Escape Of Dust Research Articles

Characteristics of columnar vortex airflow and dust escape prevention based on artificial tornado

Dust pollution resulting from industrial production posed a significant risk to worker health. To address this issue, the coupling model of airflow and dust was established using the Eulerian-Lagrange method and the effectiveness of this model was via experimental data. Then, the airflow-dust coupling diffusion results using the columnar vortex ventilation system from different jet angle θ, jet velocity vJ and suction-blowing flow ratio γ were simulated. The results indicated that the columnar vortex ventilation system generated “columnar vortex airflow” by synergistically combining the surrounding air supply jets and upper exhaust airflow. Firstly, as vJ increased, θ and γ decreased, the mutual impact between the jets would be intensified, resulting in decreased vortex stability, which in turn caused a decrease in the dust removal rate. Simultaneously, excessive θ and vJ resulted in vortex range expansion, increasing dust pollution area in the near-floor, and decreasing the dust removal efficiency. Finally, the optimal parameters were θ = 65°, vJ = 2.25 m/s, and γ = 1.06. Under the optimal parameter scheme, the dust removal efficiency of the column vortex ventilation system reached 86%. This study provided a theoretical reference for the application of the column vortex ventilation system and the improvement of the environment in industrial plants.

Numerical simulation of dual-layer granular bed filtration based on particle collision rebound effect

This article established a dual-layer granular bed filtration model based on the dust collision rebound effect and investigated the influence of dust properties and filtration air velocity on the collision rebound effect and grade efficiencies of the filter layers. The results indicated that the characteristics of dust particle size, density, and effective Young's modulus had a significant impact on the critical adhesion velocity and collision rebound effect. Large dust particle size, density, and small effective Young's modulus resulted in a larger collision rebound effect. The collision rebound effect led to a decrease in grade efficiencies of each filter layer and the dual-layer granular bed with an increase in filtration velocity. To reveal the impact of the collision rebound effect on the movement of dust in the filter material layer, the trajectory and velocity changes of dust in the granule layer were simulated and calculated. The results show that the collision rebound effect caused the dust to repeatedly collide and rebound within the granular bed, penetrating deeper into the granular bed and increasing dust escape.

Research on the shielding effect of the electrode frames in the electrostatic precipitator

ABSTRACT The electrostatic precipitator (ESP) plays an important role in the dust removal from the flue gas. Currently, the shielding effect of electrode frames seriously affects the electric field distribution and dust removal efficiency of ESPs. In order to explore the shielding effect and propose an improved measurement, an experimental setup with RS barbed electrodes and a 480 C type dust collector electrode plate was built to evaluate the corona discharge characteristics. The current density distribution on the surface of the collecting plate was tested on an ESP experimental setup. The effect of electrode frames on the current density distribution was also systematically investigated. The test results show that the current density distribution on the position that directly opposites the needle of RS corona discharge is much higher, on the contrary, the current density on the position that directly opposites the frames is almost zero. It indicates that the frames have a shielding effect on the corona discharge. Therefore, the dust collection efficiency is low in actual ESPs due to the dust escape route caused by the shielding effect. To solve the problem, a new ESP with a split-level frame arrangement was proposed. Implications: The conventional electrostatic precipitators are often affected by the electrostatic shielding effect, which leads to uneven charging. The particulate removal efficiency decreases and escape channels are very easy to form. In this study, effective measures were proposed to solve the electrostatic shielding of dust collector frames by studying their electrostatic shielding mechanism. The study provides theoretical support for the improvement of electrostatic precipitators, while improving the dust removal efficiency.

