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Menšíková, Barbora. "Vliv složení plynu na čištění plynu bariérovým filtrem." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443177.
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The diploma thesis deals with the issue of pollution of the generated gas after the gasification process and its subsequent cleaning using a barrier filter. The theoretical part of thesis consists of research on the gasification process, the effects on the gasification process, pollutants in the gas and gas cleaning with a focus on the purification of gas from tar. The experimental part of this thesis is devoted to the gasification itself in a fluidized bed gasification reactor in order to test the effect of the catalyst, which was calcined dolomite, the composition of the gas at variable parameters of water vapor and the temperature inside the laboratory filter.
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Coffey, Melody Roy. "Microbially Mediated Porosity Enhancement in Carbonate Reservoirs: Experiments with samples from the Salem, Sligo, and Smackover Formations." MSSTATE, 2004. http://sun.library.msstate.edu/ETD-db/theses/available/etd-10122004-105856/.
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This study used petrographic thin sections, scanning electron microscopy, and confocal laser microscopy to document microbially mediated dissolution of carbonate reservoir rocks. The samples studied came from three carbonate units that are hydrocarbon reservoirs; the Salem, Sligo, and Smackover formations. These samples were inoculated with bacteria, and then treated with nutrient solutions followed by ethanol to promote generation of acetic acid by bacteria. Dissolution occurred in calcite-dominated rocks and in dolomitized rocks. Noticeable changes first occurred after nine weeks of ethanol treatment and significant change only occurred after twelve weeks of ethanol treatment. The size of the vuggy pores created increased from 1 µm or less to over 5 µm, and rarely over 10 µm, in length.
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Soares, Roberto Arruda Lima. "Efeito da adi??o de carbonatos em formula??o de massa para revestimento cer?mico utilizando mat?rias-primas do Piau?" Universidade Federal do Rio Grande do Norte, 2010. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12756.
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Previous issue date: 2010-05-24Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
Piau? state is a major producer of traditional red ceramic burning as bricks, tiles and ceramic tiles, with its main production center located in the city of Teresina. The state has large reserves of raw materials that can be used in the ceramic coating as clays, quartz, talc and carbonates. However, in the preparation of ceramic bodies using only a mixture of clays with different characteristics. The study aims to evaluate the effect of adding two types of carbonates in the ceramic semiporous mass coating produced in Piau? and then to verify the potential use of these carbonates as supplementary raw material product manufactured or the feasibility of obtaining a ceramic plate that meets the specifications for the porous coating. For this, were characterized the ceramic Piau? coating mass, a calcitic carbonate and a dolomitic, were made in the levels of 2, 4, 8, 16, and 32%. The masses were formed by pressing and burneds in two environments: a laboratory furnace (1080?C, 1120?C, 1140?C, and 1160?C) and an industrial furnace (1140?C). Then, following tests of linear shrinkage water absorption, apparent porosity, bulk density and flexural strength. Furthermore, the fired specimens were tested for their macrostructure and microstructure. The results showed the possibility of using the carbonate in ceramic mass flooring produced in Piau?, as added in small proportions improved dimensional stability and increased mechanical strength of ceramics pieces. It also proved itself possible to produce porous coating when added in higher levels
O Estado do Piau? ? um grande produtor de cer?micas tradicionais de queima vermelha como tijolos, telhas e revestimentos cer?micos, com seu principal p?lo produtivo localizado no munic?pio de Teresina. O Estado possui grandes reservas de mat?rias-primas que podem ser utilizadas no setor cer?mico de revestimento como argilas, quartzo, talco e carbonatos. Por?m, na elabora??o das massas cer?micas se utiliza uma mistura de argilas com caracter?sticas diferentes. O presente trabalho tem como objetivo avaliar o efeito da adi??o de dois tipos de carbonatos em uma massa cer?mica de revestimento semiporoso produzido no Piau?, e assim verificar a potencialidade da utiliza??o destes carbonatos como mat?ria-prima complementar do produto fabricado ou a viabilidade de se obter uma placa cer?mica que atenda as especifica??es para o revestimento poroso. Para isso, foram caracterizadas a massa cer?mica de revestimento piauiense, um carbonato calc?tico e outro dolom?tico, ambos oriundos de jazidas localizadas pr?ximas a Teresina - PI. As adi??es na massa cer?mica de cada carbonato foram feitas nos teores de 2, 4, 8, 16 e 32%. As massas foram conformadas por prensagem e queimadas em dois ambientes: forno de laborat?rio (1080?C, 1120?C, 1140?C e 1160?C) e forno industrial (1140?C). Em seguida, realizados ensaios tecnol?gicos de perda ao fogo, retra??o linear, absor??o de ?gua, porosidade aparente, massa espec?fica aparente e resist?ncia mec?nica ? flex?o. Al?m disso, as amostras queimadas foram avaliadas em sua macroestrutura e microestrutura. Os resultados mostraram a possibilidade de se utilizar os carbonatos na massa cer?mica do revestimento produzido no Piau?, pois adicionado em pequenas propor??es melhorou a estabilidade dimensional e aumentou a resist?ncia mec?nica das pe?as cer?micas. Tamb?m se mostrou vi?vel para produ??o de revestimento poroso quando adicionado em teores mais elevados
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Kushnir, Alexandra Roma Larisa. "An experimental investigation of the mechanical behaviour of synthetic calcite-dolomite composites." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/43299.
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The role of dolomite on the strength and evolution of calcite-dolomite fold and thrust belts is largely unknown. Field investigations indicate that, under upper- to mid-crustal conditions, strain in natural systems is localized in calcite, resulting in a ductile response, while dolomite deforms in a brittle manner. The effect of dolomite on limestone rheology, and the potential for strain localization in composites have not yet been fully quantified.
I conducted 11 constant displacement rate (3x10⁻⁴ and 10⁻⁴ s⁻¹), high confining pressure (300 MPa), and high temperature (750°C and 800°C) torsion experiments to address the role of dolomite on the strength of calcite-dolomite composites. Starting materials were formed by hot isostatic pressing mixtures of dolomite and calcite powders (given as Dm%: Dm25, Dm35, Dm51, and Dm75) and were deformed up to a maximum shear strain of ~5.
Mechanical data show a considerable increase in yield strength with increasing dolomite content. Microstructural analysis shows that dolomite grains <~50 μm are characterized by diffuse and poorly defined grain boundaries; in Dm25 and Dm35, high aspect ratio dolomite grains are aligned into a foliation. Dolomite grains >~50 μm are characterized by well-defined grain boundaries and cleavage-controlled fracture. Electron backscatter diffraction (EBSD) shows no crystallographic preferred orientation (CPO) development in dolomite, but optical microscopy confirms brittle deformation of dolomite grains by Mode I cracks, shear fractures, and subsequent grain size reduction.
Calcite grains are internally strain-free, equiaxed to tabular in shape, and characterized by triple-junction grain boundaries. EBSD confirms a distinct CPO of calcite c-axes perpendicular to the direction of maximum stretching. The microstructure of calcite aggregates suggests grain boundary sliding, accommodated by diffusion and dislocation glide, which accommodates high shear strains without significant change in grains shape and size.
Dolomite is essentially undeformed in run products with less than 35% dolomite; calcite accommodates most of the displacement in these experiments. In contrast, for dolomite contents greater than 51%, dolomite accommodates displacement by brittle processes.
My experiments provide insights into the processes controlling rheology within bimodal calcite-dolomite systems, suggesting that a minimum dolomite-content exists (between 35% and 51%) above which dolomite significantly influences composite strength.
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Goudalier, Maryline. "Dolomitisation des calcaires du Frasnien moyen en Belgique : contrôle sédimentaire, diagénétique et tectonique." Lille 1, 1998. https://pepite-depot.univ-lille.fr/LIBRE/Th_Num/1998/50376-1998-423.pdf.
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Les fabriques dolomitiques secondaires ont ete etudiees dans les unites parautochtone et allochtone des series paleozoiques de la belgique meridionale. Les phases tectoniques paleozoique et mesozoique ont affecte les calcaires primaires et les dolomies secondaires. Des plissements et des chevauchements majeurs de direction est-ouest ont deforme les series. La faille du midi est un exemple de decollement qui separe l'allochtone du parautochtone. Les resultats ont ete obtenus sur deux groupes d'echantillons (affleurements et sondages). Les corps massifs de dolomies secondaires, observables en carrieres ont ete exploites pendant des decennies. Environ 260 echantillons ont ete analyses macroscopiquement (sections polies, repliques d'acetate et coloration). L'etude petrographique caracterise les dolomies secondaires et les ciments calcitiques. La geochimie des phases minerales (cathodoluminescence, microsonde) et l'etude microthermometrique d'echantillons representatifs determinent une chronologie au sein de la paragenese observee. La dolomitisation des dolomies du frasnien moyen en belgique a ete, en premier lieu, controlee par le contexte sedimentaire (diagenese precoce). Les fabriques dolomitiques mimetiques et destructive presentent une teinte rouge de faible intensite (en cathodoluminescence). L'homogeneite des caracteristiques selon les differentes fabriques (fdm1, fdm2 et fdd) suggere une volution pendant l'enfouissement (diagenese tardive). Les cimentations calcitiques (non ferrifere et ferrifere) posterieures a la dolomitisation ont pris place pendant une tectonique fin-varisque et post-varisque.
