Dust Concentration Measurements Research Articles

Measurement of dust concentration based on VBAI

There are almost no economic and management solutions in automated measurement of dust concentration of magnesium oxide smelting electric arc furnace mouth. Nearly a thousand degrees of heat and the strong magnetic fields created by high-current Constitutes a serious interference with the sensor. This makes close-contact measurement method becomes almost impossible. To solve the above problem, this paper proposes a measurement scheme based on VBAI (Vision Builder for Automated Inspection, a software developed by National Instruments) to calculate the dust concentration. It uses visual analysis of the means to calculate the number of dust particles per unit volume of. And then it calculates the dust concentration. Though the analysis of the actual photo of the smelting site, the relative dust concentration in the mouth of the furnace is calculate. This method will be applied to the precipitator 70 kW motor inverter control and has a high recognition rate and significant application prospects.

An Adaptive Pattern Recognition Algorithm in Coal Dust On-Line Measure

It is crucial to measure dust concentration precisely, but it normally varies with changes of working conditions. To increase precision and on-line performance of coal dust sensor, an adaptive pattern recognition algorithm was presented. The signals of unitary angular spectrums were chosen as the adaptive eigenvector for pattern recognition and pattern bank was established in advance. Furthermore, the ratio of the sum of inner signals to that of outer signals about the diffraction angular was considered as the eigenvector of subclass pattern classification. After classification, pattern could be recognized easily and rapidly. Subsequently, number of detailed patterns within different pattern groups was increased reasonably. The errors of total coal dust and respiring coal dust decline from 6% to 2.5% and from 9% to 3%, respectively. As a result, the precision of sensor achieves 95% during the measurement. It can be concluded that the adaptive pattern recognition algorithm is effective to improve the precision and real-time performance of coal dust sensor.

Application of foam to suppress rock dust in a large cross-section rock roadway driven with roadheader

The greatest source of rock dust on rock roadway heading face is the roadheader. Overexposure to respirable rock dust can be a serious health hazard to roadheader operators and other workers. One of the rock roadways, named North Belt Main Entry (NBME), belonging to the underground coal mine Zhuxianzhuang, located in east China, is being driven by the EBZ318H roadheader. The cross-section of the roadway is 15.84m2, and the heading face has a high concentration of respirable rock dust.This paper presents a study of rock roadheader dust control by foam, taking into account the dust generation characteristics. A new foam preparation system and application method has been proposed and the dust suppression effect of foam has been assessed by dust concentration measurements taken at two points next to the roadheader operator in the previously mentioned underground coal mine.The results have shown that the foam dramatically reduced the rock dust concentrations. The roadheader operator’s respirable dust exposures were lowed from 540.2mg/m3 to 84.3mg/m3, and the dust suppression efficiency reached 84.4% on the NBME heading face. In addition, the visibility and environment of the heading face was significantly improved. It is concluded that the foam showed a significant improvement on the rock dust capture efficiency, and avoided the main deficiencies of conventional water sprays.

Assessment of swine worker exposures to dust and endotoxin during hog load-out and power washing.

Field measurements of personal and area dust and endotoxin concentrations were obtained while agricultural workers performed two work tasks that have been previously unreported: hog load-out and swine building power washing. Hog load-out involves moving hogs from their pens in finishing buildings into a truck for transport to a meat processor. High pressure power washing is conducted for sanitation purposes after a building has been emptied of hogs to remove surface and floor debris. This debris consists of feed, feces, and hog dander as dust or an encrusted form. The hog load-out process necessarily increases pig activity which is known to increase airborne dust concentrations. An unintended consequence of power washing is that the material covering surfaces is forcibly ejected into the atmosphere, creating the potential for a highly concentrated aerosol exposure to workers. The load-out process resulted in a median personal inhalable mass concentration of 7.14 mg m(-) (3) and median endotoxin concentration of 12 150 endotoxin units (EU) m(-) (3). When converted to an 8-h time-weighted average for a 'total' sampler, one of the 19 samples exceeded a regulatory limit of 15 mg m(-) (3). An impinger was used to sample power washing endotoxin concentrations, which resulted in a median personal concentration of 40 350 EU m(-) (3). These concentrations were among the highest found in the literature for any occupation. With the lack of engineering controls present to reduce airborne contaminant concentrations in swine buildings, either respirator use or a reduction in exposure time is recommended while performing these tasks.

