Global warming and climate changing are serious problems challenging humanity, therefore important steps needed to be taking to neutralize such challenge. From the last century huge amount of carbon dioxide released to atmosphere cause huge damages to our globe. Technologies such as oxycombustion and chemical looping combustion had been discussed to capture and sequestration carbon dioxide at lower cost. Separation air from fuel using chemical looping or separation nitrogen from air using oxygen transport membrane (OTM) then combust pure oxygen with fuel are the main step to capture carbone dioxide in less expensive method. Each technology had its own drawback, therefore, to overcome these drawbacks an integrated system is proposed combined oxycombustion, chemical looping and OTM technologies into one system. This work aimed to model and simulate an integrated system in single reactor using liquid Antimony and Antimony trioxide as an oxygen carrier to pick up oxygen from the OTM and reduce fuel using natural circulation due to density difference between metal and metal oxide. Heat is being released inside the reactor due to exothermic oxidation reaction and temperature is increased. The temperature profile is studied in all reactor zones with respect to oxidation and reduction rate, operation temperature, metal viscosity and radiation effect. The result show that the system had a good potential to transfer heat generated from the oxidation and transfer to other zones, in which heat can be utilized and been used for heating water or generate steam.

Le charbon demeure à l’heure actuelle l’un des combustibles fossiles les plus couramment employés afin de produire de l’énergie. Son utilisation accrue dans le futur devra toutefois être conciliée avec la problématique de réduction des émissions de gaz à effet de serre. Des procédés permettant de limiter les émissions de CO2 ou de faciliter son captage, à l’image de l’oxycombustion, sont de fait actuellement développés. Leur implémentation à l’échelle industrielle implique toutefois de lever un certain nombre de verrous scientifiques liés à la compréhension des mécanismes physico-chimiques d’oxydation du charbon pulvérisé sous atmosphères plus ou moins riches en oxygène. Ce travail de thèse a de fait porté sur la mise au point d’un banc d’essais de laboratoire permettant d’étudier la combustion du charbon en reproduisant des conditions de chauffe analogues à celles rencontrées industriellement. Le brûleur hybride qui a été mis au point lors de ce travail a permis d’analyser des flammes jets de combustible solide sous atmosphères O2/N2 et O2/CO2 contenant des teneurs variables en oxygène. Une caractérisation détaillée des champs de vitesse et de température dans la chambre réactionnelle a été opérée. Des mesures de température des semi-cokes dans les flammes et de concentrations d’espèces gazeuses (CO, CO2, O2, NO, NOx et SOx) ont également été réalisées tout au long de la combustion. Des prélèvements de semi-cokes à différents temps de séjour ont enfin été opérés de sorte à obtenir des profils de dévolatilisation qui ont pu être confrontés à divers modèles empiriques issus de la littérature. L’ensemble des données que nous avons obtenues nous a permis de mettre en évidence l’impact d’un enrichissement en oxygène du milieu réactionnel sur les cinétiques de dévolatilisation et sur les mécanismes de formation de polluants tels que les NOx et les SOx. Les travaux menés sous oxycombustion ont pour leur part permis de mieux appréhender les différences fondamentales entre la combustion du charbon pulvérisé sous air et sous atmosphères O2/CO2. Pour terminer, des essais préliminaires de combustion de mélanges à base de charbon et de bois ont également été menés, la co-combustion de charbon et de biomasse constituant un autre moyen de limiter les quantités nettes de CO2 émises dans l’atmosphère. / Coal is currently one of the most widely used fossil-fuel for energy production applications. Its increasing use in the near future will have to face the greenhouse gas reduction objectives. Different processes have thus been developed to reduce CO2 emissions or ease their capture as oxy-fuel combustion for instance. The implementation of such techniques at industrial scale implies fundamental works to be undertaken to better understand the physical-chemical processes involved in the oxidation of pulverized coal under oxygen enriched environments. The present work has thus focused on the development of a lab-scale test bench allowing the study of coal combustion with heating rates similar to those met in industrial combustors. The hybrid burner that has been set up allowed the analysis of different solid fuels jet-flames under O2/N2 and O2/CO2 atmospheres containing various amounts of oxygen. A detailed characterization of the velocity and temperature fields has been carried out in the combustion chamber. Char temperatures and gaseous species concentrations (CO, CO2, O2, NO, NOx and SOx) have also been monitored during the combustion. Char samples at different residence times have finally been collected to derive devolatilization profiles that have been compared to simulated data issued from various empirical models from the literature. Obtained results clearly illustrate the impact of an oxygen enrichment of the reaction medium on devolatilization kinetics and pollutants formation including NOx and SOx. Works conducted in the fields of oxy-fuel combustion allowed to better understand the fundamental differences between pulverized coal combustion under air and O2/CO2 environment. Finally, preliminary experiments have been conducted using coal and wood blends since coal co-combustion with biomass appears to be another interesting mean to reduce net CO2 emissions into the atmosphere.

