Teses / dissertações sobre o tema "Dolomita mineral"

Orientador: Arai Augusta Bernardez Pecora
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
Made available in DSpace on 2018-08-11T13:29:17Z (GMT). No. of bitstreams: 1 Hory_RogerioIshikawa_D.pdf: 3549862 bytes, checksum: 727c6ab5dce7454b6af9546842232b2e (MD5) Previous issue date: 2007
Resumo: Este trabalho apresenta o estudo experimental do processo de combustão de carvão mineral brasileiro em reator de Leito Fluidizado Circulante (LFC) com o objetivo de avaliar as taxas de emissões de di óxido de enxofre (S02) e eficiência de conversão de carbono no processo de combustão. Para diminuir a emissão do S02 nos gases de exaustão, foi adicionado, ao carvão, quantidades de calcário dolomítico (dolomita), de modo que a relação molar entre o cálcio (Ca) presente no calcário e o enxofre (S) presente no carvão variou entre 0,0 e 2,0. A variação na relação molar Ca/S, como é denominada na literatura, foi um dos dois fatores avaliados neste trabalho. O outro fator envolvido nos testes foi o excesso de ar utilizado para combustão do carvão. Trabalhou-se com excesso de ar na faixa de 20 a 30%. Foram realizados 11 ensaios seguindo um planejamento experimental estatístico do tipo CCD (Composite Central Design) e mais 02 ensaios complementares. A relação molar Ca/S de 0,6 apresentou emissão zero de S02 e propôs-se utilizar uma nova relação molar: (Ca+Mg)/S para retratar processos de sorção com dolomitas. Para emissão zero de S02, uma relação molar (Ca+Mg)/S de 1,8 já é suficiente. Foram obtidas eficiências de conversão do carbono entre 86,0 e 93,0% para combustão do carvão
Abstract: This work presents an experimental study with Brazilian mineral coal combustion in a Circulating Fluidized Bed (CFB) reactor with the objective to evaluate the sulphur dioxide emissions (S02) and the carbon conversion efficiency in the combustion processo Dolomite was added to the coal to minimize the S02 emissions during combustion. The quantity of dolomite added was calculated based on the molar relation of calcium (Ca) present in the dolomite and sulphur (S) present in the coal. Ca/S molar relation had a variation between 0,0 and 2,0. Two factors were evaluated in this work: Ca/S relation and excess of air during combustion which had a variation between 20 and 30%. Eleven (11) experimental tests were evaluated following a statistical experimental design called CCD (Composite Central Design) and 02 (two) more complementary tests. Emissions of S02 with zero value were obtained for a Ca/S of 0,6. It was also proposed in this work a new relation for sorption of S02 with dolomite: (Ca+Mg)/S relation. Tests showed that a relation of 1.8 for (Ca+Mg)/S is sufficient for zero emissions of S02. Carbon conversion efficiency between 86.0 and 93.0 was also obtained during coal combustion
Doutorado
Termica e Fluidos
Mestre em Engenharia Mecânica

Orientador: Caio Glauco Sanchez
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
Made available in DSpace on 2018-07-28T14:08:37Z (GMT). No. of bitstreams: 1 RamirezBehainne_JhonJairo_M.pdf: 9088845 bytes, checksum: 2ca5f7e1ce6f914d007e3d0144f45e1f (MD5) Previous issue date: 1999
Resumo: Carvão mineral brasileiro da jazida de Candiota/RS foi gaseificado com ar em um reator de leito fluidizado atmosférico em escala de laboratório. Os ensaios experimentais realizados em um reator de 0,2 m de diâmetro interno permitiram, em primeira instância, avaliar o desempenho do gaseificador em função do fator de ar sem adição de partículas de dolomita, e em segundo, estudar o efeito "in-situ" deste adsorvente na captura do sulfeto de hidrogênio (H2S), contido no gás gerado. Sem adição de dolomita obteve-se um poder calorífico máximo de 2,2 MJ/Nm3 para o gás produzido e uma eficiência a mo do gaseificador perto de 43%, na faixa de fator de ar entre 0,45 e 0,60. Durante os ensaios com dolomita foi obtida uma redução máxima de 58% para o H2S, utilizando-se razão molar Ca/S igual a 4. Trabalhos da literatura mostraram maior eficiência de remoção, ainda a menor razão Ca/S. Variações foram provavelmente causadas pela alta elutriação no regime de-fluidização utilizado, considerando-se a notável diferença no menor tamanho das partículas de dolomita em relação ao carvão mineral
Abstract: Brazilian mineral coal from Candiota mine (Rio Grande do Sul State) was gasified with air in a atmospheric fluidized bed reactor at laboratory scale. Experimental essays carried out in a 0.2 m internal diameter reactor permited both, to evaluate the gasifier operation at different air factors without dolomite particles addition, and to study the effect adsorvent on the capture hidrogen sulfide (H2S), contained in the generated gas. Test were done with and without the use of dolomite. Without using dolomite, the maximum gas lower heating value was 2.2 MJ/Nm3 and the cold gas thermal eficiency was close to 43%, operating at an air factor between 0.45 and 0.60. During the experimental test with dolomite , a maximum reduction of 58% for H2S was attained using a molar ratio of Ca/S equal to 4. Literature review showed higher capture eficiencies,even at lower molar ratio (CaiS). Variances were probably caused by high dolomite elutriation in the fluidization regime, considering a notable particle size difference between adsorvent and coal
Mestrado
Termica e Fluidos
Mestre em Engenharia Mecânica

