Column flotation is commonly employed in the processing and recovery of fine mineral particles due to an increase in flotation selectivity unattainable using conventional flotation methods. Such an increase in selectivity is due to the employment of wash water, minimizing hydraulic entrainment of fine gangue particles, and the presence of quiescent operating conditions assisted by the use of various air sparging technologies. High performance air spargers increase the probability of collision and attachment between air bubbles and particles, thereby improving recovery of fine and coarse mineral particles otherwise misplaced to the tailings fraction in conventional flotation cells. Although many high-pressure spargers, including the static mixer and cavitation tube, are currently employed for the aeration of column cells, a low pressure sparger capable of providing equivalent performance while resisting a reduction in aeration efficiency does not exist. In light of escalated energy requirements for operation of air compressors necessary to provide high pressure air to existing external and internal spargers, a low-pressure and porous sparger capable of resisting plugging and scaling was developed. Following the design, construction, and optimization of such a prototype, air holdup and flotation performance testing was completed to verify the viability of the sparger as a replacement to existing aerators. Performance evaluations suggest that the sparger is capable of providing similar functionality to currently employed sparging technologies, but further work is required with regards to manipulation of the porous medium to prevent sparger fouling and sustain high aeration efficiencies. / Master of Science

La migration de particules fines dans un milieu poreux fait l’objet de nombreuses études dans différents domaines. Par exemple, la présence de particules fines dans les nappes phréatiques constitue des voies de transfert de polluants (e.g. bactéries, virus, métaux lourds) à travers les sols. Par ailleurs, les phénomènes complexes d’adsorption et de désorption des particules fines dans le milieu poreux sont la cause de multiples dégâts dans les systèmes hydrauliques (e.g. digues, puits pétroliers, filtres de traitements des eaux). Les particules fines forment des agrégats et se déposent autour des grains collecteurs affectant la perméabilité du milieu poreux. Ainsi, différents processus mécaniques et/ou physico-chimiques contrôlent le colmatage de la matrice poreuse. L’objectif de ce travail est d’étudier l’effet de l’hétérogénéité du milieu poreux (i.e. granulométrie, porosité) sur les phénomènes de transport et de dépôt des particules colloïdales en suspension. La finalité de ce travail est de donner un modèle prédictif de perméabilité afin de pouvoir estimer la pérennité du système. Dans ce but, une campagne d’essais expérimentaux est menée sur le suivi du transport et du dépôt des particules fines argileuses dans différents milieux naturels sableux. Ces travaux ont été réalisés dans des colonnes de laboratoire pour lesquels les conditions hydrauliques peuvent être contrôlées et où la concentration des fines à l’entrée de la colonne est imposée. Après injection des particules fines, le suivi de la matrice poreuse dans l’espace et dans le temps est réalisé en utilisant un banc gamma-densimétrique. L’évolution de la perméabilité caractérisant le colmatage du matériau est analysée par l’intermédiaire de la mesure de la chute de pression dans la colonne. Les expériences menées dans les différentes colonnes ont permis de mettre en évidence l’importance de la taille des grains et la porosité du milieu ainsi que la vitesse d’injection dans la formation du dépôt. D’après nos résultats, au début de l’essai le dépôt de particules se fait autour des collecteurs sur des sites de surface. Ensuite les ponts de liaison sont créés entre les grains collecteurs. Nous avons constaté que la première partie du dépôt est plus importante dans le cas de grains de taille importante. Afin d’interpréter les résultats de l’évolution de la perméabilité, nous avons utilisé le modèle de Kozeny-Carman, où nous avons introduit l’évolution du dépôt dans l’estimation de la surface spécifique du milieu. Ce modèle nous a permis également de prendre en compte l’hétérogénéité du milieu et l’évolution de chaque couche par l’intermédiaire des paramètres tels que la porosité et la tortuosité du milieu. Les observations microscopiques et les mesures de porosités sur les échantillons colmatés ont étayé les schémas de dépôt et de saturation des sites de rétention. Ce travail expérimental s’accompagne d’une modélisation par l’équation de convection dispersion avec un terme de puits simulé par une cinétique du second ordre. Elle met en évidence l’importance des particules déjà déposées ainsi que la porosité initiale du milieu et la vitesse d’écoulement. / The migration of fine particles in a porous medium is the subject of many studies in various fields. For example, the presence of fine particles in groundwater constitutes pathways of pollutants (e.g. bacteria, viruses, heavy metals) through the soil. Furthermore, the complex processes of adsorption and desorption of the fine particles in the porous medium are the cause of damage to multiple hydraulic systems (e.g. dams, oil wells, filters for water treatment). The fine particles form aggregates and settles around collecting grains affecting the permeability of the porous medium. Thus, various mechanical and / or physico -chemical processes control the clogging of the porous matrix. The objective of this work is to study the effect of heterogeneity of the porous medium (i.e. grain size, porosity) on the phenomena of transport and deposition of colloidal particles in suspension. The purpose of this work is to provide a predictive model of permeability in order to estimate the sustainability of the system. For this purpose, a campaign of experimental tests are conducted on the monitoring of transport and deposition of fine particulate clay in different natural environments sandy. These studies were conducted in laboratory columns for which the hydraulic conditions can be controlled and where the concentration of fines in the entry of the column is imposed. After injection of the fine particles, the monitoring of the porous matrix in space and time is carried out using a gamma - densimetric bench. Changes in permeability characterizing the clogging material is analyzed by means of the measurement of the pressure drop in the column. Experiences in the different columns have helped highlight the importance of grain size and porosity of the medium and the injection rate in the formation of the deposit. Our results at the beginning of the test particle deposition is around collectors on surface sites. Then the connecting bridges are created between the grains collecting. We found that the first portion of the deposit is larger in the case of large-sized grains. To interpret the results of the evolution of permeability, we used the Kozeny - Carman model, where we have introduced the evolution of the repository in estimating the surface area of the medium. This model also allowed us to take into account the heterogeneity of the environment and the evolution of each layer by using parameters such as porosity and tortuosity of the medium. Microscopic observations and measurements of porosity on samples clogged supported schemes and deposit saturation retention sites. This experimental work is accompanied by modeling the dispersion equation convection with a term well simulated by a second order kinetics. It highlights the importance of particles already deposited and the initial porosity of the medium and the flow velocity.

