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Comportement en combustion de résidus de biomasse : mise en évidence de synergies par mélange sous forme de granulés / Combustion behaviour of biomass residues : evaluation of synergies by mixture in pelletsPiednoir, Brice 21 February 2017 (has links)
La combustion de résidus de biomasse, généralement peu valorisés, pourrait apporter une solution d’approvisionnement intéressante pour la production d’énergie, allégeant la pression sur les ressources forestières. Toutefois, la composition chimique de ces résidus est à l’origine de problèmes techniques autant qu’environnementaux dans les procédés de combustion existants, ce qui limite leur utilisation. Deux de ces problèmes ont été traités dans cette thèse : les émissions de NOX et la quantité de potassium volatilisée lors de la combustion de différents résidus. Des essais de combustion ont été menés dans des réacteurs à l’échelle du laboratoire, sur des granulés de biomasse pure ou en mélange. Contrairement à la volatilisation du potassium, qui est liée à la teneur en différents éléments inorganiques, une relation linéaire forte (R² = 0,98) entre les émissions de NOX et la teneur en azote du combustible a été établie pour les granulés de biomasse pure. Des écarts par rapport à cette relation linéaire ont été observés dans le cas des essais menés sur des granulés de mélange, mettant en relief que la teneur en azote n’est pas le seul paramètre impliqué. Les travaux menés ont ainsi permis d’établir de manière originale que des synergies peuvent exister dans les granulés de mélange de résidus de biomasse, conduisant à des comportements différant de l’additivité directe des comportements des biomasses prises séparément. Ces synergies permettraient d’atténuer les problèmes causés par l’utilisation de ces résidus dans des chaudières en agissant de manière ingénieuse directement sur les propriétés des combustibles sans modification du procédé. / Combustion of biomass residues, which are generally poorly valued, could provide an attractive supply solution for energy production, alleviating pressure on forest resources. However, the chemical composition of these residues is causing both technical and environmental problems in existing combustion processes, which limits their use. Two of these problems have been addressed in this thesis: the amount of volatilized potassium and NOX emissions, when burning different residues. Combustion tests have been conducted in laboratory-scale reactors on pure and mixed biomass pellets. Variations in the amount of volatilized potassium was found to be linked to the content of multiple chemical elements for pure biomass pellets. In the case of NOx emissions, a strong correlation (R² = 0.98) with the nitrogen content of the fuel was found for pure biomass pellets. However, deviations from this linear relationship were observed for trials conducted on mixed biomass pellets, highlighting that the nitrogen content is not the only parameter involved. The work carried out thus made it possible to establish in an original way that synergies can exist in the pellets made of a mixture of biomass residues, leading to beneficial behaviors differing from the direct additivity of the biomass behaviors taken separately. These synergies could allow to mitigate the problems caused by the use of these residues in boilers by ingeniously acting directly on the properties of the fuels without modification of the process.
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DESENVOLVIMENTO E VALIDAÇÃO DE UM MÉTODO AUTOMATIZADO PARA A QUANTIFICAÇÃO DOS NÍVEIS SÉRICOS DE NITRITO/NITRATO / DEVELOPMENT AND VALIDATION OF AN AUTOMATED METHOD FOR THE MEASUREMENT OF SERUM LEVELS OF NITRITE/NITRATETatsch, Etiane 09 March 2012 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nitric oxide (NO) is a reactive free radical, acting as a messenger molecule, mediating several functions, including vasodilation, platelet aggregation inhibition and neurotransmission. Because this radical to have a short half-life, its determination is difficult, therefore, measurement of metabolites nitrite/nitrate (NOx) is most often used to evaluate NO production. The Griess reaction is the most used method for NOx quantification due to its simplicity, speed and cost-effective. Due to the biological relevance of NO, it is extremely importance to its measurement. The objective of this study was to develop and validate an analytical method for the automated measurement of serum levels of NOx by the Griess method using the Cobas Mira clinical chemistry analyzer. This study provided the development of a protocol for the automated measurement of serum levels of NOx, which is linear method (r2= 0.993, P <0.001), precise, because it showed a coefficient of variation in intra-assay precision of 8.7% and inter-assay precision of 5.6%. Moreover, we observed a recovery of 114.6% which is considered accurate study. Thus, it was concluded that the automated method presented here is linear, precise, accurate, simple and low cost, likely to be adapted to Cobas Mira analyzer and other automated systems available in clinical routine laboratory. / O óxido nítrico (NO) é um radical livre reativo, agindo como uma molécula mensageira, mediando diversas funções, incluindo vasodilatação, inibição da agregação plaquetária e neurotransmissão. Pelo fato deste radical possuir uma meia-vida curta, a sua determinação torna-se difícil, consequentemente, a mensuração de seus metabólitos nitrito/nitrato (NOx) é mais frequentemente utilizado para avaliar a produção de NO. A reação de Griess é o metodo mais utilizado na quantificação do NOx, devido a sua simplicidade, rapidez e custo-benefício. Devido à relevância biológica do NO, é de suma importância a sua mensuração. Assim, o objetivo deste estudo foi desenvolver e validar um método analítico automatizado para a mensuração dos níveis séricos de NOx pelo método de Griess, utilizando o analizador Cobas Mira®. Este estudo propiciou o desenvolvimento de um protocolo automatizado para a quantificação dos níveis séricos de NOx, sendo este método linear (r2= 0,993, P<0,001), preciso, pois apresentou um coeficiente de variação na precisão intra-ensaio de 8,7% e na precisão inter-ensaio de 5,6%. Além disso, foi observada uma recuperação de 114,6%, sendo este estudo considerado exato. Dessa forma, foi possível concluir que o método automatizado apresentado é linear, preciso, exato, simples e de baixo custo, passível a ser adaptado ao analizador Cobas Mira® e outros sistemas automatizados disponíveis em laboratórios clínicos de rotina.