Experimental and numerical investigation into the dynamics of dust lifting up from the layer behind the propagating shock wave

In a number of industrial facilities and factory buildings dust layers cover floors, walls, ceilings and various installations. The dust can be easily dispersed by pressure waves generated by weak explosions or as a result of damage of a compressed gas systems. If the obtained explosive dust-air mixture is ignited, a devastating explosion may occur. The aim of the work was to study the dust lifting process from the layer behind the propagating shock wave and to determine some important parameters, which later could be used for development and validation of the numerical model of the process. The experiments were conducted with the use of a shock tube. For measuring the dust concentration in the mixture with air, a special five-channel optical device was constructed, enabling measurements at five positions located in one vertical plane along the height of the tube. The delay in lifting of the dust from the layer and the vertical velocity of the dust cloud were calculated from the dust concentration measurements. The research was carried out for various initial conditions and for various types of dusts. The results obtained in tests with black coal dust are presented in the paper. Three shock wave velocities: 450, 490 and 518 m/s and three dust layer thicknesses, equal to 1.0, 1.5 and 2.0 mm, were taken into consideration. Measurements results of the mean vertical component of the dust cloud velocity between the layer and the first laser beam were used in a new model, where the dust dispersing process is modeled as an injection of the dust from the layer. The numerical simulations were based on the Euler or Lagrange model of the dust phase. In case of Euler model, the dust layer was replaced by injection of dust from the bottom of the channel. The calculations were performed for two models of the investigated process. In the first model, correlation was worked out for all tested dusts and in the new model, the individual correlations for every tested dust were prepared. The results obtained with use of the second model proved to be closer to the experimental results. It appeared, however, that lifting up of the dust from the thick layers, thicker than 1 mm, is a more complex process than that from a thin layers and still requires more research. Probably the problem is, that the shock wave action upon the thick layer causes its aggregation in the first stage of the dispersing process, what makes the dust lifting process more difficult.

Long‐term aerosol measurements in Gran Canaria, Canary Islands: Particle concentration, sources and elemental composition

There are very few sets of long‐term measurements of aerosol concentrations over the North Atlantic Ocean, yet such data is invaluable in quantifying atmospheric dust inputs to this ocean region. We present an 8‐year record of total suspended particles (TSP) collected at three stations on Gran Canaria Island, Spain (Taliarte at sea level, Tafira 269 m above sea level (a.s.l.) and Pico de la Gorra 1930 m a.s.l.). Using wet and dry deposition measurements, the mean dust flux was calculated at 42.3 mg m−2 d−1. Air mass back trajectories (HYSPLIT, NOAA) suggested that the Sahara desert is the major source of African dust (dominant during 32–50% of days), while the Sahel desert was the major source only 2–10% of the time (maximum in summer). Elemental composition ratios of African samples indicate that, despite the homogeneity of the dust in collected samples, some signatures of the bedrocks can still be detected. Differences were found for the Sahel, Central Sahara and North of Sahara regions in Ti/Al, Mg/Al and Ca/Al ratios, respectively. Elements often associated with pollution (Pb, Cd, Ni, Zn) appeared to share a common origin, while Cu may have a predominantly local source, as suggested by a decrease in the enrichment factor (EF) of Cu during dust events. The inter‐annual variability of dust concentrations is investigated in this work. During winter, African dust concentration measurements at the Pico de la Gorra station were found to correlate with the North Atlantic Oscillation (NAO) index.