Dissertação (mestrado)—Universidade de Brasília, Instituto de Química, Programa de Pós-Graduação em Tecnologia Química e Biológica, 2014.
Submitted by Raquel Viana (raquelviana@bce.unb.br) on 2017-03-02T20:22:21Z No. of bitstreams: 1 2014_LucasMachadoGaio.pdf: 1243325 bytes, checksum: fc84789459642da1ddb1dfbbb220c91f (MD5)
Approved for entry into archive by Ruthléa Nascimento(ruthleanascimento@bce.unb.br) on 2017-03-23T13:43:55Z (GMT) No. of bitstreams: 1 2014_LucasMachadoGaio.pdf: 1243325 bytes, checksum: fc84789459642da1ddb1dfbbb220c91f (MD5)
Made available in DSpace on 2017-03-23T13:43:55Z (GMT). No. of bitstreams: 1 2014_LucasMachadoGaio.pdf: 1243325 bytes, checksum: fc84789459642da1ddb1dfbbb220c91f (MD5)
O biodiesel é um combustível biodegradável derivado de fontes renováveis, que pode ser produzido a partir de gorduras ou óleos de origem animal ou vegetal. Este biocombustível pode substituir total ou parcialmente o óleo diesel de petróleo em motores automotivos ou estacionários. Por essas características, o biodiesel vem sendo um grande vetor de redução das emissões de diversos poluentes e no combate ao efeito estufa. Além disso, colabora para uma maior diversificação da matriz energética brasileira, que já é exemplo mundial na utilização de energias renováveis. Este trabalho reporta a preparação, caracterização e o uso da dolomita como catalisador heterogêneo em reação de transesterificação com óleo usado de fritura a fim de produzir biodiesel de 2ª geração. O óleo coletado foi fornecido pelo projeto ambiental na cidade do Gama-DF, Projeto BioGama. Segundo a literatura, a dolomita apresenta resultados positivos como catalisador na reação de transesterificação. Neste trabalho, o objetivo foi estudar as condições de tratamento do catalisador, tais como, temperatura de calcinação e impregnação de outras espécies; e as condições reacionais, tais como temperatura, tempo reacional, quantidade de catalisador e razões molares dos reagentes. Estas diferentes condições visam as melhores taxas de conversão de metil ésteres e reuso do catalisador. Foi possível realizar três ciclos catalíticos na melhor condição reacional com 100% de conversão: dolomita calcinada a 900 °C, 1 h de reação a 60 ºC, razão molar 1:6 (óleo/metanol) e 2% de catalisador (m/m). Foi possível também observar que a taxa de conversão está diretamente relacionada ao conteúdo de CaO no catalisador, o qual apresentou lixiviação ao longo dos ciclos. A fim de reduzir esta lixiviação, foram impregnados espécies de ferro, cobre, níquel e cério à dolomita, porém a perda de espécies de cálcio permaneceu inalterada, não trazendo benefícios para o processo. Sendo assim, o trabalho evidenciou positivamente o uso da dolomita como catalisador na produção de biodiesel priorizando processos mais limpos, econômicos e com altas taxas de conversão de ésteres.
Biodiesel is a biodegradable fuel derived from renewable sources that can be produced from animal or vegetable fat or oil. This biofuel can totally or partly replace diesel oil in automotive or stationary engines. Because of these characteristics, biodiesel has been a major vector in addition reduce emissions of various pollutants and combat global warming. Besides, it helps to diversify the Brazilian energy matrix, which is already a world example in the use of renewable energies. This study reports the preparation, characterization and use of dolomite as heterogeneous catalyst in the transesterification of used frying oil to produce biodiesel of 2nd generation. The oil collected was provided by an environmental project from the city of Gama - DF called BioGama Project. Dolomite has already shown positive results as a catalyst at the transesterification reaction, according to the literature. In this study, the objective was to analyze the treatment conditions of the catalyst, such as calcination temperature and impregnation of other species, and the reaction conditions such as temperature, reaction time, amount of catalyzer and molar ratios of reagents, aiming better conversion rates of methyl esters and the reuse of the catalyzer. It was possible to observe three catalystie cycles with the dolomite calcinned at 900 °C, at the best reaction condition, 1 hour reaction at 60 °C, 1:6 molar ratio (oil/methanol) with 2% of catalyst (w/w) showing 100% of conversion . It was also observed that the conversion rate was directly related to the content of CaO in the catalyst, which showed leaching throughout the cycles. In order to reduce this leaching, iron, copper, nickel and cerium species were impregnated an dolomite. However, the loss of calcium species remained unchanged and did not provide benefits for the process. Thus, this study demonstrated the positive use of dolomite as a catalyst in the production of biodiesel in a way that prioritize cleaner, economical and high rate conversion processes to produce esters.