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Entre a arquitetura experimental e a arquitetura para experiência: máquinas, corpos e próteses de Lars Spuybroek/NOX / Between the experimental architecture and architecture for the experience: machines, bodies and prosthetics Lars Spuybroek / NOXIsabela Paiva Gomes Ferrante 23 August 2013 (has links)
A experiência corporal, a capacidade sensitiva e perceptiva do corpo, sua ação e movimentos são revalorizados no processo de recepção e uso do objeto de arquitetura a partir da pós-modernidade. Partindo dessa constatação, procuramos investigar como essa renovada concepção de corpo pode ser transferida para a prática do projeto e para o desenvolvimento de uma linguagem formal e espacial pensada para a experiência do corpo. Para essa tarefa, toma-se como fio condutor a obra e os escritos do arquiteto holandês Lars Spuybroek, fundador e diretor do extinto escritório NOX (1993-2010). Seu trabalho e seus processos experimentais de projeto são pródigos nessa proposição de tornar o pensamento do corpo em um pensamento operativo aplicado à prática projetual. Via incansável experimentação e investigação tanto empírica quanto teórica, Spuybroek procura encontrar meios para a produção de um ambiente plástico e dinâmico, no qual a percepção e a completa experiência do espaço são dependentes de um corpo ativo e interativo. Do processo de projeto à experiência da arquitetura, seu trabalho resulta em uma arquitetura formada pelo conjunto edifício e corpo, que só definem nessa relação de unidade. / The bodily experience, sensory and perceptual capabilities of the body, its actions and movements are revalued in the process of reception and use of an architectural object from post-modernity on. Based on this observation, we aimed to investigate how this renewed conception of body may be shifted to the designing practice and the development of a both formal and spatial language that is thought accordingly to the body experience. For this task, we take as a guiding thread the work and writings of the Dutch architect Lars Spuybroek: founder and director of the former office NOX (1993-2010). His work and experimental design processes are lavish in that proposition of making the thought of the body into an operating thought applied to design practice. Via relentless experimentation and research both empirical and theoretical, Spuybroek seeks to find ways to bringing forth a plastic and dynamic environment in which perception and complete experience of space are dependent on an active and interactive body. From design process to the architectonic experience, his work is an architecture defined by the couple building and body, which are defined only in this relationship and unity.