A Comparative Field Study on Dust Measurements by Different Sampling Methods with Emphasis on Estimating Factors for Recalculation from Chinese ‘Total Dust’ Measurements to Respirable Dust Concentrations

In China, dust samplers were originally designed to collect 'total dust' for a short term during production, which is different from the widely adopted sampling strategy for dust. With the aim to provide the conversion factor from Chinese total dust to US and German respirable dust and to look at the influences on conversion factors from environment, production, and instruments, a comparative field study on the dust concentration measurements by different sampling methods was carried out in the same Chinese industries as in the 1989-1990 study and in some other factories. A supplemental experiment was also conducted in a wind tunnel. Dust concentration was measured with a parallel sampling strategy by using the following samplers: 10-mm nylon cyclone for US respirable dust (AR), FSP-Berufsgenossenschaftliches Institut für Arbeitssicherheit (BIA) cyclone for German respirable dust (GR), and samplers for Chinese total dust (CT). Totally, 1434 samples were collected (269 AR, 198 GR, and 967 CT), from which 429 matched sample pairs (249 pairs of AR/CT, 180 GR/CT) were available to calculate conversion ratios. Industry- and job-based conversion factors are presented in this study. The conversion factor of AR/CT was 0.38 for tungsten mines, 0.19 for copper/iron mines, 0.65 for tin mines, and 0.20 for pottery industry, while the factor of GR/CT was 0.69 for tungsten, 0.37 for copper/iron, and 0.52 for pottery. In the job category, AR/CT factors varied from 0.16 to 0.96 and GR/CT from 0.12 to 0.72. For the industries studied in 1988-1989, the AR/CT and GR/CT factors were 0.29 and 0.45, respectively. Both factors were definitely influenced by production, CT dust concentration, sample gain, and variation of dust concentration. Moreover, the respirable dust concentration by FSP-BIA was significantly higher than that by 10-mm cyclones, 63.27-73.10% more as showed also by the wind tunnel experiment. Meanwhile, the GR/CT ratio was significantly larger than the AR/CT in every industry or job with only few exceptions. The GR/CT estimates should be considered as independent ones. Following these results, there is a need to use 'ideal samplers' (consistent with the internationally accepted respirable fraction) in practice and to assess the existent samplers in order to homogenize the exposure data situation.

Mine Dust Concentration Measurement Method Based on Model of Dust Concentration and Humidity

According to the coal mine underground work place humidity changes affect the measurement precision of dust concentration, improper spray cause coal with the water loss and wastes a lot of water resources, the paper put forward a correction factor of dust concentration based on the relative humidity, establish the relation model of concentration and humidity. The test results show that: the dust concentration correction factor and relationship model of concentration and humidity are effective and scientific, it has better practicability to solve the problem of underground coal mine.

Development and Evaluation of a Semi-Empirical Two-Zone Dust Exposure Model for a Dusty Construction Trade

Drywall finishing is a dusty construction activity. We describe a mathematical model that predicts the time-weighted average concentration of respirable and total dusts in the personal breathing zone of the sander, and in the area surrounding joint compound sanding activities. The model represents spatial variation in dust concentrations using two-zones, and temporal variation using an exponential function. Interzone flux and the relationships between respirable and total dusts are described using empirical factors. For model evaluation, we measured dust concentrations in two field studies, including three workers from a commercial contracting crew, and one unskilled worker. Data from the field studies confirm that the model assumptions and parameterization are reasonable and thus validate the modeling approach. Predicted dust Ctwa were in concordance with measured values for the contracting crew, but under estimated measured values for the unskilled worker. Further characterization of skill-related exposure factors is indicated.

