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Ce travail de thèse a porté sur l'étude des perturbations hydrogéochimiques potentiellement induites par le CO2 dans un aquifère salin profond. Dans un premier temps, cet aspect a été étudié à partir de sources hydrothermales naturellement riches en CO2. Une étude de la composition chimique des eaux en fonction de l'augmentation de leur teneur en CO2 a montré une baisse de pH et un enrichissement systématique en cations majeurs et en alcalinité en fonction de la teneur en CO2. Les réactions en jeu ont été étudiées par une approche cinétique afin d'estimer la réactivité des minéraux en fonction de la perturbation en CO2, par le calcul des variations de surfaces réactives. Les résultats obtenus ont montré que la surface réactive des minéraux pouvait varier de 2 à 4 ordres de grandeur en fonction de la perturbation en CO2. Dans un second temps, une expérience d'injection d'eau saturée en CO2 a été effectuée. Une analyse de la variation de la composition chimique des eaux de l'aquifère, avant et après injection, a permis d'étudier l'impact d'une perturbation par le CO2 sur la composition de l'eau. Une attention particulière a été portée sur le comportement des métaux dissous. Les résultats ont montré une baisse du pH (de 7.3 à 5.7), accompagnée d'un enrichissement en alcalinité, cation majeurs et métaux dissous (Fe, Zn, Mn et As). Les calculs d'indice de saturation ont montré qu'une dissolution des oxydes métalliques type ferrihydrite était corrélée à l'enrichissement en métaux dissous. Une approche de cinétique chimique sur la base des résultats expérimentaux a été proposée. Cela a montré que la dissolution des oxydes métalliques obéissait à des cinétiques d'ordre complexe. Ces résultats montrent que l'effet de la perturbation par le Co2 dans les conditions choisies, engendre un enrichissement en éléments dissous, avec un effet plus significatif sur les métaux. Ces phénomènes devront être regardés de près dans l'éventualité du développement de la technologie de stockage géologique du CO2, an aquifère salin profond / The aim of this thesis was to investigate hydrogeochemical perturbation induced by CO2 in natural aquifers. In a first step, we used chemical data from natural CO2-rich hydrothermal water. We studied variation of fluid chemical composition as a function of CO2 content in order to evaluate reactivity of minerals composing the initial reservoir. Fluid chemical analyses showed decrease in pH, and systematic enrichment in alkalinity and major cations correlated to increase in CO2 content. Chemical reaction was studied by kinetic approach to estimate variation of mineral reactive surface area as function of CO2 perturbation. Results showed that mineral reactive surface area could varied by two to four orders of magnitude as a function of CO2 perturbation. In a second step a field experiment of injection of water saturated with CO2 in aquifer has been carried out. Analysis of groundwater composition before and after injection allowed to study the impact of CO2 perturbation on water-rock interaction processes. A particular focus was made on dissolved metals behavior. Results showed a decrease in pH (from 7.3 to 5.7), involved with enrichment in alkalinity by a factor two, and by approximately one order of magnitude for dissolved metals (Fe, Mn, Zn) and by a factor two for As. Saturation index showed that dissolution of metals oxide such as ferrihydrite was correlated to iron release. These results showed that, in our field experimental conditions, CO2 perturbation induced an enrichment in dissolved elements with more significant effect on dissolved metals. These results highlight the importance of proper physic-chemical characterization of fluid and reservoir rock and in-situ kinetic of reaction in the eventual option of Co2 geological storage

A numerical model was developed to evaluate the performance of detailed solid oxide fuel cell (SOFC) anode microstructures obtained from experimental reconstruction techniques or generated from synthetic computational techniques. The model is also capable of identifying the linear triple phase boundary (TPB) reaction sites and evaluating the effective transport within the detailed structures, allowing a comparison between the structural properties and performance to be conducted. To simulate the cell performance, a novel numerical coupling technique was developed in OpenFOAM and validated. The computational grid type and mesh properties were also evaluated to establish appropriate mesh resolutions to employ when studying the performance. The performance of a baseline synthetic electrode structure was evaluated using the model and under the applied conditions it was observed that the ionic potential had the largest influence over the performance. The model was used in conjunction with a computational synthetic electrode manufacturing algorithm to conduct a numerical powder to power parametric study investigating the effects of the