The thesan project: Lyman-α emitter luminosity function calibration

ABSTRACT The observability of Lyα emitting galaxies (LAEs) during the Epoch of Reionization can provide a sensitive probe of the evolving neutral hydrogen gas distribution, thus setting valuable constraints to distinguish different reionization models. In this study, we utilize the new thesan suite of large-volume ($L_\text{box} = 95.5\, \text{cMpc}$) cosmological radiation-hydrodynamic simulations to directly model the Lyα emission from individual galaxies and the subsequent transmission through the intergalactic medium. thesan combines the arepo-rt radiation-hydrodynamic solver with the IllustrisTNG galaxy formation model and includes high- and medium-resolution simulations designed to investigate the impacts of halo-mass-dependent escape fractions, alternative dark matter models, and numerical convergence. We find important differences in the Lyα transmission based on reionization history, bubble morphology, frequency offset from line centre, and galaxy brightness. For a given global neutral fraction, Lyα transmission reduces when low-mass haloes dominate reionization over high-mass haloes. Furthermore, the variation across sightlines for a single galaxy is greater than the variation across all galaxies. This collectively affects the visibility of LAEs, directly impacting observed Lyα luminosity functions (LFs). We employ Gaussian Process Regression using SWIFTEmulator to rapidly constrain an empirical model for dust escape fractions and emergent spectral-line profiles to match observed LFs. We find that dust strongly impacts the Lyα transmission and covering fractions of MUV ≲ −19 galaxies in $M_\text{vir} \gtrsim 10^{11}\, \text{M}_{\bigodot }$ haloes, such that the dominant mode of removing Lyα photons in non-LAEs changes from low-IGM transmission to high dust absorption around z ∼ 7.

Study on the coal dust deposition fraction and site in the upper respiratory tract under different particle sizes and labor intensities

In order to study the dust exposure amount and coal dust deposition rule of coal miners under different labor intensity in coal mine environment, an airflow-particle two-phase coupling calculation model of human upper respiratory tract was established based on Euler-Lagrange framework, and the airflow field in the upper respiratory tract and the characteristics of coal dust deposition were simulated and studied. By comparing the experimental data, the relative error of simulation is in the range of 1.5 %–11.2 %. The results showed that the total deposition fraction of 1 μm dust was the smallest (0.61–1.20 %), and was relatively less affected by respiratory intensity, and the overall distribution was uniform. When the dust particle size increased to 7.07 μm, the total dust deposition fraction in the nasal cavity, pharynx and larynx was in the range of 11.10 %–20.91 %, and increased with the respiratory intensity. When the dust particle size was large, the dust particles of 20 μm and 80 μm were mostly concentrated in the front of the nasal cavity, and the deposition amount of 80 μm dust was about 99.52 %. It was found that with the increase of dust particle size or the increase of labor intensity, the possibility of dust being transported into lungs became smaller. The fitting function of 7.07 μm dust escape rate and labor intensity was obtained, for example, Y7.07μm = 91.73–0.22n (n is labor intensity), and the escape rate of dust with 7.07 μm particle size was up to 88.90 %. Most of them escape from the upper respiratory tract and enter the lungs, which provides theoretical guidance for quantifying the accumulated dust exposure amount in the lungs and monitoring respiratory dust concentration.

Preparation and evaluation of humic acid-based composite dust suppressant for coal storage and transportation.

To mitigate environmental pollution caused by the escape of dust during coal storage and transportation, humic acid (HA) and grafted acrylamide (AM) were used as raw materials to prepare a composite dust suppressant suitable for coal storage and transportation. Single-factor experiments were used to explore the optimal synthesis conditions of the dust suppressant, and the microstructure of the product was studied using Fourier-transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (1H-NMR), scanning electron microscopy (SEM), and other methods. The wetting effect of the dust suppressant on coal was also investigated by way of molecular dynamics (MD) simulations. The experimental results showed that the dust suppressant had good wind erosion resistance (wind erosion rate 10.2%), shock resistance (loss rate 3.63%), and anti-evaporation performance, while the MD simulation and permeability analysis results showed that the dust suppressant had an excellent wetting effect on the coal surface. SEM images revealed that the dust suppressant can fill the gaps between coal dust particles and bond them together to form a consolidated layer, thereby effectively inhibiting the escape of dust sources during coal storage and transportation.

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.

Air curtain dust-collecting technology: Investigation of industrial application in tobacco factory of the air curtain dust-collecting system