Auxiliary ventilation in mining roadways driven with roadheaders: Validated CFD modelling of dust behaviour

The production of dust when driving mining roadways can affect workers health. In addition, there is a decrease in productivity since Mine Safety regulations establish a reduction in the working time depending on the quartz content and dust concentration in the atmosphere. One of the gate roadways of the longwall named E4-S, belonging to the underground coal mine Carbonar SA located in Northern Spain, is being driven by an AM50 roadheader machine. The mined coal has a high coal dust content. This paper presents a study of dust behaviour in two auxiliary ventilation systems by Computational Fluid Dynamics (CFD) models, taking into account the influence of time. The accuracy of these CFD models was assessed by airflow velocity and respirable dust concentration measurements taken in six points of six roadway cross-sections of the mentioned operating coal mine. It is concluded that these models predicted the airflow and dust behaviour at the working face, where the dust source is located, and in different roadways cross-sections behind the working face. As a result, CFD models allow optimization of the auxiliary ventilation system used, avoiding the important deficiencies when it is calculated by conventional methods.

Measurements of respirable dust and nanoparticle concentrations in a titanium dioxide pigment production factory

This study compared respirable dust and nanoparticle concentrations measured by different sampling devices at a titanium dioxide pigment factory. Respirable particle mass concentrations, nanoparticle concentrations, particle size distribution and particle metallic content were measured at different sampling locations. The sampling results of the Multi-orifice Uniform Deposit Impactor (MOUDI) showed that the particle size distribution at this titanium dioxide production factory fell in the range of 1–10 μ m. Generally, the higher levels of the respirable particle mass concentrations and nanoparticle number concentrations were near the packing site of the pigment titanium dioxide production factory. Metal analysis results revealed that the titanium dioxide concentrations in respirable dust and nanoparticles were within the limits specified by National Institute for Occupational Safety and Health (NIOSH). During sampling, particle metallic content analysis is essential for identifying the source of particles and for measuring respirable dust and nanoparticle concentrations.

African dust deposition to Florida: Temporal and spatial variability and comparisons to models

Mineral dust plays an important role in ocean biogeochemistry as a source of Fe which in some regions is a limiting micronutrient. Ocean models often use the output of dust transport models to estimate dust‐Fe deposition. However, models have not been adequately tested, because of the dearth of long‐term dust deposition measurements. Here we present the results of a 3 year deposition study in a nine‐station network in Florida which is impacted by African dust every year, and we compare these measurements with estimates from global dust models. Wet deposition (WD) and bulk deposition (BD) rates of soil‐related elements (Al, Fe, and Mn) were highly correlated and remarkably uniform across the state; they exhibited an extremely strong summer maximum that closely matched concurrently measured dust concentrations in Miami. The average dust WD across the network was about 150 μg cm−2 yr−1, and the BD rate was 200 μg cm−2 yr−1. Dry deposition (DD), defined as the difference between BD and WD, was a minor component, about 20–30% of the total. In a comparison with nine dust models in the Aerosol Comparisons between Observations and Models project (AeroCom) database, models correctly characterized the seasonal cycle of deposition but most substantially underestimated summer deposition. The ratios of WD to DD in the models varied greatly, ranging from about 1:1 to 30:1 in contrast to the Florida Atmospheric Mercury Study station ratio, which was about 3:1 to 4:1. These results show a clear need for more dust deposition measurements in regions dominated by oceanic air masses and for a better understanding of the treatment of deposition processes in models.

Increase in African dust flux at the onset of commercial agriculture in the Sahel region

The Sahara Desert is the largest source of mineral dust in the world. Emissions of African dust increased sharply in the early 1970s (ref. 2), a change that has been attributed mainly to drought in the Sahara/Sahel region caused by changes in the global distribution of sea surface temperature. The human contribution to land degradation and dust mobilization in this region remains poorly understood, owing to the paucity of data that would allow the identification of long-term trends in desertification. Direct measurements of airborne African dust concentrations only became available in the mid-1960s from a station on Barbados and subsequently from satellite imagery since the late 1970s: they do not cover the onset of commercial agriculture in the Sahel region approximately 170 years ago. Here we construct a 3,200-year record of dust deposition off northwest Africa by investigating the chemistry and grain-size distribution of terrigenous sediments deposited at a marine site located directly under the West African dust plume. With the help of our dust record and a proxy record for West African precipitation we find that, on the century scale, dust deposition is related to precipitation in tropical West Africa until the seventeenth century. At the beginning of the nineteenth century, a sharp increase in dust deposition parallels the advent of commercial agriculture in the Sahel region. Our findings suggest that human-induced dust emissions from the Sahel region have contributed to the atmospheric dust load for about 200 years.