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Wang, Tingting. "Breakdown of the Ostwald step rule - The precipitation of calcite and dolomite from seawater at 25 and 40 °C." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114570.
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The scarcity of recent dolomite contrasts strongly with its common abundance in ancient sedimentary rocks, leading to the paradox commonly referred to as the "dolomite problem". Despite many attempts, dolomite has never been precipitated at room temperature from natural seawater in the absence of bacterial mediation. It has been proposed that natural environments conducive to dolomite formation may be dynamic systems, in which the water chemistry (pH, alkalinity, saturation state with respect to specific minerals) fluctuates in response to variations in environmental conditions such as biological activity, temperature, salinity. Nevertheless, there is little literature dedicated to simulating such environmental changes. In this study, we simulated the dynamic nature of natural environments by alternating between intervals of dissolution and precipitation in natural seawater through purging gases of different CO2 partial pressures (pCO2). By alternating between periods of aragonite supersaturation and undersaturation, aragonite was obtained during the first few cycles at 25 and 40oC, but only calcite was detected in the 18th cycle of the experiments at 25oC. In contrast, neither calcite nor dolomite were detected in the precipitates after 20 and 25 cycles at 40oC. Parts of the objectives in this study—breaking the Ostwald Step Rule and synthesizing calcite from natural seawater at 25oC—were achieved, but the 40oC experiment did not yield the result we hoped for. One possible explanation is that stable calcite nuclei may not have accumulated to a high enough concentration after 25 cycles at 40oC that sufficient calcite surfaces were available to offset the nucleation of aragonite. Another explanation is that stable pre-nucleation clusters, whose conformation may also be dependent on solution composition and temperature, control the crystallization of a set calcium carbonate polymorph.La rareté de la dolomite récente contraste avec son abondance dans des roches sédimentaires anciennes, conduisant au paradoxe communément appelé "le problème de la dolomite". Malgré de nombreuses tentatives, en l'absence de médiation bactérienne, la dolomie n'a jamais été précipitée à la température ambiante à partir de l'eau de mer naturelle. Il a été proposé que les environnements naturels propices à la formation de dolomite peuvent être des systèmes dynamiques, pour lesquels la chimie de l'eau (pH, alcalinité, l'état de saturation à l'égard de minéraux spécifiques) fluctue en réponse aux variations des conditions environnementales (par ex.: l'activité biologique, la température, la salinité). Cependant, il y a très peu de la littérature consacrée à la simulation de ces changements environnementaux. Dans cette étude, nous avons simulé, en alternant entre des intervalles de dissolution et de précipitation dans l'eau de mer naturelle par une purge de gaz de différentes pressions partielles en CO2 (pCO2), la nature dynamique des milieux naturels. En alternant entre des périodes de sur-saturation et sous-saturation par rapport à l'aragonite, seule de la calcite a été détectée après le 18ième cycle à 25 °C. En revanche, nous n'avons observé ni calcite et ni dolomite dans les précipités aragonitiques après 20 et 25 cycles à 40 °C. Une partie des objectifs de cette étude - contrer règle d'Ostwald sur les transformations successives (états intermédaires) et la synthèse de calcite dans l'eau de mer naturelle à 25 °C - ont été atteints, mais l'expérience à 40oC n'a pas donné le résultat espéré. Une explication possible est que des noyaux stables de calcite ne se sont pas accumulés à une concentration assez élevée après 25 cycles à 40 °C, que suffisamment de surface calcitique était disponible pour contrer la nucléation de l'aragonite. Une autre explication est que la stabilité des grappes de pré-nucléation, dont la conformation dépend possiblement de la chimie de la solution et de la température, se forment et contrôlent la cristallisation d'un polymorphe spécifique de carbonate de calcium.
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ESTRADA, MALDONADO C. FABIOLA. "Contribution a l'etude du systeme ca-mg-co#2-h#2o : dissolution de la calcite et de la dolomite dans l'eau de mer et dans des solutions de nacl de 0 a 300c." Toulouse 3, 1991. http://www.theses.fr/1991TOU30223.
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Le but de ce travail est de contribuer a la connaissance des lois qui regissent la stabilite des carbonates dans la nature, en particulier dans les solutions hydrothermales et dans les eaux interstitielles des sediments marins. Apres analyse des donnees de la litterature, l'auteur est amenee, entre autres, a mesurer jusqu'a cent degres les constantes apparentes de dissociation de l'acide carbonique et le produit de solubilite de la calcite dans l'eau de mer. De meme, les premieres determinations experimentales du produit de solubilite de la dolomite a haute temperature sont realisees dans des solutions de chlorure de sodium. Pour tous les parametres etudies, des interpolations en fonction de la temperature sont proposees en tenant compte des mesures effectuees et des donnees de la litterature. A l'issue de cette etude il est etabli que le produit de solubilite de la calcite dans l'eau de mer diminue lorsque la temperature augmente, effet difficile a deceler uniquement a partir des donnees en dessous de vingt-cinq degres. Des essais de dissolution de longue duree montrent que l'eau de mer est sursaturee par rapport a l'anhydrite des quatre-vint-dix degres et suggerent que la calcite joue un role dans la cristallisation de phyllosilicates magnesiens. Par ailleurs, des essais a deux cents degres conduisant a la dolomitisation de la calcite en milieu marin permettent de calculer le produit de solubilite de l'anhydrite et mettent en evidence les presences simultanees de calcite magnesienne, dolomite calcique et magnesite calcique. Pour tous les parametres etudies, a l'exception de la constante de dissolution du gaz carbonique, les courbes en fonction de la temperature dans l'eau de mer s'ecartent sensiblement des courbes dans les solutions de chlorure de sodium dans la gamme de concentration consideree
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Lundin, Linnéa. "Interpretation of the P-T-XCO2 environment during metamorphism of carbonates, central Utö, Stockholm archipelago." Thesis, Stockholms universitet, Institutionen för geologiska vetenskaper, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-93279.
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This thesis attempts to interpret the metamorphic condition and fluid composition experienced by metacarbonates on Utö, located in the south-eastern parts of the Stockholm archipelago. Utö is a part of the Svecofennian domain, and the area Bergslagen, that has hosted several mines over the last millennia. The bedrock in this area has been dated by the U-Pb technique to 1.90-1.87 Ga, placing it in the Paleoproterozoic era (Allen et al. 1996, Lundström et al. 1998). The rocks, of the studied area on the island of Utö, are mainly metacarbonates with a varying purity and thin layers of volcanic ash. These rocks become more felsic towards the north-western coast as the layers of felsic ash become more dominant. To determine the P-T-XCO2 of metamorphism, metacarbonates were examined, in the field, in thin sections and mineral chemistry was determined by SEM analysis. Three samples were collected along a 1km transect, along which the assemblage calcite + dolomite + quartz + tremolite + diopside was observed. Petrographic and SEM analysis were performed to gather chemical data from coexisting calcite and dolomite in order to calculate temperature using the calcite-dolomite geothermometer. Chemical data from the SEM analysis were also run with AX and THERMOCALC together with pressure data received from a study by Engström (2011) of the adjacent island, Persholmen, to generate a T- XCO2 diagram. Pressure was estimated to 3.1 +/- 1.3 kbars, temperature calculated to 442°C 30°C and XCO2 to range from 0,00067-0,0038 with the standard deviation taken in to account. These results record equilibration with a CO2-bearing hydrous fluid at greenschist facies conditions.Metamorphic map of Sweden
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Fox, Michael E. "An Assessment of Shock Metamorphism for Jeptha Knob, A Suspected Impact Crater in North-Central Kentucky." Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1415624495.
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Bourrouilh-Le, Jan Françoise G. "Diagenese des carbonates de plates-formes, recifs et mangroves, en atlantique et pacifique. Controle de la diagenese par les variationsthermo-glacio-eustatiques d'emersion-submersion. Aragonite, calcite, dolomite, phosphate." Paris 6, 1990. http://www.theses.fr/1990PA066061.
