Dust Reduction Efficiency Research Articles

Numerical simulation of the dynamic wetting of coal dust by spray droplets

The dust particles generated during coal mining and processing are generally removed by spray dust reduction. The dynamic process via which spray droplets wet and wrap coal dust can directly affect the spray dust reduction efficiency. Here, we analyzed the contact wetting and wrapping process of dust particles by droplets under different particle size ratios and different initial droplet velocities. The results show that the larger the particle size ratio θ of the droplets and dust particles, the greater the variation in the dimensionless spreading coefficient. When the particle size ratio is more than 2, the droplets can completely wrap the coal dust particles. If the initial velocity is too small, the droplets will shrink and return to form a single sheet after coming into contact with the coal dust. With increasing velocity, the dimensionless spreading coefficient increases rapidly, and the coal dust is moistened and rapidly wrapped. By experimenting with various spray atomization characteristics, when the spray pressure is 6 MPa，the droplet size distribution in the spray field accounting for the highest proportion is 10 μm. Under the optimized parameters, the settling efficiency of respirable dust at each measuring point of mine return air duct reaches 86.2% on average.

Influence of air inlet distance on coal dust pollution characteristics in working environment during tunneling based on CFD method

Coal dust is one of the pollutants generated during the coal tunneling process. However, the air inlet distance will increase with the advancement of the working face, resulting in the redistribution of the air flow field, further affecting the pollution characteristics of coal dust. This effect weakens the effectiveness of dust removal equipment. Therefore, transient CFD modeling was used to study the influence of air inlet distance on air flow, dust migration distance, and dust concentration distribution in the breathing zone and achieve the highest dust reduction efficiency. Results showed that the air flow formed two reflows in the tunnel under forced ventilation. When the air inlet distance increased from 6.0 m to 8.4 m, wind flow diffusion distance (along the return side coal wall) Lp and air inlet distance d can be described as Lp = 34.272–7.108d + 0.570d2 . Furthermore, the dust diffusion time to the outlet increased from 35 s to 40 s, and the dust migration distance increased as a power function of air inlet distance. Meanwhile, the dust migration distance in the first 10 s accounted for 45–50% of that for the entire time period. In addition, the dust migration distance decreased only after 25 s, and the dust concentration in the return side breathing zone gradually increased. Finally, air curtains and dust removal fans were recommended for dust control, and the dust in the daily tunneling process can be effectively controlled when da = 15.0 m and de = 8.0 m. The dust reduction efficiency was 85.29–99.90%. The research results provide technical support for the dust outlet installation of dust extraction fans during tunneling and guidance for dust control in the similar working environment.

An Experimental Investigation of the Impact of Surface Tension and Viscosity on the Atomization Effect of a Solid Cone Nozzle

To investigate the influence of surface tension and viscosity on the atomization performance of solid cone nozzles and improve their dust reduction efficiency in industrial and mining enterprises, this study employed a self-built PDPA dust-fog coupling experimental system to explore the effects of different surface tension and viscosity solutions on atomization performance from three aspects: axial, radial, and fog field distribution. The experimental results indicate that compared with surface tension, surface tension has a greater influence on droplet size and velocity in the axial direction. In the radial direction, increasing surface tension and reducing viscosity within a certain range can make the droplet size and velocity distribution more uniform. Additionally, surface tension and viscosity significantly affect the fog field distribution. It was found that a decrease in surface tension can result in a closer proximity of the droplet velocity and size expansion area to the nozzle, while an increase in viscosity can lead to a more prolonged stable area. Furthermore, optimizing the surface tension and viscosity can significantly enhance the efficacy of dust reduction for respirable dust. Consequently, the application of the aforementioned atomization principles to regulate the fog field characteristics of solid cone nozzles can effectively mitigate dust in the production process and augment the dust reduction rate of industrial and mining enterprises.

Study on dust reduction characteristics and mechanism of softened mine water

ABSTRACT At present, the intensity of coal mining is increasing gradually, and the concentration of coal dust in roadways under integrated mining is high, making it difficult to control. As a result, the mechanism and technology of dust reduction remain one of the key points of efficient mining research. To study the influence of physical and chemical properties of mine water on dust reduction efficiency, this work used spray dust reduction experiment system to assess dust reduction efficacy of several solutions at 3～6MPa, and the differences in the dedusting characteristics and atomization characteristics of each group of each solution were analyzed. The result demonstrates that softened mine water’s surface tension and contact angle fall significantly, spray droplet size lowers, and fog dispersion becomes more symmetrical. When compared to before softening, the dust reduction efficiency of softened water (SW) is 72.52% for total dust and 69.74% for respiratory dust, considerably improving the working environment of underground coal miners and optimizing mining efficiency.

