Thesis (MScIng)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: Due to economic and environmental constraints mining operations are placed under increasing pressure to effectively manage and operate tailings disposal operations. Restrictions imposed on water usage and tailings operations footprint have led to higher density and wider particle size distribution slurries conveyed to tailings areas. One means of efficiently disposing the tailings is co-disposal. In this method a concentrated fine vehicle slurry is used to convey a coarser fraction. This produces a higher density of tailings, with a number of advantages both upstream and downstream of the tailings process. Limited research has been conducted on the effect of coarse particles on the non-Newtonian rheological properties of these slurries. This lack of information complicates the design and reliable operation of these systems. This project aims at gaining a clearer understanding as to the mechanisms involved in the addition of coarse particles to a fine clay slurry vehicle; and to provide a means of estimating the measured slurry rheological properties. A number of experiments were designed to test the slurry (both Kaolin only, and Kaolin-coarse particle mixtures) rheological properties using a Couette viscometer (for the dynamic flow properties of yield stress and plastic viscosity) and a vane instrument (for the static yield stress measurements). The slurries were prepared in varying Kaolin clay solids concentrations with reverse osmosis water. Glass beads and two types of industrial sand were used as the coarse fractions. All of the coarse particles had a similar size but varied significantly in shape. Slurry pH and temperature readings were monitored throughout the tests. Tests were done initially on clay only slurries. The rheological properties of these slurries were repeatable, and no noticeable variations of properties with time were observed. The yield stress (both static and dynamic) and plastic viscosity data were well correlated with established relationships. Coarse particles were added to the clay only slurries, and then removed. The remaining clay only slurry exhibited the same rheological properties as the initial clay only slurry. The presence of coarse particles increased all the measured rheological properties (i.e. dynamic yield stress, Bingham viscosity, and static vane yield stress) in a fashion resembling the effect of adding clay to a clay only slurry. In addition, the change in measured rheological property by addition of coarse particle was independent of the clay fraction in the clay slurry. Furthermore, with both the clay only slurries and clay and coarse sand slurries, a constant linear relationship existed between the static and dynamic yield stress. Several correlations from the literature were found to provide reasonable prediction of the rheological property variations observed. These empirical and semi-empirical models however did little to explain the mechanisms involved in coarse particle addition. A new correlation has been proposed, Residual Clay Concentration, which predicts the change in rheological property based on an additional clay concentration, which in turn is a linear function of the coarse particle concentration. The accuracy of this model further strengthens the belief that the coarse particle acts in a similar fashion to a floc. By means of a case study example the importance of selecting an appropriate model for design was illustrated. The Residual Clay Concentration method provided the most conservative results. This combined with its theoretical basis strengthens the models recommendation for use in design. / AFRIKAANSE OPSOMMING: As gevolg van ekonomiese en omgewings beperkinge word mynwese nywerhede onder toenemende druk geplaas om doeltreffende afvalstroom bestuur en operasie toe te pas. Beperkinge geplaas op water gebruik en afvalstroom area-groote ly tot hoër digthede en wyer partikel-grooteverspreidings van flodders vervoer na afval areas. Een manier om van die afval doeltreffend ontslae te raak en te berg is deur medeberging. In die metode word ‘n gekonsentreerde fyn flodder gebruik as draer van ‘n growwer partikel-fraksie. Dit ly tot ‘n hoër digtheid flodder, met verskeie voordele in beide die op – en afstroom prosesse. Beperkte navorsing is gedoen op die effek van growwe partikels op die nie-Newoniese rheolgiese eienskappe van hierdie flodders. Hierdie tekort aan informasie maak die effektiewe, betroubare bedryf en operasie van die sisteme meer ingewikkeld. Hierdie projek is daarheen gemik om ‘n beter begrip te ontwikkel met betrekking tot die meganismes betrokke in die byvoeging van growwe partikels aan ‘n fyn klei-agtige flodder draer; en om ‘n manier te voorsien wat die rheologiese eienskappe kan beraam. Verskeie eksperimente was ontwerp om die flodders (beide slegs Kaolien, en Kaoliengrowwe partikel mengsels) se rheologiese eienskappe te toets deur die gebruik van ‘n Couette-viskometer. Die Couette viskometer was gebruik om die dinamiese eienskappe (van grens-spanning, en plastiese viskositet) te meet. ‘n Vaan apparaat is gebruik om die eienskap van statiese grens-spanning te meet. Die flodders was voorberei in verskeie Kaolien konsentrasies met tru-osmosis water. Glas krale en twee tipes industriële sand is gebruik as die growwe fraksies. Al die growwe partikels het soortgelyke groottes gehad, maar het grootliks verskil in vorm. Die flodder pH en temperatuur lesings