular lateral shape in most of the current studies. Since they often fail to meet the dust control requirements of the special-shaped dust control area formed by space constraints and other factors, this problem can be solved by alternative development of trapezoidal air curtains (TAC). The core technology of such air curtain aimed at a special-shaped dust control area was proposed. Using numerical simulation via Fluent, the structural optimizations of air curtain unit were realized. The air supply effects of divergent and contracted TAC were compared, with the new calculation model of air volumes, which results were applied to the special-shaped dust control area. Numerical simulations verified by field application proved that under higher dust concentration conditions, the mixed air curtain case with added TAC outperformed the fully rectangular case by higher dust control efficiency (97.75% versus 96.16%), saving about 40.4% air volume.

Dust Control Technology in Dry Directional Drilling in Soft and Broken Coal Seams

High rate of dust generation and serious dust diffusion in dry directional drilling in soft and broken coal seams (SBCS) have long been critical problems in the mining process. To solve these problems, in this study, a dust hood was designed and applied to realize non-contact dust control in drilling holes. The optimal performance of the dust hood was achieved when different technical parameters, including the gap width between the dust hood and the drill pipe, the air-slot width of the sealing device, the slag discharge pressure, and the air curtain pressure were controlled at 2 mm, 0.2 mm, 0.3 MPa, and 0.5 MPa, respectively. As a result, the dust concentration was reduced from 540 mg/m3 to 15 mg/m3, with dust control efficiency reaching 97.2%. The in situ test results confirmed good dust control effects, as the dust control efficiency reached 98.3% after using the dust hood.

Insight into dust control performance of a reverse circulation drill bit using multiphase flow simulation

ABSTRACT A feature of reverse circulation pneumatic down-the-hole (DTH) hammer drilling system is its ability to reduce the emission of respirable dust which is known to be harmful to drilling workers and equipment. The enhanced dust control performance of the drilling system requires better understanding and insight into the airflow behavior at the bottom of the borehole. To investigate the transportation and distribution of cuttings under various drilling parameters, and to evaluate the dust control performance, we conducted a series of simulations using computational fluid dynamics (CFD) multiphase modeling. Finite volume analysis was performed on a reverse circulation drill bit with an optimized structure reported in a previous study. The results show that increasing the input airflow rate can directly improve the dust control efficiency. The rising value in terms of cuttings feed concentration, rate of penetration (ROP), particle diameter, and specularity coefficient would decrease the dust control performance. Furthermore, the characteristics of the cutting distribution vary with the operating parameters and demonstrate the multiphase flow pattern in the RC-bit. This work may provide instructive insights into cutting transportation under various drilling parameters commonly considered in the drilling process and promote the development of dust suppression with efficient drilling operations.

Air curtain dust-collecting technology: Investigation of factors affecting dust control performance of air curtains in the developed transshipment system for soybean clearance based on numerical simulation

Transshipment of compacted soybean is characterized by labor-intensive processes, long operating times, and a great amount of dust that cannot be collected by sealed devices. This dust significantly reduces air quality of the workshop and represents a great threat to human health. Solving this problem has been a great challenge in the soybean storage industry. For this reason, in the present study the concept of a transshipment system for soybean clearance was proposed. This system can simultaneously achieve real-time transshipment of falling materials and air curtain control of fugitive dust. The main factors influencing the performance of the air curtain dust control system were investigated using numerical simulation, and the effects of the exhaust-to-pressure ratio K and air curtain outlet velocity V on dust control efficiency were determined. Results showed that the width of the dust-collecting paths increased with increasing K and V values. We also found out that dust-escape paths were mainly concentrated in the transition height between the complete air curtains and local air curtains. At the beginning of the process, dust control efficiency rapidly increased and the increment rate became slower as K increased. When K = 1.5 and V = 5–6 m/s, dust control efficiency reached values up to 95.54–96.27%. Based on numerical simulation results, the prototype transshipment system for soybean clearance was developed, and the effectiveness of air curtain dust control was validated via smoke tracing experiments. After the application of the developed system, occupational lung disease can be significantly reduced, and transshipment efficiency per clearance can be enhanced by approximately 67% (about 50,113￥ can be saved in terms of energy consumption and labor resources). An extra granary can be saved after using the newly developed system for 36.5–52.1 clearances.

Numerical simulation and experimental study of vortex blowing suction dust control in a coal yard with multiple dust production points

The dust removal efficiency of the existing dust control technologies for coal yards involving multiple dust production spots is low and cannot satisfy the requirements stipulated by the existing standards. This paper proposes a new type of vortex blowing suction dust control technology. The principle of dust control was examined through numerical simulations. The dust control efficiency of the single suction and vortex blowing suction methods was compared experimentally. The results indicated that most of the dust particles were collected by the vortex, and they moved in a spiral from the bottom to the top. The highest vortex airflow performance corresponded to an optimal blowing ratio of 4.814. The experimental comparison indicated that the dust removal performance of the vortex blowing suction technique was better. Specifically, for the formal and latter techniques, dust removal efficiency was 93.25% and 41.19%, and dust escape rate was 6.31% and 46.60%, respectively.

