The flow of solid liquid mixtures (slurries) has attracted much attention in research work because of its importance to industry. Prediction of pressure losses associated with slurry flow helps pipe designers select the correct pipe sizes for optimum energy consumption, equipment sizing and reliable operation of the pipeline networks. Many workers developed empirical correlations, but due to the randomness of the problem they seem of limited use in design applications because they do not contain an assessment except by trial and error, which is costly. The existence of more than one particle size poses more complexities to the slurry flow problem but it is in need in practical applications. The aims of this work are justified under the light of the observations on the state of the art in slurry transport. An experimental program is designed to highlight the effects of this problem through a predetermined set of test runs. The variables are grouped to optimise the number of experiments and to remove the effect of dimensions on the prediction method The test rig is built to serve the aims of this exercise and test runs conducted, results grouped and discussed for polyfractional slurries. A mathematical model is developed in the form of an empirical correlation. Statistical tests are employed to verify the goodness of fit. Finally, conclusions and recommendations for further work are listed.

Magnetic photocatalysts were synthesised by coating a magnetic core with a layer of photoactive titanium dioxide. This magnetic photocatalyst is for use in slurry-type reactors in which the catalyst can be easily recovered by the application of an external magnetic field. The first attempt at producing this magnetic photocatalyst involved the direct deposition of titanium dioxide onto the surface of magnetic iron oxide particles. The photoactivity of these Fe3O4/TiO2 was lower than that of single-phase TiO2 and was found to decrease with an increase in the heat treatment. These observations were explained in terms of an unfavourable heterojunction between the titanium dioxide and the iron oxide core. Fe ion diffusion from the iron oxide core into the titanium dioxide matrix upon heat treatment, leading to a highly doped TiO2 lattice, was also contributing to the observed low activities of these samples. These Fe3O4/TiO2 particles were found to be unstable, with photodissolution of the iron oxide phase being encountered. This photodissolution was dependent on the heat treatment applied, the greater the extent of the heat treatment, the lower the incidence of photodissolution. This was explained in terms of the stability of the iron oxide phases present, as well as the lower photoactivity of the titanium dioxide matrix. In fact, the observed photodissolution was found to be induced-photodissolution. That is, the photogenerated electrons in the titanium dioxide phase were being injected into the lower lying conduction band of the iron oxide core, leading to its reduction and then dissolution. Thus, the approach of directly depositing TiO2 onto the surface of a magnetic iron oxide core proved ineffective in producing a stable magnetic photocatalyst. The introduction of an intermediate passive SiO2 layer between the titanium dioxide phase and the iron oxide phase inhibited the direct electrical contact and hence prevented the photodissolution of the iron oxide phase. Improvements in the photoactivity were seen to be due to the inhibition of both the electronic and chemical interactions between the iron oxide and titanium dioxide phases. Preliminary optimisation experiments revealed that a thin SiO2 layer is sufficient for inhibiting the photodissolution. The thickness of the TiO2 coating was found not to have a significant effect on the photocatalytic performance of the coated particles. Finally, heat treating for 20 minutes at 450??C was sufficient for converting the titanium dioxide into a photoactive phase, longer heating times had no beneficial effect on the photoactivity.

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 117-131).

Thesis (Ph. D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2006. / Yiacoumi, Sotira, Committee Chair ; Tsouris, Costas, Committee Co-Chair ; Pavlostathis, Spyros, Committee Member ; Tannenbaum, Rina, Committee Member ; Sherrill, David, Committee Member.