is deurentyd nagegaan. Toetse was aanvanklik gedoen op die klei-alleenlike flodders. Die gemete reologiese eienskappe van die flodders was herhaalbaar, en geen opmerkbare veranderinge van die eienskappe met betrekking tot tyd is gemeet nie. Die grens-spanning (beide statiese en dinamiese) en plastiese viskositeit is goed gekorrelleer met gevestigde verhoudinge. Growwe partikels is aan die klei-alleenlike flodders bygevoeg, en daarnae verwyder. Die oorblywende klei-alleenlike flodder het dieselfde gemete rheologiese eienskappe getoon as die oorspronklike klei-allenlike flodder. Die teenwoordigheid van growwe partikels het na ‘n toename van al die gamete rheologiese eienskappe gelei wat fisies baie soortgelyk is aan die byvoeging van klei tot ‘n klei-alleenlike flodder. Verder, met beide die klei-alleenlike en klei-growwe partikel flodders het ‘n konstante liniëre funksie tussen die statiese en dinamiese grens-spannings bestaan. Verskeie verhoudings uit die literatuur het goeie korrelasie bewerkstellig met die waargenome rheologie veranderinge. Hierdie empiriese en semi-empiriese modelle doen egter min om die megansimes betrokke in die toevoeging van growwe partikels te verduidelik. ‘n Nuwe korrelasie is voorgestel, naamlik die Residu Klei Konsentrasie. Hierdie model voorspel die verandering in reologiese eienskappe gebaseer op ‘n addisionele klei konsentrasie, wat ‘n liniëre funkise is van die growwe partikel konsentrasie. Die goeie korrelasie gesien met die model versterk die idée dat die growwe partikel in ‘n soortgelyke manier as ‘n flok gedra in die teenwoordigheid van ander flokke. Deur middel van ‘n tipiese industriële voorbeeld is die belangrikheid in die keuse van die regte korrelasie geillustreer. Die Residu Klei Konsentrasie metode het die mees konservatiewe resultate gelewer. Hierdie feit gekombineerd met die model se soliede teoreitiese beginsels versterk dit as voorgestelde korrelasie vir ontwerp.

Deep slurry injection is a process of solid waste disposal that involves grinding the solid waste to a relatively fine-grained consistency, mixing the ground waste with water and/or other liquids to form slurry, and disposing of the slurry by pumping it down a well at a high enough pressure that fractures are created within the target formation. This thesis describes the site assessment criteria involved in selecting a suitable target reservoir for deep slurry injection. The main goals of this study are the follows: <ul> <li>Identify the geological parameters important for a prospective injection site</li> <li>Recognize the role of each parameter</li> <li>Determine the relationships among different parameters</li> <li>Design and develop a model which can assemble all the parameters into a semi-quantitative evaluation process that could allow site ranking and elimination of sites that are not suitable</li> <li>Evaluate the model against several real slurry injection cases and several prospective cases where slurry injection may take place in future</li> </ul> The quantitative and qualitative parameters that are recognized as important for making a decision regarding a target reservoir for deep slurry injection operations are permeability, porosity, depth, areal extent, thickness, mechanical strength, and compressibility of a reservoir; thickness and flow properties of the cap rock; geographical distance between an injection well and a waste source or collection centre; and, regional and detailed structural and tectonic setup of an area. Additional factors affecting the security level of a site include the details of the lithostratigraphic column overlying the target reservoir and the presence of overlying fracture blunting horizons. Each parameter is discussed in detail to determine its role in site assessment and also its relationship with other parameters. A geological assessment model is developed and is divided into two components; a decision tree and a numerical calculation system. The decision tree deals with the most critical parameters, those that render a site unsuitable or suitable, but of unspecified quality. The numerical calculation gives a score to a prospective injection site based on the rank numbers and weighting factors for the various parameters. The score for a particular site shows its favourability for the injection operation, and allows a direct comparison with other available sites. Three categories have been defined for this purpose, i. e. average, below average, and above average. A score range of 85 to 99 of 125 places a site in the ?average? category; a site will be unsuitable for injection if it belongs to the ?below average? category, i. e. if the total score is less than 85, and the best sites will generally have scores that are in the ?above average? category, with a score of 100 or higher. One may assume that for sites that fall in the ?average? category there will have to be more detailed tests and assessments. The geological assessment model is evaluated using original geological data from North America and Indonesia for sites that already have undergone deep slurry injection operations and also for some possible prospective sites. The results obtained from the model are satisfactory as they are in agreement with the empirical observations. Areas for future work consist of the writing of a computer program for the geological model, and further evaluation of the model using original data from more areas representing more diverse geology from around the world.

