Dust Concentration Distribution Research Articles

Gas-particle flow induced erosion of economizer in low-low temperature electrostatic precipitators: Numerical prediction and engineering application

In this work, the gas-particle flow and the induced erosion in the economizer region in low-low temperature electrostatic precipitator were investigated by CFD-DPM-EPM coupling approach. The results show that positioning the economizer on the vertical flue or employing a vertical tubes arrangement for the heat exchange tubes, utilizing a small expansion angle (less than 35°) in the expansion section, ensuring a more uniform distribution of inlet gas velocity and dust concentration, and incorporating short and densely positioned guide plates in the expansion section can effectively reduce erosion in the low-temperature economizer. The above results were applied to the economizer equipped with the low-low temperature electrostatic precipitator of a 1000 MW unit in a certain power plant, and the wear situation was significantly improved. The research findings can serve as a reference for diagnosing and analyzing erosion phenomena in low-temperature economizer, and can guide the improvement design to prevent erosion.

Research on the dust-control technology of a double-wall attached-ring air curtain on an excavation face.

On the basis of the jet theory of airflow fields and the gas-solid two-phase flow theory, we studied the law of dust migration in a simulated dusting space. We used the control variable method and numerical simulation software to explore the airflow field and dust concentration distribution on the working surface of the dusting under different inlet wind speeds and different attached blades of the double-walled annular air curtain. We determined the speed of the inlet of the annular air curtain to be 30 m/s. When the angle of the attached blade was 30°, the dust concentration of the driver and other workers was controlled below 100 mg/m3, which produced the best dust control effect is the best. Using real data, we built a similar test platform to test the airflow field and dust concentration. Through data measurement and analysis, we proved that a dust control system with a double-wall attached-ring air curtain formed a circulating airflow field that could shield dust and effectively reduce dust concentration in the simulated space. The dust removal efficiency of total dust and exhaled dust reached 98.5% and 97.5%, respectively. We compared the test data and simulation results and concluded that the double-wall attached-ring air curtain could effectively ensure the safety of mine production and provide a better underground working environment for operators.

Mathematical Modelling of Dust Transfer from the Tailings in the Alagir Gorge of the RNO-Alania

Introduction. Mathematical modelling of the aerodynamics of mountain gorges is an actual means of studying possible man-made emissions in various meteorological conditions that increase the transfer of pollutants in the direction of densely populated areas. Aerodynamics and climatic conditions are unique for various mountain gorges. This requires a separate study for each specific case. The paper studies the distribution of dust aerosol from the Unal tailings dump, located near the village of Verkhny Unal (Alagir Gorge, RNO-Alania, RF), with south and south-easterly winds. With these wind directions, the dust of the tailings dump is carried by air currents in the north direction, towards Alagir. The aim of the study is to obtain a forecast for the surface concentration of dust with an increased content of lead, zinc and other elements near densely populated areas of the flat part of RNO-Alania.Materials and Methods. The model takes into account the terrain, surface wind roses and dust deposition processes. The calculations were carried out for the case of neutral stratification and without taking into account the influence of seasonal factors using a mathematical model previously published by the authors.Results. The model prediction of the dust concentration distribution obtained from calculations is shown. The frequencies and amplitudes of oscillations of unsteady jet streams in the cross section of the Alagir gorge are analyzed. Based on the data of satellite sensing of the Earth’s atmosphere, the frequency of winds leading to the transfer of dust in the direction of densely populated areas is estimated.Discussion and Conclusion. The Unal tailings dump is a source of pollutants and over many years of its existence, soil contamination can be significant. Field studies of the soil in the Alagir area and, possibly, measures for its reclamation are necessary.