The air curtain system can collect the dust particles from hard-to-seal sources, which proves to be a feasible method for satisfying the increasing dust prevention requirements in China. In this study, aiming at addressing the dust escape problem at the tobacco stem loading point in a tobacco factory, a rotational flow air curtain dust-collecting system with a size of 2m x 2m x 2m was used for dust collection. The dust-collecting characteristics using the original dust suction hood and the developed air curtain dust-collecting system were analyzed and compared. Results show that the external dust concentration when the original dust suction hood operated was as high as 83.65 mg/m3, with a dust-collecting efficiency of only 16.35 %, suggesting serious dust escape; after the use of the developed air curtain dust-collecting system, the dust-collecting efficiency reached up to 86.93∼94.76 % under the same operating conditions. By studying the influence of two factors, air curtain jet velocity and exhaust-to-pressure ratio, on the dust collection efficiency of the air curtain system, at an exhaust-to-pressure ratio of 0.8 and an air curtain jet velocity of 13.5 m/s, the corresponding dust-collecting efficiency reached a maximum of 94.76 %. The present test results confirmed a better application effect of the developed air curtain dust-collecting system than the original dust-collecting system at the industrial loading point. Using the developed air curtain dust-collecting system is mainly aimed at the dust source, reduce the dust in the workshop dissemination and dispersion that can lower the transmission path of COVID-19 via aerosol.

Airborne flow dynamics near free-falling bulk materials: CFD analysis from analytical pressure field

The dust generated and spread by free fall of bulk materials is analyzed through CFD simulations that allow visualization of the velocity vector field and the air masses close to the main material stream (core) that generate preferential paths for the formation and escape of dust. The air velocity field near a free-falling bulk material is obtained through a CFD solution from the analytical pressure field; the model was fed with properties described in empirical studies allowing comparison and validation. CFD results allow visualization of the boundary layer formed close to the bulk material stream. The results indicate the existence of a critical height that, when reached, transforms the pressure field inducing the emergence of a toroidal vortex around the mainstream. This causes the expansion of the boundary layer leading to an increase in particle absorption and formation of dust dispersion zones. A relationship between the critical height and the material stream diameter is proposed. The results indicate that the fluid viscosity inside the boundary layer is constant - before its complete expansion - and after increases linearly. A linear viscosity model, adapted from Einstein's proposal, is applied in the CFD model to establish the relationship to the induced airflow as a function only of the fall height and core diameter.

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%.

Improved foam application at the tunnel face with large ventilation volume and low pressure supplied water

Due to large energy loss, current foam technology for dust suppression requires high inlet water pressure, but performance is poor where ventilation volume is high. This paper proposes modifying key foam device components, including the agent mixing device, foam generator, and nozzle, to address these problems. A cavitating jet pump was simultaneously employed for accurate agent mixing and flow meter, guaranteeing accurate agent flow and low energy loss. A vertical foam generator was designed to increase foam volume and ensure even foam distribution among the foam nozzles. The two-layered foam nozzles were designed and fabricated using 3D printing to ensure even and thick foam impact area on the dust source, effectively blocking dust escape passages. Experiments were performed in the laboratory and on a real heading face. Ventilation volume was 560–570 m3/min for the field experiment with initial total dust concentration 589–679 mg/m3. The proposed system reduced required inlet water pressure to 0.87 MPa, while achieving 86.8% average total dust suppression efficiency and reducing long-term time average respirable dust concentration to 3.9–5.7 mg/m3. This study will help improve performance and expand application fields for foam dust suppression technology.

Investigation on the design of atomization device for coal dust suppression in underground roadways

During mining operations, large amounts of coal dust escape from the heading faces. This dust presents a serious hazard to the health and safety of workers in the excavation roadways. In this study, a device was designed to capture the escaped dust in a timely way. The device was suitable for heading with forced ventilation and it could generate a fog layer with a certain thickness through the twice atomization process. The fog layer could cover the entire roadway section to filter and remove the coal dust escaping from the heading face. The performance of the proposed device was experimentally studied under different working conditions. The experimental results showed that, with the increasing of the water pressure (Pw), the particle sizes of droplets decreased while the coverage radius increased and its increasing rate gradually decelerated. Meanwhile, as the air pressure (Pa) increased, the coverage radius displayed an upward trend, and the particle sizes of the droplets decreased gradually. In this study, four different water-air pressure ranges were tested to cope with the different field conditions. Then, the proposed device and obtained test results were applied at Zhangcun Coal Mine in China. The application results indicated that the total and respirable dust suppression efficiency of the device has increased 24.8% and 43%, respectively, compared to the traditional water curtain. Also, the device was estimated to have saved approximately 25% in water consumption when compared with the water curtain method. Therefore, it is believed that the new atomization device would be ideal for replacing traditional water curtains for the suppression of hazardous dust particles in underground coal mines.