Study on dust suppression performance of a new spray device during drilling and blasting construction in the metro tunnel

In order to solve the problems of excessive blasting dust concentration and portal pollution in a metro tunnel of a central urban area, a new spray device is discussed and its related parameters are studied in this paper. Through field sampling and an experimental spray dust settling platform, the particle size distribution characteristics of the tunnel blasting dust and the applicability of the nozzle are analysed. The tunnel and spray device are simulated by CFD software, and the variation laws of the droplet field concentration, velocity and particle diameter under different different incident angles, pressures and wind velocity are studied. The dust suppression performance of the new partition spray device is tested through field application. The results show that the droplet field generated by the spray device can effectively cover the whole section of the tunnel. At the same angle of incidence, the high concentration area first increases and then decreases in the direction away from the device, and the maximum concentration section gradually shifts away from the spray device. With the increase of the incident angle, the growth and attenuation trend of the high concentration region gradually flattens. The best incident angle for partitioning and dust reduction is 30°. When the nozzle pressure is set to 8 MPa, the parameters such as concentration, velocity and particle size distribution are the most appropriate. The effect of the air velocity at the air outlet on the characteristics of the droplet group generated by the device is not obvious. The field application shows that when the spray device is used, the dust reduction efficiency of respiratory dust and total dust at each measuring point is higher than 70 %. Compared with the original dust control measures, the average dust reduction efficiency is increased by 30 %, which can effectively improve the working environment of constructors in the tunnel and prevent the outward diffusion of dust.

Preferential binding effect of cocoa powder on fried donuts through the electrostatic coating method

SummaryDonuts are the snack food which are coated with powdered seasonings to increase flavour and shelf life. In this regard, electrostatic coating is being developed for efficient coating method and to overcome uneven coating and dust production. During electrostatic coating, charged powder particles produce even coating on target surface. Electrostatic coating of cocoa powder was carried out at high voltage (0–20 kV) and the results were compared to manually coated fried donuts. Cocoa powder particles had irregular polygonal and polyhedral shapes with an average particle diameter (18.12 ± 0.91 μm). The values of adhesion, dust reduction and transfer efficiency were higher at 15 kV and lower values at 0 kV. Coated sample at 15 kV showed the lowest change in weight loss (05.99%) during the storage. Due to an even coating of cocoa powder at 15 kV, donuts exhibited pleasant taste, uniform and dark brown colour. While, shelf life of coated donuts at 15 kV lasts up to 29 days as compared to other samples. It can be concluded from the results that the electrostatic coating of donuts with cocoa powder was best at 15 kV with higher transfer efficiency, adhesion and consumer acceptability.

Synthesis and performance of a novel high-efficiency coal dust suppressant based on biopolysaccharide-xanthan gum

The coal production process produces a lot of dust, which pollutes the environment and threatens the occupational health of workers. Although many dust suppressants for coal dust control have been developed, the implementation of current dust suppressants does not meet the requirements due to their poor foaming, stability, and wettability effects. In our current study, the effect of xanthan gum (XG) on the properties and foaming ability of the composite surfactant ALAP has been investigated. The research shows that with the increase of CXG, the foaming volume of the solution increases by nearly 30% on average. The liquid-carrying capacity, the foaming delay period, and the liquid-draining half-life of the foam are also improved, while the performance of wetting coal dust decreases. Compared with traditional water-soluble polymers, XG molecules have a special double helix structure and plenty of polar functional groups, which can form a stable 3D network system with surfactant molecules. XG molecules could not only effectively improve the foaming performance of low-concentration ALAP, the liquid-carrying ability, and the stability of foam, but also reduce the burst rate of the bubbles. In our investigations, the dust reduction effect of the XG/ALAP systems have been comprehensively evaluated through the field application of the heading face. The dust reduction efficiency of total dust and respirable dust can reach nearly 90% and 85% respectively, which is 2.2 times and 2.5 times higher than that of water spraying. The XG/ALAP systems also effectively improve the visibility of the working surface. With the consideration of all the above-mentioned factors, the composition range of the high-efficiency dust suppressant is obtained as: 0.7‰≥CXG ≥ 0.5‰ and 4‰≥CALAP ≥ 3‰.

Experimental research on atomization process and dust reduction performance of swirl pressure nozzle.