Fine Particulate Matter Reduction through Crop Surface Adsorption in an Agricultural Field Using the Coefficient Derived from Wind Tunnel Experiments

Fine dust can have serious effects on human health and crop growth. Fodder crops can reduce airborne dust by coagulating soil particles and reducing wind speed on the surface and have the effect of reducing fine dust by adsorbing it on the crop surface. In this study, the dust reduction coefficient of crops was derived through a self-manufactured wind tunnel experiment to quantitatively assess the dust reduction effect of crops by type and planting density. Additionally, a dust reduction formula considering crop growth and weather conditions during the cultivation period was derived. The dust reduction coefficient was measured by the gravimetric method and the real-time size distribution of dust concentration before and after the crop. The PM reduction coefficient showed triticale at PM-2.5 82.2 mg/m3, PM-10 120 mg/m3, and barley at PM-2.5 14.5 mg/m3, PM-10 26.9 mg/m3 under moderate planting density. During the general planting density cultivation period of triticale and barley, PM-10 was reduced by 37.8 kg/ha and 8.5 kg/ha, respectively, and PM-2.5 was reduced by 25.9 kg/ha and 4.6 kg/ha. The dust reduction effect during the cultivation period was up to 126.1 kg/ha in terms of PM-10 when triticale was cultivated with densely sowing planting density.

Research on Dust Migration and Dust Deposition Rules of Breathing Zone in Fully Mechanized Mining Face.

The dust in the breathing zone of the fully mechanized mining face poses a serious threat to the lives and health of the workers, and clarifying the distribution and settlement pattern of the dust in the breathing zone is an important foundation for reducing dust concentrations in the breathing zone and improving the workers' working environment. The dust concentration distribution at the mining face and the settlement results of different dust particle sizes along the breathing zone were analyzed in detail using a combination of computational fluid dynamics simulation and downhole measurements by establishing a highly simulated 3D solid model of the 2302 fully mechanized mining face at the Xinqiao coal mine. The study's findings reveal that dust from advanced support and coal-cutting processes converge within 20-60 m of the coal mining region, generating a high-concentration pollution zone at the height of the sidewalk breathing zone. The particle size of dust in the breathing zone is primarily concentrated between 1 and 40 μm, and the fully mechanized mining face is split into a rapid settling area, a medium settling area, and a slow settling area based on particle size settling speed. Eddy currents in the return airway lead to an increase in dust particles of 20-40 μm in the breathing zone area. The results of the study can provide a theoretical basis for dust management at the fully mechanized mining face for the breathing zone area.

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.

Influence of vehicle and pavement characteristics on dust resuspension from soil pavement of open-pit mine

It is essential to explore the distribution characteristics of dust concentration distribution near the surface of soil pavement in open-pit mines to develop effective dust control measures. Therefore, in this study, the dust resuspension process of soil pavement was analyzed by building the dust resuspension experimental system of open-pit mine, and the change rules of dust concentration under different factors were investigated. The results showed that under the action of wheel rolling, the dust moved around the wheel along the vertical direction, and the diffusion trajectory in the horizontal direction was approximately parabolic. After re-suspension of the open-pit mine soil pavement, the area of high dust concentration behind the wheel is roughly triangular. The relationship between the average dust concentration (Total dust, Respirable dust and PM2.5) and the vehicle speed and weight were fit to a power function, while the relationship with silt content and water content were quadratic. Vehicle speed and water content had significant effect on the total dust, respirable dust (RESP) and PM2.5 average concentration, while vehicle weight and silt content had little effect on the respirable dust and PM2.5 average concentration. When the water content of mine soil pavement reached 3 %, the average dust concentration could be reduced to <10 mg/m3, and the vehicle speed should be reduced as much as possible under the mine production permitting conditions.