O processo de espessamento e clarificação dos efluentes das usinas de beneficiamento de carvão mineral com a adoção de sedimentadores é uma prática consagrada ao longo de todo o mundo uma vez que é necessário o reaproveitamento da água utilizada tanto por questões econômicas como ambientais. O primeiro sedimentador, tipo espessador, a entrar em operação industrial na região carbonífera de Santa Catarina foi instalado na Mina Barro Branco da Carbonífera Rio Deserto em 2007. O equipamento era dotado de lamelas de PVC e foi instalado como alternativa às bacias de decantação, que apresentam alto custo de construção e operação. Contudo, o equipamento se mostrou ineficaz devido a deposição de sólidos nas lamelas. Essa dificuldade levou a adoção de outros modelos de sedimentadores de fluxo vertical que não utilizam lamelas. Esse trabalho apresenta os dados disponíveis da operação do equipamento com as lamelas na Mina Barro Branco e resultados atuais da operação dos sedimentadores da Mina Esperança sem lamelas. Nesse segundo caso foi medida a vazão, concentração de sólidos e dos metais ferro, alumínio e manganês, nos fluxos de entrada e saída. No efluente clarificado mediu-se ainda o pH e a turbidez. Registraram-se dados de uma operação satisfatória, com impacto importante na redução dos custos no transporte e deposição dos rejeitos finos e no tratamento do overflow clarificado possibilitando o descarte de acordo com a Legislação Ambiental. / The process of thickening and clarifying the effluents of mineral coal processing plants with the use of settlers is a well-established practice throughout the world since it is necessary to reuse the water used for both economic and environmental reasons. The first settler, a thickener type, to enter into industrial operation in the Santa Catarina coal region was installed at the Barro Branco Mine of the Carbonifera Rio Deserto in 2007. The equipment was equipped with PVC lamellae and was installed as an alternative to the decantation basins, which have a high cost of construction and operation. However, the equipment proved to be ineffective due to deposition of solids in the lamellae. This difficulty led to the adoption of other models of vertical flow settlers that do not use lamellae. This work presents the available data of the operation of the equipment with lamellae in the Mina Barro Branco and current results of the operation of the settlers in the Mina Esperança without lamellae. In this second case the flow, concentration of solids and iron, aluminum and manganese metals in the inflow and outflow were measured. In the clarified effluent the pH and turbidity were also measured. Data were recorded for a satisfactory operation, with a significant impact on the reduction of costs in the transportation and deposition of the fine tailings and in the treatment of the clarified overflow, allowing the disposal according to the Environmental Legislation.

L'objectif de cette thèse est d'étudier la décontamination en ions de solutions aqueuses par les oxydes échangeurs d'ions en s'intéressant plus particulièrement à l'adsorption du strontium par le nonatitanate de sodium. Le but est de développer un modèle prédictif qui tienne compte des phénomènes physico-chimiques mis en jeu et des écarts à l'idéalité dans la solution, mais également dans le matériau. Pour cela, le calcul des coefficients d'activité des ions en solution a été calculé à partir d'une approche basée sur la théorie MSA (Mean Spherical Approximation) où les phénomènes spécifiques d'association ont été pris en compte. Cela a permis de calculer les coefficients d'activité des ions dans les mélanges ternaires. La validité des lois de mélange de Zdanovskii-Stokes-Robinson et McKay-Perring a également été précisée. Deux modèles d'activité, représentant les interactions à longues distances et à courtes distances, ont été utilisés pour l'étude des ions dans le solide. Les isothermes d'adsorption à différentes concentrations ont alors été modélisées. Une étude pH-métrique a également été conduite sur le nonatitanate de sodium afin de déterminer la constante d'hydrolyse ainsi que le taux d'hydrolyse du solide. Une étude structurale et morphologique a permis de mettre en évidence qu'avec des solutions très acides le nonatitanate de sodium se dissout et précipite de nouveau sous différentes formes cristallographiques du TiO2. / The objective of this thesis is to study the ionics decontamination of aqueous solutions by ionic oxide exchangers with a particular focus on the strontium adsorption by the sodium nonatitanate. The goal is to develop a predictive model takes into account the phenomena involved, and the deviations to the ideality into the solution but also in the material.The activity coefficients of the ions in solution have been calculated from an approach based on the MSA theory (Mean Spherical Approximation), where the specific association phenomenons have been taken into account. This allowed for calculating the ionic activity coefficients in the ternary mixtures. The validity of mixture laws of Zdanovskii-Stokes-Robinson and McKay-Perring has been also specified. Two activity models, which represent the long and the short-range interactions, have been used for the ionic studied in the solid. The adsorption isotherms at various concentrations have been hence modeled.A pH-metric study has also been performed on the sodium nonatitanate in order to determine the hydrolysis constant as well as the solid hydrolysis rate. A structural and morphologic study allowed for highlighting that for highly acidic solutions the sodium nonatitanate is dissolved and precipitated again under different crystallographic forms of the TiO2.

Offshore production fluids from the reservoir are often transported in pipelines from the wellheads to the platform and from the platform to process facilities. At low flow velocity water, sand or liquids like condensate could settle at the bottom of pipelines that may lead to grave implications for flow assurance. During shutdown the settled heavy liquid (e.g. water), could result in corrosion in pipelines, while following restart stages the settled water could form water plugs that could damage equipment, while settled sand could also form a blockage that needs to be purged. Furthermore, there is a requirement to know the quantity of water and base sediment for fiscal metering and custody transfer purposes. A series of experiments were carried out to observe low water cut in oil and water flows in four inch diameter pipeline. Similarly low sand concentrations in water and sand, water, air and sand flows were observed in two inch diameter pipelines. Conductive film thickness sensors were used to ascertain structural velocities, height and dense phase fractions. Comparisons are made between two cases in order to gain better understanding of the behaviours and dispersal process of low loading denser phase in multiphase flows. The arrangement enabled production of flow regime maps for low water cut oil and water flow, as well as water sand and water, air and sand flows, structural velocities and denser phase removal velocities were also ascertained. Actual in-situ liquid velocities were obtained experimentally. A novel detection of sand in water and water and sand flows was produced. The experimentally obtained film thickness was in agreement with two fluid model predictions. Thus, confirming use of conductive sensors for dense phase classification, film thickness, velocity and holdup measurements in pipelines.

