Dusting is one of the major problems in the operation of lime kilns because dust particles interfere with kiln operation and reduce its efficiency. A numerical model is developed to predict the rate of dust formation in rotary lime kilns. The model consists of four major components: 1) a 3D model for the kiln gas, solving fluid flow, heat transfer, and combustion in the gas region; 2) a 1D model for the kiln bed, solving for variation of the solids composition, including moisture content, along the kiln; 3) a 3D model to predict the motion of the solids in the bed, and to estimate the reaction rates; 4) a mathematical model to predict the rate of particle pickup from the bed. Additionally, motion of dust particles was modeled, for the first time, using Stochastic Separated Flow model (a Lagrangian approach). The developed model of particle tracking enables the user to predict distribution of dust particles in the gas section of the kiln. Different components of the model were validated using experimental data published in the literature. The developed model was used to simulate operation of a full-scale lime kiln at typical operating conditions, i.e. at different fuel and air flow-rates. Dusting signatures were also estimated for each setting to determine the effect each operating condition has on dusting. The results presented in this thesis indicate that dust formation is mainly affected by the kiln gas velocity. Effect of other operating conditions was found to be negligible within the ranges studied. The results presented here suggest that dust formation can be controlled by minimizing the input gas flow rate.

Dusting is one of the major problems in the operation of lime kilns because dust particles interfere with kiln operation and reduce its efficiency. A numerical model is developed to predict the rate of dust formation in rotary lime kilns. The model consists of four major components: 1) a 3D model for the kiln gas, solving fluid flow, heat transfer, and combustion in the gas region; 2) a 1D model for the kiln bed, solving for variation of the solids composition, including moisture content, along the kiln; 3) a 3D model to predict the motion of the solids in the bed, and to estimate the reaction rates; 4) a mathematical model to predict the rate of particle pickup from the bed. Additionally, motion of dust particles was modeled, for the first time, using Stochastic Separated Flow model (a Lagrangian approach). The developed model of particle tracking enables the user to predict distribution of dust particles in the gas section of the kiln. Different components of the model were validated using experimental data published in the literature. The developed model was used to simulate operation of a full-scale lime kiln at typical operating conditions, i.e. at different fuel and air flow-rates. Dusting signatures were also estimated for each setting to determine the effect each operating condition has on dusting. The results presented in this thesis indicate that dust formation is mainly affected by the kiln gas velocity. Effect of other operating conditions was found to be negligible within the ranges studied. The results presented here suggest that dust formation can be controlled by minimizing the input gas flow rate.

This thesis encompasses the study of the mid-infrared (IR) dust properties in diffuse high latitude cirrus and in the dense environments of supernova remnants (SNRs) in the plane of our Galaxy. Unlike the well known emission properties of dust grains in the diffuse ISM in the far-IR and submillimeter, the mid-IR spectrum is still relatively unconstrained. We extend the correlation of dust emission with H I column densities to mid-IR wavelengths and look for evidence of variations in the emissivity of dust associated with local and halo gas. This is accomplished by spatially correlating the IR maps from the IRIS/IRAS survey at 12, 25, 60 and 100 μm with H I column density maps inferred from 21-cm line emission observations obtained with the GBT (at a 9′ resolution). We find that IVCs (halo clouds thought to be part of the Galactic fountain) show color ratios consistent with a dust evolution scenario in which large dust grains are shattered into smaller ones (VSGs). The low 12 μm emission found suggests a reduced abundance of PAHs in IVCs. We also address the IR extragalactic emission seen in our residual maps and quantify its power spectrum behaviour. Continuing with the mid-IR theme, we conducted a comprehensive study of the morphology and energetics of SNRs in the plane of our Galaxy. We make use of the Spitzer MIPSGAL (at 24 and 70 μm) and GLIMPSE (at 8 μm) surveys to detected infrared counterparts to SNR candidates in Green’s catalog. We find that a third of the sample shows IR emission and calculate the corresponding fluxes. We explore the relation between IR colors to place constraints on the different IR SNRs emission mechanisms. Aided by archival radio data, we find that most candidates detected show IR-to-radio ratios consistent with SNRs with a few exceptions displaying ratios seen in H II regions. Finally, we explore the connection between the IR and the high-energy X-ray emission of SNRs and find a good morphological association between the 24 μm emission and the X-ray features in younger remnants. The IR power is often greater.

We report on the dynamics of interstellar dust grains above the plane of the Milky Way. Our Galactic model closely matches its large-scale observed properties, namely the luminosity output, the gas content and distribution, as well as the extinction of starlight by dust. The gravitational model is composed of a central bulge, a disk and a dark matter halo. In spite of the fact that the emphasis in the results is for our Galaxy, we also discuss the effects of varying key galactic parameters, such as the total luminosity output and gas distribution. The parameter space of the main dust grain properties is also explored; these include the grain type (graphite and silicate) and size (0.001 - 0.3 micron). The grains were launched at various positions in the Milky Way, but always in the disk-halo connection region; namely at three Galactocentric radii (5, 8 and 11 kpc) and three initial heights (150, 300 and 1000 pc). The grains were subject to radiation pressure, a gravitational force, as well as Coulomb and collisional drag with the gas. Due to the large size of the parameter space, there is a wide variety of possible grain dynamics. Indeed, depending on the physical conditions in which the grains were launched, the grains could either: (1) fall down towards the midplane, (2) stay at the same height, (3) rise at a more or less constant speed, (4) rise and then fall down, (5) rise and then stabilize at some height, and (6) be quickly expelled into the intergalactic medium. In general, graphite grains reach greater heights than silicate grains. The smaller grains (of radius a = 0.01 and 0.001 micron) tend to stay at the same height they started at. The classical grain (a = 0.1 micron) is the most sensitive to radiation pressure and usually reaches the highest heights, even if they are modest. The largest grain we have studied (a = 0.3 micron) also responds well to radiative forces, but its large mass prevents it from going as high as the classical grain, and it even falls down towards the midplane under some circumstances. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2007-09-20 12:47:04.861