A numerical simulation of dust pollution law under traditional electric rake operation: A case study of Shuiyindong gold mine

The Shuiyindong gold mine in Guizhou is used as a case study in this paper to study patterns of dust pollution occurring with traditional electric-rake operation. In particular, the study uses the northern quarry of the twenty-third line in the first middle section of the second mining area and establishes a three-dimensional simulation model of equal size. It uses Computational Fluid Dynamics (CFD) to simulate and analyse the airflow traces and distribution of dust concentration in the relevant roadway during each stage of the electric-rake operation. The simulation results show that the airflow in the working roadway has a spiral movement and produces reverse dirty-wind circulation towards the end. Dust flows out of the working roadway from the 8th second of operation, and dust concentration reaches a peak in the working roadway at the 12th second of operation at an average dust concentration of 37.5 mg/m³. The dust concentration drops rapidly from the 120th second and reaches the maximum dust concentration permitted for operation at the 180th second of operation. The validity of the simulation is tested by comparing the actual measured data at the site with the simulation results. Finally, the simulation results are analysed using violent Python, and the solution is used to divide the roadway into areas according to the human breathing range. The paper analyses the distribution of dust concentration at an average human breathing height, providing an established theoretical basis for dust-control work in mines.

Health damage assessment of reconstruction dust from old industrial buildings under multi-process.

The regeneration of old industrial buildings produces considerable construction dust, thereby seriously threatening the occupational health of construction workers. The existing articles concerning the exposure and health impacts of reconstruction dust in enclosed spaces are limited, but this research field has received increasing attention. In this study, multi-process during the demolition and reinforcement stages of a reconstruction project were monitored to determine the respirable dust concentration distribution. A questionnaire survey was conducted to obtain the exposure parameters of reconstruction workers. Moreover, a health damage assessment system for the reconstruction process of old industrial buildings was established by applying the disability-adjusted life year and human capital method to explore the health damage caused by the generated dust at different stages to the construction personnel. The assessment system was applied to the reconstruction stage of an old industrial building regeneration project in Beijing to obtain dust health damage values for different work types and to conduct comparative analysis. The results indicate that there are significant differences in the dust concentration and health damage at different stages. During the demolition stage, the manual demolition of concrete structures has the highest dust concentration, reaching 0.96mg/m3. This exceeds the acceptable concentration by 37%, and the health damage cost is 0.58 yuan per person per day. In the reinforcement stage, the dust concentration generated by mortar/concrete mixing is the highest, but the risk level is acceptable. The health damage cost of concrete grinding, which is 0.98 yuan per person per day, is the highest. Therefore, it is necessary to strengthen the protective facilities and improve the reconstruction technology to reduce dust pollution. The results of this study can help in improving the existing dust pollution control measures at construction sites to reduce the risk of dust hazards during reconstruction.

Blasting dust diffuse characteristics of spiral tunnel and dust distribution model: similar experiment and numerical modeling.

The special linear shape of spiral tunnel changes the air flow structure during tunnel construction and changes the diffuse and distribution of blasting dust. Mastering the blasting dust distribution and diffuse mechanisms can provide theoretical basis for ventilation layout and dust removal measures during spiral tunnel construction. To study the influence of spiral shape on dust diffusion and concentration distribution after tunnel blasting, a similar scale model of 1:20 and full-scale numerical model of spiral tunnel during construction were established. The similarity criterion and the similarity ratio of each physical quantity are derived from the dust motion equation. The dust distribution and diffuse characteristics in the spiral tunnel under different dust release quantity and release velocity were studied by model experiment. The dust distribution and diffuse characteristics in spiral tunnel with different curvature radius were studied by numerical simulation. The dust distribution model is refined based on the research results. The dust distribution model divides the tunnel into heavily polluted area and slightly polluted area, and the influence characteristics of the curvature radius on the dust export area are found. The layout of ventilation systems can be optimized according to the volume of heavily polluted areas. The heavily polluted area should be as small as possible; the dust in the heavily polluted area should be discharged to the slightly polluted area in an orderly manner to avoid the accumulation of dust. Dust removal measures can also be arranged according to the dust export location to improve dust removal efficiency.

Effects of operating parameters on the performance of moving bed filter

High-temperature gas purification technique is of great significance for environmental protection. Moving bed filtration is considered a promising technique. In this study, the moving granular bed filter with the gas-solid counter flow was proposed. The pressure drop and the collection efficiency were investigated with respect to the superficial gas velocity, the mass flow rate of the filtration granules and the dust inlet concentrations. In addition, the dust concentrations at different bed heights were measured with isokinetic sampling. The experimental results indicate that an increasing filter gas velocity or a decreasing mass flow rate of the granule leads to a decrease in dust collection efficiency. An empirical equation was given by combining the single particle filtration analysis with the measured dust concentration distribution along the vertical height of the filter to calculate the moving bed filtration efficiency.