This work aimed to evaluate the subsystems of a novel mediated oxycombustion system and determine the expected final conditions of the integrated subsystems. The subsystems included a cerium based oxygen transport membrane, transport membrane coatings to assist in the pickup and release of oxygen, and a molten intermediary oxygen carrier. Various doping levels of yttrium and zirconium were investigated, both as singular dopants and in a co-doped scheme. Regression analysis was performed to quantitatively evaluate how each dopant affected the material properties. Zirconium was not found to have statistically significant effects, although an effect was clearly noted on pure ceria. Functions of the doping level of yttrium were found for relative density, hardness, and the contributing factors of electrical conductivity. Chemical looping combustion experiments were performed to determine viable candidates for oxygen pickup and release coatings. It was discovered that a release coating was not necessary due to the use of a reactive fluid, and iron showed promise as a pickup coating but short of showing statistical significance. The ability of antimony oxide to react with hydrocarbon fuels and be regenerated by oxygen was investigated to determine the reaction rates. It was discovered that a co-doping scheme of yttrium and zirconium at a level of 8.33% (1/12th) each achieved the highest oxygen flux with a value of 3.671x10-7 mol O/s/cm2. All of the subsystems were we analyzed and a complete, theoretical system was described. It is recommended that the shape of the oxygen transport membrane be of a single-closed-end cylinder. This allows the increase of oxygen permeation with a smaller device footprint. It was found that the system would be capable of combusting 6.699 grams of carbon based fuel per minute per square meter of footprint. This equates to a heat rate of 3.6 kilowatts per square meter when utilizing a medium volatile bituminous coal. This value will continue to be improved as further research is conducted into the components of the system.

Today, and for the foreseeable future, coal and other fossil fuels will provide a major portion of the energy services demanded by both developed and developing countries around the word. In order to reduce the emissions of carbon dioxide associated with combustion of coal for electricity generation, a wide range of carbon capture technologies are being developed. This thesis models the oxyfuel carbon capture process for pulverized coal and presents performance and cost estimates of this system in comparison to other low-carbon fossil fuel generators. Detailed process models for oxygen production, flue gas treatment, and carbon dioxide purification have been developed along with the calculation strategies necessary to employ these components in alternative oxyfuel system configurations for different types of coal-fired power plants. These new oxyfuel process models have been implemented in the widely-used Integrated Environmental Control Model (IECM) to facilitate systematic comparisons with other low-carbon options employing fossil fuels. Assumptions about uncertainties in the performance characteristics of gas separation processes and flue gas duct sealing technology, as well as plant utilization and financing parameters, were found to produce a wide range of cost estimates for oxyfuel systems. In case studies of a new 500 MW power plant burning sub-bituminous Powder River Basin coal, the estimated levelized cost of electricity (LCOE) 95% confidence interval (CI) was 86 to 150 [$/MWh] for an oxyfuel system producing a high-purity [99.5 mol% CO2] carbon dioxide product while capturing 90% of the flue gas carbon dioxide. For a CoCapture oxyfuel system capturing 100% of the flue gas CO2 together with all other flue gas constituents, the estimated LCOE 95% CI was 90 to 153 [$/MWh] (all costs in constant 2012 US Dollars). Using the IECM, an oxyfuel system for CO2 capture also was compared under uncertainty to an existing amine-based post-combustion capture system for a new 500 MW power plant, with both systems capturing 90% of the CO2 and producing a high-purity stream for pipeline transport to a geological sequestration site. The resulting distribution for the cost of CO2 avoided showed the oxyfuel-based system had a 95% CI of 44 to 126 [$/tonne CO2] while the amine-based system cost 95% CI ranged from 50 to 133 [$/tonne CO2]. The oxyfuel cost distribution had a longer tail toward more expensive configurations but over 70% of the distribution showed the oxyfuel-based system to be ~10[$/tonne CO2] lower in cost compared to the amine-based capture system. An evaluation of several low-carbon generation options fueled by coal and natural gas further considered both direct and indirect greenhouse gas emissions. This analysis showed oxyfuel to be economically competitive with all capture system considered, and also indicated oxyfuel to be the preferred carbon capture technology for minimizing overall carbon intensity. Combined, these results suggest that oxyfuel is a promising carbon capture technology, and the only one which offers the unique ability to capture all the combustion gases to become a truly zero emission coal plant. Realization of the latter option, however, is contingent on the development of new regulatory policies for underground injection of mixed flue gas streams that is outside the scope of this thesis.