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Les controles globaux de la diagenese des carbonates de plates-formes, recifs et mangroves en atlantique et pacifique, allant de l'holocene a 23 ma, sont au nombre de 6: 1. La sedimentation de haute energie, 2. Les paleotemperatures oceaniques, 3. Les variations du niveau des oceans, 4. Les phases d'emersion-submersion, 5. Les sols phosphato-bauxitiques, 6. Les relations avec l'expansion oceanique. En consequence, les variations thermo-glacio-eustatiques controlent les variations de la nappe phreatique ou lentille de ghyben-herzberg des plates-formes, iles et atolls, et donc la diagenese. La diagenese aragonitique comporte lithification et dissolution. La diagenese calcitique augmente avec le temps, l'ion sr#+#+ en etant le marqueur. La diagenese bauxitique et surtout phosphatee nait par evolution pedogenetique de produits volcano-sedimentaires pieges dans les karsts. Elle contribue a la diagenese dolomitique (li, mn, mg. . . ). La diagenese dolomite dans 2 exemples: mangrove d'andros, bahama, et facies corallien a rhodolithes du pacifique, montre le role d'ions tels que li, na, k, mn, et le transport de l'ion mg#+# par les molecules d'eau. La dolomitisation est une suite de relais ioniques ou n'interviennent que les equilibres d'hydratation et de deshydratation de l'ion mg#+#+. Li, mn, na, k, sont des catalyseurs et les mineraux pre- ou paradolomitiques pourraient se former. Ces differentes diageneses sont contemporaines et concurrentes, pour donner un etat de carbonate plus stable: calcite, puis dolomite
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Perez, Fernandez Andrea. "Etude expérimentale sur l'échange isotopique dans le système eau-roches carbonatées." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30398.
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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 cristauxThe 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
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Silva, Neto Gilson da. "Estudo de Mat?rias-Primas do Rio Grande do Norte para Uso em Revestimento Poroso: Influ?ncia do teor de dolomita e temperatura de calcina??o nas propriedades f?sico-mec?nicas." Universidade Federal do Rio Grande do Norte, 2007. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12875.
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Previous issue date: 2007-07-04The state of Rio Grande do Norte presents a great potentiality for the production of ceramic tiles because of having natural raw material in quantity and quality making its economical exploration possible, beyond the great energetic differential of the state, the natural g?s. This works aims to study the influence of the dolomite and granulometry concentration and calcinations temperature in the obtaining of formulations for porous coverings which have to be coherent to the project,s specifications. The experiments have involved the physical-chemical and mineralogical characterizations of raw materials and mechanical tests in the dry and burnt proof bodies preceding a mixture experiment planning with the use of the response surface methodology, in order to get the best raw materials combinations to produce a ceramic mass with specific properties. The twelve ceramic masses studied in this work were prepared by the via dry process, characterized, shaped by uniaxial pressing and sinterized in the temperatures of 940?C, 1000?C, 1060?C, 1120?C and 1180?C, using a fast burning cycle. The crystalline phases formed during the sintering in the temperatures in study have revealed the presence of anorthite and diopside beyond quartz with a remaining phase. These phases were the main responsible ones by the physical- mechanical properties of the sinterized proof bodies. The proof bodies after the sintering stage have presented water absorption higher than 10% and a good dimensional stability in all studied temperatures. However, the flexural breaking strength results in the temperatures of 940?C, 1000?C and 1060?C, under the temperature zone of the vitrification of ceramic whiteware do not reach the flexural breaking strength specific for the porous wall tile (15 MPa), but in the temperature of 1120?C next to the vitrification temperature zone, some whiteware ceramic (formulations) has reached the specified value for the porous wall tile. The results of this work have showed that the studied raw materials have great importance for used in the production of porous wall tiles (BIII)
Rio Grande do Norte apresenta uma grande potencialidade para produ??o de revestimento cer?mico, haja vista, possuir mat?rias-primas naturais em quantidade e qualidade possibilitando sua explora??o econ?mica, al?m do grande diferencial energ?tico do Estado, que ? o g?s natural. Este trabalho objetiva estudar a influ?ncia da concentra??o de dolomita, sua granulometria e temperatura de sinteriza??o na obten??o de formula??es para revestimento poroso que atendam as especif?ca??es do projeto. Os experimentos envolveram a caracteriza??o f?sico qu?mico e mineral?gica das mat?rias-primas, e ensaios mec?nicos nos corpos de prova secos e queimados, precedendo-se de um planejamento de experimento de mistura, com o uso da metodologia de superf?cie de resposta, a fim de se obter as melhores combina?oes das mat?rias-primas para produzir massa cer?mica com propriedades especif?cas. As doze massas cer?micas estudadas foram preparadas pelo processo via seca, caracterizadas, conformadas por presagem uniaxial e sinterizadas nas temperaturas de 940?C, 1000?C, 1060?C, 1120?C, e 1180?C, utilizando um ciclo de queima r?pido. As fases cristalina formadas durante a sinteriza??o nas temperaturas em estudo, revelaram a presen?a de anortita e diopsita, al?m de quartzo com fase remanescente. Estas fases foram as principais respons?veis pelas propriedades f?sico-mec?nicas dos corpos de provas sinterizados. As fases cristalina formadas durante a sinteriza??o nas temperaturas em estudo, revelaram a presen?a de anortita e diopsita, al?m de quartzo com fase remanescente. Estas fases foram as principais respons?veis pelas propriedades f?sico-mec?nicas dos corpos de provas sinterizados. Os corpos de prova ap?s sinteriza??o apresentaram absor??o de ?gua superior a 10%, e uma boa estabilidade dimensional em todas as temperaturas estudadas, entretanto, os resultados da tens?o de ruptura ? flex?o nas temperaturas ( 940?C, 1000?C,e1060?C) abaixo da faixa de temperatura de gresifica?ao das massas cer?micas, n?o atigiram o valor de TRF especificado para revestimento poroso(15 MPa), por?m, na temperatura de 1120?C pr?xima da faixa da temperatura de gresifica??o, algumas massas cer?micas (formula??es) j? atingiram o valor especificado para revestimento poroso. Os resultados desse trabalho mostraram que, as mat?rias primas estudadas possuem grande potencial para serem utilizadas na fabrica??o de revestimento poroso (BIII)
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Tourneret, Christophe. "Maclage et état de contraintes dans les roches carbonatées du domaine fragile : application à des plates-formes d'avant-pays de chaînes (Pyrénées, Alpes)." Montpellier 2, 1990. http://www.theses.fr/1990MON20240.
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Cette these comporte trois parties: une partie theorique concernant la possibilite de determiner les tenseurs de contraintes a partir des macles des carbonates rhomboedriques dans le cas de tectonites polyphasees. Pour des echantillons biphases, des resultats importants ont ete obtenus a partir de donnees synthetiques: on montre notamment que la permutation de deux contraintes principales est analysable par les methodes inverses. La deuxieme partie concerne les applications geologiques des methodes mises au point. Dans le quercy et en bourgogne, on obtient des resultats tout a fait coherents avec ceux obtenus par la microtectonique classique et a l'aide des methodes failles. Ces deux regions sont neanmoins differentes et complementaires: en quercy, on attribue l'ensemble des structures compressives a une seule phase tectonique, d'age pyreneen, alors qu'en bourgogne, l'analyse des donnees montre que la tectonique compressive est clairement polyphasee. Dans les deux cas, des perturbations de contraintes le long d'accidents preexistants sont mises en evidence. La notion de phase tectonique est discutee en fonction de ces nouveaux resultats. La troisieme partie concerne un travail effectue a pau, au sein de la societe nationale elf aquitaine: on a determine la direction de la contrainte horizontale majeure n11020, a l'aide des ovalisations de trous de forage dans les environs immediats de pau. Cette direction est replacee dans le cadre general de la tectonique actuelle en france
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BEAREZ, CHRISTINE. "Transformation catalytique de composés représentatifs de la matière organique sédimentaire sur minéraux naturels et synthétiques." Poitiers, 1985. http://www.theses.fr/1985POIT2022.
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Influence catalytique des mineraux naturels sur l'evolution de composes naturels importants: le cholesterol et l'acide stearique. Les transformations de ces composes ont ete etudiees sur diverses roches: argiles, calcite, dolomite et anhydrite et sur des catalyseurs connus dans des conditions aussi representatives que possible du milieu naturel. Quel que soit le solide considere la transformation catalytique est beaucoup plus rapide que la reaction thermique
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Xaza, Abongile. "Investigating hydrogeochemical processes of groundwater, Heuningnes Catchment, South Africa." University of the Western Cape, 2020. http://hdl.handle.net/11394/7961.