Le but de cette étude est de mieux comprendre l’effet d’une fertilisation en lisier de porc sur la productivité d’une plantation de saule tout en évaluant les risques d’impact négatif sur l’environnement. Nous avons évalué la réponse des plants à des quantités croissantes de lisiers en plus de la comparer à celle d’une fertilisation minérale. Nous avons aussi vérifié l’impact du lisier sur les teneurs nutritionnelles du sol ainsi que sur les concentrations en nitrates et phosphore de la solution du sol. Bien que l’azote du lisier soit moins efficace que celui des engrais minéraux, les résultats de notre étude montrent que le lisier est un bon engrais pour les plantations de saules. En effet, les rendements sur deux ans des parcelles ayant reçu les quantités croissantes de lisier étaient de l’ordre de 30,3 à 32,9 t/ha. Nous avons observé l’augmentation des teneurs en nitrate, cuivre et zinc dans le sol en fonction des apports croissants de lisier. Ces teneurs ont d’ailleurs diminué lors de la deuxième saison de croissance, ce qui pourrait être dû au prélèvement par les saules. Les concentrations printanières des eaux de lysimètres indiquent que la quantité maximale de lisier telle que testée lors de nos essais comporte un certain facteur de risque de lessivage des nitrates. Nous n’avons pas analysé la solution du sol des parcelles fertilisées avec des quantités plus faibles de lisier, mais nous pouvons croire qu’elles auraient induit des concentrations en nitrate comportant moins de risque de lessivage tout en assurant une productivité considérable. / The aim of this study is to investigate the effect of the use of pig slurry as fertilizer on the productivity of a willow plantation, while evaluating the risk of a negative impact on the environment. We evaluated plant response to increasing slurry amounts and compared this response to the effect of mineral fertilization. We also verified the impact of slurry on soil nutritional content as well as on nitrate and phosphorus concentrations in the soil. Although slurry nitrogen was less efficient than mineral fertilizer, the results of our study show that slurry constitutes an effective fertilizer for willow plantations. In fact, yields over two years on plots that received increasing amounts of slurry were on the order of 30.0 to 32.9 t/ha. We observed an increase in soil levels of nitrates, copper and zinc as a function of increasing slurry amounts. These levels actually decreased during the second growing season, possibly due to uptake by the willows. Springtime concentrations of water in lysimeters indicated that the maximum amount of slurry tested in our experiments was accompanied by a certain risk of nitrates leaching into the soil. We did not analyze the soil solution of plots fertilized with lower amounts of slurry, but it seems likely that these nitrate concentrations would have had a lower risk of leaching while still ensuring considerable productivity.

En raison de leur bonne résistance mécanique à haute température, les superalliages base nickel sont employés dans les turbines aéronautiques et de production d’énergie. Ils doivent alors être capables de résister aux phénomènes d’oxydation « sèche » intervenant entre 900 et 1500°C. Ces matériaux sont donc protégés par des revêtements à base d’aluminure de nickel (β-NiAl). De plus, dans les sections les plus chaudes des turbines (T>1050°C), une barrière thermique (BT) est ajoutée afin de diminuer l’impact de la température sur le substrat. Dans le cadre du projet de recherche Européen « PARTICOAT », le travail décrit dans cette thèse a porté sur l’élaboration d’un système complet de revêtements protecteurs (BC+BT) à l’aide d’un procédé en une seule étape, à partir d’une barbotine obtenue par dispersion de microparticules d’Al dans une base aqueuse, milieu susceptible de satisfaire aux directives environnementales européennes. Des caractérisations rhéologique et physico-chimique ont montré la stabilité de la barbotine jusqu’à sept jours. Après dépôt de cette dernière par pulvérisation, un traitement thermique adapté a conduit, via la formation intermédiaire d’Al liquide, à l’obtention d’un revêtement d’aluminure de nickel (β-NiAl) comparable à ceux obtenus par les procédés industriels actuels. L’oxydation des particules d’Al permet la formation simultanée d’une « mousse » d’alumine (concept PARTICOAT) superficielle. Après validation des mécanismes réactionnels mis en jeu sur un substrat modèle de nickel pur, l’extrapolation du procédé à différents superalliages base nickel (René N5 (SX), CM-247 (DS), PWA-1483 (SX) et IN-738LC (EQ)) a donné des revêtements présentant différentes compositions et microstructures. Un intérêt particulier a alors été porté sur l’étude de l’influence des éléments d’alliage (Cr, Ta, Ti) et de leur ségrégation au sein du revêtement. Le comportement à haute température des échantillons revêtus a pu être évalué à l’aide de tests d’oxydation isotherme (1000h sous air entre 900 et 1100°C). Il a ainsi été montré que les phénomènes d’oxydation et d’interdiffusion régissent les mécanismes de dégradation. Par ailleurs, l’électrodéposition de cérine préalablement à l’application du procédé de revêtement PARTICOAT a permis de limiter fortement les phénomènes d’interdiffusion et de stabiliser la couche d’aluminure de nickel. / Because of their good mechanical resistance at high temperature, Ni-based superalloys are used for aero-engine and land-based turbines but undergo “dry” oxidation between 900 and 1500°C. These materials are thus coated with nickel-aluminide coatings (BC). An additional thermal barrier coating (TBC) is generally applied in the hottest sections of the turbines (T>1050°C) to lower the impact of the temperature on the substrate. In the framework of the European research programme “PARTICOAT”, this PhD work was focused on the growth mechanisms of a full protective coating system (BC+TBC) in a single step process, using a water-based slurry containing a dispersion of Al micro-particles to satisfy the European environmental directives. The rheological and physico-chemical characterizations showed the slurry stability up to seven days. After depositing the latter by air spraying, a tailored thermal treatment resulted in a nickel-aluminide coating (β-NiAl) similar to the conventional industrial ones but through an intermediate Al liquid phase stage. Simultaneously, the oxidation of the Al micro-particles brought aboutthe formation of a top alumina “foam” (PARTICOAT concept). After a validation step of the mechanisms involved in pure Ni substrate, the extrapolation of the process to several Ni-based superalloys (René N5 (SX), CM-247 (DS), PWA- 1483 (SX) and IN-738LC (EQ)) revealed different coating compositions and microstructures. A particular attention was therefore paid onto the effect of alloying elements (Cr, Ta, Ti) as well as their segregation in the coating. The high temperature behaviour of the coated samples has been studied through isothermal oxidation (1000h in air between 900 and 1100°C) and showed that the oxidation and interdiffusion phenomena ruled the degradation mechanisms. Besides, the electrodeposition of ceria before the application of the PARTICOAT coating allowed to strongly limit interdiffusion phenomena and stabilized the nickel aluminide coating.