Les travaux menés dans cette Thèse ont consisté à développer un pilote expérimental prouvant la faisabilité de la capture de CO2 par boucle chimique calcium en utilisant des chaudières du type Lit Fluidisé Circulant. Ceux-ci ont été conduits en deux phases: une phase expérimentale à l'échelle du laboratoire avec l'interprétation théorique des résultats et une phase expérimentale à l'échelle du pilote dans le but de valider le procédé. Les résultats expérimentaux à 1'échelle du laboratoire ont permis de montrer que le frittage de CaOest la cause de la décroissance du taux de carbonatation au cours des cycles successifs calcination/carbonatation. La vitesse de frittage étant accélérée par la présence de CO2 pendant la phase de calcination. Les analyses menées sur les échantillons calcinés ont révélé l'apparition d'une structure de micrograin à l'intérieur des grains initiaux de carbonate. Les micrograins de CaO non frittés sont le siège de la réaction de carbonatation.Un procédé de capture de CO2 par boucle chimique calcium a été conçu et réalisé. Il se compose de deux lits fluidisés circulants, un réacteur de carbonatation assurant la capture du CO2 et un réacteur de calcination permettant la régénération de la chaux. Ces deux lits fluidisés circulants sont couplés de façon à permettre un fonctionnement continu du procédé de capture de CO2. Malgré le faible rendement de capture obtenu à l'échelle de ce pilote (entre 18 à 23%), ces résultats apparaissent encourageants pour le développement de cette technologie, compte tenu du fait que beaucoup de facteurs limitant le rendement de capture disparaissent avec le changement d'échelle. / The works led in this Thesis consisted in developing an experimental pilot proving CO2 capture feasibility by calcium chemical looping using Circulating Fluidised Bed as boilers. These were undertaken in two step: At the laboratory scale with theoretical interpretation of the experimental results and at the pilot scale in the aim to validate the process.The experimental results on the scale of the laboratory allowed to show that the sintering of CaO bring about the decreasing of the carbonation rate during calcination/carbonation cycles. The sintering velocity are accelerated by CO2 during the calcinations step. The analysis of the calcined samples showed a micrograins structure inside the initial carbonate grains The not sintered CaO micrograins are the location of the carbonation reaction.A process of CO2 capture by calcium chemical looping was designed and built. It was made by two circulating fluidized beds, a carbonator where the CO2 capture were performed and the calcinator allowing the lime regeneration. These two circulating fluidized beds are coupled allowing a continuous CO2 capture.In spite of the low capture efficiency obtained on the scale of this pilot (from 18 to 23 %), these results seem encouraging for the development of this technology, considering the fact that many limiting factors of the capture efficiency disappear with the change of scale.