Methodology for assessing the dustiness of the air environment of the working areas of foundries

The content of harmful substances in the air is an important parameter of the working conditions of foundry workers. Due to the peculiarities of the technology, there are many sources of intense dust emission in the foundry. The distribution of dust concentrations in the atmosphere of the workshops was determined from the equation of the dust balance in the workshop room. The possibility of obtaining by calculation an objective picture of the distribution of dust in various sections of foundries is shown. Data from various studies were used to determine the density and dust at various sites of foundries. The results of the theoretical calculations show that in foundries, dust capture is an effective means of reducing the dustiness of the air of working areas.

Analysis of the Dust-Concentration Distribution Law in an Open-Pit Mine and Its Influencing Factors.

In this study, a solar-powered multipoint network monitoring method was used to record dust-particle concentrations and meteorological indicators in the Anjialing open-pit coal mine in the Pingshuo mining area. The factors influencing the concentrations of particulate matter of different maximum diameters (PM2.5, PM10, and total suspended particulates; TSPs) and the regularity of the spatial distribution were examined. The results show that the highest dust concentration and thus the most serious dust pollution occur in winter, and the lowest dust concentration is found in summer. There are peaks in dust concentration in December and January to February, and the pollution is more serious at these times. On a given day, the pollution is higher between 11:00 and 13:00, but it does not exceed the 24 h air concentration limits specified in the Chinese Ambient Air Quality Standard (GB3095-2012). It was found that the PM2.5 and PM10 concentrations are positively correlated with humidity and air pressure, and they are negatively correlated with wind speed, temperature, and noise. The TSP concentration is positively correlated with temperature and negatively correlated with humidity. The results of this study provide theoretical guidance and a reference for the distribution law of dust concentration in open-pit coal mines.

CFD Model Studies of Dust Dispersion in Driven Dog Headings

Dust is one of the most burdensome hazards found in the environment. It is composed of crushed solids that pose a threat to the health and life of people, machines and machine components. At high concentration levels, it can reduce visibility. All of these negative phenomena occur during the process of underground mining, where dust hazards are common. The negative impact of dust on the efficacy of the mining process prompts research in this area. The following study presents a method developed for model studies of dust dispersion in driven dog headings. This issue is immensely important due to the fact that these dog headings belong to a group of unidirectional excavations (including tunnelling). This paper presents the results of model studies on dust dispersion in driven dog headings. The main focus is on the analysis of the distribution of dust concentration along a dog heading during the mining process. In order to achieve this goal, a model test method based on the finite volume method, which is included in the group of CFD methods, was developed. Analyses were carried out for two different values of dust emission from the face of the excavation for the transient state. The results made it possible to determine areas with the highest potential for dust concentration. The size and location of these areas are mainly dependent on the amount of dust emissions during the mining process. The results can support the process of managing dust prevention and protection of workers during the mining excavation process.

Numerical simulation investigation on optimal air volume for dilution dust-gas by forced ventilation in fully mechanized driving face.

In order to ensure the best dust removal on the basis of the optimal gas emission, and to determine the best dust and gas exhaust air volume, numerical simulation research was carried out on the airflow-dust-gas field of the fully mechanized driving face. The results indicate that under different air volumes, with an increase in the distance from the head-on, the airflow velocity of the fully mechanized driving face first increased and then decreased, and gradually tended to be stable. When Q = 800-900 m3/min, the head-on gas dilution ability is strong and the range of high gas content was the minimum. When Q > 900 m3/min, the gas dilution efficiency was reduced and easy to cause secondary dust. In the height of the respiratory zone, the relationship between the dust concentration distribution and air volume is [Formula: see text], and that between the gas content and air volume is [Formula: see text]. Finally, the optimal air volume range was determined to be Q = 800-900 m3/min. By comparing the measured and simulated airflow velocity, dust concentration, and gas content, the average errors were 6.77%, 6.83%, and 7.73%, respectively, which proves the reliability of the numerical simulation results.