Les superalliages base nickel sont couramment utilisés dans les parties chaudes des turbines aéronautiques et de production d’énergie. Les températures employées, supérieures à 900°C, nécessitent de concevoir des revêtements protecteurs pour lutter contre les phénomènes d’oxydation. Les revêtements couramment utilisés, composés pour la plupart de la phase β-NiAl, permettent de retarder les phénomènes de dégradation en développant une couche d’alumine. Dans les sections les plus chaudes, une barrière thermique composée de céramique, associée à un système de refroidissement interne complètent le dispositif de protection en permettant d’abaisser la température effective au niveau du substrat métallique.Ces revêtements sont cependant onéreux et utilisent de nombreux produits polluants. Les travaux de cette thèse, qui s’inscrivent dans le cadre du projet européen Particoat, se proposent d’élaborer un système barrière thermique en une seule étape reposant sur l’application d’une barbotine à base aqueuse comprenant des microparticules d’aluminium, suivi d’un traitement thermique approprié. L’aluminium contenu dans les sphères devient liquide puis réagit avec le substrat pour former une couche d’intermétallique riche en aluminium par diffusion à l’état solide. Simultanément les coquilles des sphères s’oxydent pour former une structure mousse en surface du substrat qui va conférer au système son isolation thermique. La cohésion des deux parties est assurée par l’oxyde thermique qui se forme à la surface du revêtement inter métallique. Les mécanismes mis en jeu lors des différentes étapes, ont été étudiés sur un substrat modèle, le nickel, ainsi que sur trois superalliages industriels (René N5, PWA 1483 et CM-247). Les revêtements ainsi élaborés ont été testés en condition d’oxydation isotherme et cyclique entre 900 et1100°c pour le nickel et entre 1000 et 1100°C pour les superalliages revêtus. L’ensemble montre une bonne résistance du système barrière thermique élaboré par barbotine. / Nickel superalloys are commonly used in the high temperature sections of aero- and land-based turbines blades. Protection of these materials by coatings is required to improve their resistance to oxidation beyond 900°C. The conventional process consists of a β-NiAl, which allows to form a protective alumina scale with alow oxidation kinetic. In the hottest parts of the turbine, a ceramic is used as a thermal barrier coating in addition to an internal cooling system in order to diminish the temperature seen at the metallic substrate surface. However, these existing methods are expensive, long and pollutant. Thus, this PhD thesis aims at producing a new thermal barrier system in one step, in the frame of the European project Particoat. Its concept is to apply on the substrate an aqueous slurry containing aluminum microparticles. Then, during an appropriate heat treatment the metallic particles sinter and oxidize completely resulting in a quasi-foam structure made of alumina hollow spheres (TBC). Simultaneously, the diffusion of the Al into the substrate creates a bond coat below the TBC. This coating formation is studied on model alloy (pure nickel) and on three different superalloys (René N5, PWA-1483 and CM-247). The pure nickel coated system is tested during isothermal and cyclic oxidation between 900°C and 1100°C whereas the degradation of the superalloys is realized upon cyclic oxidation at 1000°C and 1100°C. The overall results show a good resistance of this new thermal barrier system, enlightened by an industrial aluminide coatings comparison.