Numerical Simulation of Dust Dispersion and Pollution in Breathing Zone of Fully Mechanized Mining Face

In order to more accurately analyze the law of dust escape in the position of breathing zone of fully mechanized coal face, a geometric model of fully mechanized coal face is established in 1205 fully mechanized coal face of Xinan Coal Mine. The movement law of dust with the wind field in the fully mechanized coal face is simulated by FLUENT software, and the dust in the area of breathing zone at different positions is also simulated. The situation is analyzed in detail. The simulation results show that the overall movement law of air flow in the whole working face is from small to large and then to small. When the air flow passes through the area near the shearer, the local space becomes smaller, the wind speed increases and transverse movement occurs. The dust produced by the shearer cutter diffuses into the space of the shearer and its downwind side roadway accompanied by the air flow. A high concentration dust belt is formed in the area near the shearer. The dust contaminated area in front of the Hydraulic support and the space breathing belt of the sidewalk increases gradually with the prolongation of dust production time and covers the height of the whole breathing belt after 80 s of dust production.

Development of Charge Pelletizing Technology Based on Electric Arc Furnace Dust for Pyrometallurgical Processing in Rotary Kilns

New technology is developed for Waelz treatment of electric arc furnace dust with the addition of calcium oxide to a charge. In this case, lead and halides are transferred into distillates. Calcium ferrite and zinc oxide remain in clinker. Clinker is sent for leaching zinc followed by zinc electrolysis from solution. The insoluble residue of calcium ferrite is used in ferrous metallurgy. The efficiency of this technology is determined by the process of charge preparation for loading into a Waelz kiln. In order to provide complete reaction of zinc ferrite with calcium oxide, it is necessary to provide effective component mixing; in order to provide selectivity of halide and lead liberation, reducing distillate volume, a powder mixture is pelletized. Exploratory research is conducted for preparing pellets of a mixture of electric arc furnace dust with lime, and the effect of some binder reagents on pellet strength is demonstrated. The following optimum parameters are determined for charge pelletizing from electric arc furnace dust and calcium-containing flux under conditions of a plate-like granulator: pelletizing duration 15 min; granule moisture content 19–20%. With the use of an intense type mixer-pelletizer, the optimum moisture content is 13–14%, which is connected with the improved conditions for pellet compaction. Comparison of various inorganic and organic additives for mixture granulation shows that the best are additives containing sodium hydrate sulfate, although their optimum consumption is unacceptable for the technology of material pyrometallurgical treatment. The presence in the production mixture of calcium-containing flux makes it possible to use it also as a binding additive for pelletizing calcium hydroxide in the form of an aqueous suspension. Feeding a pelletized mixture of electric arc furnace dust with lime into a Waelz kiln makes it possible to provide effective reaction of charge components in the kiln and to reduce to reduce escape of dust.

Study on the Control of Industrial Dust from Alumina Production Process

The dust from industrial process does harm to the human health, the equipments and environment. Based on the comparison between bag filter and electrostatic precipitator, bag filter was used to control the dust from the industrial process with the filter cloth of polypropylene fiber needled felt. During run time, the filtration rate should be less than 1.59m/min and the pressure of the draught fan should be 3100Pa with the wind speed in the range of 22m/s to 24m/s, which eliminated the dust formation. And the size of dust hood should be heightened and lengthened in order to decrease dust escape and the cone angle of the dust hood should be more than 60°. In additon, in order to prevent the blocking of the ash unloading device, the best angle of the ash discharging pipe should be 60°. The dust collection system run well for five years and the collection efficiency was more than 99.0%, which created the benefits of environment, economics and society.

Modeling the influence of forced ventilation on the dispersion of droplets ejected from roadheader-mounted external sprayer

In order to reveal the influence of forced ventilation on the dispersion of droplets ejected from roadheader-mounted external sprayer, the paper studies the air-flowing field and the droplet distribution under the condition of gentle breeze and normal forced ventilation in heading face using the particle tracking technology of computational fluid dynamics (CFD). The results show that air-flowing tendency in the same section presents great comparability in the period of gentle breeze and forced ventilation, and the difference mainly embodies in the different wind velocity. The influence of ventilation on the dispersion of droplets is faint under the gentle breeze condition. The droplet can be evenly distributed around the cutting head. However, under the normal forced ventilation, a large number of droplets will drift to the return air side. At the same time, droplet clusters are predominantly presented in the lower part of windward side and the middle of the leeward side around the cutting head. In contrast, the droplet concentration in other parts around cutting head decreases a lot and the droplets are unable to form close-grained mist curtain. So the dust escape channel is formed. In addition, the simulation results also reveal that the disturbance of air flow on the droplet distribution can be effectively relieved when using ventilation duct with Coanda effect (VDCE). Field experiment results show that the dust suppression efficiency of total dust and respirable dust increases respectively by 10.5% and 9.3% when using VDCE, which proves that it can weaken the influence of airflow on droplet dispersion.