O minério de ferro produzido no complexo de Carajás traz consigo características mineralógicas que conferem um elevadíssimo teor de Fe em todas as suas frações granulométricas. Dessa forma, ao final da cadeia produtiva, tanto os produtos comerciais mais grosseiros quanto os finos contem cerca de 62% de Fe contido na sua composição. Importante destacar que em Carajás as fases no processamento desse minério são apenas para cominuição e classificação por tamanho. Não existem etapas de concentração e os produtos são diferenciados por suas respectivas curvas granulométricas: o “granulado” - mais grosseiro (> 13 mm), o “Sinter-Feed” (< 13 mm e > 0,5 mm) e o “pellet feed” (< 0,15 mm). Garantir a correta distribuição granulométrica da matéria prima é uma premissa de mercado. A ultima etapa da classificação é feita através de hidrociclones e gera um overflow ultrafino de altíssima superfície específica maior que 6.500 Blaine e com 45% até 95 % < 7 μm. E ainda possui um elevado teor de Fe - cerca de 62 %. Dessa forma os objetivos gerais dessa pesquisa buscaram a solução para essa oportunidade de recuperar e vender esses rejeitos. O estudo sugeriu através de ensaios com tecnologias capazes de desaguar os ultrafinos gerados para 9,00 % de umidade, que é o valor que permite a movimentação e o manuseio desses rejeitos, além de permitir sua incorporação na blendagem de produtos mais grossos. Desse modo, foram realizados experimentos em diversos laboratórios externos e em escala piloto na Usina de Carajás com amostras dos dois rejeitos ultrafinos das duas fases de hidrociclonagem: o natural e o moído. Ficou evidente que o equipamento tem de combinar necessariamente e de forma eficiente dois fatores essências ao desaguamento: elevadíssimas pressões e altas temperatura na operação desses ultrafinos. A produtividade atingida foi da ordem de 50 t/h x m² para o rejeito da hidrociclonagem do Sinter Feed e 40 t/h x m² para o rejeito dos hidrociclones da Moagem. / The Iron ore that is produced in Carajás mining complex brings mineralogical characteristics that give a very high Fe content in all its size fractions. Thus, at the end of the production chain both coarser and fine contains about 62% Fe contained in its composition. Importantly, in Carajás stages in the processing of this ore are for reduction and classification by size. There is thus no concentration steps and products are differentiated by their respective size distribution curves: the "grain" - coarser (> 13 mm), the "Sinter-Feed" (<13 mm and > 0.5 mm) and the "pellet feed" (<0.15 mm). Ensure proper particle size distribution of the raw material is a market premise. The last step of classification is made using hydrocyclones and generates an overflow ultrafine high specific surface area greater than 6.500 Blaine and with 45% to 95% <7 μm. And has a high Fe content - about 62%. The overall objectives of this research sought the solution to this opportunity to recover and sell these “tailings”. The study suggested by testing with technologies capable of flowing into the ultrathin generated to 9.00% of moisture, which is the value that allows movement and handling these wastes, and allows their incorporation into the blending of thicker products. Thus, experiments were carried out in several external laboratories and pilot-scale plant in the Carajás with samples of both ultrafine “tailings” of the two phases of hydrocycloning: the natural and the ground. It was evident that the equipment must necessarily match and two efficiently factors essences to dewatering: very high pressure and high temperature operation of these “tailings”. The productivity achieved was around 50 t/h x m² in reject of the Sinter Feed hydrocycloning and 40 t/h x m² to reject of the grinding hydrocyclones.