In this study, experimental studies on atomization process and dust reduction performance of four swirl nozzles with different inlet/outlet diameter ratio (D) were performed. The results of the atomization process study of the nozzle show that with the increase of D, the droplet breakup range of the spray field is gradually increasing, but the droplet breakup intensity of the spray field is gradually decreasing. At D = 3.33 and 3.63, droplet breakup occurs mainly in the range of 0-4mm in the strong turbulent region. At D = 3.75, droplet breakup occurs mainly in the range of 0-2mm in the strong turbulent region. At D = 3.96, droplet breakup occurs mainly in the range of 0-1mm in the strong turbulent region. Droplet breakup in the spray field at D = 3.33 and D = 3.67 was better than that at D = 3.75 and D = 3.96. From the dust reduction experimental results, the dust reduction efficiency increases and then decreases with the increase of D. The dust reduction efficiency is highest among the four nozzles at D = 3.67. Based on the dust reduction curves of four different D of nozzles, it is predicted that the optimal dust reduction condition will be achieved at D of 3.60, which provides a reference for the design and optimization of nozzles.

Research on dust suppression technology of fully mechanized mining workers by section control of airflow

Taking the 20106 fully mechanized mining face of Wangjialing coal mine as the engineering background, this paper analyzes the action relationship between the dusty air flow and fresh air flow formed by the coal caving and dust production of the fully mechanized mining machine, and through the establishment of mathematical model and field test, the best matching parameters of the relative position between the axial and radial air outlet of the segmented air control and dust control system and the head-on of the working face are obtained. The field application shows that after the optimization of the parameters of the wind and dust control system, the dust reduction efficiency of the total dust concentration at the driver’s position and each transfer point can be increased by about 80%, and the dust reduction efficiency at the driver’s position can reach 91.8%. The high concentration dust is controlled within 2m in front of the work, which can prevent the escape and diffusion of dust to the rear, and the working environment is significantly improved.

Research and application of dust reduction technology for supersonic spiral an atomizers

To solve the problem of dust pollution, a new type of ultrafine spiral atomization nozzle with a small droplet size and strong dust reduction ability was developed according to the principle of air-water spray and the generation law of vortex airflow. Numerical simulation software is used to simulate the velocity and streamline distribution of the air flow field inside the air flow director under different parameters, and the best spiral effect parameters of the air flow director for the directional air flow are obtained. Set up an experimental platform to determine the performance parameters of the ultrafine spiral atomization nozzle and compare the dust suppression performance of the ultrasonic dry mist to study its dust suppression performance. The results show that when the angle between the spiral trough and the tapered wall is α = 30° and the ratio of the diameter of the top surface of the air flow director to the height d = 1.25, the air flow director has the best directional air flow spiral effect. When the air supply pressure of the supersonic nozzle and spiral groove is 0.4 MPa, the atomization angle of the supersonic spiral atomizer is the largest, the D90 of the droplet group is 19.7 μm, and the comprehensive atomization performance is the best. At this time, the total dust reduction efficiency is 92.18%, which is better than the ultrasonic dry mist for dust suppression and dust reduction. The efficiency is 81.97%. When the full-section spiral pneumatic dust control system with an ultrafine spiral atomization nozzle as the core is applied to the 06 return airway of the Mindong No. 1 Mine, the dust reduction efficiency of the respirable dust is 88.8% ~ 91.58%.

Study on dust migration law and spray dedusting technology in parallel double belt transportation

To effectively solve the problem of dust pollution caused by the parallel double-belt transportation of coal in a coal preparation plant, taking the Huangyuchuan coal preparation plant as an example, a numerical model of the air flow-dust distribution was established by means of simulation. The flow lines between the strips of tape and the tail of the tape machine will gather, and there will be backflow on the right side of the 3001 tape and left side of the 3002 tape. Under the action of wind current, most of the dust particles larger than 10 μm are distributed in the range of 0–5 m on both sides of the tape; dust particles smaller than 10 μm spread to the entire preparation workshop. Combined with field test verification, dust pollution is mainly concentrated at the guide trough, the feed inlet, the rear of the machine, and the joint of the belt corridor. Based on this, a targeted spray dust reduction treatment plan is proposed. By measuring the dust concentration before and after the treatment of dust-polluted areas, it is proven that the dust reduction efficiency of this plan can reach more than 90%.