[pt] Um gerador de pasta de gelo foi desenvolvido para o estudo experimental de suas características de transferência de calor. Uma das características da pasta de gelo é que pode ser bombeada como qualquer líquido. O gerador de pasta de gelo é um evaporador, do tipo trocador de calor de superfície raspada com intensificação mecânica de transferência de calor. Foi estabelecida a influência de vários parâmetros na transferência de calor no gerador de pasta de gelo: a vazão mássica, a velocidade de rotação do raspador, a temperatura da parede na interface, a temperatura de operação da solução aquosa, entre outros. Estudou-se tanto a transferência de calor com ou sem mudança de fase. Utilizaram-se soluções aquosas de etanol com diferentes concentrações. A pasta de gelo era produzida continuamente sem acumulação no evaporador. O gerador era parte de um sistema integral contendo os seguintes componentes: o sistema de medição da fração de gelo on-line, através da medição da massa específica da pasta de gelo; uma bomba helicoidal de cavidade progressiva, que permitia controlar a vazão, por meio de um variador de freqüência; um aquecedor elétrico, atuando como carga térmica, com a possibilidade de variar a capacidade desta carga térmica e, com isto, o controle da temperatura de operação do sistema; e o sistema de aquisição de dados. Foi estabelecido um modelo para determinar, experimentalmente, o número de Nusselt e, por conseguinte, o coeficiente interno de transferência de calor da pasta de gelo. Utilizou-se uma unidade condensadora convencional, com R22 como fluido refrigerante. A pasta de gelo resultante era bombeada continuamente em um circuito fechado, assegurando o estudo de um fluido homogeneamente distribuído, visto que o circuito não permitia a acumulação de pasta de gelo. Os sistemas de geração de pasta de gelo apresentam potencial para reduzir significativamente os custos de capital inicial e operação, quando comparados com tecnologias de sistemas de termoacumulação estáticos de gelo ou dinâmicos, como o ice harvesting. / [en] An ice slurry generator for was developed for the experimental study of its heat transfer characteristics. One of the main characteristic of ice slurry is that it can be pumped as any liquid. The ice slurry generator is an evaporator, with mechanical heat transfer enhancement, by surface scraping. The dependence of several parameters on heat exchanger performance was established. They included: mass flow rate, scraped rotational velocity, surface temperature, solution operating temperature. Single and two-phase flow was studied. Aqueous ethanol solutions, of different concentrations, were used. Ice slurry was produced on a continuous basis. The experimental apparatus consisted of the heat exchanger itself, an on-line ice mass fraction measurement device, a helicoidal positive displacement variable flow rate pump, an electrical heater, the data acquisition system and a R22 condensing unit. The ice slurry was pumped continuously on a closed circuit, providing a homogeneous fluid, as no accumulation of ice was possible. Ice slurry systems have the potential of significant reduction on capital and maintenance costs, when compared to traditional technologies, static or dynamic, of ice thermoaccumulation.

O objetivo deste estudo foi avaliar parâmetros para o desenvolvimento de métodos visando à determinação elementar em alumina, cimento e quartzo por espectrometria de emissão óptica com plasma indutivamente acoplado (ICP OES) com amostragem de suspensão. Alguns elementos foram investigados como possíveis candidatos a padrões internos (PIs) Be, Dy, Gd, In, La, Sc, Y, Yb eTl. Amostras de material de referência certificado (CRM) de alumina (Alumina Reduction Grade 699), de cimento Portland (1889a Blended with Limestone e 1886a White Portland cement with low iron) do National Institute of Standard and Technology (NIST), e amostras de quartzo, cedidos pelo Departamento de Física da Universidade Federal de São Carlos (UFSCar), denominados T-4FI, T-2FI e T-4GR, foram utilizadas na otimização instrumental, no desenvolvimento e na avaliação da exatidão do método. Nanopartículas de sílica de alta pureza (Wacker HDK&#174; T40), Wacker Chemie AG foram utilizadas no estudo de adsorção dos elementos e padrões internos como proposta de produção de material calibrante para a análise direta de sólidos. Para a escolha dos PIs foram construídos gráficos de correlação usando valores de potenciais de excitação, energias de ionização e temperaturas de fusão dos analitos e dos candidatos a PIs. Análise exploratória por agrupamentos hierárquicos (HCA) e análise dos componentes principais (PCA), também foram realizadas. A avaliação de desempenho do ICP OES foi feita em meio das suspensões das amostras a partir do estabelecimento de figuras de mérito como sensibilidade, robustez, seletividade e repetibilidade. Na otimização do foram considerados os parâmetros potência, vazão de nebulização e vazão de gás auxiliar. A determinação de Ca, Fe, Ga, Na, Si e Zn em alumina foi feita após dissolução em forno de micro-ondas com posterior precipitação do Al(III) com NH3. O uso de padrão interno foi essencial para a exatidão do método, com recuperações do CRM que variaram de 83 a 117%. Para a matriz cimento foram avaliados o efeito da concentração de ácido nítrico na extração dos analitos ( Al, Ca, Cr, Fe, K, Mg, Mn, Na, P, S, Si, Sr, Ti e Zn) e na adsorção dos elementos candidatos a PIs (Be, Sc, In, Dy). As determinações por suspensão e uso de padrão interno (exceto para Cr, S e Zn), com 0,5% v v-1 de HNO3, nebulizador Burgener e condições robustas do ICP geraram resultados com recuperações entre 68 e 119%. As determinações de Al, Ba, Cr, Fe, K, Li, Mg, Na, Sr e Ti em quartzo foram executadas com introdução de suspensão e ausência de padrão interno, usando condições do ICP similares àquelas adotadas na determinação elementar para matriz de cimento. Nesse caso as recuperações