La formation de gels de silice dans les procédés hydrométallurgiques est très souvent problématique pour la performance des étapes de séparation solide-liquide, en raison du colmatage des filtres. Ces étapes interviennent en aval des étapes de lixiviation visant à mettre en solution les éléments d'intérêts, notamment dans des milieux à forte acidité. Egalement mis en solution au cours de ces attaques acides, le silicium précipite alors sous forme d'oxyde de silicium et forme des gels extrêmement préjudiciables à la filtration. Dans le cadre d'une collaboration avec ERAMET Research, centre de recherche d'ERAMET, groupe minier français qui conçoit des procédés hydrométallurgiques, nous avons étudié l'influence des conditions de lixiviation d'un minerai spécifique sur la cinétique de dissolution du silicium ainsi que sur les mécanismes de précipitation de la silice en milieu acide. Nous avons montré qu'en-dessous d'une valeur de pH égale à 2, la silice polymérise pour former des gels suivant des mécanismes indépendants de la composition ionique de la solution. L'étude structurale des gels obtenus, réalisée par diffusion de rayonnement aux petits angles (SAXS) nous a conduit à proposer un modèle pour la mésostructure qui permet de comprendre leur impact sur les vitesses de filtration. Par la suite, des stratégies consistant à modifier la mésostructure des gels par des approches physiques ou physico-chimiques ont été considérées. Les résultats obtenus ont montré la possibilité d'utiliser à court terme ces stratégies pour améliorer la filtrabilité des gels de silice dans un procédé hydrométallurgique. / The formation of silica gels in hydrometallurgical processes is very often problematic for the performance of the solid-liquid separation steps, due to clogging of the filters. These steps are carried out downstream of leaching aiming to solubilize the elements of interests, in particular in solutions with strong acidity. Also dissolved during acidic leaching, the silicon then precipitates in the form of silicon oxide and forms gels extremely detrimental to filtration. In collaboration with ERAMET Research, a research center of ERAMET, a french mining group that designs hydrometallurgical processes, we studied the influence of the leaching conditions of a specific ore on the dissolution kinetics of silicon as well as on the mechanisms of precipitation of silica in an acidic solution. We have shown that below a pH value of 2, silica polymerizes to form gels following mechanisms independent of the ionic composition of the solution. Based, on the structural study of the gels, carried out by small angle radiation scattering (SAXS) we proposed a model for the mesotructure, which explain the impact on filtration rates. Subsequently, strategies to modify the mesostructure of the gels by physical or physicochemical approaches were considered. The results have shown the potentialities of these strategies in the short term to improve the filterability of precipitated silica gels in a hydrométallurgical process.

Made available in DSpace on 2014-06-11T19:34:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-12-06Bitstream added on 2014-06-13T20:05:56Z : No. of bitstreams: 1 cruz_oc_dr_jabo.pdf: 582231 bytes, checksum: 0d0f21ba758e5ca444fec02d67a3b555 (MD5) / Funep / Os hidrociclones são equipamentos amplamente utilizados pela indústria em processos envolvendo separação sólido-líquido, porém, ainda, pouco divulgados na agricultura irrigada brasileira. Buscou-se neste trabalho determinar a perda de carga e avaliar o desempenho de um hidrociclone de geometria “Rietema” como pré-filtro de partículas sólidas. Os testes foram realizados no Centro Federal de Educação Tecnológica de Uberaba - MG - Brasil utilizando um hidrociclone de geometria “Rietema”. Este equipamento possui um diâmetro de 19,20 cm na parte cilíndrica e opera com vazões variando entre 10 m3 h-1 e 27 m3 h-1. Os materiais particulados usados em suspensão foram: solo franco-argiloso e areia de rio. Os resultados mostraram que a perda de carga máxima média foi de 52 kPa e 47 kPa para as suspensões aquosas de areia e solo, respectivamente. Seu melhor desempenho ocorreu operando com suspensão aquosa de areia, apresentando eficiência total de 92,31% para a vazão de 26,97 m3 h-1. Dentre as conclusões pode-se inferir que o equipamento avaliado é eficiente para remoção de partículas de areia, podendo ser utilizado como pré-filtro em sistemas de irrigação. / The hydrocyclones are equipments widely used by industry in cases involving solid-liquid separation, but still, little reported in brazilian irrigated agriculture. The proposal of this research was to determining the head loss and evaluate the performance of a hydrocyclone of geometry “Rietema” as a pre-filter of solid particles. The tests were performed in the Centro Federal de Educação Tenológica de Uberaba - MG - Brazil using a hydrocyclone of Rietema geometry. This equipment has a diameter of 19.20 cm at the cylindrical part and operates with flows ranging between 10 m3 h-1 and 27 m3 h-1. The materials used in particulate suspension were: clay loam soil and sand from river. The results showed that the average maximum head loss was 52 kPa and 47 kPa of aqueous suspensions of sand and soil, respectively. Its best performance occurred operating with slurry of sand, presenting total efficiency of 92.31% for flow rate of 26.97 m3 h-1. Among the conclusions can be inferred that the equipment is judged effective at removing particles of sand and can be used as pre-filter in irrigation systems.