Research on Dust Migration Law and Dust Reduction Efficiency in the Operation Process of Tunnel Boring Machine

At present, most dust reduction methods do not consider the difference of dust particle diameter distribution along the tunnel and the applicability of droplet group under different parameters. In order to improve the dust reduction efficiency of each section, the particle size analyzer was used to analyze the dust samples of each section along the tunnel, and the migration law of dust of each particle diameter during the construction of Tunnel Boring Machine (TBM) was studied. The dust falling efficiency of droplets with different particle diameter under different sets of parameters was determined by the experimental platform built by ourselves. Research indicates: along the axis of tunnel, the farther away from the face of the tunnel, the higher the peak volume frequency of dust, and the distribution range of dust gradually narrowed to the direction of small particle diameter. The settling distance of dust with different particle diameter is quite different, and the content of small particle diameter dust shows an upward trend as a whole. The reduction efficiency of dust first increases and then decreases with the particle diameter, and there is particle diameter of the optimum dust reduction efficiency under the action of the same droplet group. The calculation formula of the air and water flow of the air-water nozzle and the particle diameter of the optimum dust reduction efficiency are put forward. This research can provide basis and guidance for multistage dust reduction and nozzle parameter setting in different sections of the tunnel.

Influence of swirl intensity on atomization characteristics and dust-reduction using pressure swirl nozzle

ABSTRACT Pressure swirl nozzles are widely applied in various mineral industries, and their excellent spray performances have been found to be directly related to dust removal results. In this study, in order to examine the influencing effects of the swirl intensity levels of pressure swirl nozzles on atomization characteristics and dust-reduction efficiency, five spiral guide grooves were added for the purpose of improving the quality of the atomization and dust control. The swirl intensities of pressure swirl nozzles were first theoretically investigated using the established models. The effects of the swirl intensities on the atomization angles and distributions of the atomization sizes were comparatively studied using theoretical calculations, numerical simulations, and experimental methods. A dynamic wind tunnel was built in order to conduct dust-reduction experiments with different swirl intensities. The proximate and ultimate analysis results and the sizes of the coal samples were characterized, and the mechanism of the dust reduction was summarized. The results demonstrated that the applications of spiral guide grooves improved the atomization angles and coverage areas by up to 98.8° and 73%, respectively. At the same time, the enhancements of the swirl intensities were observed to reduce the uniformity index of the distribution sizes,` which significantly decreased the Sauter mean diameter (SMD) from 101.3 μm to 22.1 μm. The atomization results revealed that the increasing of the stagger angles benefited the larger atomization angles and smaller SMD. In addition, the proposed theoretical model had achieved better prediction accuracy. Also, the high atomization quality had obviously improved the dust-reduction ability of the pressure swirl nozzles, with the efficiency of total dust and respirable dust removeable increased by approximately 11.23% and 9.33%, respectively.

The influence of surfactant on the wettability of coal dust and dust reduction efficiency

The influence of surfactant on the wettability of coal dust and dust reduction efficiency

Optimization of spray dust suppression device in return air tunnel of a coal mine based on CFD technology

A wet and dry dual-purpose dust reduction device was developed to reduce the level of harm caused to mineworkers by the respirable dust generated in a fully mechanized working face in a coal mine, and specifically those workers located in the return airway [1]. First, spraying experiments were carried out to generate data showing an efficient dust reduction effect. Then, the data obtained from the experiments were imported into computational fluid dynamics (CFD) software for the numerical simulation of spraying [2]. The influence of the outward extension distance of the nozzle (Ls) and the spraying pressure (Pw) on the coverage capacity of the dust capture mesh and the distribution of the spray field was determined. According to the experiments, the optimal nozzles were 2.4-mm round-orifice nozzles with X-shaped flow guide cores. When Ls = 25 cm and Pw = 7 MPa, the spray field covered the dust capture mesh to the greatest degree, and effective dust reduction was achieved. Field application and measurements were carried out in the return airway of the 117 fully mechanized working face of Jinjitan Coal Mine, China. The dust reduction efficiency was found to reach 90.25%. Following the reduction in dust, the concentrations of respirable dust in the return airway at distances of 20, 50, and 80 m from the fully mechanized working face were 0.250, 0.203, and 0.179 mg/m3, respectively. As a result, the dust pollution problem in the return airway was effectively solved, and the airway environment was significantly improved.

Study on spray dust removal law for cleaner production at fully mechanized mining face with large mining height

Aiming at the problem that it is difficult to control high dust hazard in fully mechanized mining face with large mining height, an airflow-droplet coupled model was established based on the Euler-Lagrange method. Through a custom-developed nozzles atomization experimental system, main parameters were measured, and the built-in butterfly division core nozzle with an aperture of 1.6 mm was selected. The simulation results showed that the range of 1# ~ 3# hydraulic supports on the leeward side of the coal cutter was the best area to prevent dust from spreading to the sidewalk. The spray scheme of four groups of hydraulic supports was used, and each group had six nozzles. The vertical-horizontal combined dispersion scheme and 30° spray scheme were adopted. Besides, the distribution law of average size and concentration of droplets was revealed. After field application, the dust-reduction efficiency of the optimal scheme was 38.3% higher than that of the original scheme.