Made available in DSpace on 2014-12-17T15:42:08Z (GMT). No. of bitstreams: 1 FranciscoCBS_DISSERT.pdf: 2327685 bytes, checksum: 7ea91ee570c997cb17e15b80242eeaa3 (MD5) Previous issue date: 2013-07-30
The present work was to carry out a study on the adsorption of hydrogen sulfide (H2S) in arrays synthesized from a commercial clay mineral formed by a mixture of dolomite and quartz. To produce the ion exchange matrix were made using aqueous solutions of salts of cobalt II chloride hexahydrate (CoCl2.6H2O) II cadmium nitrate tetrahydrate (Cd (NO3)2.4H2O) I mercuric chloride (HgCl) nitrate and chromium III pentahydrate (Cr (NO3)3.5H2O). The arrays were subjected to hydrogen sulphide gas passage for one hour. To check the amount of gas adsorbed was used gravimetric process. The best result was in the adsorption matrix doped with cadmium and the solution retained for a longer time than the largest amount of H2S was the cobalt matrix. The matrix unmodified exhibited poor adsorption capacity. The characterization of the matrices were used XRD, XRF and IV. Mother with cadmium showed a high capacity in ion exchange, because the percentage of cadmium increased from 0% to 81.38% by replacing atoms of calcium and silicon which increased from 96.54% to 17.56% and 15, 72% to 0.32%, respectively, but also the best performance in adsorption of H2S adsorbing 11.89507 mg per gram of matrix
O presente trabalho teve como finalidade realizar um estudo sobre a capacidade de adsor??o de g?s sulf?drico(H2S) em matrizes sintetizadas a partir de um argilomineral comercial formado por uma mistura de dolomita e quartzo. Para produzir as matrizes foram feitas trocas i?nicas utilizando as solu??es aquosas dos sais: cloreto de cobalto II hexaidratado(CoCl2.6H2O), nitrato de c?dmio II tetraidratado (Cd(NO3)2.4H2O), cloreto de merc?rio I (HgCl) e nitrato de cromo III pentaidratado(Cr(NO3)3.5H2O). As matrizes foram submetidas a passagem de g?s sulf?drico durante uma hora. Para verificar a quantidade de g?s adsorvido foi utilizado o processo de gravimetria. O melhor resultado na adsor??o foi com a matriz dopada com a solu??o de c?dmio e a que reteve por mais tempo a maior quantidade de H2S, foi a matriz com cobalto. A matriz n?o modificada apresentou uma fraca capacidade de adsor??o. Na caracteriza??o das matrizes foram utilizadas an?lises de DRX, FRX e IV. A matriz com c?dmio apresentou uma alta capacidade na troca i?nica, pois a porcentagem de c?dmio passou de 0% para 81,38%, substituindo ?tomos de c?lcio e de sil?cio que passaram de 96,54% para 17,56% e de 15,72% para 0,32%, respectivamente, como tamb?m, o melhor desempenho na adsor??o, adsorvendo 11,89507mg de H2S por grama de matriz

Submitted by Alice Araujo (alice.caraujo@ufpe.br) on 2018-04-10T15:55:06Z No. of bitstreams: 1 DISSERTAÇÃO Amanda Carvalho de Oliveira.pdf: 2263727 bytes, checksum: 22f93d628978d5390207b58b778d4bf8 (MD5)
Made available in DSpace on 2018-04-10T15:55:06Z (GMT). No. of bitstreams: 1 DISSERTAÇÃO Amanda Carvalho de Oliveira.pdf: 2263727 bytes, checksum: 22f93d628978d5390207b58b778d4bf8 (MD5) Previous issue date: 2016-12-07
CAPES
O processo de flotação ocorre, predominante, em meio alcalino e o controle do pH se faz com a adição de reagentes reguladores. Os reguladores alcalinos mais utilizados são hidróxido de sódio, hidróxido de cálcio e carbonato de sódio, os quais dissociam liberando além da hidroxila, os íons Na+, Ca2+ e CO32- que podem influenciar o resultado da flotação. O trabalho teve por objetivo contribuir para uma escolha racional dos reguladores de pH, uma vez que na prática industrial a escolha costuma ser feita com base nos custos. Foi estudada a influência dos principais reguladores alcalinos na flotação de quartzo e dolomita. Medidas de potencial zeta, análises espectroscópicas na região do infravermelho e medidas de condutividade elétrica foram realizadas. Na flotação do quartzo com amina (50 g/t) até o limite de 10 ppm de íons Fe3+ na polpa, o tipo de regulador não afetou significativamente a flotabilidade. A partir da concentração de 10 ppm de íons férricos, a regulagem do pH com o carbonato de sódio apresentou as melhores condições de flotabilidade. O resultado foi explicado com base na precipitação dos íons Fe3+ com a formação de Fe2(CO3)3(s). Na flotação de dolomita com amina (100 g/t), uma recuperação de 86,5% foi obtida com o uso do hidróxido de cálcio em pH 12. Nessa faixa de pH a amina encontra-se na forma molecular e a superfície do mineral com excesso de cargas positivas. Dessa forma, sugere-se uma adsorção via interação química N-Ca e por ligações de hidrogênio. Na flotação da dolomita com oleato de sódio, o regulador carbonato de sódio é o mais indicado, pois o íon CO32- precipita os íons Ca2+ e Mg2+ dissociados do mineral.
The flotation process occurs in alkaline medium and the pH control is done with the addition of regulatory reagents. The most used alkaline regulators are sodium hydroxide, calcium hydroxide and sodium carbonate, which dissociate, releasing, in addition to hydroxyl, Na+, Ca2+ and CO32- ions, which can influence the flotation result. The aim of this work was to contribute to a rational choice of pH regulators, since that industrial practice the choice of the regulatory is usually made based on costs. In this case, was studied the influence of the main alkaline regulators on the quartz and dolomite flotation. Measurements of zeta potential, spectroscopic analyzes in the infrared region and measurements of electrical conductivity were performed. In the flotation of quartz with amine (50 g/t) up to the limit of 10 ppm of Fe3+ in the pulp, the type of regulator didn’t affect significantly the floatability. From the concentration of 10 ppm of Fe3+, pH regulation with sodium carbonate showed the best floatability conditions. The result was explained based on Fe3+ precipitation with formation of Fe2(CO3)3. In the flotation of dolomite with amine (100 g/t), a recovery of 86,5% was obtained with the use of calcium hydroxide in pH 12. In this pH range the amine is in molecular form and the surface of the mineral with excess positive charges. In this way adsorption it occurred likely through chemical interaction N-Ca and hydrogen bonding. In the flotation of dolomite with sodium oleate, the sodium carbonate regulator is the most indicated because the CO32-precipitates the Ca2+ and Mg2+ dissociated from the mineral.