The objective of the present work was to demonstrate the possibilities to reduce the emission of fine particle forming alkali during co-combustion of wood with peat in a full scale (150 kW) grate fired boiler. For this purpose the particle emissions from a 150 kW district heating grate fired boiler situated in northern part of Kramfors, Sweden, were studied. During the experiment the district heating boiler was fired with sawdust fuel with a 0, 10 and 20 wt-% (zero, low, high) peat content respectively. Mass concentrations and particle size distribution were measured by using a DLPI (13-step low-pressure cascade impactor) with a precyclone. The particle matter was analyzed for morphology and elemental composition using SEM/EDS (Scanning electron microscopy/energy dispersive spectroscopy). In addition, chemical equilibrium model calculations were used to interpret the experimental findings. The present study clearly shows that reduction of fine particles (&lt; 1 um) is possible when co-combusting wood pellets with peat pellets in grate fired boilers. When 10 wt % peat was added to the wood/peat fuel mixture the fraction of fine particles was significantly decreased (about half of that emitted during pure softwood pellet combustion). The fine particles were for all fuel types/mixtures dominated by potassium, chlorine, sulfur, sodium and zinc. The result from this work therefore shows that a significant reduction of fine particle alkali is possible when co-combusting wood pellets with peat. The results from the thermo-chemical calculations suggest that a significant share of the potassium is retained in the bottom ash as a K rich silicate slag and as KAlSi2O6(s) (Leucite) when co-combusting sawdust with peat. / <p>Validerat; 20110920 (anonymous)</p>

No description available.

Lung diseases such as asthma and chronic obstructive pulmonary disease (COPD) are major health burdens on the global population. To treat diseases of the lung, topical therapies using dry powder inhalers (DPIs) have been employed. However, a relatively small amount of dose (5.5 - 28 %) reaches the lung during DPI therapy leading to high inter-patient variability in therapy response and oropharyngeal deposition. Strategies were assessed to take patient variability in inhalation performance into account when developing devices to reduce throat deposition and to mitigate flow rate dependency of the emitted aerosol. A cyclone-spacer was manufactured and evaluated with marketed and in-house manufactured formulations. An in vivo study showed that a high resistance inhaler would produce longer inhalation times in lung disease patients and that a spacer with high resistance may prove a suitable approach to address inter-patient variability. Two spacer prototypes were evaluated with cohesively- and adhesively-balanced particle blends. The data suggested that the throat deposition dramatically decreased for the emitted particles when the spacers were used with the inhalers (e.g. 18.44 ± 2.79% for salbutamol sulphate, SS 4 kPa) due to high retention of the formulation within the spacer (87.61 ± 2.96%). Moreover, variation in fine particle fraction and dose was mitigated when increasing the flow rate (82.75 ± 7.34 %, 92.2 ± 7.7 % % and 77.0 ± 10.1 % at 30, 45 and 60 Lmin-1, respectively). The latter was an improvement over previous proposed DPI spacers, where variability in emitted dose due to airflow rate was a major issue. Due to the different physicochemical properties of the active pharmaceutical ingredients used in the formulation, throat deposition and respirable fraction for adhesively-balanced particles (e.g. SS) were double that of the cohesively- balanced particles (salmeterol xinafoate, SX) (e.g. 65.83 ± 8.99 % vs. 45.83 ± 5.04 % for SS:Coarse Lactose (CL) and SX:CL, respectively). Scanning electron microscopy revealed that surface-bound agglomerates were more freely removed from the carrier, but subject to decreased impaction-type deagglomeration forces in the spacer than for carrier-bound drug. An ex vivo study using breath profiles from healthy volunteers identified the minimization of differences between adhesively- and cohesively-balanced blends when full breath profiles were studied compared to square-wave airflow. Therefore the use of constant flow for in vitro testing should not be the sole flow regime to study aerosolization when developing new inhalation devices and formulations.