variaram de 90 a 107%. A adsorção dos analitos e padrões internos sobre as nanopartículas de sílica pode ser uma alternativa para a preparação de padrões de calibração quando se deseja realizar a introdução direta do material sólido em suspensão. / The aim of this study was to evaluate parameters for the development of methods for elements determination in alumina, cement and quartz by inductively coupled plasma optical emission spectrometry (ICP OES) with slurry sampling. Some elements were investigated as candidates for internal standards (ISs) Be, Dy, Gd, In, La, Sc, Y, Yb and Tl. Samples of certified reference material (CRM) of alumina (Alumina Reduction Grade - 699), Portland cement (blended with the 1889a and 1886a Limestone White Portland cement with low iron) from the National Institute of Standards and Technology (NIST), and quartz samples, suplied by the Department of Physics from Federal University of São Carlos (UFSCar), named T-4FI, T-2FI and T4GR were used to optimize instrumental, method development and accuracy evaluation of the method. Nanoparticles of high purity silica (Wacker HDK T40 &#174;), Wacker Chemie AG were used in the study adsorption of the analytes and internal standards as calibrating material for direct analysis of solids. Correlation graphs using excitation potentials, ionization energies and melting point temperatures were used for chosing the best ISs. Exploratory analysis using hierarchical cluster analysis (HCA) and principal component analysis (PCA) were also performed. Optimization of ICP OES was performed in aqueous and slurry samples to establishment figures of merit, such as sensitivity, robustness, selectivity and repeatability. In the optimization of ICP, power supply, nebulizer flow rate and auxiliary gas flow rate were considered. The determination of Ca, Fe, Ga, In, Si and Zn in alumina was made after decomposition in a microwave oven with subsequent precipitation of Al(III) with NH3 gas. The internal standard was essential to obtain the accuracy of the method, with recoveries of CRM analysis ranging from 83 to 117%. For the cement analysis was evaluated the effect of nitric acid concentration over analytes extraction (Al, Ca, Cr, Fe, K, Mg, Mn, Na, P, S, Si, Sr, Ti and Zn) and ISs candidate adsorption (Be, Sc, In and Dy). Determinations of the elements in cement slurry with the internal standard (except for Cr and Zn), with 0.5% v v-1 HNO3, nebulizer Burgener and robust conditions of ICP produced results with recoveries between 68 and 119%. The determinations of Al, Ba, Cr, Fe, K, Li, Mg, Na, Sr and Ti in quartz were performed with the slurry introduction and without of internal standard, using similar conditions of those adopted for cement matrix. In this case the recoveries ranged from 90 to 107% with addition and recovery test. The adsorption of the analytes and internal standards on silica nanoparticles could be an alternative for the preparation of calibration standards when considering performing the direct introduction of solid material.

[pt] O uso da pasta de gelo começou recentemente a ser aplicado em sistemas de refrigeração e condicionamento de ar. Como principais vantagens deste fluido, podem ser citados: a possibilidade de armazenar calor latente do gelo e a possibilidade de ser bombeado como a água fria. Assim, o pasta de gelo pode ser usado para o armazenamento térmico no lugar da água fria ou do gelo, desde que, até determinadas concentrações, possa ser bombeado através dos trocadores de calor. Para que esta tecnologia seja aceita extensamente, informações de engenharia são requeridas nas características de transporte nos equipamentos de troca de calor. Um dispositivo experimental foi desenvolvido para estudar os coeficientes de transporte do pasta de gelo em um trocador de calor de placas, utilizando água como carga térmica a resfriar. Foram investigadas várias situações para diferentes frações iniciais e vazões do pasta de gelo. As condições de entrada da carga térmica, foram mantidas constantes. São monitoradas a temperatura, a queda de pressão, a fração do gelo sólido e a vazão do pasta de gelo no trocador de calor, assim como a vazão e a de temperatura na parte da carga térmica. Os resultados mostram que o coeficiente global de troca de calor aumenta com aumento da fração inicial do gelo. A capacidade do resfriamento do trocador de calor aumenta consideravelmente, em relação da água, quando a pasta de gelo, é utilizada como fluido secundário. Finalmente, a queda de pressão aumenta com o aumento da fração inicial de gelo. / [en] The use of the ice slurry is recently applied in the refrigeration and air conditioning systems. Advantages such as the possibility to store latent heat on ice and the possibility of being pumped as cold water can be considered. Ice slurries can be used both for cold storage in place of chilled water or ice and as a secondary refrigerant since, up to certain concentrations, they can be pumped directly through distribution pipeworks and heat exchangers. For ice slurries to become more widely accepted, however, more engineering information is required on fluid flow and heat transfer characteristics. An experimental device was developed to study the transport properties of the ice slurry in plate heat exchangers. Several situations were investigated for different initial fractions and flows of ice slurry. The conditions of the thermal load (pure water), had been kept constant. The temperature field, the pressure loss, the initial fraction and the flow of ice slurry are monitored in the heat exchanger, beyond the flow and the temperature field is monitored in the part of the thermal load. The overall heat transfer coefficient, increases in function of the initial ice fraction. The capacity cooling of the heat exchanger increases with the use of ice slurry when compared to pure water. Finally can be showed that the loss of pressure increases for higher initial ice fraction.