La tesis denominada "Tratamiento de Remediación de Efluentes Metalúrgicos con énfasis en el abatimiento de Cobre con Dolomita", muestra el proceso de Tecnología de Limpieza como una alternativa de solución en la remediación de efluentes metalúrgicos con el empleo de la dolomita calcinada y sin calcinar, mediante Pruebas Metalúrgicas Experimentales se logro reducir las concentraciones del ión de cobre disuelto presente en los Efluentes provenientes del Proceso Metalúrgico de Flotación de la Planta Concentradora de la UNI, al cual se denominará “EFLUENTE METALÚRGICO UNI” y el Efluente Metalúrgico de la Solución de Sulfato de Cobre, que denominaremos “EFLUENTE METALÚRGICO UNMSM”, el cual fue generado a nivel Laboratorio por la Lixiviación del Mineral Tostado de Calcopirita. De este modo, la aplicación del Tratamiento de Remediación tuvo como objetivo lograr que ambos efluentes metalúrgicos tratados con dolomita presenten altos porcentajes de reducción con mínimas concentraciones de cobre, los cuales son indicadores de una mejora en el Proceso de Tratamiento de Efluentes Metalúrgicos provenientes principalmente de procesos metalúrgicos de plantas concentradoras. En la presente Tesis, se empleo el mineral de la dolomita, el cual es un mineral no metálico de carbonato doble de calcio y magnesio (CaCO3.MgCO3), que se comporta como un efectivo reactivo de remediación, debido a las propiedades fisicoquímicas siendo una de ellas la neutralización de los metales pesados donde se verifica que, es mas eficiente que, la cal para neutralizar la capacidad de generación de acidez que poseen los metales pesados. Los resultados la presente Tesis nos permite afirmar que el peso óptimo de la Dolomita Comercial de Agregados Calcáreos es de 2 g. en estado sin calcinar donde se determino que para un volumen de efluente metalúrgico de flotación de 100ml, la concentración inicial de 0,269 g/L (269 ppm) se redujo hasta el valor de 0,007 g/L (7 ppm), con un porcentaje de reducción de 97.39%., en un tiempo óptimo de 20 minutos. Cabe resaltar que la dilución S/L es de 2/100 y se aplico una velocidad de agitación de la mezcla (dolomita y efluente metalúrgico) de 700 RPM.
Tesis

Made available in DSpace on 2014-12-17T14:07:00Z (GMT). No. of bitstreams: 1 ElidaNMGP_DISSERT.pdf: 266264 bytes, checksum: 55a4fffa9b1f2a291d7fc9168a9d61cd (MD5) Previous issue date: 2011-04-16
The destructive impact of improper disposal of heavy metals in the environment increases as a direct result of population explosion, urbanization and industrial expansion and technological developments. Argil are potential materials for adsorption of inorganic and the pelletization of it is required for use in adsorptive columns of fixed bed. The low cost and the possibility of regeneration makes these materials attractive for use in the purification process, capable of removing inorganic compounds in contaminated aquatic environments. In this work was made pellets of a mixture of dolomite and montmorillonite by wet agglomeration, in different percentages. The removal of Pb (II) was investigated through experimental studies, and was modeled by kinetic models and isotherms of adsorption. The materials were characterized using the techniques of XRD, TG / DTA, FT-IR, and surface area by BET method. The results showed the adsorption efficiency of the contaminant by the composite material studied in synthetic solution. The study found that the adsorption follows the Langmuir model, and the kinetics of adsorption follows the model of pseudosecond order
O impacto destrutivo da disposi??o inadequada de metais pesados no meio ambiente aumenta como resultado direto da explos?o populacional, urbaniza??o e expans?o industrial e tecnol?gica. Argilas s?o potenciais materiais para adsor??o de compostos inorg?nicos e a pelletiza??o destes ? necess?ria para utiliza??o em colunas adsortivas de leito fixo. O baixo custo e a possibilidade de regenera??o fazem desses materiais um atrativo para a utiliza??o em processos de purifica??o, capazes de remover compostos inorg?nicos em ambientes aqu?ticos contaminados. Neste trabalho foram preparados pellets com mistura de montmorilonita e dolomita atrav?s da aglomera??o por via ?mida, em diferentes raz?es. A remo??o de Pb(II) foi investigada, atrav?s de estudos experimentais, e foi modelada segundo modelos de cin?tica e isotermas de adsor??o. Os materiais foram caracterizados atrav?s das t?cnicas de DRX, TG/DTA, FT-IR, e ?rea superficial pelo m?todo BET. Os resultados mostraram a efici?ncia adsortiva do contaminante estudado pelo material composto em solu??o sint?tica e foi verificado que a adsor??o segue o modelo de Langmuir e a cin?tica de adsor??o segue o modelo de pseudo-segunda ordem

Orientadores : Job Jesus Batista, Eric W. Mountjoy
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Geociencias
Made available in DSpace on 2018-08-02T04:11:22Z (GMT). No. of bitstreams: 1 Lopes_JaneNobre_D.pdf: 9849976 bytes, checksum: 71f5c11a311420b6010b5fe223dc0b95 (MD5) Previous issue date: 2002
Doutorado