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Masters of ScienceThis study was conducted to investigate hydrogeochemical processes controlling the evolution of groundwater chemistry and their influence on water quality in the Heuningnes Catchment. The role or influence of hydrogeochemical processes in groundwater quality in aquifer systems remains poorly understood. One of the ways of improving such understanding is to employ different techniques to explore key processes that govern groundwater quality in aquifer systems. Therefore, the present study investigated hydrogeochemical processes of groundwater resources and identified key processes that explained its quality from a spatiotemporal perspective. The quantitative approach that provides the ability to assess relationships between variables both spatially and temporally was applied. Groundwater sampling was done on four occasions during July 2017, October 2017, March 2018, and July 2018. Identification of hydrogeochemical processes controlling the evolution of groundwater chemistry and quality was done using various complementary tools. These tools included classification of the main water types, evaluation of water-rock interaction by means of stoichiometry analysis and bivariate correlation plots, inverse geochemical modelling, and statistical analysis (hierarchical cluster analysis and factor analysis). Physical parameters were measured in situ, while water samples were collected from boreholes, piezometers, springs, and artesian boreholes for laboratory analysis for major ions analysis. Descriptive and bivariate statistical methods were used to summarise and evaluate the strength of the relationship between variables, while multivariate statistical methods were applied to group similar samples based on their chemical compositions. Tri linear Piper diagrams were generated to characterize water type based on double normalizing the proportions of cations and anions, while correlation and stoichiometric analysis were applied to identify hydrogeochemical processes influencing groundwater chemistry. The results generated from the trilinear Piper diagrams confirmed the dominance of sodium and chloride ions in waters of the Heuningnes Catchment. Groundwater of a Na/Cl type is typical for a coastal aquifer characterised by saline, deep ancient groundwater. The lower parts of the Catchment were characterised by saline groundwater. The results indicated that shallow groundwater samples within the study area were more mineralised as compared to deep groundwater with EC values ranging between 20.8 and 2990 mS/m, with waters within the Table Mountain Group region (TMG), recording the lowest values. Deep groundwater for boreholes and artesian boreholes located upstream in the Catchment was fresh and yielded some of the lowest EC values recorded with an EC value below 50 mS/m. Generally, EC values increased from the upper TMG region of the Catchment towards the Bokkeveld shale region downstream and were highest during the dry season of 2018. The results indicated strong geological influences on water chemistry. Bivariate correlation and stoichiometric analysis identified cation exchange, adsorption, evaporation, weathering of carbonates, sulphates and silicate minerals as processes influencing the chemistry of groundwater in the Heuningnes Catchment. The Saturation Index (SI) results showed a change of calcite, dolomite, aragonite, gypsum, anhydrite, halite, melantinterite, siderite and sylvite from being undersaturated to oversaturated at some areas for the different seasons along the flow path. The mass-balance modelling results indicated that ion exchange and reverse ion exchange processes were more dominant at low elevations along the same flow path during the dry periods. However, at high elevations along the flow path, silicate weathering was the dominant process taking place. The findings of this study demonstrated the influence of hydrogeochemical processes in changing the water chemistry along the flow paths. In conclusion, the study showed the value of utilising various assessment tools as complementary techniques to improve the understanding about hydrogeochemical processes, and its influence on evolution of groundwater chemistry and quality. Based on the findings of the study the following recommendations were made for future studies; the sample points or sample boreholes in the study Catchment should be increased; and to have more sampling trips to enable better comparison between the possible processes
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Hesser, Sarina. "Analys av röda missfärgningar i Gåsgruvans marmor." Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-81919.
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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.
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Nugroho, Fadjari Lucia. "Contribution à l'étude de l'élimination des pollutions phosphorées dans les eaux résiduaires." Toulouse, INSA, 1990. http://www.theses.fr/1990ISAT0003.
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Le point de depart de cette etude est une analyse des mecanismes biologiques qui sont a la base des techniques de dephosphoration biologique. Cette 1ere phase debouche sur l'idee qu'il devrait etre interessant pour ameliorer la stabilite de ces procedes de passer par la formation d'un phosphate insoluble parmi lesquels nous avons selectionne la struvite nh#4mgpo#4. Ce schema semble realisable en utilisant une biomasse fixee sur un support capable de relarguer des ions mg#+#+ dans l'effluent a traiter. La 2eme partie de notre travail a consiste a rechercher un support convenable. Nous avons finalement selectionne la dolomie semi-calcinee. Au cours des essais de caracterisation de ce support il est apparu qu'il avait par lui-meme un pouvoir dephosphorant a l'etude duquel nous avons consacre la 3eme partie de notre etude. La dolomie semi-calcinee, dans les conditions de concentrations en ions po#4#3# d'un effluent urbain, conduit a la formation tres superficielle d'un precipite de phosphate de calcium non stchiometrique que les techniques esca ont permis d'identifier. Les conditions de mise en uvre ont ete etudiees des points de vue hydraulique et granulometrique. Il semble qu'une mise en uvre en poudre fine, en finition d'un traitement biologique classique soit la plus avantageuse. Les performances obtenues sont comparables a une bonne dephosphoration chimique par la chaux avec une depense en reactifs en tres forte diminution par rapport a cette technique et un ph apres traitement autorisant un rejet direct sans correction. Le pouvoir d'echange reste faible. La regeneration acide est possible mais conduit a une consommation importante du produit par solubilisation ce qui lui retire tout interet pratique. Nous avons releve la courbe d'equilibre a 25#oc entre l'adsorbant et l'effluent a traiter et montre qu'il pouvait se modeliser selon un isotherme de freundlich. Pour terminer, les directi
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Djayaprabha, Herry Suryadi, and 葉鏹元. "Influence of Calcined Dolomite on Engineering Properties and Durability of Ground Granulated Blast Furnace Slag Based Cementitious Materials." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/996d6z.
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博士國立臺灣科技大學
營建工程系
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This study explored the advantages of calcined dolomite powder being used for producing clinkerless ground granulated blast furnace slag (GGBFS/slag) based cementitious material. The natural dolomite powder burned at a complete decarbonation temperature (about 900°C) is referred to calcined dolomite. Some earth oxide minerals (e.g. CaO and MgO) which were decomposed from dolomite (CaMg(CO3)2) through calcination process can use as an economical alternative activator, when compared with the strong alkaline activator solution. The hydration mechanism of the calcined dolomite-activated slag (slag-dolomite) is the dissolution of calcined dolomite which involved reaction of CaO with H2O to form Ca(OH)2. The hydration of CaO rises the heat and accelerates the dissolution of the active SiO2 in the slag and produces calcium silicate hydrate (C-S-H) gel. In this study, the optimum dosage of calcined dolomite for activating slag was explored with the respect to the compressive strength development of slag-dolomite binder at different amounts from 0 to 40 wt% (weight percentage). The optimum mixture was found at the amount of 80 wt% GGBFS and 20 wt% calcined dolomite. The optimum 28-day compressive strength of calcined dolomite-activated slag (slag-dolomite) binder and mortar reached approximately 30.7 MPa. While those of slag-dolomite concrete with calcined dolomite amount of 20 wt% reached 35.8 MPa which satisfied the design strength requirement for structural concrete as specified by ACI 318 code. The X-ray diffraction (XRD) tests indicated the hydration product of slag-dolomite binder were the C-S-H, Ca(OH)2, SiO2, CaCO3, and Ca0.936Mg0.064CO3, together with the appearance of SiO2 in the specimen with the calcined dolomite amount of 20 wt% and more. The dynamic elastic moduli of slag-dolomite binder, mortar, and concrete were examined by means of non-destructive impulse excitation technique (IET). It was found that the 28-day dynamic Young’s and shear moduli of the hardened slag-dolomite mixture with calcined dolomite dosage of 20 wt% were 13.51 and 5.35 GPa for the binder, 29.01 and 12.15 GPa for the mortar, 33.95 and 13.67 GPa for the concrete, respectively. The stress-strain curves of slag-dolomite concrete fit well with the prediction of stress-strain relationship model for ordinary Portland cement concrete. The thermal properties of slag-dolomite binder were investigated by thermal conductivity test. The addition of calcined dolomite has an apparent effect on increasing the thermal conductivity of hardened binder specimen at 28 days by about 7.03, 12.79, 22.41, and 28.77% with the added amount of calcined dolomite of 10, 20, 30, and 40 wt%, as comparing with those of pure slag binder. The heat transference of fire through slag-dolomite binder specimens was investigated by measuring the reverse-side temperature, which was visualized by the temperature contour of thermal images. The test exhibited that after a 25 mm thick of slag-dolomite binder specimens exposed to 1000 ± 100°C flame for 30 min, the measured reverse-side temperature reached approximately in the range of 93 to 101°C. The resistance of slag-dolomite mortar specimens under elevated temperatures was investigated by evaluating the residual compressive strength. The obtained results showed that heating slag-dolomite mortar specimens to 300ºC resulted in a noticeable increase in the compressive strength of all slag-dolomite mortar mixtures comparing with the original strength. The loss of compressive strength was observed after being exposed to an elevated temperature of 600ºC, due to the calcium hydroxide crystal decomposed back to calcium oxide and water, which was proved by XRD investigation. However, the slag-dolomite mortar still can maintain the original compressive strength by 64.2, 61.4, 59.0, and 61.3% for the amount of calcined dolomite from 10, 20, 30, and 40 wt%.
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Cleven, Nathan R. "Role of Dolomite Content on the Mechanical Strength and Failure-Mechanisms in Dolomite-Limestone Composites." 2008. http://hdl.handle.net/2429/1112.
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Variably dolomitized limestone samples from the Rundle Group in Western Alberta, Canada were
deformed under a variety of confining pressures and at room temperature in a triaxial rock press.