O objetivo deste estudo foi avaliar parâmetros para o desenvolvimento de métodos visando à determinação elementar em alumina, cimento e quartzo por espectrometria de emissão óptica com plasma indutivamente acoplado (ICP OES) com amostragem de suspensão. Alguns elementos foram investigados como possíveis candidatos a padrões internos (PIs) Be, Dy, Gd, In, La, Sc, Y, Yb eTl. Amostras de material de referência certificado (CRM) de alumina (Alumina Reduction Grade 699), de cimento Portland (1889a Blended with Limestone e 1886a White Portland cement with low iron) do National Institute of Standard and Technology (NIST), e amostras de quartzo, cedidos pelo Departamento de Física da Universidade Federal de São Carlos (UFSCar), denominados T-4FI, T-2FI e T-4GR, foram utilizadas na otimização instrumental, no desenvolvimento e na avaliação da exatidão do método. Nanopartículas de sílica de alta pureza (Wacker HDK&#174; T40), Wacker Chemie AG foram utilizadas no estudo de adsorção dos elementos e padrões internos como proposta de produção de material calibrante para a análise direta de sólidos. Para a escolha dos PIs foram construídos gráficos de correlação usando valores de potenciais de excitação, energias de ionização e temperaturas de fusão dos analitos e dos candidatos a PIs. Análise exploratória por agrupamentos hierárquicos (HCA) e análise dos componentes principais (PCA), também foram realizadas. A avaliação de desempenho do ICP OES foi feita em meio das suspensões das amostras a partir do estabelecimento de figuras de mérito como sensibilidade, robustez, seletividade e repetibilidade. Na otimização do foram considerados os parâmetros potência, vazão de nebulização e vazão de gás auxiliar. A determinação de Ca, Fe, Ga, Na, Si e Zn em alumina foi feita após dissolução em forno de micro-ondas com posterior precipitação do Al(III) com NH3. O uso de padrão interno foi essencial para a exatidão do método, com recuperações do CRM que variaram de 83 a 117%. Para a matriz cimento foram avaliados o efeito da concentração de ácido nítrico na extração dos analitos ( Al, Ca, Cr, Fe, K, Mg, Mn, Na, P, S, Si, Sr, Ti e Zn) e na adsorção dos elementos candidatos a PIs (Be, Sc, In, Dy). As determinações por suspensão e uso de padrão interno (exceto para Cr, S e Zn), com 0,5% v v-1 de HNO3, nebulizador Burgener e condições robustas do ICP geraram resultados com recuperações entre 68 e 119%. As determinações de Al, Ba, Cr, Fe, K, Li, Mg, Na, Sr e Ti em quartzo foram executadas com introdução de suspensão e ausência de padrão interno, usando condições do ICP similares àquelas adotadas na determinação elementar para matriz de cimento. Nesse caso as recuperações variaram de 90 a 107%. A adsorção dos analitos e padrões internos sobre as nanopartículas de sílica pode ser uma alternativa para a preparação de padrões de calibração quando se deseja realizar a introdução direta do material sólido em suspensão. / The aim of this study was to evaluate parameters for the development of methods for elements determination in alumina, cement and quartz by inductively coupled plasma optical emission spectrometry (ICP OES) with slurry sampling. Some elements were investigated as candidates for internal standards (ISs) Be, Dy, Gd, In, La, Sc, Y, Yb and Tl. Samples of certified reference material (CRM) of alumina (Alumina Reduction Grade - 699), Portland cement (blended with the 1889a and 1886a Limestone White Portland cement with low iron) from the National Institute of Standards and Technology (NIST), and quartz samples, suplied by the Department of Physics from Federal University of São Carlos (UFSCar), named T-4FI, T-2FI and T4GR were used to optimize instrumental, method development and accuracy evaluation of the method. Nanoparticles of high purity silica (Wacker HDK T40 &#174;), Wacker Chemie AG were used in the study adsorption of the analytes and internal standards as calibrating material for direct analysis of solids. Correlation graphs using excitation potentials, ionization energies and melting point temperatures were used for chosing the best ISs. Exploratory analysis using hierarchical cluster analysis (HCA) and principal component analysis (PCA) were also performed. Optimization of ICP OES was performed in aqueous and slurry samples to establishment figures of merit, such as sensitivity, robustness, selectivity and repeatability. In the optimization of ICP, power supply, nebulizer flow rate and auxiliary gas flow rate were considered. The determination of Ca, Fe, Ga, In, Si and Zn in alumina was made after decomposition in a microwave oven with subsequent precipitation of Al(III) with NH3 gas. The internal standard was essential to obtain the accuracy of the method, with recoveries of CRM analysis ranging from 83 to 117%. For the cement analysis was evaluated the effect of nitric acid concentration over analytes extraction (Al, Ca, Cr, Fe, K, Mg, Mn, Na, P, S, Si, Sr, Ti and Zn) and ISs candidate adsorption (Be, Sc, In and Dy). Determinations of the elements in cement slurry with the internal standard (except for Cr and Zn), with 0.5% v v-1 HNO3, nebulizer Burgener and robust conditions of ICP produced results with recoveries between 68 and 119%. The determinations of Al, Ba, Cr, Fe, K, Li, Mg, Na, Sr and Ti in quartz were performed with the slurry introduction and without of internal standard, using similar conditions of those adopted for cement matrix. In this case the recoveries ranged from 90 to 107% with addition and recovery test. The adsorption of the analytes and internal standards on silica nanoparticles could be an alternative for the preparation of calibration standards when considering performing the direct introduction of solid material.