The influence of the lighting program on broiler activity and dust production

Among the factors influencing dust production on the farms, animal activity is probably the least studied. Animal activity is strongly affected by circadian rhythms and it is altered by the rearing conditions, especially the management of light and the feeding strategy. In this study, a broiler flock was evaluated until 35 d of age with the general objective of studying the factors influencing the production of dust, particularly the effect of animal activity, as affected by the lighting program. In an experimental room, 2 daily dark periods of 6 and 4 h with 158 birds divided in 12 groups, reared on wood shavings, were evaluated. A TEOM analyzer was used to measure dust concentrations, whereas animal activity was determined by observation of birds on video tapes. Animal activity was defined by an activity index, which was determined by direct evaluation of birds on video tapes. The animal activity index was closely related to the lighting program (0.084 and 0.556 during dark and light periods, respectively) and was maximum at wk 4 of the rearing period. The dust concentrations during light periods were on average 4 times higher than during dark periods, with a maximum average concentration of 2.82 mg x m(-3) during the last week of the cycle. Particulate matter emission was on average 2.08 mg x animal(-1) x hour(-1). Dust concentration increased linearly with bird weight and daily variations in dust production were characterized. As a result, a direct cause-effect relationship between animal activity and dust concentration was obtained (r(2) = 0.89).

Dust-Emission from Abrasive Sanding Processes in the Malaysian Wooden Furniture Industry

A series of sanding experiments were carried out in a large dust tunnel, using an orbital sander with an aluminum oxide abrasive of 150 grit size, on twelve different hardwood species. Dust concentration measurements were taken using gravimetric isokinetic air-quality samplers. A field survey of 25 wooden furniture-manufacturing mills to ascertain the dust exposure levels at the sanding sections and also evaluate the labor productivity losses encountered among workers as a result of dust exposure. The results found that dust emission in the sanding process was primarily determined by the amount of wood removed. Further, the dust exposure levels at the sanding section in the furniture-manufacturing mills were above the standard 5 mg m-3 level and hence, control of dust emission and the use of dust protection gears by the workers must be enforced in the furniture-manufacturing mills to ensure the health and safety of the workers. Without such measures, labor productivity among the workers would be reduced.

새만금 지역 간척지 및 인근 농경지에서의 비산 및 부유먼지의 지역별, 시기별 모니터링

A study on fugitive dusts was conducted at Saemangeum reclaimed land and the neighboring farm located at the west coast of Korea. After the area was completely reclaimed in 2006, halophyte plants and several windbreak systems were installed. The distributions of suspended dust particle was regularly measured through field experiment. The size of dust source area was also analyzed periodically and then it was determined to be in the following order: Buan > Gimje > Gunsan. The suspended dust which were dispersed to the neighboring areas were significantly affected by the size of the soil particles, wind velocity and wind direction. The results of Big Spring Number Eight (BSNE) experiments also showed that the concentration of the fugitive dust generated from the reclaimed land was reduced remarkably by the presence of halophyte plants. Recently, in 2008, the measured dust concentration rate was decreased by an average of 30.6%. The average dust concentration is expected to decrease further as more areas are being covered by halophyte plants.