manufacturing properties on the performance. An improvement in the overall performance was observed in structures which maximized the number of reaction sites and had well established transport networks in the ion phase. From the manufacturing parameters studied a performance increase was observed in structures with low porosity and ionic solid volume fractions near the percolation threshold, and when the anodes were manufactured from small monosized particles or binary mixtures comprising of smaller oxygen ion conductive particles. Insight into the anode thickness was also provided and it was observed that the current distribution within the anode was a function of the applied overpotential and an increase in the overpotential resulted in the majority of the current production to increase and shift closer to the electrode-electrolyte interface. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2013-10-01 09:41:47.617

Made available in DSpace on 2014-12-17T15:42:05Z (GMT). No. of bitstreams: 1 AnaLPFC.pdf: 1922699 bytes, checksum: c82e91dbc8eb0d49eecb97284bc06938 (MD5) Previous issue date: 2009-08-14 / Due to its physico-chemical and biological properties, related to the abundance and low cost of raw material, chitosan has been recognized as a material of wide application in various fields, such as in drug delivery systems. Many of these properties are associated with the presence of amino groups in its polymer chain. A proper determination of these amino groups is very important, in order to properly specify if a given chitosan sample can be used in a particular application. Thus, in this work, initially, a comparison between the determination of the deacetylation degree by conductometry and elemental analysis was carried out using a detailed analysis of error propagation. It was shown that the conductometric analysis resulted in a simple and safe method for the determining the degree of deacetylation of chitosan. Subsequently, experiments were performed to monitor and characterize the adsorption of tetracycline on chitosan particles through kinetic and equilibrium studies. The main models of kinetics and adsorption isotherms, widely used to describe the adsorption on wastewater treatment systems and the drug loading, were used to treat the experimental data. Firstly, it was shown that an apparent linear t/q(t) ? t relationship did not imply in a pseudo-second-order adsorption kinetics, differently of what has been repeatedly reported in the literature. It was found that this misinterpretation can be avoided by using non-linear regression. Finally, the adsorption of tetracycline on chitosan particles was analyzed using insights obtained from theoretical analysis, and the parameters generated were used to analyze the kinetics of adsorption, the isotherm of adsorption and to ropose a mechanism of adsorption / Devido ?s suas propriedades f?sico-qu?micas e biol?gicas, associadas ? abund?ncia e ao baixo custo da mat?ria-prima, a quitosana tem sido considerada um material de ampla aplica??o em diversos campos, tais como em sistemas de libera??o de f?rmacos. Muitas dessas propriedades est?o associadas ? presen?a de grupos amino em sua cadeia polim?rica. Uma determina??o apropriada desses grupos amino ? muito importante, com o objetivo de especificar adequadamente se uma dada amostra de quitosana pode ser usada em uma particular aplica??o. Dessa forma, neste trabalho, inicialmente, foi realizada uma compara??o entre a determina??o do grau m?dio de desacetila??o atrav?s de an?lises condutim?trica e elementar usando uma minuciosa an?lise de propaga??o erro. Foi mostrado que a an?lise condutim?trica resultou em um m?todo simples e seguro para determina??o do grau m?dio de desacetila??o da quitosana. Posteriormente, foram realizados experimentos a fim de monitorar e caracterizar o processo de adsor??o de tetraciclina em part?culas de quitosana, atrav?s de estudos cin?ticos e de equil?brio. Os principais modelos cin?ticos e de isotermas de adsor??o, amplamente usados para descrever a adsor??o em sistemas de tratamento de efluentes e de incorpora??o de f?rmacos, foram utilizados nos dados experimentais. Primeiramente, foi mostrado que uma aparente rela??o linear t/q(t) ? t n?o implica em um mecanismo de adsor??o de pseudo-segunda-ordem, diferentemente do que tem sido repetitivamente relatado na literatura. Foi encontrado que esta interpreta??o err?nea pode ser evitada atrav?s do uso de uma regress?o n?o-linear. Finalmente, a adsor??o de tetraciclina em part?culas de quitosana foi analisada, utilizando os conhecimentos obtidos de uma an?lise te?rica, e os par?metros gerados foram usados para analisar a cin?tica de adsor??o, a isoterma de adsor??o e para propor um mecanismo de adsor??o