The aim of this research is to establish the mechanical behaviour and brittle constitutive laws of
limestone and dolomite composites. This data can then be used to develop strength profiles of
thrust faults in the Rocky Mountain Fold and Thrust Belt. For example, many of the thrust faults
in the Canadian Foreland are composed of limestone–dolomite composites, yet the mechanical
properties of these composites remain unknown. Sample protoliths were selected for their similar
grain sizes and grain size distributions, low porosity and low silica content in order to best examine
relationships between these parameters and the distribution of strain between the dolomite and
calcite.
This study shows that increasing dolomite content correlates to an increase in strength at low
and medium confining pressures. At high confining pressures, distributed brittle deformation adds
complexities that are attributed to textural controls. Microstructural analysis of deformed samples
shows that at approximately thirty to forty-five weight percent dolomite is interconnected via a
dolomite grain network that provides a load-bearing capacity to the dolomite. This load-bearing
capacity correlates to dramatic jumps in the strength of dolomite–limestone composites observed
with increasing confining pressures.
Inherent weaknesses in calcite grains such as twin planes and cleavage intersections are exploited
by fractures resulting in reduced peak strengths of calcite-rich composites. Calcite generally
absorbs strain and distributes it into finer spaced fracture networks than in dolomite. In
dolomitized rock that still contains calcite cleavage within dolomite is not exploited, rather transgranular
cracks break dolomite down into irregular and angular particles. At near pure dolomite
content and at high confining pressure dolomite will fracture and disaggregate along cleavage.
Comminuted dolomite grains commonly show a larger distribution of sizes and have more irregular shapes than contiguous comminuted calcite grains. Comminuted calcite particles are commonly
much smaller than comminuted dolomite grains and show more regular shapes and an even grain
size distribution.
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Krátký, Ondřej. "Distribuce stopových prvků v karbonatitech pomocí in-situ metod, se zvláštním zřetelem k REE." Master's thesis, 2017. http://www.nusl.cz/ntk/nusl-356497.
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Carbonatites are unique and enigmatic magmatic rocks of unclear origin, with very specific mineralogy and geochemical properties. They are predominantly composed of magmatic calcite or other carbonate minerals (Le Bas 1987) and have low content of SiO2 (Le Maitre 2002). Origin of these peculiar magmas is still not clear but they appear to represent an important "window" into processes in Earth's mantle. They are considered either as residual melts from a fractionated carbonated nephelinite or melilitite (Gittins 1989; Gittins and Jago 1998), as immiscible fractions of CO2-saturated silicate melts (Freestone and Hamilton 1980; Amundsen 1987; Kjarsgaard and Hamilton 1988, 1989; Brooker and Hamilton 1990; Kjarsgaard and Peterson 1991; Church and Jones 1995; Lee and Wyllie 1997; Dawson 1998; Halama et al. 2005; Brooker and Kjarsgaard 2011), or as primary melts which are were generated from CO2-bearing peridotite through partial melting (Wallace and Green 1988; Sweeney 1994; Harmer and Gittins 1998; Harmer et al. 1998; Ying et al. 2004). Abundances of rare earth elements (REE) are often high in carbonatites because carbonatitic magmas can dissolve these elements much easily than silicate magmas (Nelson et al. 1988). Carbonatitic magma can also dissolve large quantities of Sr, Ba, P and mainly Zr and Nb,...
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Sayed, Mohammed Ali Ibrahim. "Stimulation of Carbonate Reservoirs Using a New Emulsified Acid System." Thesis, 2013. http://hdl.handle.net/1969.1/150980.
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The scope of work can be divided into; the measurement of the rheological properties of a new emulsified acid system that can be suitable for high temperature applications, a study of the performance of the new emulsified acid in stimulating both calcite and dolomite formations, measuring the reaction rate and diffusion coefficient when the new emulsified acid systems react with both calcite and dolomite, and testing the new emulsified acid using core samples obtained from carbonate reservoirs.
The droplet size has a practical impact on the performance of emulsified acid. A good understanding and characterization of the emulsified acid by its size distribution will lead to better understanding of its stability, rheology and how it reacts with carbonate rocks. The influence of the concentration of the new emulsifier on the droplet size, droplet size distribution and upon the rheology of emulsified acids is studied in detail.
The emulsified acid reaction kinetics with calcite rocks was studied before in few studies, and very little work was done with dolomite. One of the main objectives of the present work is to study in detail the reaction of the emulsified acid with both calcite and dolomite rocks using the rotating disk apparatus.
Most of the previous studies on the emulsified acid were done using core samples that were saturated with brine or deionized water. One of the main objectives of the present work is to study in detail the effect of the presence of crude oil in the reservoir rock on the performance of emulsified acids.
Lastly, an innovative technique of emulsifying the chelating agents is evaluated for high temperature applications. The rheology of the emulsified chelating agent is measured using an HPHT rheometer. Also, the reaction of the new emulsified chelating agent with calcite is studied using the rotating disk apparatus, and coreflood experiments were performed using chelating agents and calcite core samples.
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Rabie, Ahmed 1978. "Reaction of Calcite and Dolomite with In-Situ Gelled Acids, Organic Acids, and Environmentally Friendly Chelating Agent (GLDA)." Thesis, 2012. http://hdl.handle.net/1969.1/148152.
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Well stimulation is the treatment remedy when oil/gas productivity decreases to unacceptable economical limits. Well stimulation can be carried out through either "Matrix Acidizing" or fracturing with both "Hydraulic Fracturing" and "Acid Fracturing" techniques. "Matrix Acidizing" and "Acid Fracturing" applications involve injecting an acid to react with the formation and dissolve some of the minerals present and recover or increase the permeability. The permeability enhancement is achieved by creating conductive channels "wormholes" in case of "Matrix Acidizing" or creating uneven etching pattern in case of "Acid Fracturing" treatments.
In both cases, and to design a treatment successfully, it is necessary to determine the distance that the live acid will be able to penetrate inside the formation, which in turn, determines the volume of the acid needed to carry out the treatment. This distance can be obtained through lab experiments, if formation cores are available, or estimated by modeling the treatment. The successful model will depend on several chemical and physical processes that take place including: the acid transport to the surface of the rock, the speed of the reaction of the acid with the rock, which is often referred to as "Reaction Rate", and the acid leak-off. The parameters describing these processes such as acid diffusion coefficient and reaction kinetics have to be determined experimentally to ensure accurate and reliable modeling.
Hydrochloric acid and simple organic acids such as acetic and citric acids have been used extensively for stimulation treatments. The diffusion and reaction kinetics of these acids, in a straight form, were investigated thoroughly in literature. However, solely these acids are used in a simple form in the field. Acid systems such as gelled, crosslinked gelled, surfactant-based, foam-based, or emulsified acids are used to either retard the reaction rate or to enhance acid diversion. Literature review shows that additional work is needed to understand the reaction and report the diffusion and kinetics of these systems with carbonate. In addition, a new chelating agent (GLDA) was recently introduced as a stand-alone stimulating fluid. The kinetics and the mass transfer properties of this acid were not studied before.
Therefore, the objective of this work is to study the reaction of different acid systems with calcite and dolomite and report the mass transport and kinetic data experimentally. Lactic acid, a chelating agent (GLDA), and in-situ gelled HCl-formic acids were investigated in this study. In some cases, rheology measurements and core flood experiments were conducted. The data were combined with the reaction study to understand the behavior of these acids and examine their efficiency if injected in the formation.
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Aguiar, João Diogo da Silva. "Analysis, testing and development of safe cleaning methods of rusted stone material." Master's thesis, 2014. http://hdl.handle.net/10362/14153.
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Three different treatments were applied on several specimens of dolomitic and calcitic marble, properly stained with rust to mimic real situations (the stone specimens were exposed to the natural environment for about six months in contact with rusted iron). Thirty six marble specimens, eighteen calcitic and eighteen dolomitic, were characterized before and after
treatment and monitored throughout the cleaning tests. The specimens were characterized by
SEM-EDS (Scanning Electron Microscopy coupled with Energy Dispersion System), XRD (XRay Diffraction), XRF (X-Ray Fluorescence), FTIR (Fourier Transform Infrared Spectroscopy) and color measurements. It was also made a microscopic and macroscopic analysis of the stone
surface along with the tests of short and long term capillary absorption.
A series of test trials were conducted in order to understand which concentrations and contact times best suits to this purpose, to confirm what had been written to date in the literature. We sought to develop new methods of treatment application, skipping the usual methods of applying chemical treatments on stone substrates, with the use of cellulose poultice, resorting to the agar, a gel already used in many other areas, being something new in this area, which possesses great applicability in the field of conservation of stone materials.
After the application of the best methodology for cleaning, specimens were characterized again in order to understand which treatment was more effective and less harmful, both for the operator and the stone material. Very briefly conclusions were that for a very intense and deep penetration into the stone, a solution of 3.5% of SDT buffered with ammonium carbonate to pH
around 7 applied with agar support would be indicated. For rust stains in its initial state, the use of Ammonium citrate at a concentration of 5% buffered with ammonium to pH 7 could be applied more than once until satisfactory results appear.
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Arsalan, Naveed. "Surface energy characterization of reservoir rocks." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-05-3616.