Geologic sequestration of carbon dioxide (CO 2) in a deep, saline aquifer is being proposed for a power-generating facility in Florida as a method to mitigate contribution to global climate change from greenhouse gas (GHG) emissions. The proposed repository is a brine-saturated, dolomitic-limestone aquifer with anhydrite inclusions contained within the Cedar Keys/Lawson formations of Central Florida. Thermodynamic modeling is used to investigate the geochemical equilibrium reactions for the minerals calcite, dolomite, and gypsum with 28 aqueous species for the purpose of determining the sensitivity of mineral precipitation and dissolution to the temperature and pressure of the aquifer and the salinity and initial pH of the brine. The use of different theories for estimating CO2 fugacity, solubility in brine, and chemical activity is demonstrated to have insignificant effects on the predicted results. Nine different combinations of thermodynamic models predict that the geochemical response to CO2 injection is calcite and dolomite dissolution and gypsum precipitation, with good agreement among the quantities estimated. In all cases, CO2 storage through solubility trapping is demonstrated to be a likely process, while storage through mineral trapping is predicted to not occur. Over the range of values examined, it is found that net mineral dissolution and precipitation is relatively sensitive to temperature and salinity, insensitive to CO2 injection pressure and initial pH, and significant changes to porosity will not occur.

Detta arbetes mål har varit att hjälpa företaget SMA Mineral att utreda de rödamissfärgningar som allt oftare påträffats i deras marmor. Rapporten är högst visuellpå mikroskopisk nivå, och avhandlar vad missfärgningarna beror på. Provmaterialhar undersökts och karakteriserats mineralogiskt och geokemiskt, och typer avmissfärgningen har identifierats. Även en förklaring över de geologiska processersom ger upphov till missfärgningarna har formats. De metoder som använts underarbetet är egna undersökningar med komplement av en litteraturstudie påavhandlingar som handlar om just missfärgningar i marmor. Provmaterial harinhämtats från tre olika platser i gruvan, dessa har sågats och tvättats och några haräven slipats och polerats. Detta material har sedan använts genom hela arbetet.Optiska observationer med hjälp av binokulär har dokumenterats digitalt, detta gavinformation om att missfärgningen ligger mellan karbonatkristallerna, och sannolikthar varit av en mer löslig karaktär i ett tidigare skede. Utifrån detta kategoriserasmissfärgningen till två olika typer. Typ A förekommer som asymmetriska,koncentrerade fläckar på och mellan kristaller men till synes oregelbundet, medantyp B följer mikrofina sprickor och kan ses i bandade regelbundna formationer imaterialet. Järnrika kristaller upptäcktes i missfärgningarnas omedelbara närhet ochhär skapades hypotesen om att det är järnoxider som orsakat föroreningarna. ÄvenSEM-analyser har gjorts för att kunna identifiera den geokemiska sammansättningenav missfärgningarna. Resultaten från SEM- och XRF-analyserna bekräftade tesen, dåjärn förekom i varierande grad i samtliga analyser utom en. Dessutom hittadeshematit som i sig lämnar röda spår, samt ren rost i form av goetit. Ävenlitteraturstudien bekräftade att förekomster av järnrika mineral i marmor förr ellersenare kommer att orsaka missfärgningar.
The goal of this project has been to assist SMA mineral, a limestone producer, tofind the source of red discolourations found in their crystalline limestone. Thediscolouration has appeared on a more regular basis than before and is starting tobecome a problem for the company.This is a highly visual report focused on a microscopical level, that follows thestudy and finding of the origin of the red discolourations. Specimens from threedifferent locations in the quarry have been collected, then cut to proper sizes to fitthe needs for the scans and examinations suited for the project. Some of the sampleswere polished to fit the requirements of SEM. The material has been opticallyanalysed through a binocular microscope and documented with high resolutionimages. This was the first major breakthrough, since the discolouration showed tobe placed between the carbonate crystals, and appeared to have been more of asolution-like substance at some point. Based on the findings, the discolourationcould be categorised inte two types, type A appears as an irregular spotting oncrystal surfaces with a deeper red colour, whilst type B can be found in fine cracksin the material and follows a more regular pattern. Lots of minerals rich in ironwere also found in close proximity to the discolourations, which led to a hypothesisthat iron oxides might be the source of the problem. The thesis was confirmed bySEM- and XRF analyses of the material. Iron in different weight-percentages wasfound in all of the analyses except for one.The mineralogical and geochemical properties of the discolouration has beendefined, and the geological process that leads to the discolouration is explained.