Development of a global model of mineral dust aerosol microphysics

Abstract. A mineral dust module is developed and implemented into the global aerosol microphysics model, GISS-TOMAS. The model is evaluated against long-term measurements of dust surface mass concentrations and deposition fluxes. Predicted mass concentrations and deposition fluxes are in error on average by a factor of 3 and 5, respectively. The comparison shows that the model performs better near the dust source regions but underestimates surface concentrations and deposition fluxes in more remote regions. Including only sites with measured dust concentrations of at least 0.5 μg m−3, the model prediction agrees with observations to within a factor of 2. It was hypothesized that the lifetime of dust, 2.6 days in our base case, is too short and causes the underestimation in remote areas. However, a sensitivity simulation with smaller dust particles and increased lifetime, 3.7 days, does not significantly improve the comparison. These results suggest that the underestimation of mineral dust in remote areas may result from local factors/sources not well described by the global dust source function used here or the GCM meteorology. The effect of dust aerosols on CCN(0.2%) concentrations is negligible in most regions of the globe; however, CCN(0.2%) concentrations change decrease by 10–20% in dusty regions the impact of dust on CCN(0.2%) concentrations in dusty regions is very sensitive to the assumed size distribution of emissions. If emissions are predominantly in the coarse mode, CCN(0.2%) decreases in dusty regions up to 10–20% because dust competes for condensable H2SO4, reducing the condensational growth of ultrafine mode particles to CCN sizes. With significant fine mode emissions, however, CCN(0.2%) doubles in Saharan source regions because the direct emission of dust particles outweighs any microphysical feedbacks. The impact of dust on CCN concentrations active at various water supersaturations is also investigated. Below 0.1%, CCN concentrations increase significantly in dusty regions due to the presence of coarse dust particles. Above 0.2%, CCN concentrations show a similar behavior as CCN(0.2%).

Characteristics of Dust Cloud Formation

Dust concentration and turbulence measurements are basic and important measurements in process industry for dust explosion prevention and protection. In this paper' principles of measurement, measured data of dust concentration and flow field from large scale test site and factories under real working conditions, dust concentration and turbulence patterns are presented, and a method of determination of characteristics of dust cloud formation was introduced.

Windows pollution problems of the dust concentration measurement based on scattering method

The windows are separated the measurement system from the dust space in the light Scattering dust concentration measurement system. The windows are polluted unavoidably by the dust and the measurement error is produced. Based on the Mie Scattering theory, the measurement error is researched in this paper. The numerical simulation results show that the measurement error is related to the particles diameter distribution and the refractive index, but is independent of the particles average diameter. A novel photoelectricity sensor is developed in this paper in order to solve the measurement error by the windows pollution. The calculated method is brought out which can amend the measurement errors by the windows pollution and improve the measurement accuracy.

A revised conversion factor relating respirable dust concentrations measured by 10 mm Dorr-Oliver nylon cyclones operated at 1.7 and 2.0 L min−1

Accurate measurement of workplace respirable dust concentration is an essential step in eliminating lung disease in any occupational setting. In the United States (U.S.) coal mining industry, this measurement process has relied upon a personal sampler that includes a 10 mm Dorr-Oliver (DO) nylon cyclone operated at a flow rate of 2.0 L min(-1) to collect a respirable dust sample. Dust concentrations measured with this sampler are multiplied by 1.38, which was empirically derived, to convert them to measurements approximating the United Kingdom British Medical Research Council (BMRC) definition of respirable dust upon which the health effects of coal mine dust are based. The International Organization for Standardization (ISO) subsequently refined the respirable dust definition and the U.S. National Institute for Occupational Safety and Health (NIOSH) 1995 Criteria for a Recommended Standard presented a conversion multiplier of 0.857 to apply to the 2.0 L min(-1) DO (in addition to the1.38 multiplier) to obtain equivalent ISO concentrations, as approximated by the 1.7 L min(-1) DO. However, the conversion multiplier 0.857 was derived indirectly from a limited size distribution data set rather than a direct comparison of the DO samplers. The present analysis focuses on providing a more accurate conversion multiplier derived from direct comparisons of the 2.0 L min(-1) (with 1.38 BMRC equivalency multiplier) and 1.7 L min(-1) DO cyclones. A weighted linear regression analysis of this database suggests that a more accurate estimate of the conversion multiplier is 0.815.