Secondary working fluids (secondary refrigerants, heat transfer fluids, antifreezes, brines) have long been used in various indirect re-frigeration and heat pump systems. Aqueous solutions (water solu-tions) have long been used as single phase (liquid only) secondary working fluids for cooling in supermarkets, ice rinks, heat recovery systems, heat pumps and other applications. However, aqueous solutions are increasingly used also for freezers in supermarkets and other applications in low temperature refrigeration. Of importance when comparing different secondary working fluids for indirect systems are the following basic thermophysical properties: freezing point, density, viscosity, specific heat, and thermal conductivity. Reliable data of these properties are needed to choose suitable fluid and to make technical calculations of an indirect refrigeration or heat pump system. The main intention of this work has been to select thermophysical property data with good or acceptable technical accuracy of a number of aqueous solutions that can be used by the refrigeration and heat pump industry, rather than focusing on a limited number of property values or scientifically very accurate measuring techniques. A thorough literature search was in view of this made to find the most reliable property values of aqueous solutions. Detailed literature references are given for thermo-physical properties of the following aqueous solutions, without other additives: Ethylene and propylene glycol, ethyl and methyl alcohol, glycerol, ammonia, potassium carbonate, calcium, lithium, magnesium and sodium chlorides as well as potassium acetate and potassium formate. Some laboratory measurements were made of most of the fluid types when literature values were incomplete or deemed unreliable. Methods used are briefly described and results are given. Much of the work was reported on in the Engineering Licentiate Thesis: Thermophysical properties of liquid secondary refrigerants, A Critical Review on Literature References and Laboratory Measure-ments (Melinder 1998a). That material forms the basis for the charts and tables used in the IIR-publication Thermophysical properties of liquid secondary refrigerants (Melinder, 1997). The present thesis reports on an update made since 1998, including re-view work done on two additional fluids not covered in Melinder (1998a). The thesis describes how the selection of property values results in tables and charts intended for the industry. Coefficients for poly-nomial equations are generated from these property values using a Matlab program and this material is intended as a useful tool for computer treatment. Aqueous solution of ethyl alcohol is used as example to see how this process is made. This choice of fluid can also be seen as a test of this method, as the basic thermophysical properties of aqueous solutions of ethyl alcohol present more chal-lenges than the other fluids examined. A comparison is made of a few types of aqueous solutions used as secondary working fluids for two types of applications. The first example is bedrock heat pumps and the second is cooling cabinets in a supermarket. An effort is made to see how the additive con-centration affects the thermal performance. Most aqueous solutions used as single-phase secondary fluids can also be used as ice slurry, a fluid consisting of liquid and ice where small ice crystals are produced, usually with some type of ice generator. The ice crystals are then transported to the cooling object from which heat is removed when ice crystals melt. This results in less temperature change in the cooling object and makes it also possible to reduce the volume flow rate and to use smaller pipe dimensions in the system. In order to choose a secondary fluid for ice slurry use and to make correct technical calculations of the ice slurry system there is a need to examine and evaluate thermo-physical properties and other aspects of ice and of the aqueous solution used. For dimensioning purposes it is of interest to estimate ice mass fraction and enthalpy values and enthalpy-phase diagrams can serve that purpose. This thesis presents enthalpy-phase diagrams made by author that besides isotherms contain lines with ice fraction and lines connecting enthalpies at freezing point and 1, 2, etc. to 10 K below the freezing point curve. / QC 20100609