Dust Generation Rate Research Articles

Study on Sulfide Ore Dust Dispersion and Dust Reduction Measures Based on Simulation

Sulfide ore dust is at risk of explosion. To analyze the concentration distribution of sulfide ore dust in the ore loading, transporting, and unloading operations, the migration and dispersion processes of sulfide ore dust were simulated by using FLUENT software and taking the dust generation rate, roadway air velocity, and dust source position as variables. The concentration of sulfide ore dust was analyzed from the four-dimensional perspective of time and space. The results show that the maximum concentration of sulfide ore dust is determined by the dust generation rate. The roadway air velocity exhibits dual effects on the migration and deposition of sulfide ore dust. The ore loading position significantly impacts the distribution of sulfide ore dust, manifesting in varying degrees of superposition effects. Based on the results, this paper proposes a comprehensive dust reduction measure in the form of water curtain and dynamic ventilation, effectively minimizing the concentration of sulfide mine dust within the roadway.

Characterization of the Emissions and Crystalline Silica Content of Airborne Dust Generated from Grinding Natural and Engineered Stones.

In this study, we systematically characterized the airborne dust generated from grinding engineered and natural stone products using a laboratory testing system designed and operated to collect representative respirable dust samples. Four stone samples tested included two engineered stones consisting of crystalline silica in a polyester resin matrix (formulations differed with Stones A having up to 90wt% crystalline silica and Stone B up to 50wt% crystalline silica), an engineered stone consisting of recycled glass in a cement matrix (Stone C), and a granite. Aerosol samples were collected by respirable dust samplers, total dust samplers, and a Micro-Orifice Uniform Deposit Impactor. Aerosol samples were analyzed by gravimetric analysis and x-ray diffraction to determine dust generation rates, crystalline silica generation rates, and crystalline silica content. Additionally, bulk dust settled on the floor of the testing system was analyzed for crystalline silica content. Real-time particle size distributions were measured using an Aerodynamic Particle Sizer. All stone types generated similar trimodal lognormal number-weighted particle size distributions during grinding with the most prominent mode at an aerodynamic diameter of about 2.0-2.3 μm, suggesting dust formation from grinding different stones is similar. Bulk dust from Stone C contained no crystalline silica. Bulk dust from Stone A, Stone B, and granite contained 60, 23, and 30wt% crystalline silica, respectively. In Stones A and B, the cristobalite form of crystalline silica was more plentiful than the quartz form. Only the quartz form was detected in granite. The bulk dust, respirable dust, and total dust for each stone had comparable amounts of crystalline silica, suggesting that crystalline silica content in the bulk dust could be representative of that in respirable dust generated during grinding. Granite generated more dust per unit volume of material removed than the engineered stones, which all had similar normalized dust generation rates. Stone A had the highest normalized generation rates of crystalline silica, followed by granite, Stone B, and Stone C (no crystalline silica), which likely leads to the same trend of respirable crystalline silica (RCS) exposure when working with these different stones. Manufacturing and adoption of engineered stone products with formulations such as Stone B or Stone C could potentially lower or eliminate RCS exposure risks. Combining all the effects of dust generation rate, size-dependent silica content, and respirable fraction, the highest normalized generation rate of RCS consistently occurs at 3.2-5.6 µm for all the stones containing crystalline silica. Therefore, removing particles in this size range near the generation sources should be prioritized when developing engineering control measures.

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

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

Experimental study on the influence of wetting agent addition on the water adsorption and impact crushing dust generation of coal

AbstractThis study is aimed at investigating the influence of wetting agent addition on the water adsorption capacity, dust generation capacity and dust particle size distribution of coal. To achieve this aim, nonylphenol ethoxylate 10 wetting agent was used as an additive to prepare a 0.1% concentration solution, and a comparative test was conducted on different coal types from three coal mines in different provinces. The test results suggest that the natural saturated water adsorption time of coal was shortened by 33%–67% through wetting agent addition. Therefore, wetting agents are effective for enhancing water injection operations that require a limited construction period. The influence of wetting agent addition on the saturated water adsorption amount differed significantly for different coal types, and the wetting agent did not generally improve the saturated water adsorption rate. However, wetting agent addition alone did not lower the dust generation rate from coal. For a given moisture content, the wetting agent influenced the particle size distribution of dust generated during impact crushing differently between types of coal. For the three coal types investigated, wetting agent addition reduced the concentration of airborne by up to 8%.