Dust reduction method based on water infusion blasting in open-pit mines: a step toward green mining

ABSTRACT This research proposes a new dust reduction method based on water infusion blasting in order to effectively minimize the dust production during blasting in open-pit mines. The proposed method was applied at the Haerwusu open-pit coal mine, China. A high-speed camera was used to record the dynamic process of dust generation during blasting. The images acquired from the main locations of the dust were analyzed using the gray level recognition method in MATLAB. The proposed method was then numerically simulated using ANSYS/Fluent software. Finally, the field experiment was conducted to verify the method by analyzing its dust reduction efficiency. The numerical results show that the dust reduction rate of about 78% can be achieved when the water bag is filled at the height of 1.8 m according to the blast design parameters of the mine (burden = 11 m, spacing = 7 m, hole diameter = 0.25 m, hole depth = 20 m). The experimental results achieved a 75% dust reduction rate, which meets the requirements of reducing blasting dust pollution in the studied mine. These investigations and findings conclude that the proposed method is effective, technically feasible, and economical. It can be widely applied to other open-pit mines as a green mining technology.

Numerical simulation and field test of dust control effect of exhaust ventilation in fully mechanized face

In view of the ventilation status of xiaobaodang coal mine fully mechanized driving face, this paper puts forward the idea of using full extraction ventilation to solve the problem of pollution air leakage in long pressure short suction ventilation, which provides a new idea for dust control of fully mechanized excavation in xiaobaodang coal mine. Solid geometry model of fully mechanized driving face is established by SolidWorks. The influence of different distance between suction outlet and head-on and different air volume on dust migration distribution and dust control effect is analyzed by fluent. The results show that the best dust control effect is obtained when the air volume is set at 300m3 / min and the distance between the suction outlet and the head-on is 5m. The dust concentration is lower than 10mg / m3 in the air duct side, 8m in the central section of the air duct and 16m in the height of the respiratory zone on the pedestrian side. The dust control effect is better at the side far away from the air duct. The measured results are consistent with the numerical simulation results. In addition, the optimized dust control method was verified on site, and the dust reduction efficiency at the driver's place and personnel walking position reached 62.8% and 82.8% respectively.

Experimental study on the improvement of wetting performance of OP-10 solution by inorganic salt additives

Inorganic salt additives can further improve the wetting performance of surfactants, thereby increasing the dust-reduction efficiency of spraying. In this study, the improvement on the performance of OP-10 surfactant solution was investigated through experiments on surface tension, reverse osmosis, water retention, and dust-reduction efficiency via spraying. The experimental results showed that when the concentration of OP-10 solution was lower than CMC, the inorganic salt additives had a certain effect on the surface tension of the solution. With the increase of the concentration of the additives, the surface tension of the solution continued to decrease. All four types of inorganic salt additives can improve the wetting performance of the surfactant to a certain extent and improved the reverse osmosis moisture absorption of coal dust. Two types of additives, i.e., CaCl2 and Na2SO4, had better performance than the other two types. CaCl2 also had good water retention properties, which can slow down the evaporation of water. After adding CaCl2 with a mass fraction of 0.5% in the OP-10 solution, the dust-reduction efficiencies for both the total dust and the respirable were improved to a certain extent. With the increase of the water supply pressure, the improvement of the dust-reduction efficiency by the Additive was less obvious. After adding the inorganic salt additives into OP-10 surfactant solution, the improvement on the dust-reduction efficiency of the respirable dust was more significant than that of the total dust.

Effect of outlet diameter on atomization characteristics and dust reduction performance of X-swirl pressure nozzle

In this study, experimental studies on the atomization characteristics and dust reduction performance of six different X-swirl nozzles with different outlet diameters were performed. The results of the nozzle atomization characteristics shows that, as the diameter of the nozzle increased, the flow rate of the nozzle gradually increased, while the flow coefficient kept decreasing almost linearly. Meanwhile, with the increase of the outlet diameter, the nozzle range and droplet velocity decreased continuously, while atomization angle and droplet size exhibited an increasing trend in general. From results of the dust-reduction experiment, considering the dust-reduction efficiency and water consumption, it is more appropriate to select a nozzle with an outlet diameter of 1.2 mm when the water supply pressure is higher than 4.0 MPa. When the water supply pressure was low, as the diameter of the outlet increased, the dust-reduction efficiencies of the nozzle for both the total dust and the respirable dust increased significantly. Therefore, under low water supply pressure, when the water consumption at the engineering application site is not limited, using a nozzle with a larger outlet diameter can achieve higher dust-reduction efficiency.