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The fundamental forces of adhesion are responsible for the spreading of fluids such as crude oil/brine on the reservoir rock surface. These physico-chemical interactions determine the surface energetics of a reservoir and thus their wetting phenomena. Inverse Gas Chromatography is introduced to characterize the surface energy of carbonates (calcite and dolomite) and sandstones (Ottawa sand and Berea sandstone). The behavior of the polar and non-polar interaction forces was investigated at varying water coverage and at different temperatures. The results indicated that in general as the water coverage increased, the Lifshitz-van der Waals component of surface energy decreased to nearly that of the bulk water, while the acid-base component also showed a decreasing trend. The Lifshitz-van der Waals component of surface energy always decreased with increase in temperature, while the acid-base properties mostly increased with temperature with the exception of calcite.text
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Παπαδοπούλου, Ευτυχία. "Μελέτη ιδιοτήτων ασβεστόλιθων για ρόφηση διοξειδίου του άνθρακα σε ρευστοστερεά κλίνη." Thesis, 2008. http://nemertes.lis.upatras.gr/jspui/handle/10889/986.
Full textAbstract:
Στην διάρκεια της παρούσας εργασίας μελετήθηκε η ικανότητα ρόφησης CΟ2 καθώς και η απομείωση (attrition) δώδεκα υλικών (8 ασβεστίτες και 4 δολομίτες) τόσο πριν όσο και αφού είχαν υποστεί θερμική διάσπαση-ενανθράκωση. Σύμφωνα με τα αποτελέσματα τα μη θερμικά κατεργασμένα υλικά επέδειξαν μικρότερα ποσοστά απομείωσης συγκριτικά με τα θερμικά κατεργασμένα. Το ποσοστό απομείωσης των υλικών χωρίς θερμική κατεργασία δεν αποτελεί μέτρο πρόβλεψης του ποσοστού απομείωσης του υλικού μετά από θερμική κατεργασία.
Στην συνέχεια μελετήθηκε η επίδραση των συνθηκών θερμικής διάσπασης (θερμοκρασία και διάρκεια) του υλικού Α1 με αρχικό μέγεθος κόκκων 0.71mm
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Ntibane, Thabile Malecia. "A comparison between two calcite-rich deposits in palaeoproterozoic dolomitic units of the Transvaal supergroup: beestekraal; North West province and lime acres; Northern Cape." Thesis, 2018. https://hdl.handle.net/10539/26733.
Full textAbstract:
A thesis/dissertation submitted in partial fulfilment of the requirements for the degree Master of Science in Economic Geology, University of the Witwatersrand Faculty of Science School of Geosciences, 2018The Malmani and Campbellrand Subgroups have small zones of calcite that did not undergo dolomitisation when it took place within the Transvaal Supergroup. To get the calcite rich zonations of limestone the Malmani and Campbellrand Subgroups may have avoided dolomitisation and dedolomitisation during the geological events of the Transvaal Supergroup. This project integrated geological mapping, petrology, microprobe analysis, mineral identification, bulk geochemistry and point geochemistry in an attempt to understand and compare the calcite rich limestone zonations that occur in the Malmani and Campbellrand Subgroups. The calcite rich limestone either preexisted the deformation of the Transvaal Supergroup or resulted from dedolomitisation of the deformed Transvaal Supergroup. The Campbellrand Subgroup of the Griqualand West Basin is composed of shallow shelf carbonates that were deposited under shallow subtidal conditions, whereas the Malmani Subgroup has the Oaktree Formation which is generally dolomitic, except in the Crocodile River fragment. The sedimentary structures on the Lime Acres Member are interbedded by fine grained limestone, chert and dolomitic matrix. The Lime Acres Member has two NS fault which have high grade limestone between them and on the far western side of the faults, dolomite ore deposit lies on the eastern side. The limestone structures and textures which are found on the western side of the fault 2 (F2) and eastern side of the fault 1 (F1) in Lime Acres were well preserved. The dip is at about 3⁰ -7⁰ to the west. The Oaktree Formation in the Malmani Subgroup hosts the carbonate deposit at Beestekraal which comprises dolomitic limestone with chert-rich and chert-poor zones within the limestone. The deposit dips to the west at an angle of about 33⁰ and strikes NS. There are four faults that cut across the deposit and these are striking WE. The faults form normal faults that are fairly steep. Folding is noted in the hanging wall where the WE faults that cut across the deposit. The Campbellrand Subgroup deposit is interbedded with limestone and dolomites. The dolomite is coarse grained and can be classified as replacement rock that formed by diagenetic replacement of the older limestones, while the limestone is fine-crystalline and can be classified as primary limestone i.e. not dedolomitised. The dolomite crystals show twinning and cross-cuttings of cleavage planes under a microscope and has proven to have Mg/Ca value of 0.8 -0.9 with a shallow dip. The characteristics that affect each site are different as Lime Acres has preserved sedimentary structures such as stylolite and stromatolites, whereas such structures are lacking at Beestekraal, where there is a dominance of calcite rich veinlets. The calcite veinlets have upgraded the dolomites at Beestekraal, while the chert downgrades the deposit. Faults, calcite veinlets and quartz inclusions were post depositional of the limestone and dolomite deposit. No evidence was found that the faults could have eroded, downgrade or upgraded the limestone zones. The faults fissures are filled with reddish-clay at Lime Acres and deformed chert at Beestekraal. Re-entrance angles, twinning, fenestrae and cross-cutting cleavage planes were noted in both electron microprobe analysis and petrology analysis. These features are consistent with dolomite structures. There is evidence of three geological events that have occurred on both site where; • Deposition of the magnesium-calcite occurred; iv • Some silica and calcite veinlets were introduced by fluids, the fluid introduction put pressure on the deposit which resulted in compaction. Re-entrance angles formed during compaction and left the prominent calcite veinlets. The calcite veins only appear in Beestekraal; • Faulting occurred post the formation earlier compaction evensts. The faulting caused compression of the existing structures and resulted in wavy stylolites at Lime Acres, deformation along the faults and mud fissures being introduced to the joints. There was uniformity between the X-Ray Fluorescence, X-Ray Diffraction, and electron microprobe analysis results. Both sites have similar mineral composition which are rich in calcium with little deformation. The study has found that the mining areas have somehow not been altered during the dolomitasation phase that affected the Transvaal Supergroup rocks. The pockets of high calcium deposits can be classified as primary limestone, which was somehow preserved during the dolomitisation phase. Post depositional alterations had two different effects on the sites. At Lime Acres the chert, which filled the contacts between the different bedding, was compressed due to high pressure from the overlying material and faulting. The traces of chert have been noted as stylolite and small traceable carbon partings/bands within the limestone and dolomites. At Beestekraal there is infill of iron rich and chert material, which occurs within the cleavage planes and contacts. Both sites have significantly increased calcium content with low magnesium content in production zones, having little impurities from the chert and dolomites that overlie the limestone. The Mg/Ca ratios showed that for all zones used for cement and lime production the Mg/Ca ratios are below 0.6 and 0.1 respectively. Mg/Ca ratios closer to 1 and above are not economically viable for lime and cement production. The low Mg/Ca ratios indicate that the dolomites are more of magnesium calcite content and of primary depositional environment than secondary.
XL2019
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Κανελλοπούλου, Δήμητρα. "Φυσικοχημική διερεύνηση της αποσάρθρωσης δομικών υλικών ιστορικών μνημείων και μέθοδοι προστασίας." Thesis, 2012. http://hdl.handle.net/10889/5439.
Full textAbstract:
Σημαντικός αριθμός μνημείων και έργων τέχνης είναι κατασκευασμένα από πέτρα, μάρμαρο κατά πρώτο λόγο, και έπειτα από ασβεστόλιθο και από άλλα πυριτικά υλικά. Η παρούσα εργασία επικεντρώθηκε στη μελέτη της διάλυσης του μαρμάρου σε διάφορες συνθήκες με απώτερο στόχο την αποκάλυψη του μηχανισμού της φυσικοχημικής αυτής διεργασίας τόσο για την περίπτωση ασβεστιτικών όσο και δολομιτικών μαρμάρων. Η κατανόηση του μηχανισμού του προβλήματος είναι απαραίτητη για την κατάλληλη προσέγγιση και επιλογή των μεθόδων προστασίας. Έτσι, στην παρούσα εργασία επιχειρήθηκε:
α) Ο προσδιορισμός του μηχανισμού διάλυσης από πειράματα μέτρησης της κινητικής της διάλυσης του μαρμάρου σε ακόρεστα ως προς το βασικό συστατικό (ασβεστίτης, δολομίτης) διαλύματα και σε διαφορετικές συνθήκες ακορεστότητας.
β) Η αναστολή της διάλυσης με την προσθήκη υδατοδιαλυτών τασιενεργών ουσιών και η διερεύνηση του μηχανισμού δράσης τους.
γ) Η δημιουργία δυνητικά προστατευτικών επικαλύψεων των επιφανειών του (ασβεστιτικού) μαρμάρου με στρώματα ανόργανων αλάτων.