Experimental Estimation of Dust Generation Under ELM-Like Transient Heat Loads in Divertor Plasma Simulator-2

Although plasma-facing components composed of tungsten are less likely to generate dust when compared to other materials, dust generation is still possible during severe transient phenomena in fusion devices. The generation of tungsten dusts was experimentally investigated by exposing tungsten targets to a transient heat flux factor (FHF) simulated by a high-energy pulsed laser so that the rate of dust generation would be analyzed. The rate of dust generation is observed to be increased linearly with respect to FHF: G [mg/min] = C (FEX – F0), where FEX is the experimental value of FHF, F0 is the threshold FHF, and C [mg∙m2∙s1/2/min∙MJ] = 0.0031 ± 0.0002. FHF indicates that the characteristics of dusts such as size and FHF are similar to those observed in several toroidal fusion devices. The threshold of FHF for dust generation was also observed as 41 MJ/m2∙ s1/2, which is similar to that of the international thermonuclear experimental reactor ITER (50 MJ/m2∙ s1/2).

The Composition of Emissions from Sanding Corian® with Different Sandpapers.

Laboratory tests were conducted to characterize the composition of emissions from sanding Corian®, a solid-surface composite material mainly composed of alumina trihydrate (ATH) and acrylic polymer. Three sandpaper materials (ceramic, silicon carbide, and aluminum oxide) were tested to distinguish the contribution of aluminum-containing dust in the emission from Corian® and sandpaper itself. The result can help identify the main cause of the pulmonary fibrosis from exposure to aluminum-containing dust while sanding Corian®. Airborne dust samples were measured using direct-reading instruments and collected using a Micro-Orifice Uniform Deposit Impactor (MOUDI) for estimating the normalized dust generation rate. The size-classified dust samples from MOUDI were analyzed for elemental aluminum content. Additionally, air samples were analyzed for characterizing methyl methacrylate (MMA). The results from the direct-reading instruments reveal that the size distribution of particulate from sanding Corian® differs from that of sawing Corian®, showing that the size distribution of dust is affected by the fabrication process. The normalized respirable dust generation rate indicates that more respirable dust was generated during sanding Corian® board. However, the use of aluminum oxide sandpaper does not result in a higher aluminum content in the respirable dust from sanding Corian®, suggesting that the aluminum content of the respirable dust is primarily originated from Corian® itself. The generation rates of MMA from sanding did not vary much among all types of sandpapers, and they were much lower than that of sawing, likely due to the higher temperature in the sawing process.

A study on the influencing factors and trends of the falling extra-fine aluminium flake dust generation rate

In order to provide a theoretical basis for reducing dust dusting, study the dusting characteristics of flake dust in production sites. Prediction calculation method of flake aluminium powder dust generation rate through research. Measure the mass loss of powder during different falling heights, different wind speeds and different solid flow diameters. The dust generation rate of the dust fall is calculated by mass loss of aluminium powder. Analyse the dust generation rate affected by falling heights, wind speeds and solid flow diameters. This study shows that the dust generation rate increases exponentially with the falling height, increases linearly with the wind speed, and decreases with the solid flow diameter. By combining these results with the dust generation theory by Marc, we obtained a calculation model of the flake aluminium dust generation rate, and this model has good accuracy with an average error of only 11.71% compared with the experimental values.

The effect of geometries and cutting parameters of conical pick on the characteristics of dust generation: Experimental investigation and theoretical exploration

Understanding the characteristics of dust generation is the basis of effective dust control. To reveal the influence of pick geometries and cutting parameters on the characteristics of dust generation during roadheader cutting, this paper conducted an experimental investigation and theoretical exploration on the effects of tip angle, attack angle and cutting speed on the cumulative proportion of small size dust and the mass rate of dust generation. It was found that tip angle and attack angle considerably affected dust generation, whereas the effect of cutting speed could be ignored. The positive relationships between tip angle and both cumulative proportion and mass rate of dust generation were observed. A larger attack angle can reduce dust generation. The change of the cutting force and the size of the damaged zone are the fundamental reasons for the difference of dust generation under varying conditions. In general, the cutting process with a smaller tip angle of pick and a larger attack angle appears beneficial to abate dust generation. This study would enhance the fundamental understanding of coal dust generation, which will provide guidance for selecting suitable pick geometries and cutting parameters to ameliorate environment quality and obtain a cleaner production environment.

The effect of coal proximate compositions on the characteristics of dust generation using a conical pick cutting system

To investigate the characteristics of coal dust generation when cut by a roadheader, a system was designed for performing cutting experiments. The aerodynamic diameter distribution of dust was tested by a laser particle size analyzer. Correlations between the coal proximate compositions and the characteristics of dust generation were studied. Results showed that fixed carbon had significantly positive correlations with the cumulative proportion of respirable dust and the rate of dust generation. The bonded high-density pulverized core could be responsible for reducing the correlation with fine particulate matter. The presence of moisture had inhibitory effects on dust generation. Volatile matter had a slightly negative influence on dust generation, and ash was considered to have no effect. More attention should be focused on heading faces with high fixed carbon and low moisture. This study provides essential guidance for understanding the characteristics of dust generation and improving dust reduction technologies.