Les signatures isotopiques des minéraux carbonatés sont utilisées pour caractériser de nombreux processus géochimiques. Cette thèse a pour but de déterminer les vitesses auxquelles ces signatures isotopiques peuvent être altérées lors des interactions entre les fluides et les minéraux. A cette fin, une série d'études expérimentales a été conduite avec la dolomite (CaMg(CO3)2), la magnésite (MgCO3) et la calcite (CaCO3). On a mesuré l'évolution temporelle des compositions isotopiques de Ca et Mg pendant une série d'expériences de dissolution en réacteur fermé de la dolomite à des températures de 50°C à 126°C. A T < 120°C la composition isotopique du calcium dans la phase fluide est identique à celle de la dolomite initiale, mais au-delà de cette température, la signature isotopique du calcium dans le fluide (delta(44/42)Ca fluid) après 4 semaines était 0.6±0.1‰ plus lourde que l'originale. En revanche, le rapport delta(26/24)Mg du fluide reste égal à celui de la dolomite à toutes les températures étudiées. Ces résultats indiquent un double transfert de calcium vers et depuis la structure de la dolomite à T > 120°C. En outre, ces résultats suggèrent que la difficulté de la dolomite à précipiter à température ambiante doit être la conséquence de l'incapacité de Mg à s'incorporer dans la structure du minéral. Dans une autre étude on a conduit des expériences de dissolution de la magnésite à 25°C en solution aqueuses pour différents pH et pression de CO2. On a trouvé que la composition isotopique du fluide à proximité de l'équilibre chimique était différente de celle du solide, ce qui reflète un double transfert de Mg en direction et hors du minéral à température ambiante. Cependant, un seul mécanisme de fractionnement ne peut expliquer le comportement isotopique de Mg observé. La dernière partie de ce travail, consacrée au fractionnement isotopique du carbone dans le système calcite-eau, montre une évolution du fractionnement isotopique de cet élément vers le fractionnement isotopique à l'équilibre d'une durée d'une année après l'atteinte de l'équilibre chimique entre la calcite et l'eau. Les vitesses de rééquilibrage des isotopes de carbone sont ainsi quatre ordres de grandeurs plus lentes que la vitesse d'équilibrage de la calcite avec la solution. Ceci suggère que l'étape limitante dans le processus de rééquilibrage des isotopes du carbone est le transport de cet élément dans le cristal après l'échange isotopique à la surface de ce dernier. Les résultats de cette thèse indiquent que la signature isotopique de Mg, Ca et C des carbonates n'est pas invariante à l'échelle des temps géologiques et qu'elle peut être altérée durant l'interaction de ces minéraux avec l'eau. Ainsi, la préservation des signatures isotopiques des carbonates requiert d'une faible perméabilité des roches ou bien quelque mécanisme inhibant les échanges des métaux et du carbone à la surface des cristaux
The isotopic signatures of carbonate minerals have been applied to illuminate a plethora of natural geochemical processes. This thesis is aimed to assess the rates and or conditions at which such isotope signatures might be altered by fluid-mineral interaction through a series of systematic experimental studies performed with dolomite (CaMg(CO3)2) magnesite (MgCO3) and calcite (Ca-CO3). Ca and Mg isotopic compositions were measured as a function of time during closed-system stoichiometric dolomite dissolution experiments at 50 to 126°C. Although identical to that of the original dolomite at low temperatures, at temperatures >120 °C, the calcium isotopic signature of fluid phase (delta(44/42)Ca fluid) became 0.6±0.1‰ higher than that of the dissolving dolomite over a 4-week period. In contrast, the delta(26/24)Mg fluid, remained equal to that of the dolo-mite both at low and high temperatures. This set of experiments evidences the two-way transfer of calcium in and out of the dolomite structure at elevated temperatures. The results suggest that the inhability of dolomite to precipitate at these conditions is due to the difficulty of Mg to be reincorporated in the dolomite structure. In a follow-up study, magnesite was dissolved at 25°C in the presence of fluids with distinct pH and CO2 pressures. The isotopic compositions of the fluid differed from that of the solid at near-to chemical equilibrium indicating the two-way transfer of magnesium into this mineral at ambient temperatures. A single fractionation mechanism cannot explain the distinct Mg isotope behaviors observed. Further work on carbon isotope exchanges in the calcite water system shows a slow by steady evolution of the carbon isotopic composition towards the accepted equilibrium fractionation factor over the course of nearly year-long experiments after the system had attained bulk chemical equilibrium. Carbon isotope reequilibration rates were found to be approximately four orders of magnitude slower than that of bulk calcite dissolution, suggesting that the rate limiting step to the carbon isotope reequilibration process is the transport of carbon into and out of the bulk mineral after it has exchanged on the surface. The results of this thesis suggest that the Mg, Ca and C isotopic signatures in carbonate minerals are not invariant over geological time-frames and can be readily altered by water-mineral interaction. Such results indicate that the preservation of carbonate mineral signatures require low permeability rock formations or some inhibitory mechanism limiting metal and carbon exchange

In der Arbeit werden Aufschluss- und Sortierergebnisse miteinander kombiniert, um die Anreicherung des Wertstoffs unter Berücksichtigung beider Teilprozesse auf einer vergleichbaren Basis bewerten zu können. Hierfür werden der Literatur vorhandene Modelle entnommen und erweitert, wodurch sich neuartige Parameter definieren lassen. Am Beispielsortierschritt Magnetscheidung wird anhand zweier unterschiedlicher Erze die Beurteilung der Teilprozesse auf Grundlage des vorgeschlagenen Vorgehens dargestellt. Mit Hilfe der Untersuchung der magnetischen Eigenschaften der Erze kann der Einfluss des gewählten Merkmals auf den Verlauf der berechneten Grenzkurven gezeigt werden. Weiterhin erfolgt eine Darstellung der Möglichkeiten durch die Nutzung moderner mineralogischer Analysemethoden zur Berechnung von Mineralsuszeptibilitäten, basierend auf Aufschluss- und Suszeptibilitätsmessungen von Merkmalklassen, sowie das direkte Berechnen von Trennfunktionen mit Hilfe von Aufschlussanalysen der Trennprodukte.