Field Testing of Roof Bolter Canopy Air Curtain Operating Downwind of the Continuous Miner

Roof bolter canopy air curtains (CACs) are gaining acceptance as a respirable dust control device that can provide roof bolter operators with protection from overexposure to respirable coal mine dust. Both lab and field studies on the effectiveness of roof bolter CACs have been published. Field studies have shown the effectiveness to be variable. However, in all previous field studies, none has been conducted when the roof bolting machine operates downwind of the continuous miner (CM)—a scenario for which the CAC was designed to provide respirable dust control. This study, performed by researchers from the National Institute for Occupational Safety and Health (NIOSH), was conducted to test a CAC on a roof bolter machine operating downwind of the CM. The results of testing demonstrated that the roof bolter CAC can effectively provide respirable dust protection for roof bolter operators with dust control efficiencies ranging from 11 to 40%.

The development of an optimized evaluation system for improving coal dust suppression efficiency using aqueous solution sprays

Coal dust has been a serious hazard for the global coal mining industry, and water spray has been commonly used for coal dust suppression. To effectively optimize the dust control efficiency of the aqueous solution, an evaluation system of the solution wettability was investigated and constructed. Different static wetting features (surface tension, contact angle, spreading work, sink time, capillary rise weight and drop penetration time) and dust control efficiency of the solution were studied under different surfactant concentrations. The relationship between static wetting features and an evaluation system was analyzed by the analytic hierarchy process. Additionally, the correlations between static wetting parameters and dust suppression efficiency were investigated. The results indicated that the surfactant concentrations causing the optimal values of different static wetting parameters were inconsistent, and it is not suitable for optimizing the solution wettability based on a single wetting parameter. The weight coefficients of surface tension (0.3265) and sink time (0.2383) on the evaluation system were better than that of other parameters. Additionally, three wetting parameters (surface tension, sink time and spreading work) that have the best correlations with dust control efficiency were used as simple and efficient evaluation indexes to construct the evaluation system. Based on the developed evaluation system, the optimal surfactant concentration was determined.

Investigation of the dust control performance of a new transverse-flow air curtain soft-sealing system

On account of certain technological requirements, it is difficult for some industrial processes that generate dust to be sealed in a fixed pattern and ventilated for dust discharge, mainly automatic welding, pressure casting, wood processing, and crop production, which has become a significant bottleneck in dust control. The present study developed a transverse-flow soft-sealing dust control system, in which four novel air curtain generators were arranged in a square pattern within the region where dust was generated to create end-to-end planar transverse-flow air curtains and achieve soft sealing. The air suction inlet was placed centrally above the area where dust was generated; under the suction airflow, the dusty air was gradually diluted and driven away to effectively suppress dust escape. The flow field characteristics in the area where dust was generated and the performance of the developed sealing system in controlling fine smoke dust were qualitatively analyzed using a tracing experiment with smoke dust. Tracing experimental results on leaf powder qualitatively reveal directional dust control of large dust particles. Moreover, the dust control efficiency was evaluated under different conditions to quantitatively investigate the effects of air curtain outlet velocity, exhaust-to-pressure ratio, and jet angle. The results show that with a greater air supply and air suction rate, the airflow exhibited a more obvious entrainment effect and stronger dust exhaust and discharge, and simultaneously, the formed tracing smoke column had a clearer boundary. At an air curtain outlet velocity of 6.27–8.39 m/s and a corresponding air supply rate of 17.00–22.57 m3/min, a stable air curtain was formed, which achieved remarkable dust control at an exhaust-to-pressure ratio of 0.8–1.0. With an increase in the air curtain jet angle, the dust control efficiency of the system first increased but subsequently decreased. In the present study, the appropriate air curtain jet angle was 10–20° for the developed soft-sealing system. In conclusion, when the air curtain outlet velocity, exhaust-to-pressure ratio, and jet angle were 6.27 m/s, 0.6, and 15°, respectively, the dust control efficiency of the developed soft-sealing system reached 92.6%.

Field study results of a 3rd generation roof bolter canopy air curtain for respirable coal mine dust control

A 3rd generation roof bolter canopy air curtain (CAC) has been developed and constructed by J.H. Fletcher & Co., Inc. As with the previous generation of the CAC, this design uses the principle of providing uniform airflow across the canopy area as recommended by the National Institute for Occupational Safety and Health. The new modifications include a plenum that is constructed of a single flat aluminum plate, smaller-diameter airflow openings, and a single row of perimeter nozzles designed to prevent mine air contaminated by respirable dust from entering the CAC protection zone. Field testing was conducted on this new 3rd generation design showing reductions in coal mine respirable dust exposure for roof bolter operators. Dust control efficiencies for the CAC for the left bolter operator (intake side) ranged from approximately 26%–60%, while the efficiencies for the CAC for the right bolter operator (return side) ranged from 3% to 47%.