The Composition of Emissions from Sawing Corian®, a Solid Surface Composite Material.

We conducted detailed analyses of the composition of emissions from sawing Corian®, a solid surface composite material, in a laboratory testing system. The analyses included the aluminum content of size-selective dust samples, semivolatile organic compounds (SVOCs) in respirable dust samples, and volatile organic compounds (VOCs). The normalized respirable dust generation rate found using a Micro-Orifice Uniform Deposit Impactor was 5.9 milligrams per gram (mg g-1) suggesting that 0.59% of the mass removed from sawing Corian® becomes respirable dust. The alumina trihydrate content of the dust was consistently above 85% in most parts of the respirable size range, verifying an earlier finding that it is the dominant composition of the airborne particles of all sizes, including ultrafine particles. VOC analyses revealed that methyl methacrylate (MMA) was the most abundant compound, with a generation rate of 6.9 mg g-1 (0.69% of the mass removed from sawing Corian® became MMA vapor). The SVOC analysis only found a small amount of MMA (0.55%) in the bulk dust.

Correlation analysis of three influencing factors and the dust production rate for a free-falling particle stream

The effects of three factors (i.e., drop height h, hopper outlet diameter d0, and material temperature T) on the dust generation rate derived from a free falling particle stream were investigated via full factorial experiments. The correlation between the three factors and dust generation rate was also analysed. Results show that T and h affect the first fugitive dust rate largely, whereas the second fugitive dust rate is mainly dominated by h and d0. Through analysing the first fugitive dust percentage data, it is found that h and T should be considered first for higher temperatures and lower flow rates, whereas h and d0 can be considered under contrasting conditions, and h should be controlled in the remaining two sets of conditions. Relationships between the influencing factors and total and first fugitive dust rates were developed via multiple regression to quantify the dust emission rates for different contact surfaces (rigid or water).

The Generation Rate of Respirable Dust from Cutting Fiber Cement Siding Using Different Tools.

This article describes the evaluation of the generation rate of respirable dust (GAPS, defined as the mass of respirable dust generated per unit linear length cut) from cutting fiber cement siding using different tools in a laboratory testing system. We used an aerodynamic particle sizer spectrometer (APS) to continuously monitor the real-time size distributions of the dust throughout cutting tests when using a variety of tools, and calculated the generation rate of respirable dust for each testing condition using the size distribution data. The test result verifies that power shears provided an almost dust-free operation with a GAPS of 0.006 g m-1 at the testing condition. For the same power saws, the cuts using saw blades with more teeth generated more respirable dusts. Using the same blade for all four miter saws tested in this study, a positive linear correlation was found between the saws' blade rotating speed and its dust generation rate. In addition, a circular saw running at the highest blade rotating speed of 9068 rpm generated the greatest amount of dust. All the miter saws generated less dust in the 'chopping mode' than in the 'chopping and sliding' mode. For the tested saws, GAPS consistently decreased with the increases of the saw cutting feed rate and the number of board in the stack. All the test results point out that fewer cutting interactions between the saw blade's teeth and the siding board for a unit linear length of cut tend to result in a lower generation rate of respirable dust. These results may help guide optimal operation in practice and future tool development aimed at minimizing dust generation while producing a satisfactory cut.

Experimental study of dust emission: Comparison between high-temperature and ambient-temperature materials

The generation of dust during the handling of high-temperature materials, which fall or impact contact surfaces, can be a significant source of danger for the health of operators. A greater knowledge on the effective control of these falling and impact processes must be illustrated. This paper presents recent experimental research on the characteristics and dust generation rates of materials of different temperatures during the free falling process. The results show that when experimental conditions are the same, the high-temperature material has a larger dispersion radius and a smaller impact velocity compared to the ambient-temperature material. In all cases, the first fugitive dust rate (ηw) which is produced by falling process increased as the material temperature (T) increased. The second fugitive dust rate (ηs) which is emitted by impacting process and the total dust rate (ηr) which consists of ηw and ηs, all decreased sharply at first with increasing T, after which the ηs–T curves has a gentle sloping section but the ηr–T curves increases slightly. In addition, a comprehensive analysis of the factors contributing to dust generation is also included in this paper. It was found that the effect of temperature on dust generation was more obvious with increasing percentage of the first fugitive dust.