Search for Phobos and Deimos gas/dust tori using in situ observations from Mars Global Surveyor MAG/ER

More than 490 elliptical aerobraking and science phasing orbits made by Mars Global Surveyor (MGS) in 1997 and 1998 provide unprecedented coverage of the solar wind in the vicinity of the orbits of the martian moons Phobos and Deimos. We have performed a comprehensive survey of magnetic field perturbations in the solar wind to search for possible signatures of solar wind interaction with dust or gas escaping from the moons. A total of 1246 solar wind disturbance events were identified and their distribution was examined relative to Phobos, the Phobos orbit, and the Deimos orbit. We find that the spatial distribution of solar wind perturbations does not increase near or downstream of Phobos, Phobos’ orbit, or Deimos’ orbit, which would have been expected if there is significant outgassing or dust escape from the martian moons. Of the 1246 magnetic field perturbation events found in the MGS data set, 11 events were found within 2000 km of the Phobos orbit, while three events were found within 2000 km of the Deimos orbit. These events were analyzed in detail and found to likely have other causes than outgassing/dust escape from the martian moons. Thus we conclude that the amount of gas/dust escaping the martian moons is not significant enough to induce detectable magnetic field perturbations in the solar wind. In essence we have not found any clear evidence in the MGS magnetic field data for outgassing or dust escape from the martian moons.

Dust escape mechanism from Io

The analysis done of the data obtained by Ulysses and Galileo spacecrafts throughout the Jovian system has confirmed that dust that escapes from Jupiter in collimated streams proceeds from volcanic ejections produced in Io. The volcanoes eject a mixture of dust and gases of sulfur and oxygen. Although the speeds of the ejections are just near a half of the escape velocity, the volcanic material escapes. It has been inferred that electromagnetic forces might play an important role in order to understand the physical mechanism that allows some dust particles (grains) to escape from Io. Dust escape from Io must accomplish at least three different conditions: first of all, grains must have a micrometer size, grains must acquire a minimum electrostatic charge and third, they must get a high enough altitude to be in contact with the surrounding Jovian plasma and being dragged. In this investigation we obtain three results: the maximum and minimum ejection velocities of 15 Ionian known plumes, the maximum escape radii for grains emitted in those plumes and the maximum time of permanence for such dust particles before they escape from the Jovian environment considering a single particle model.

Electromagnetic Escape of Dust from the Solar System

AbstractCollisions of asteroids and among Zodiacal cloud particles produce large amounts of submicron-sized debris, much of which is immediately ejected from our solar system by electromagnetic forces. We investigate the trajectories of tiny grains started on circular uninclined orbits within the Zodiacal cloud and find that they reach high ecliptic latitudes during the current configuration of the solar magnetic.field, perhaps accounting for particles detected by the Ulysses spacecraft at latitudes up to 80°. When the solar magnetic field is reversed, particles are more strongly confined to the ecliptic plane and escape the solar system less readily. Both fluxes and spatial densities of sub-micron sized Zodiacal dust particles vary with time through the dependence of orbital dynamics on the 22-year solar cycle.

Stabilizer/lubricant for rigid PVC foams

This chapter discusses the various measures of explosion prevention, including dust control, ignition sources, and inerting, with respect to selected items of industrial plant. The principles of explosion prevention are largely based on common sense and experience gained from industries and incidents since the hazard was first recognized. The two areas where preventive measures is most effective are those concerned with ignition sources and the inerting of the atmosphere into which the dust is suspended. The chapter discusses that the control of unnecessary dust suspensions and accumulations reduces the possibility of a dust explosion. Effective measures are employed at the planning stage of a new plant, although the general principles of dust control are applied successfully to existing plant. In the selection of plant items that produce continuously suspended, dust should be avoided. Equipment should be dust tight, joints being flanged and gasketed in order to prevent the escape of dust into the workroom, which is be facilitated by operating the process under a slightly negative pressure.