This thesis has two major purposes: (1) to investigate the impact carshave on Particulate Matter (PM) level in a limited area and (2) to demonstratethrough Computational Fluid Dynamics (CFD) the possibility toclean a limited area of PM with a system installed on a car.This thesis was performed in collaboration with Volvo Car Corporation(VCC) at Torslanda, Göteborg. All experimental data was sampledat three occasions: 24th of February, 14th of March and 3rd of June andwere compared to similar recent studies for verication. Computer calculationwere conducted in July and August with experimental data asinitial conditions. ANSYS v16.0 Fluent Meshing and ANSYS v16.0 Fluentwere used as computational software to set up and calculate the problem.The result of the experiments shows that with increased number ofcars there is an increased value of PM. It also shows that a cars ventilationsystem can be used to collect small PM. Result from CFD derivationsdisplayed that a cleaning system mounted in a car will decrease number ofPM with 5-20% in 250 seconds in a closed domain and 4% in 135 secondsin a open domain.

No description available.

No description available.

The addition of coarse particles to a flocculating fine particle slurry increases the Bingham yield stress of the resulting mixture, which can drastically alter the laminar-to-turbulent transition velocity. The objective of this study is to quantify the effect of coarse particle size and volume concentration on mixture rheology. Fine particle (kaolin) mixtures of 10% to 22% (by volume) were prepared, to which sand particles were added to provide a coarse solid concentration of 5% to 20% (by volume). Sand particles of two different sizes – 90 and 190 microns – were added and these kaolin-sand-water mixtures tested with a concentric cylinder viscometer. At higher total solids concentrations, the Bingham yield stress of the bimodal mixture can increase by as much as 80% over that of a kaolin-only slurry. Coarse particle diameter had little effect. This study demonstrates that the use of existing correlations should be eschewed. System-specific high-quality measurements are necessary. / Chemical Engineering

Class of 2015 Abstract / Objectives: To evaluate the in vitro performance of various pressurized metered dose inhaler (pMDI) formulations by cascade impaction primarily focusing on throat deposition, fine particle fraction (FPF), and mass-median aerodynamic diameter (MMADR) measurements Methods: Ten solution pMDIs were prepared with varying cosolvent species in either low (8% w/w) or high (20% w/w) concentration. The chosen cosolvents were either alcohol (ethanol, n-propanol) or acetate (methyl-, ethyl-, and butyl acetate) in chemical nature. All formulations used HFA-134a propellant and 0.3% drug. The pMDIs were tested by cascade impaction with three different inlets to determine the aerodynamic particle size distribution (APSD), throat deposition, and FPF of each formulation. Theoretical droplet evaporation time (DET), a measure of volatility, for each formulation was calculated using the MMADR. Results: Highly volatile formulations with short DET showed consistently lower throat deposition and higher FPF than their lower volatility counterparts when using volume-constrained inlets. However, FPF values were not significantly different for pMDI testing with a non-constrained inlet. The MMADR values generated with volume-constrained inlets did not show any discernible trends, but MMADR values from the non-constrained inlet correlated with DET. Conclusions: Formulations with shorter DET exhibit lower throat deposition and higher FPF, indicating potentially better inhalational performance over formulations with longer DET. There appear to be predictable trends relating both throat deposition and FPF to DET. The shift in MMADR values for volume-constrained inlets suggests that large diameter drug particles are preferentially collected in these inlets.