The city of Kalgoorlie in Western Australia has been labeled an “asthma hot spot” attributed to mining activity, prompting further investigation into toxic elements (Lee et al., 2006). Inhalation of nickel-bearing particles is a particular concern due to the presence of a nickel smelter 10km upwind of the city. The toxicological properties of nickel are well-documented, thus the primary objective is the characterization of phases identified as problematic in the lungs. To determine the smelter’s influence on nickel bioaccessibility in the soils throughout the city of Kalgoorlie, surface soil samples were taken from areas within the city and compared to soils near the smelter and outside the city, distant from the smelter. Soils were sieved to isolate the respirable fraction (<10um) potentially associated with lung disease and analyzed using a simulated lung fluid to determine the concentration of nickel soluble in the lungs. The soluble nickel represents the fraction that may be involved in allergic or asthmatic reactions, while the insoluble compounds may be of concern as some are carcinogenic. Further soil characterization was done using a six step sequential extraction and mineralogical analysis to identify nickel-bearing minerals. The influence of the smelter activity on nickel bioaccessibility in the soils within Kalgoorlie is low, but soils near the smelter host significantly higher nickel concentrations and higher bioaccessibility. Respiratory nickel bioaccessibility in soils ranges from 1 to 3% in and outside the city of Kalgoorlie, while the area surrounding the smelter increases to up to 6.8%. In each case, there is a direct correlation between bioaccessibility percent and percent nickel bound in the water-soluble and exchangeable fractions, but the simulated lung fluid dissolves more nickel in each sample than is present in these two fractions, potentially due to the presence of weak chelating agents in the solution. Respiratory bioaccessibility is low in Kalgoorlie soils because nickel occurs primarily in sulfides, with minor oxides and silicates, all relatively insoluble in lung fluid. However, the high concentrations of these compounds could be of concern, as they are potential carcinogens at high concentrations. Lee, Y.P., Cook, A., Thompson, P., Weinstein, P. 2006. Epidemiology. 17(6):283-284 / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2008-07-07 10:29:10.129

Rasmussen et al. (2001) observed that Sb concentrations were enriched in household dust relative to outdoor garden soil samples and suspected the enrichment may be due to anthropogenic internal sources. Antimony trioxide (Sb2O3) is commonly found in various halogen flame-retardants and is a suspected carcinogen (IARC, 1989). North Americans spend a significant proportion of their time indoors, and are frequently exposed to dust. Therefore, characterizing potentially harmful metal(loid)s (i.e. Sb2O3) has become of increasing priority to various governmental agencies. A combination of micro-analytical synchrotron techniques (micro X-ray fluorescence (µXRF), micro X-ray diffraction (µXRD), micro X-ray absorption near-edge spectroscopy (µXANES)) and environmental scanning electron microscopy (ESEM) were used to characterize five archived samples provided by Health Canada. Two samples were in the 90th percentile for Sb content in household dust from a suite of 50 houses studied by Rasmussen et al. (2001). The corresponding garden soils of these houses were also analysed. The fifth sample was a children’s bedroom from a house studied in detail by Walker et al. (2010). Synchrotron microanalysis of Sb presents many challenges, given its high absorption energy (31 KeV), and the relatively low concentrations and small particles in house dust. An appropriate experimental set-up was optimized after several trials. Antimony within household dust is currently not of toxicological concern (EU, 2008). Micro-XRF maps of household dust samples and corresponding garden soils from sample to sample displayed distinct element correlations of Sb with other elements. This suggests that Sb species present within homes are not restricted to a single source. Potential sources are Pb based or Sb containing pigments (Naples Yellow), metal alloys and possibly flame-retardants. The lack of correlation between Sb hot spots in the garden soil sample compared to the household dust suggests the source of interior Sb may not be external. A collaborative project with another student in the Environmental Studies Masters program was conducted to examine the potential for interdisciplinary work. Effective communication was the greatest barrier but there was success in the creation of a forum where people could critically think about the various nuances of household dust. / Thesis (Master, Environmental Studies) -- Queen's University, 2010-12-24 14:37:03.016

No description available.

Dust storms have a great many environmental implications in the world's dry lands where they are particularly common. Four main classes of dust event are identified and defined: dust storms, dust haze, blowing dust and dust devils. The geography of dust storms is analysed in each of eight major world regions: Africa, the Middle East, South-west Asia, Europe and the USSR, China, Australia, North America and Latin America. Terrestrially observed meteorological data and data from remote sensing platforms are employed to identify the major source areas in each region, their seasonality, diurnal patterns of activity and trajectories of long-range transport. Among the important controls on the frequency distribution of dust storm activity are the meteorological conditions that generate dust-raising winds, and a number of meteorological systems commonly cause dust storms in all global regions. These include low pressure fronts with intense baroclinal gradients, pressure gradient winds between moving or stationary air masses, katabatic winds and convectional cells. The nature of the surface upon which deflation occurs is also important; typical dust-producing geomorpholological units include alluvial spreads, lacustrine deposits, desert depressions, loess deposits and reactivated fossil dunes. Dust storm activity is prone to considerable variation. The seasonal characteristics are explicable with reference to the meteorological systems generating dust, the state of ground cover, particularly vegetation, and the effects of seasonal rainfall. Substantial variations also occur from year to year, and land use and climatic variations can substantially affect their occurrence.

No description available.

No description available.