Dust transport behaviour in the Nanwenhe extra-large stepped underground metal mine stope

This paper is aimed at studying the dust behaviour of a super-large stepped stope, which is essential in reducing the dust hazards and setting up effective dust control facilities. In this paper, a three-dimensional model is established for the super-large stepped stope of Nanwenhe. Based on the theory of gas-solid two-phase flow, the Fluent software was applied to carry out a numerical simulation of the air flow distribution in the stope and the dust concentration distribution from multiple dust sources. The simulation results reveal that air flow is affected by the roof fault, resulting in it being diverted to the connecting roadway of the return air roadway, the roof of the lower stope and the interior of the stope. A part of the air flow flows back to the upper stope operation area at a speed of 0.3–0.6 m/s. The dust produced by the shovelling and dumping operations forms a high concentration dust belt with a length of 41 m, a width of 3.6 m and an average concentration of over 260 mg/m³. A portion of the dust flows back to the operation area by bypassing the ore pillar, with a concentration of 60–80 mg/m³. The reliability of our simulation method was verified by field measurements of the air flow velocity and dust concentration. Finally, a new intelligent wind-fog combined dust removal system was designed according to the dust concentration distribution, which achieved an overall dust removal efficiency of 76.9%. These research results provide certain references for the study of dust migration law in underground metal mines and the development of dust removal equipments.

Simulation study on crucial parameters of long-compressive and short-suction ventilation in large section roadway excavation of LongWangGou coal mine.

LongWangGou coal mine auxiliary inclined shaft heading face has a large section, fast heading speed, and large dust production. The problems of high concentration and wide distribution of dust in the roadway air are very prominent. To improve the efficiency of roadway ventilation and dust removal, long-compression and short suction (after this referred to as LCSS) are adopted. The dust concentration and airflow field distribution in the roadway are numerically simulated by FLUENT. The change of the position between the pressure duct and the exhaust duct and the different pressure-extraction ratios affect the distribution of airflow velocity, the formation of vortex zone, and the distribution of dust concentration in the roadway. When Ly=25 m, Lc=5.0 m, W=1.2, a wind curtain is formed at 5 m in front of the heading face to prevent dust from spreading deeper into the roadway.

Analysis of dust hazard characteristics in 59 ferrous metal foundry enterprises in Ningbo City