Experimental study of flow regimes and dust emission in a free falling particle stream

The flow regimes in a free falling particle stream and the dust emission rate are experimentally explored in this paper. The results show that the particle stream could be divided successively into the stable regime, the transitive regime and the dispersive regime. The length of each regime is quantitatively identified. In our testing range, the dust emission rate (ηr) increases monotonically with Z and the gratitude gradually increases when the particle stream impacts onto the rigid surface in the transitive regime. The dust generation rate shows linear to the dimensionless drop height. However, the rate decreases slightly monotonically with the drop height (Z) when the particle stream impacts onto the surface in the dispersive regime. The dust generation rate presents an exponent relation with the dimensionless drop height. The empirical equation about ηr is derived. It is found that the second fugitive dust still emits under the condition that the particle stream impacts into the water surface when the hopper outlet diameter is from 1 to 8mm. Reducing the expanding level and the impaction intensity of the particle flow is considerably important when the contact surface is in the transitive regime and the dispersive regime, respectively.

On the Characterization of the Generation Rate and Size-Dependent Crystalline Silica Content of the Dust from Cutting Fiber Cement Siding.

A laboratory testing system was developed to systematically characterize the dust generation rate and size-dependent crystalline silica content when cutting or shaping silica containing materials. The tests of cutting fiber cement siding in this system verify that it provides high test repeatability, making it suitable for the targeted characterizations. The mass-based size distributions obtained from a gravimetric-based instrument and a direct reading instrument both show bimodal lognormal distributions with a larger mode ~13 µm and another mode <5 µm for the dusts from cutting four different brands of fiber cement siding. The generation rates of respirable dust obtained from the two instruments are comparable, and the results from each instrument are similar for the four brands. The silica content in the airborne dusts, however, strongly depends on the amount of silica used in the respective product. It is also observed that the silica content in the airborne dust from cutting the four brands of fiber cement siding showed the same trend of an increase with the aerodynamic diameter of the dust, approaching the silica content levels found in their respective bulk samples. Combining the results for both the dust size distribution and size-dependent silica content, it is found that most of the respirable crystalline silica (RCS) resides in the dust ~2.5 µm in aerodynamic diameter. These results would help guide the development of specific engineering control measures targeted at lowering workers' exposure to RCS while cutting fiber cement siding. With the high repeatability using the laboratory testing system, the dust generation rate could then be characterized under different operating conditions, and with the deployment of various engineering control measures. This would greatly facilitate the systematic evaluation of the control effectiveness and the selection of the optimal control solutions for field trials.

Simulation of air quality and cost to ventilate swine farrowing facilities in winter

We developed a simulation model to study the effect of ventilation airflow rate with and without filtered recirculation on airborne contaminant concentrations (dust, NH3, CO, and CO2) for swine farrowing facilities. Energy and mass balance equations were used to simulate the indoor air quality and operational cost for a variety of ventilation conditions over a 3-month winter period, using time-varied outdoor temperature. The sensitivity of input and output parameters on indoor air quality and operational cost were evaluated. Significant factors affecting model output included mean winter temperature, generation rate of contaminants, pit-air-exchange ratio, and recirculation ratio. As mean outdoor temperature was decreased from −2.5°C to −12.5°C, total operational costs were increased from $872 to $1304. Dust generation rate affected dust concentrations linearly. When dust generation rates changed −50% and +100% from baseline, indoor dust concentrations were changed −50% and +100%, respectively. The selection of a pit-air-exchange ratio was found critical to NH3 concentration, but has little impact on other contaminants or cost. As the pit-air-exchange ratio was increased from 0.1 to 0.3, the NH3 concentration was increased by a factor of 1.5. The recirculation ratio affected both IAQ factors and total operational cost. As the recirculation ratio decreased to 0, inhalable and respirable dust concentrations, humidity, NH3 and CO2 concentrations decreased and total operational cost ($2216) was 104% more than with pit-fan-only ventilation ($1088). When the recirculation ratio was 1, the total operational cost was increased by $573 (53%) compared to pit-fan-only. Simulation provides a useful tool for examining the costs and benefits to installing common ventilation technology to CAFO and, ultimately, making sound management decisions.