La Simulation aux Grandes échelles (LES) est de plus en plus présentée comme un outil à part entière dans le développement des chambres de combustion des turbomachines. Dans ce contexte, les écoulements réactifs considérés sont complexes et, dans un souci de validation, la LES doit montrer ses capacités sur des configurations modèles. Le but de cette thèse est de démontrer le potentiel de la LES pour la prédiction des écoulements vrillés réactifs non prémélangés de chambres de combustion modèles. - La LES est tout d'abord appliquée sur une configuration turbulente avec une hypothèse de prémélange parfait, afin d'étudier l'influence de la modélisation de la cinétique chimique, des modèles de combustion turbulente et de leur paramètres internes. Dans ces conditions, chacun de ces modèles montre ses avantages et désavantages. - L'hypothèse de prémélange parfait est ensuite retirée et l'étude réalisée permet d'évaluer l'influence de la prise en compte du mélange air/carburant dans un injecteur vrillé, des pertes thermiques et des conditions limites acoustiques. - Enfin, une chambre de combustion non prémélangée est simulée afin de démontrer les capacités du modèle de flamme épaissie sur ce type de flamme, pour lequel il n'a pas été initialement développé. Les résultats obtenus sont encourageants et démontrent, entre autres, la bonne représentation du positionnement de la flamme. / Large Eddy Simulation (LES) is considered as the next generation tool for the development of turbomachinery combustion chambers. In this specific context, reactive flows are of very complex nature and, as a validation goal, LES needs to prove its capabilities on academic configurations. This dissertation aims at demonstrating LES capabilities for the simulation of non-premixed reactive flows that can be found in swirled academic combustion chambers. - LES is first applied to a turbulent reacting configuration with a perfect premixing assumption. Chemical kinetics, turbulent combustion models and their internal parameters are studied. For this flow condition, each model shows his advantages and disadvantages. - Then, the perfect premixed hypothesis is removed, allowing the evaluation of mixing, thermal losses and acoustic boundary conditions for this swirled injector. - Finally, a non premixed combustion chamber is simulated with the dynamically thickened flame model, which was not developped for this kind of reactive flow. However, results are encouraging and demonstrate that the flame localisation is well represented by LES.

Le biodiesel est un biocarburant, composé d'un mélange de mono-esters d'acide gras saturés et insaturés avec une longue chaîne carbonée. Ce travail de thèse présente les données de la littérature sur l'origine du biodiesel et son procédé de fabrication ; sont présentées aussi les performances et les émissions des moteurs diesel fonctionnant au biodiesel et la cinétique d'oxydation du biodiesel. Des efforts ont été faits pour mettre en évidence les principales différences entre les esters méthyliques et éthyliques tout en montrant que d'autres recherches sont encore à développer. Pour ces raisons, les délais d'auto-inflammation de cinq esters méthyliques et éthyliques ont été mesurés dans un tube à onde de choc : l'acrylate d'éthyle, l'acrylate de méthyle, le crotonate d'éthyle, le crotonate de méthyle et le butanoate d'éthyle. Les mécanismes cinétiques détaillés d'oxydation des cinq esters étudiés ont été générés automatiquement en utilisant le logiciel EXGAS. L'oxydation du butanoate d'éthyle, molécule modèle d'esters éthyliques d'huiles végétales (EEHV) a été étudiée dans un réacteur piston à pression atmosphérique pour une gamme de température allant de 500 à 1200 K. Les résultats représentent les profils de concentration des réactifs, les intermédiaires stables et les produits finaux. Le modèle cinétique a été validé de façon satisfaisante par une comparaison entre les résultats simulés et expérimentaux / An increasingly popular biofuel is biodiesel, composed of a mixture of saturated and unsaturated fatty acid methyl or ethyl esters, with a long aliphatic main chain. This PhD dissertation provides a literature review concerning the origin of biodiesel, its manufacturing process, performance and emissions of diesel engines fueled with biodiesel, and the kinetics of oxidation of biodiesel. Efforts were made to highlight the main differences between methyl and ethyl esters while showing where further research needs to be developed or pursued. For these reasons, the autoignition of five esters were measured behind reflected shock tube: ethyl acrylate, methyl acrylate, ethyl crotonate, methyl crotonate, and ethyl butanoate. Detailed mechanisms for the oxidation of the five studied esters were automatically generated using the version of EXGAS software. In addition, the oxidation of ethyl butanoate as a model compound for Fatty Acid Ethyl Esters (FAEE) has been investigated in tubular plug flow reactor at atmospheric pressure over wide range of temperature (500-1200 K). The results consist of concentration profiles of the reactants, stable intermediates, and final products. The model was again validated satisfactorily by comparison between computed results and the generated experimental data