Le charbon est l’une des ressources fossiles les plus économiques pour la production d’énergie. Cependant, il présente des inconvénients liés à l’impact environnemental lors de sa combustion qui produit CO2, principal gaz à effet de serre, ainsi que d’autres gaz et particules polluants et nocifs pour la santé. Afin de lutter contre ces effets, plusieurs procédés sont envisagés dont l’oxycombustion (possibilité de séquestrer CO2 en sortie du système de combustion) et la co-combustion charbon/biomasse sachant que le bilan carbone est neutre pour la biomasse. Pour caractériser ces procédés, un dispositif expérimental a été développé. Il s’agit d’un four à chute qui permet de reproduire en laboratoire les conditions expérimentales prévalant dans les chaudières industrielles dont une vitesse de chauffe des particules de l’ordre de 104 K s-1. Ce dispositif a permis d’étudier la réaction de dévolatilisation de différents solides pulvérisés (charbons, biomasse) à différentes températures (de 600 à 1400 °C). Pour comparer les procédés de combustion et d’oxycombustion, la dévolatilisation sous N2 (étape préliminaire à la combustion sous air) et sous CO2 (étape préliminaire à l’oxycombustion) a été étudiée pour différents charbons à différentes températures. Les résultats obtenus montrent que l’influence de l’atmosphère gazeuse sur la dévolatilisation du charbon n’est significative que pour des températures supérieures à 1200 °C. L’influence des différentes conditions opératoires sur les émissions de particules (PM2.5) issues de la combustion du charbon et de la biomasse a été évaluée et des corrélations sont mises en évidence entre l’intensité d’émission des particules et la nature du combustible, la température et l’atmosphère gazeuse. Une étude cinétique de la pyrolyse a été effectuée et les paramètres cinétiques correspondants déterminés par modélisation à partir de plusieurs schémas cinétiques réactionnels. / Coal is the most economically attractive fossil fuel and the main resource used for electricity production. However, the main issue with coal combustion is the greenhouse gas as well as other gases and particulates matter leading to environmental and human concerns. In order to reduce the environmental impact of coal utilization, researches are conducted to improve the combustion process and to use other carbon-based fuels. The first approach includes the oxy-fuel combustion that can be coupled with Carbon Capture and Storage process (CCS). The second approach promotes the partial substitution of coal by carbon-neutral fuels, such as biomasses, which are promising fuels.For the evaluation of the application of these technologies, an experimental device was developed. This device is a drop tube furnace (DTF) in which high particle heating rate (approximately 104–105 K s−1) has to be achieved in order to characterize solid fuels under conditions similar to those taking place in power plant furnaces. DTF allowed to investigate pyrolysis reaction involving coal and/or biomass particles at different temperatures (600-1400 °C). The comparison between the oxy-combustion and the conventional air combustion process starts with the investigation of the pyrolysis step. The impact of N2 (for conventional air combustion) and CO2 (for oxy-fuel combustion) atmospheres during pyrolysis of different coals at different temperatures was investigated. Results showed that the coal devolatilization is influenced by the gas under which the fuel devolatilization is carried out (N2 or CO2) only at high temperatures (>1200 °C). The influence of different operating conditions on PM2.5 emission were experimented for coals or biomass, including combustion atmosphere (air or oxy-fuel conditions), particle residence time and temperature. A kinetic study of the pyrolysis was carried out and the corresponding kinetic parameters were determined by modeling from several kinetic reaction schemes.

Le dioxyde de carbone, provenant de la combustion d’énergies fossiles, est l’un plus important gaz à effet de serre. La réduction des émissions de CO2 à l’atmosphère s’imposant, une solution consiste en la capture et la séquestration du CO2 par oxy-combustion. Avant l’étape de séquestration, le CO2 doit être purifié. Les procédés de séparation des gaz nécessitent une bonne connaissance des propriétés thermodynamiques des équilibres entre phases. C’est pourquoi un nouvel appareil expérimental, permettant l’étude de la solubilité d’un mélange de gaz (CO2, O2, NOx, SO2) dans des solutions aqueuses, a été développé. Dans un premier temps, l’étude du système CO2-eau a permis de valider l’appareil expérimental pour les domaines de température et de pression de l’étude (293 ,15-393,15 K, jusqu’à 5 MPa). Ensuite, les données sur le système CO2-eau-NaOH étant rares dans la littérature, ce système a été étudié. Les données expérimentales obtenues ont été comparées à un modèle développé dans l’étude. Les modèles de coefficient d’activité de Pitzer et de NRTL électrolyte sont comparés. La dernière étape de l’étude est l’optimisation des paramètres du modèle NRTL-e par ajustement sur les données expérimentales. / Production of carbon dioxide from burning fossil fuel participates in the global warming. This issue generates a growing interest for CO2 capture and storage from oxy fuel combustion. Before the sequestration step, the CO2 has to be purified from impurities. Separation processes require a good knowledge of thermodynamics properties of phase equilibria. In this context a new experimental device was designed and set up in the LaTEP to allow the study of the solubility of gas mixture involved in CO2 capture and storage processes (CO2, O2, NOx, SO2). The apparatus was, first, validated by studying the CO2-water system in the temperature range from 293.15 K to 393.15 K and at pressure up to 5 MPa. Then, the CO2-water-NaOH was studied because few data are available in the scientific literature. Experimental data obtained was compared with a model developed in this work. This model is based on a thermodynamic description of physical chemical phenomena occuring in a vapour liquid system. Two model of activity coefficient are compared (Pitzer and electrolyte-NRTL). The last step of this study is the parameter optimization for e-NRTL.