Objective: To analyze the post distribution of dust concentration in ferrous metal foundry enterprises and evaluate the occupational health risks, and provide basis for policies of the formulation of pneumoconiosis prevention and control. Methods: From August to September in 2020, the basic information, dust hazard information and occupational health management information of 59 ferrous metal casting enterprises were investigated, the dust concentration distribution was analyzed, and the risk assessment was carried out by using the quantitative assignment model. The dust concentration is tested by LSD method after logarithmic treatment. The 3 times time weighted average allowable exposure concentration of dust is taken as the peak concentration limit of dust; The time weighted average allowable exposure concentration of dust converted by exposure time is taken as the time weighted average exposure concentration limit of dust, and whether the time weighted average exposure concentration and peak concentration of dust at the same post exceed the limit is taken as the basis for exceeding the limit of dust post concentration to calculate the post exceeding the limit rate. Results: The dust hazards were mainly distributed in the posts of sand treatment, molding, sand falling, sand cleaning and cutting and grinding. Dust exposure time weighted average concentration was 0.44 (0.03, 5.11) mg/m(3), peak exposure concentration was 1.30 (0.18, 10.94) mg/m(3), and the over standard rate of Posts was 38.92% (79/203) . Weighted average exposure concentration of other dust (total dust) in the cutting and grinding post is 1.50 (0.15, 7.40) mg/m(3), peak exposure concentration is 0.90 (0.07, 12.48) mg/m(3), and the post exceedance rate is 4.88% (2/41) . Weighted average exposure concentration of silica dust (exhaling dust) in dust operation posts of investment casting enterprises is 0.43 (0.05, 6.35) mg/m(3), peak exposure concentration is 0.90 (0.12, 8.28) mg/m(3), and the post over standard rate is 35.77% (49/137) ; Weighted average exposure concentration of other dust (total dust) at the cutting and grinding post is 2.00 (11.00, 21.00) mg/m(3), and the post exceedance rate is 2.50% (2/80) . There was no significant difference in the concentration of respirable dust between sand casting and investment casting (P>0.05) . The concentration of respirable dust in sand casting was higher than that in sand treatment, molding and sand cleaning posts (P<0.05) . The concentration of silica dust in investment casting was higher than that in sand treatment and molding posts, and that in sand cleaning posts was higher than that in sand treatment posts (P<0.05) . 98.48% (454/461) of the dust operation posts have an occupational health risk value greater than or equal to 400, and 1.52% (7/461) of the dust operation posts have an occupational health risk value of 200~399. Conclusion: there is a high rate of exceeding the standard in the dust work posts in the ferrous metal foundry enterprises in Ningbo, and the workers have a high occupational health risk of pneumoconiosis or metal and its compound pneumoconiosis. Targeted measures should be taken to reduce the occupational health risk.

Research on law and mechanism of dust explosion in bag type dust collector

The bag type dust collector will accumulate dust during long-term operation, and the high temperature during operation will cause dust explosion. In this paper, with the dust removal system involved in the “8·2” Kunshan dust explosion accident taken as the research background, the minimum ignition temperature and lower explosion limit experiments are carried out on aluminum powder with different particle sizes (10–60 μm) by using the lowest ignition temperature test device and the 20 L near-spherical explosive device. The dust concentration distribution and temperature field in the bag type dust collector are analyzed through the CFD-FLUENT software. Through the analysis of the experimental results, it is found that when the particle size of aluminum powder is 19 μm, the minimum ignition temperature is 585 °C, and the lower explosion limit of concentration is 0.04 kg/m3. The simulation results indicate that the dust particles gather in the dust collecting bucket, and the aluminothermic reaction occurs in the dust collecting bucket. The temperature of the upper and right parts in the dust collecting bucket is above 600 °C, which exceeds the minimum ignition temperature. At the interface between the dust hopper and the dust collecting bucket, the concentration of aluminum powder reaches 0.126 kg/m3, which exceeds the lower explosion limit of aluminum powder.

Numerical Modelling of Blasting Dust Concentration and Particle Size Distribution during Tunnel Construction by Drilling and Blasting

In order to reduce the blasting dust concentration in the tunnel during the drilling and blasting, accelerate the tunnel excavation process, and improve the working environment for the construction workers, a three-dimensional geometric model of dust transport was established based on the gas-solid two-phase flow model using the DesginModeler software, and the discrete phase model (DPM) in the FLUENT software was used to simulate the variation of dust concentration and the distribution of dust particle size at different locations along the tunnel route within 1200 s after tunnel blasting. The results showed that the concentration of blasting dust gradually decreased over time, with the fastest decrease in the range of 2 s to 120 s, and after 900 s, the dust concentration stabilized. The overall spatial distribution of the dust concentration showed a trend of decreasing from the palm face to the tunnel entrance and from the bottom plate to the upper part. The distribution pattern of dust with different particle sizes was not the same along the length of the tunnel. The large particles settled in the area of 25 m from the palm face under the action of gravity. With the increases of distance, the mass flow rate decreased, and the dust particle size became smaller, but the proportion of small particles gradually increased, while the R-R distribution index increased. The results in this study were confirmed to be reliable by comparing the measured data to provide guidance for the dust reduction technology in tunnel blasting, so as to quickly remove the dust generated during the blasting process and improve the engineering construction efficiency.