Comparaison des caracteristiques mineralogiques et des proprietes mecaniques de melanges equiponderaux de fillers calcaires, dolomitiques ou quartzeux avec 5 liants : ciment portland, ciment alumineux, ciment au laitier, cendres volantes chaux eteinte et fumees de silice condensees chaux residuaire. Evocation d'un nouveau liant routier, par melange de cendres volantes, fumees de silice condensees et chaux (l'additivite des proprietes se realisant pour des proportions particulieres)

Geochemical processes involving the interaction of fluids and minerals occur in nearly every environment on the surface and in the crust of the Earth. The variety of fluid–mineral processes on the Earth is quite diverse, and these various processes can occur under a large range of geochemical conditions. Aqueous dissolution and alteration, hydration, protonation, solution–precipitation, diffusion, and fluid and isotope exchange are among the many fluid–mineral interaction processes that contribute to the overall cycling of elements on Earth. This dissertation uses analog experiments to examine fluid­–mineral interaction processes found in different geological environments and under a range of environmental conditions. The first part of this dissertation examines the reactive and diffusive exchange of oxygen isotopes that results from performing a dolomite breakdown experiment under a temperature, pressure, and fluid condition analogous to a contact metamorphic environment. The second two parts of the dissertation involve the development of new methods for the growth of nanocrystalline fayalite and intermediate composition olivine. The final two parts of this dissertation focus on the interaction of olivine with either H2O or acidic solutions (0.005 M H2SO4 or 0.01 M HCl) at low temperature and pressure. The first of these two parts experimentally uses different surface area olivine powders that are reacted with low pH fluids in non-buffered, closed system experiments where pH and solution composition are allowed to change. The second of these two parts uses various analytical techniques that can examines changes to the surfaces of olivine single crystals at the nanoscale resulting from experiments performed under environmental conditions where the fluid–mineral interaction transitions from dissolution at low temperature and pressure to alteration at moderate temperature and pressure. Though the individual projects contained within this dissertation are varied, they share the common theme of using experiments to examine fluid­–mineral interaction processes.

Potassic siliceous dolomites in the Horsethief Creek aureole, S.E. British Columbia, Canada record peak contact-metamorphic conditions of ≈2.2 kbars and 650 °C in the inner aureole. The protolithic dolostones have varying but small amounts of disseminated quartz (≤ 5 volume percent) and K-feldspar (≤15 volume percent) but have interbedded numerous chert nodules and layers. Subvertical joints and veins cut across layering. Six isograds can be identified: phlogopite; tremolite+K-feldspar; diopside; diopside+phlogopite; diopside+dolomite; and at highest grade forsterite. The prevalence of isobarically divariant mineral assemblages, paucity of high XCO2 mineral assemblages, widespread development of hydrous minerals often in high abundance (up to 65 volume percent) and a ≈7 per mill (0/00) depletion (from ≈23 0/00 to ≈16 0/00) in δ18O are all evidence for substantial syn-metamorphic fluid flow. The almost complete de-dolomization of the inner and middle aureole suggests that metamorphism was not isochemical and that silicametasomatism took place. Heterogeneity in the distribution of index minerals and the potassic phases reflect varying bulk composition as well as variable fluid infiltration. Infiltration-driven near-isothermal reactions are documented in the rocks in form of numerous samples showing a texture interpreted to record prograde reaction of diopside to tremolite. A petrographic break is observed at the tremolite+K-feldspar isograd. While rocks up-grade of this isograd are dominated by isobarically divariant assemblages, rocks down-grade are characterized by isobarically univariant assemblages. This break may record a sudden change in infiltration character. The proposed model of contact metamorphism in the impure siliceous dolomites of the Horsethief Creek aureole is: 1) Intrusion of the Horsethief pluton triggered metamorphic reactions in the siliceous dolomites and the underlying pelitic rocks. 2) Buoyant fluids evolving in the metapelites at temperatures >530 °C rose along subvertical joints in and across the different lithologies and infiltrated the dolostone. 3) Infiltration of silica-bearing aqueous fluids triggered pervasive reaction in the siliceous dolomites. Rocks in the outer aureole did not experience significant infiltration because temperatures were too low to trigger the dehydration reaction in the underlying metapelites. Plutonic fluids may only have played a minor role, and bedding parallel flow likely was also only minor.