Le réchauffement climatique principalement dû aux émissions importantes de CO₂, gaz à effet de serre de référence, encourage les chercheurs à trouver des solutions pour lutter contre ce phénomène. Les techniques consistant à capter et stocker ou valoriser le CO₂ sont des solutions pertinentes, mais qui nécessitent d'avoir du CO₂ le plus pur possible. Parmi ces techniques, l'oxycombustion parait assez prometteuse pour produire du CO₂ en forte concentration. Toutefois, selon la nature du combustible et la pureté de l'oxygène, certains polluants peuvent apparaître tels que le CO et les NOx. Pour réaliser cette purification, la catalyse est un moyen efficace permettant de transformer simultanément le NO et le CO respectivement en N₂ et CO₂. L'objectif de cette étude est donc, de mettre au point des catalyseurs actifs pour la réduction des NOx en N₂ par le CO, dans un milieu oxydant et en présence d'eau. Deux types de catalyseurs ont été choisis : les métaux nobles (Pd, Pt, Rh) supportés et les oxydes de métaux de transition (Co, Cu, Al). Les résultats obtenus montrent que les catalyseurs à base de Pt sont plus performants et que leur activité catalytique augment pour les échantillons supportés sur un support neutre (SiO₂) ou réductible (TiO₂) que ce soit en présence ou en absence d'eau. Les oxydes mixtes de métaux de transition, obtenus par voie hydrotalcite, montre que la nature du cation bivalent joue un rôle important. Les oxydes mixtes Co-Cu ont montré une meilleure activité que les matériaux composés d'un seul de ces deux éléments. Cependant, l'ajout d'eau dans le flux réactionnel conduit à une baisse d'activité des catalyseurs contenant du Cu. / Global warming, mainly due to high CO₂ emissions, reference greenhouse gas, motivates researchers to find solutions to combat this phenomenon. The techniques of capturing and storing or reuse of CO₂ are revelant solutions, but which require a CO₂ as pure as possible. Among these techniques, oxyfuel combustion seems promising enough to produce CO₂ in high concentration. However, depending on the nature of the fuel and the oxygen purity, some pollutants may appear such as CO and NOx. To carry out this purification, catalysis is an effective means for simultaneously converting NO and CO respectively into N₂ and CO₂. The objective of this study is to develop active catalysts for NOx reduction in N₂ by CO, in oxidizing conditions and presence of water. Two types of catalysts were chosen : supported noble metals (Pd, Pt, Rh) and transition metal oxides (Co, Cu, Al). The results obtained show that the Pt-based catalysts were more efficient and that their catalytic activity increases for the samples supported on a neutral support (SiO₂) or reducible (TiO₂) whether in the presence or absence of water. The mixed oxides of transition metals, obtained by hydrotalcite, show that the nature of the bivalent cation plays an important role. Co-Cu mixed oxides showed better activity than materials composed of only one of these two elements. However, the addition of water to the reaction flow led to a decrease in activity of the Cu-containing catalysts.