δ) Η σύγκριση των αποτελεσμάτων μέτρησης του ρυθμού διάλυσης τόσο παρουσία όσο και απουσία προσθέτων ουσιών με βιβλιογραφικές αναφορές, και αποτελέσματα από πειράματα υπαίθριας έκθεσης και από πειράματα έκθεσης δοκιμίων σε συνθήκες επιταχυνόμενης διάβρωσης σε θάλαμο αλατονέφωσης (παρουσία και άλλων παραγόντων, όπως μικροοργανισμοί, μικροβιοκτόνες ενώσεις). Ο στόχος της σύγκρισης αυτής ήταν η επιλογή του καταλληλότερου μοντέλου για την αξιόπιστη δοκιμή νέων υλικών και μεθόδων προστασίας του μαρμάρου.
Για τη διεξαγωγή των δοκιμών, επιλέχθηκαν τρεις τύποι μαρμάρου που απαντώνται σε μνημεία και γλυπτά στην Ευρώπη: Carrara (ασβεστίτης >98%), Πεντελικό (ασβεστίτης >98%) και Ekeberg (δολομίης ~93%).
Τα διαλύματα που χρησιμοποιήθηκαν στις μετρήσεις, κινητικής της διάλυσης ήταν ακόρεστα ως προς ασβεστίτη και παρασκευάζονταν με την αραίωση κατάλληλων όγκων stock διαλυμάτων CaCl2, MgCl2, NaHCO3, NaCl, και η αρχική τιμή του pH ρυθμιζόταν στο 8.25 με προσθήκη 0.01N NaOH. Μετά την αποκατάστασης ισορροπίας στα ακόρεστα διαλύματα εργασίας, γινόταν προσθήκη ακριβώς ζυγισμένης σκόνης μαρμάρου ή η εμβάπτιση των δοκιμίων (στερεωμένων σε ειδικό στήριγμα). Τρεις μέθοδοι χρησιμοποιήθηκαν για τις μετρήσεις της κινητικής της διάλυσης του μαρμάρου: συνθήκες ελεύθερης μεταβολής (free drift), συνθήκες σταθερού pH (pH-stat), συνθήκες σταθερού κορεσμού. Για τα ασβεστιτικά μάρμαρα, οι μετρήσεις του ρυθμού διάλυσης τόσο του μαρμάρου (κονιοποιημένου ή δοκιμίων) όσο και της πρότυπης ένωσης αναφοράς (ασβεστίτης) συναρτήσει της ακορεστότητας των διαλυμάτων έδειξαν γραμμική εξάρτηση. Σε όλες τις περιπτώσεις, οι ρυθμοί που υπολογίσθηκαν ήσαν της αυτής τάξης μεγέθους με τους αντίστοιχους ρυθμούς του καθαρού ασβεστίτη. Η θερμική κατεργασία του Πεντελικού μαρμάρου οδήγησε σε σημαντική αύξηση του ρυθμού διάλυσης, και η εξάρτηση των μετρούμενων ρυθμών, R, από τον σχετικό υπερκορεσμό, σ, ήταν μη γραμμική, με n>1. Για το δολομιτικό μάρμαρο Ekeberg, από το διάγραμμα του ρυθμού διάλυσης συναρτήσει της σχετικής ακορεστότητας σ, η προσαρμογή των δεδομένων στην R=kdσn έδωσε την τιμή n=2, οπότε εξήχθη το συμπέρασμα, ότι το στάδιο που καθορίζει τη διάλυση του δολομιτικου μαρμάρου είναι η επιφανειακή διάχυση.
Μετρήθηκε και η διαλυτότητα τόσο του δολομιτικού όσο και των λοιπών τύπων μαρμάρου. Τα ασβεστιτικά μάρμαρα Πεντελικό και κρυσταλλίνα Θάσου έδωσαν τιμές για το γινόμενο διαλυτότητας κοντά στην αντίστοιχη τιμή για τον καθαρό ασβεστίτη (8.48) ενώ τα υπόλοιπα ασβεστιτικά (Carrara, Σπηλιά, Διονύσου) έδωσαν υψηλότερες τιμές διαλυτότητας. Τα δύο δολομιτικά μάρμαρα έδωσαν την αυτή τιμή για τη σταθερά διαλυτότητας, η οποία ευρίσκεται εντός των ορίων τιμών που έχουν αναφερθεί στην βιβλιογραφία για στοιχειομετρικό δολομίτη.
Σε όλες τις περιπτώσεις ο ρυθμός διάλυσης του μαρμάρου βρέθηκε ότι ελέγχεται από την επιφανειακή διάχυση των δομικών λίθων στο οριακό στρώμα του υγρού. Η ρόφηση κάποιας ουσίας πάνω στο στερεό θα μπορεί να δεσμεύει τα ενεργά κέντρα και θα έχει αποτελεσματική δράση στην επιβράδυνση της διάλυσης. Έγινε μελέτη ρόφησης ουσιών με ιοντιζόμενες φωσφορικές και φωσφονικές ομάδες σε σκόνες των μαρμάρων Πεντελικού, Carrrara και Ekeberg (ισόθερμοι ρόφησης). Το HEDP μελετήθηκε σε μεγαλύτερη έκταση, τόσο γιατί η παρουσία του στα ακόρεστα διαλύματα είχε ως αποτέλεσμα τη σημαντικότατη αναστολή της διάλυσης, όσο και διότι ως ουσία με ιονιζόμενες δραστικές ομάδες αποτελεί μοντέλο για την μελέτη της επίδρασης ανάλογων ουσιών σε κρυσταλλικά στερεά τα οποία διαθέτουν κατιόντα μετάλλων στην επιφάνειά τους. Η προσθήκη του αναστολέα HEDP στα ακόρεστα διαλύματα είχε ως αποτέλεσμα τη μείωση του ρυθμού διάλυσης σε ανάλογο βαθμό με την προ-ρόφησή του. Η προσθήκη του HΕDP στα ακόρεστα διαλύματα, έδωσε μικρότερους ρυθμούς διάλυσης σε σύγκριση με τους αντίστοιχους ρυθμούς οι οποίοι ελήφθησαν από δείγματα στα οποία η ουσία αυτή είχε προ-ροφηθεί στο στερεό (πειράματα σε σκόνες και δοκίμια ασβεστιτικών μαρμάρων). Το HEDP εκτός από την επιβράδυνση της διάλυσης (ακόμα και κατά 80-90 %), βρέθηκε ότι είχε αρνητική επίδραση στη μορφολογία των κρυστάλλων του μαρμάρου.
Ο στόχος της επόμενης σειράς πειραμάτων ήταν η δημιουργία επικαλύψεων σε συμπαγή δοκίμια μαρμάρου. Οι επικαλύψεις αυτές, αποτελούντο από ανόργανα άλατα, μικρότερης διαλυτότητας σε υδατικά διαλύματα, σε σύγκριση με τον ασβεστίτη. Τα διαλύματα αντιδραστηρίων κατεργασίας (HCl, ΕDTA, γαλακτικού οξέος, oξικού οξέος, H3PO4, HEDP, NTMP , N(phosphomethyl-) imino diacetic acid) εφαρμόσθηκαν με: α) επίχριση με πινέλο, β) επίθεση εμποτισμένων υφασμάτων, γ) εμβάπτιση των δοκιμίων στα αντίστοιχα διαλύματα. Αποτελεσματικότερος τρόπος εφαρμογής ήταν η εμβάπτιση. Ο χαρακτηρισμός των επιφανειών, και των αντίστοιχων επιστρώσεων και η ταυτοποίησή τους έγινε με XRD, FΤ-IR και SEM. Στην συνέχεια, τα σύνθετα υλικά (μάρμαρο+επικάλυψη), υποβλήθηκαν σε πειράματα διάλυσης σε διαλύματα ακόρεστα ως προς ασβεστίτη προκειμένου να δοκιμασθεί η αποτελεσματικότητά τους στην προστασία της επιφάνειας του μαρμάρου από τη διάβρωση. Η επεξεργασία με φωσφορικό οξύ, είχε ως αποτέλεσμα την δημιουργία παχέος στρώματος διένυδρου, όξινου φωσφορικού ασβέστιου (CaHPO42H2O, DCPD). Με δεύτερη εμβάπτιση σε διάλυμα όξινου φωσφορικού νατρίου η υδρόλυση των αρχικά σχηματισθέντων κρυστάλλων DCPD, οδήγησε στον σχηματισμό ψευδομορφικών κρυστάλλων OCP οι οποίοι και σχηματίζουν στρώμα περίπου 100 μm, το οποίο καλύπτει πλήρως την επιφάνεια του μαρμάρου και παρουσιάζει εξαιρετική πρόσφυση στην επιφάνεια. Οι δοκιμές διάλυσης σε ακόρεστα διαλύματα, έδειξαν ότι διαλύεται μόνο η επικάλυψη.