The Uitkomst Complex is located within the Great Escarpment area close to the town of Badplaas, approximately 300 km due east of Pretoria, in the Mpumalanga Province, South Africa. This complex is believed to represent a layered conduit system related to the 2.06 Ga Bushveld Complex. The succession from the bottom up comprises the Basal Gabbro- (BGAB), Lower Harzburgite- (LHZBG) and Chromitiferous Harzburgite (PCR) Units, collectively referred to as the Basal Units, followed by the Main Harzburgite- (MHZBG), Upper Pyroxenite-(PXT) and Gabbronorite (GN) Units, collectively referred to as the Main Units. The Basal Unit is largely hosted by the Malmani Dolomite Formation, in the Pretoria Group of the Transvaal Supergroup sediments. The Lower Harzburgite Unit contains numerous calc-silicate xenoliths derived from the Malmani Dolomite. The Basal Units host the economically important nickel-bearing sulphide and chromite deposits exploited by the Nkomati Mine. An area of extensive localized talc-chlorite alteration is found in the area delineated for large scale open cast mining. This phenomenon has bearing on the nature and distribution of the sulphide minerals in the Chromitiferous Harzburgite and to a lesser extent the Lower Harzburgite Units. The Basal Unit is comprised of both near pristine areas of mafic minerals and areas of extensive secondary replacement minerals. Of the olivine minerals, only fosterite of magmatic origin is found, the fosterite suffered hydrothermal alteration resulting in replacement of it by serpentine and secondary magnetite. Three different types of diopside are found, the first is a primary magamatic phase, the second is a hybrid “transitional” phase and the third, a skarn phase. Hydrothermal alteration of the matrix diopside led to the formation of actinolite-tremolite pseudomorphs. This secondary tremolite is intergrown with the nickeliferous sulphide grains. Chromite grains are rimmed or replaced by secondary magnetite. Pyrrhotite grains is also rimmed or replaced by secondary magnetite. Talc and chlorite is concentrated in the highly altered rocks, dominating the PCR unit. Primary plagioclase and calcite do not appear to have suffered alteration to the same extent as the other precursor mafic magmatic and hydrothermal minerals. It is suggested that the PCR was the first unit to be emplaced near the contact of the dolomite and shale host rock. The more primitive mafic mineral composition and presence of chromitite attest to this interpretation. The LHZBG and MHZBG units may have been emplaced simultaneously, the LHZBG below and the MHZBG above. Interaction and partial assimilation of the dolomitic country rock led to a disruption of the primary mafic mineralogy, resulting in the preferential formation of diopside at the expense of orthopyroxene and plagioclase. Addition of country rock sulphur resulted in sulphur saturation of the magma and resulted in the observed mineralization. The downward stoping of the LHZBG magma, in a more “passive” pulse-like manner led to the formation of the calc-silicate xenolith lower third of this unit. It is proposed that the interaction with, and assimilation of the dolomitic host rock by the intruding ultramafic magmas of the Basal Units are responsible, firstly, for the segregation of the nickeliferous sulphides from the magma, and secondly for the formation of a carbonate-rich deuteric fluid that affected the primary magmatic mineralogy of the Basal Unit rocks. The fluids released during the assimilation and recrystallization of the dolomites also led to the serpentinization of the xenoliths themselves and probably the surrounding hybrid and mafic- ultramafic host rocks. The CO2-rich fluids migrated up and outward, while the H2O-rich fluids remained confined to the area around the xenoliths and LHZBG unit. The H2O-rich fluid is thought to be responsible for the retrograde metamorphism of the precursor magmatic and metamorphic minerals in the Lower Harzburgite Unit. The formation of an exoscarn within the dolomitic country rocks and a selvage of endoskarn on the contact form an effective solidification front that prevented further contamination of the magma. It is also suggested that these solidification fronts constrained the lateral extent of the conduit. The CO2-enriched deutric fluid was able to migrate up to the PCR unit. Here the fluid was not removed as effectively as in the underlying parts of the developing conduit. This resulted in higher CO2-partial pressures in the PCR unit, and the stabilization of talccarbonate assemblages that extensively replaced the precursor magmatic mineralogy. Intrusion of the magma into the shales, which may have been more susceptible to assimilation and greater stoping, led to a broadening in the lateral extent of the Complex, in the Main units above the trough-like feature occupied by the Basal Units. Late-stage, hydrous dominated fluid migration is inferred to have been constrained to the central part of the conduit. This is demonstrated by the dominance of chlorite in the central part of the Uitkomst Complex in the study area. The Uitkomst Complex was further deformed by later intrusions of dolerite dykes. Weathering of the escarpment led to exposure of the conduit as a valley and oxidation of the surficial exposed rocks.
Thesis (PhD)--University of Pretoria, 2012.
Geology
unrestricted

In der Arbeit werden Aufschluss- und Sortierergebnisse miteinander kombiniert, um die Anreicherung des Wertstoffs unter Berücksichtigung beider Teilprozesse auf einer vergleichbaren Basis bewerten zu können. Hierfür werden der Literatur vorhandene Modelle entnommen und erweitert, wodurch sich neuartige Parameter definieren lassen. Am Beispielsortierschritt Magnetscheidung wird anhand zweier unterschiedlicher Erze die Beurteilung der Teilprozesse auf Grundlage des vorgeschlagenen Vorgehens dargestellt. Mit Hilfe der Untersuchung der magnetischen Eigenschaften der Erze kann der Einfluss des gewählten Merkmals auf den Verlauf der berechneten Grenzkurven gezeigt werden. Weiterhin erfolgt eine Darstellung der Möglichkeiten durch die Nutzung moderner mineralogischer Analysemethoden zur Berechnung von Mineralsuszeptibilitäten, basierend auf Aufschluss- und Suszeptibilitätsmessungen von Merkmalklassen, sowie das direkte Berechnen von Trennfunktionen mit Hilfe von Aufschlussanalysen der Trennprodukte.

The geological sequestration of carbon dioxide (CO2) is one of the options of controlling the greenhouse gas emissions. However, leakage of CO2 from the storage reservoir is a risk associated with geological sequestration. Over longer times, large-scale groundwater motion may cause leakage of dissolved CO2 (CO2aq). The objectives of this thesis are twofold. First, the modelling study analyzes the leakage of CO2aq along the conducting pathways. Second, a relatively safer mode of geological storage is investigated wherein CO2aq is injected in a carbonate reservoir. A reactive transport model is developed that accounts for the coupled hydrological transport and the geochemical reactions of CO2aq in the porous media. The study provides a quantitative assessment of the impact of advection, dispersion, diffusion, sorption, geochemical reactions, temperature, and heat transport on the fate of leaking CO2aq. The mass exchange between the conducting pathway and the rock matrix plays an important role in retention and reactions of leaking CO2aq. A significant retention of leaking CO2aq is caused by its mass stored in aqueous and adsorbed states and its consumption in reactions in the rock matrix along the leakage pathway. Advection causes a significant leakage of CO2aq directly from the reservoir through the matrix in comparison to the diffusion alone in the rock matrix and advection in a highly conducting, but thin fracture. Heat transport by leaking brine also plays an important role in geochemical interactions of leaking CO2aq.  Injection of CO2aq is simulated for a carbonate reservoir. Injected CO2-saturated brine being reactive causes fast dissolution of carbonate minerals in the reservoir and fast conversion of CO2aq through considered geochemical reactions. Various parameters like dispersion, sorption, temperature, and minerals reaction kinetics are found to play important role in the consumption of CO2aq in reactions.

Research Funders:

(i) Higher Education Commission (HEC) of Pakistan

(ii) Lars Erik Lundberg Scholarship Foundation, Sweden