Dust Control Effectiveness of Drywall Sanding Tools

In this laboratory study, four drywall sanding tools were evaluated in terms of dust generation rates in the respirable and thoracic size classes. In a repeated measures study design, 16 participants performed simulated drywall finishing tasks with each of four tools: (1) ventilated sander, (2) pole sander, (3) block sander, and (4) wet sponge. Dependent variables of interest were thoracic and respirable breathing zone dust concentrations. Analysis by Friedman's Test revealed that the ventilated drywall sanding tool produced significantly less dust, of both size classes, than did the other three tools. The pole and wet sanders produced significantly less dust of both size classes than did the block sander. The block sander, the most commonly used tool in drywall finishing operations, produced significantly more dust of both size classes than did the other three tools. When compared with the block sander, the other tools offer substantial dust reduction. The ventilated tool reduced respirable concentrations by 88% and thoracic concentrations by 85%. The pole sander reduced respirable concentrations by 58% and thoracic by 50%. The wet sander produced reductions of 60% and 47% in the respirable and thoracic classes, respectively. Wet sponge sanders and pole sanders are effective at reducing breathing-zone dust concentrations; however, based on its superior dust control effectiveness, the ventilated sander is the recommended tool for drywall finishing operations.

Experimental Research on Reducing the Dust of BOF in CO2 and O2 Mixed Blowing Steelmaking Process

The thermodynamic theory and experimental research on reducing the dust generation in CO2 and O2 Mixed Blowing (COMB) steelmaking process have been undertaken. In labo-scale experiment, data show that the amounts of dust and iron loss keep on decreasing as CO2 blowing rate increases. Further, dust sampled from 30 t BOF conventional process in Fujian Sanming Iron and Steel Plant has been analyzed, and the dust generation rate in the conventional process reduced from 666 g/s at the 1.5 min point to 215 g/s at the end of blowing. Introducing the technology of the stepped CO2 blow, the average generation rate of dust is reduced by 12.5% in this experiment compared with the conventional one, while the average generation rate of T-Fe in dust is reduced by 12.7%. This improvement has been made keeping the same decarburization rates. Therefore the stepped CO2 blowing rate has remarkable effect on dust generation. This research has proved that COMB steelmaking process is effective on a decrease in dust generation along with improved iron yield.

Combined Single-Drop and Rotating Drum Dustiness Test of Fine to Nanosize Powders Using a Small Drum

A dustiness test has been developed that performs both a single-drop and a continuous rotation test using a 6-g sample. Tests were completed on pigment-grade and ultrafine TiO2, two grades of corundum (Aloxite), yttrium-stabilized zirconia (Y-zirconia) granules, fumed silica, goethite, talc and bentonite. The generated particles were quantified by counting and sizing at 1-s time resolution using the TSI Fast Mobility Particle Sizer and the TSI Aerodynamic Particle Sizer and by collecting the particles on a filter for weighing. The method generated reproducible amounts and size distributions of particles. The size distributions had two more or less separated size modes >0.9 microm and in addition all materials except TiO2 pigment-grade and Aloxite F1200 generated a size mode in the range from approximately 100 to approximately 220 nm. Pigment-grade TiO2 had the lowest dustiness and ultrafine TiO2 the highest dustiness as measured by particle number for both the single-drop and rotation test and as measured by mass for both tests combined. The difference was a factor of approximately 300. Three types of dust generation rate time profiles were observed; brief initial burst (talc, both grades of corundum), decaying rate during rotation period (fumed silica, TiO2 ultrafine and pigment grade, bentonite) and constant rate (Y-zirconia, goethite). These profile types were in agreement with the differences in the ratio of amount of particles generated during the single drop to the amount generated during the single-drop and rotation test combined. The ratio ranged a factor approximately 40. The new test method enables a characterization of dustiness with relevance to different user scenarios.

Factors contributing to the poor bulk behavior of meat and bone meal and methods for improving these behaviors

Meat and bone meal (MBM), a product of the rendering industry, is a potential feedstock for numerous bio-based applications. Design of processing equipment for MBM is difficult due to MBM’s bulk behaviors; it flows less easily than many other granular materials, and it tends to foul the surfaces of processing equipment. This study examines the major factors contributing to MBM’s poor bulk behavior, including moisture content, fat content, particle size distribution and temperature, and the relative importance of these factors. Potential methods for improving MBM’s bulk properties, including use of an anti-caking agent, dehydration, fat extraction, milling and refrigeration are also studied. The effects of these factors were determined by a standard laboratory measurement, the Hausner ratio, as well as by the rate of surface-fouling and dust generation using a pilot-scale aspirator. In contrast to past studies with other granular materials, moisture content was shown to have an insignificant effect on MBM’s bulk behavior. The results, however, show that MBM fat content is a major determinant of the bulk behavior of the MBM. Reduction of fat content resulted in major changes in MBM’s bulk behavior, by all measures used. Less dramatic changes were achieved through refrigeration to solidify the fat and/or treatment with an anti-caking agent.