Υπαίθρια Έκθεση. Επαληθεύθηκε η ανασταλτική δράση του HΕDP στην διάλυση των δοκιμίων του μαρμάρου τα οποία εκτέθηκαν στους σταθμούς υπαίθριας έκθεσης. Γενικά, οι τασιενεργές ουσίες που δοκιμάσθηκαν προστάτευσαν τα δοκίμια του μαρμάρου σε μεγαλύτερο βαθμό από τις υδρόφοβες ουσίες γεγονός το οποίο υπογραμμίζει την σημασία της αλληλεπίδρασης ουσίας-υποστρώματος και το οποίο είναι σε συμφωνία με τα ευρήματα από τα πειράματα που διεξήχθησαν στους αντιδραστήρες batch..
Θάλαμος αλατονέφωσης. Σε συνθήκες επιταχυνόμενης διάβρωσης, επαληθεύθηκε για μια ακόμα φορά η ανασταλτική δράση ουσιών όπως το HΕDP, οι οποίες μπορούν να αλληλεπιδράσουν με το μάρμαρο. Είναι αξιοσημείωτο ότι τα αποτελέσματα των μετρήσεων της κινητικής της διάλυσης τα οποία ελήφθησαν από την υπαίθρια έκθεση δοκιμίων ήσαν συγκρίσιμα με τα αποτελέσματα των μετρήσεων σε αντιδραστήρες τύπου batch. .
Η μέθοδος μέτρησης της κινητικής της διάλυσης σε ακόρεστα διαλύματα και σε συνθήκες σταθερού κορεσμού, έχει τη δυνατότητα σε μικρό σχετικά χρονικό διάστημα να δώσει ικανοποιητικές πληροφορίες σχετικά με τη συμπεριφορά των δοκιμίων μαρμάρου σε διαβρωτικό περιβάλλον αλλά και να χρησιμεύσει σε δοκιμές ελέγχου και προκαταρκτικής αξιολόγησης (screening) σειράς υποψήφιων για την προστασία του μαρμάρου ουσιών.A significant number of historic monuments and artworks have been made of stone, mainly of marble, lime and silicate materials. The work in the present thesis, is focused on the investigation of the kinetics of marble dissolution under various conditions. These studies contribute to the understanding of the mechanism of dissolution, for of calcitic and dolomitic marbles. Understanding the mechanism of the problem is essential for the selection and the implementation of methods for the protection of monuments. More specifically, in the present work it was attempted to achieve the following tasks: a) Determination of dissolution mechanism, through measurements of the kinetics of marble dissolution in solutions undersaturated with respect to the main component (calcite, dolomite) under various undersaturation conditions at controlled conditions. b) Dissolution inhibition by addition of water soluble compounds and investigation of the mechanism of their interaction with the calcitic surfaces. c) Formation of potentially protective coatings on marble surface consisting of sparingly soluble inorganic salts. d) Comparison of marble dissolution rates (in the presence and in the absence of different water soluble substances) with the respective values reported in the literature and with results from marble specimens exposed outdoors or under accelerated weathering conditions in a salt spray chamber (with or without other agents, including colonization with microorganisms, treatment with biocides). The aim of this comparison was the selection of the best model for the reliable testing of novel methods and materials for the protection of marble. Three marble types were selected in the present investigation. These types have been frequently used as building materials in monuments and sculptures in Europe: Carrara (>98% calcite), Pentelic (>98% calcite) and Ekeberg (>93% dolomite). A number of compounds were selected for the investigation of their effectiveness of protection against marble weathering due to wet precipitation: VPA3-7 (surfactant) and HEDP (organophosphorus compounds), Hydrophase superfici (hydrophobic substannce) and Algophase (biocide). To study the effect of microorganisms on the weathering of marble specimens exposed outdoors, they were inocculated with a bacteria culture consisting of (Geodermatophilus sp BC 508 isolated from limestone rock (Noto, Syracuse, Italy) , Micromonospora sp. BC 562 isolated from Pentelic marble), fungi (Coniosporium apolliniis MC518 isolated from marble from Tarragona Cathedral (Spain) and Coniosporium uncinatum MC557 isolated from Carrara marble statue (Messina, Italy).) The aim of the measurements of the rates of marble dissolution in solutions undersaturated with respect to calcite, as a function of the relative undersaturation was the attainment of a better understanding for the mechanism underlying marble dissolution. Undersaturated working solutions were prepeared by dilution of proper stock solutions of CaCl2, MgCl2, NaHCO3, NaCl, and pH was initially adjusted to 8.25 with 0.01N NaOH. After equilibration of undersaturated solutions in the reactor, known amount of marble was introduced, either in powder form (suspension) or in rod form (fixed on special scaffold). Depending on the control of the parameters possible the following types of experiments were done and the dissolution rates were measured: free drift (all variables change with the exception of temperature), constant pH (pH only is kept constant), constant undersaturation (the activities of all species in the undersaturated solutions are kept constant). The dissolution rates of calcitic marble (both in powders and slabs) and calcite powder showed linear dependence on the relative undersatutation. In all cases, the rates of dissolution were of the same order of magnitude with the rates corresponding to (synthetic) calcite powder. Thermal pretreatment of pentelic marble powder resulted to higher dissolution rates. In this case, the dependence of the rates measured with respect to the relative undersatutation was found to be non-linear, (R=Kdσn , n>1). In the case of Ekeberg marble, the dependence of the rates of dissolution on the relative undersatutation was found to be non-linear, as well with n = 2. It may therefore be concluded that the dissolution is surface diffusion controlled. In the present work, solubilities for different types of marbles investigated in aqueous solutions were calculated from measurements of specimens equilibrated with electrolyte solutions over a time period exceeding the 2 years. For Pentelic and Crystallina Thassou marbles, values of solubility products were close to the value of pure calcite, while those for the rest of the calcitc marbles (Carrara, Spilia, Dionysoy) were higher. For the dolomitc marbles Ekeberg and Thassos White, the values obtained were almost identical and close to the values reported for stoichiometric dolomite. In all cases, the rate of dissolution was found to be controlled by surface diffusion. The adsorption of a substance on marble surface could possibly affect the dissolution process. The adsorption of substances posessing ionisable phosphate and phosphonate groups on marble powders (Pentelic, carrara, Ekeberg) was investigated through the respective adsorption isotherms. HEDP was mainly studied in this section, because its presence in undersaturated solutions inhibited dissolution to a large extent, and also because it could be considered as a model substance for the investigation of the effect of substances with similar functional groups on crystalline solids with metal cations on their surface. The presence of HEDP in the undersaturated solutions resulted in the reduction of the marble dissolution rates, proportionally to the extent of HEDP adsorption on the substrate. The dissolution rates obtained were lower than those obtained in experiments were HEDP was pre-adsorbed on the substrate (both in marble powder and in marble rod tests). HEDP showed strong inhibition effect (even by 80-90%) but also showed negative effect on the morphology marble crystallites. The aim of the next series of experiments was the formation of coatings on pentelic marble slabs. The coatings tested in the present investigation, consisted of inorganic salts , less soluble than calcite. Treatment solutions (HCl, ΕDTA, lactic acid, H3PO4, HEDP, NTMP , N(phosphomethyl-) imino diacetic acid) were applied by:a) brush, b) impregnated patch and c) immersion. The most effective way was impregnation. XRD, FT-IR and SEM were used for the characterization of the surfaces and of the composition of the coatings. The “new” composite (marble + coating) materials were then subjected to dissolution experiments in solutions undersaturated with respect to calcite. Treatment of marble with phosphoric acid resulted in formation of a thick layer of CaHPO42H2O, DCPD. Following a second treatment with sodium hydrogen phosphate solution, the iniatially formed DCPD crystals were hydrolyzed to pseudomorfic OCP crystals, resulting to a layer of 100 um thickness with complete coverage of the surface and good adhesion on the substrate. Dissolution experiments showed that only the coating was dissolved. T Outdoors exposure. The inhibiting effect of HEDP on dissolution was verified in the case of the exposed marble specimens. The surfactant substances tested seemed to protect the specimens more than the hydrophobic compounds, which empasizes the importance of substance-substrate interaction and is in good agreement with batch experiment results. Salt spray chamber. The inhibiting effect of HEDP on dissolution was again verified in the case of the marble specimen exposedunder accelerated weathering conditions. Results of the measurements of the kinetics of marble dissolution obtained from outdoors exposure tests of marble slabs, were comparable to those obtained from batch reactor experiments. Measurement of dissolution kinetics in working solutions under constant undersaturation conditions is a method capable of providing satisfactory information on the behaviour of marble specimen under weathering conditions and a useful tool on testing and evaluating the efficiency of candidate protective methods and products in a short time (suitable as preliminary screening tool).
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Ahmad, Nawaz. "REACTIVE TRANSPORT MODELLING OF DISSOLVED CO2 IN POROUS MEDIA : Injection into and leakage from geological reservoirs." Doctoral thesis, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-184204.
Full textAbstract:
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