Pollution is one of the greatest concerns with pulverized coal combustion. With tightening standards on pollution emissions, more information is needed to create better design models. Burner modifications are the most efficient changes that can be made to assure sufficient carbon burnout and low NOx emissions. Experiments were performed in the BYU Flat Flame Burner (FFB) lab, operating under fuel rich conditions for pyrolysis experiments and fuel lean conditions for char oxidation experiments. Effects of temperature, coal rank, residence time, and post flame oxygen content on mass release, nitrogen release, and reactivity were examined. Elemental and Inductively coupled plasma (ICP) analyses were used to determine the mass and nitrogen release of coals and chars. FT-IR was used to determine gas phase nitrogen compositions on selected experiments. Results of char oxidation experiments were fit to a first-order model to obtain an Arrhenius pre-exponential factor, while activation energies were approximated using a published correlation. CPD model calculations were used to find experimental residence times and particle diameters that obtained full pyrolysis yields. Oxy-fuel experiments were performed by switching the burner diluent gas from N2 to CO2. Oxy-fuel experiments exhibited a rank effect in nitrogen release. Bituminous coal tests showed no statistically significant difference in mass or nitrogen release between the two conditions. A sub-bituminous coal exhibited a greater mass and nitrogen release for the same residence time under the CO2 environment, which could be due to early gasification of the char. Two samples of a chemically treated coal with different additive concentrations were tested against an untreated sample for combustion enhancement. The treated samples showed an increase on the order of 15% absolute in pyrolysis yield compared to the untreated sample. An increase in reactivity on the order of 35% was observed for the higher concentrated sample, but not for the lower treatment concentration. Gas phase nitrogen measurements showed both HCN and NH3 at the 1300 K gas temperature condition. HCN and NH3 release during pyrolysis was largely rank dependent, with more HCN formed initially than NH3 for 5 of the 6 samples. However, a Polish bituminous coal was found to have more NH3 than HCN. These nitrogen species data can be used to evaluate or refine nitrogen transformation mechanisms.

L’étude de matériaux conducteur mixtes (ionique et électronique) connait un intérêt croissant depuis plusieurs années dans le domaine de l’énergie, principalement lié au développement des électrodes pour les piles à combustible de type SOFC (Solid Oxide Fuel Cell) ou des réacteurs catalytiques membranaires (CMR) pour le réformage du méthane de synthèse ou pour le procédé d’oxycombustion. Dans ce dernier cas, la réalisation de membranes conductrices mixtes de structure pérovskite du type La1-xAxFe1-yByO3- permet la séparation de l’oxygène de l’air à haute température (900°C) avec une sélectivité quasiment infinie sans circuit électrique extérieur. Les mécanismes limitant le transport de l’oxygène à travers la membrane ont été étudiés à l’aide d’un dispositif de caractérisation original composé d’électrodes, permettant la mesure du potentiel électrochimique de l’oxygène à la surface de la membrane. L’influence de la substitution du cation en site A puis en site B sur les propriétés de semi-perméabilité à l’oxygène a été étudiée au sein des matériaux pérovskites La0,5A0,5Fe0,7B0,3O3-(A = Ca, Sr, Ba et B = Al, Co, Cu, Ga, Mg, Mn, Ni, Sn, Ti, Zn). Les résultats obtenus avec cette technique originale nous ont permis de mieux cerner les mécanismes limitant le transport d’oxygène à travers la membrane. L’influence de la microstructure de la membrane sur les propriétés de semi-perméabilité à l’oxygène a également été étudiée et un modèle d’évolution des propriétés de semi-perméabilité en fonction de la microstructure a été proposé. Cette compréhension des mécanismes de transport nous a permis d’orienter les recherches vers l’élaboration de nouvelles architectures de membranes. / Since few years, the study of mixed conducting materials (ionic and electronic) knows an increasing interest in the energy area, especially with the development of electrodes for Solid Oxide Fuel Cell (SOFC) or Catalytic Membrane Reactors (CMR) for the methane reforming in synthesis gas or for oxyfuel process. In this latter case, the mixed conductor membrane with La1-xAxFe1-yByO3- perovskite structure allows the separation of oxygen from air at high temperature (900°C) with a quasi-infinite selectivity without outside electric circuit, with an interesting economical cost. The oxygen transport mechanisms through the membrane are studied thanks to an original electrodes system composed of a zirconia point micro-electrode and a metallic reference electrode. This system allows the measurement of the oxygen electrochemical potential at the membrane surface. The influence of cation substitution in A-site then B-site in La0.5A0.5Fe0.7B0.3O3-(A = Ca, Sr, Ba and B = Al, Co, Cu, Ga, Mg, Mn, Ni, Sn, Ti, Zn) perovskite materials has been studied. The results obtained by this original system led us to a better understanding and a identification of the rate determining step of oxygen transport mechanism through the membrane. The influence of the microstructure on oxygen semi-permeation has been studied and an evolution model of semi-permeation properties with microstructure has been shown. The understanding of oxygen transport mechanisms led to the development and the elaboration of news architectures of membranes.