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Activité et sélectivité de catalyseurs de stockage-réduction des NOx pour la dépollution automobile. Influence de la nature des réducteurs présents / Activity and selectivity of catalysts of storage-reduction of the NOx for the automobile cleanup. Influence of the nature of the present reducersMasdrag, Liliana 28 June 2012 (has links)
Ce travail porte sur le procédé NSR (NOx Storage-Réduction) de dépollution des gaz d'échappement automobile Diesel. Des catalyseurs contenant 2,12% Pt déposés sur alumine, cérine-zircone ou cérine modifiée, ont été caractérisés et évalués dans des conditions NSR, avec un regard particulier sur la sélectivité de la réduction des NOx. Les tests catalytiques sont effectués dans des conditions complexes : cycles 60s de stockage (mélange pauvre)/ 4s de réduction (mélange riche), avec des traces de réducteurs dans la voie pauvre et d’oxydant dans la voie riche. Des sélectivités importantes en N2O (gaz à effet de serre) ont pu être observées. Les émissions de N2O varient en fonction de la nature du support, de la température et des réducteurs mis en œuvre (C3H6, CO, H2 ou mélange C3H6+CO+H2). Dans certaines conditions, la présence de réducteur dans les phases pauvres contribue à la majorité du N2O émis lors des cycles NSR. Ces valeurs sont en bon accord avec les résultats obtenus en parallèle en régime stationnaire (SCR). A 200°C, H2 donne la plus grande sélectivité en N2O, essentiellement à cause de la réduction partielle des NOx en milieu pauvre. En revanche, à 300°C, C3H6 est le réducteur le plus sélectif en N2O, toujours avec une forte contribution des phases pauvres. Les résultats sont plus homogènes avec les catalyseurs supportés sur oxydes redox car ils favorisent la transformation des réducteurs dans la voie riche (réactions du gaz à l’eau et reformage de C3H6), conduisant à mélange réducteur moyenné. Les propriétés redox du support permettent aussi de limiter les émissions de NH3. / Lean reduction of NOx was studied on NSR (NOx storage-reduction) catalyst, with a special attention on N-compound selectivities. Platinum (2.12wt%) catalysts supported on various supports (alumina, ceria-zirconia and modified ceria) were characterized and evaluated in cycling conditions. Catalytic tests were performed and realistic and complex conditions: 60s for the storage phases (lean periods)/ 4s for the reduction (rich pulses). Gas mixture was composed of reducers and oxidants in both lean and rich atmosphere. In these conditions, high N2O emissions were measured (powerful greenhouse gas). The N2O selectivity depends on the redox properties of the support, the temperature and the chemical nature of the reducer (C3H6, CO, H2 or C3H6+CO+H2 mixture). In some conditions, more than half of the N2O production can occur during the storage phase, in lean condition. These results are in good agreement with those obtained in specific SCR tests. At 200°C, H2 lead to the higher N2O selectivity especially due to the partial NOx reduction in the lean period. At 300°C, N2O emission is mainly favoured with C3H6, with still a high contribution of the lean pulses. Results are less distinct with supported catalysts on redox material, due to the support involvement in the reducer transformation reactions (water gas shift and steam reforming), leading to a blend of reducers in the rich pulses. In addition, lower NH3 emissions were observed on platinum supported on redox oxides.
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Étude des processus de formation et élimination du N2O lors de la Réduction Catalytique de NOx par le NH3 (NH3-SCR) / Study of the formation and elimination of N2O in the Selective Catalytic Reduction of NOx by NH3 (NH3-SCR)Valdez Lancinha Pereira, Mafalda 15 December 2016 (has links)
Le projet de thèse a eu pour but l’étude de la formation et de l’élimination du N2O par des catalyseurs cuivre-zéolithe ou fer-zéolithe, utilisés pour le procédé de réduction catalytique sélective des NOx par l'ammoniac (NH3-SCR). Dans ce processus de réduction des NOx, les principales voies de formation de N2O sont la décomposition du nitrate d’ammonium (NH4NO3) et l’oxydation de NH3. L’étude bibliographique a montré une contribution plus importante de la décomposition du nitrate d’ammonium. La recherche s’est donc focalisée dans l’étude de la décomposition du nitrate d’ammonium en empruntant deux axes : la décomposition du NH4NO3 commercial et la formation in situ suivi de la décomposition du nitrate d’ammonium.Les catalyseurs, utilisés pour cette étude, ont été, tout d'abord, amplement caractérises par différentes techniques d’analyse physico-chimique afin de connaitre particulièrement la concentration et forme de déposition des métaux, l’acidité et la taille des cristaux.Après avoir abordé la décomposition du NH4NO3 commercial sans catalyseur, l'étude s'est orientée sur l'effet de l'interaction avec un catalyseur. La nature du gaz vecteur, les conditions hydrodynamiques et la quantité de NH4NO3 ont aussi été évaluées.La décomposition sous conditions statiques, i.e. sans entrainement du NH4NO3 liquide, conduit principalement le N2O. En revanche, les chemins réactionnels suivis sous conditions dynamiques dépendent du mode de déposition du nitrate d’ammonium. Les agrégats solides de nitrate d'ammonium en contact avec la surface externe du catalyseur se décomposent directement en N2O, surtout quand le nitrate d’ammonium liquide ne peut pas être entrainé par le gaz vecteur. L’absence de catalyseur favorise la décomposition vers l’azote par l’interaction entre le NH3 et du HNO3 libérés lors de la dissociation du NH4NO3. D’autre part, en présence d’un catalyseur, le NH3 formé tend à s’adsorber et à s’oxyder à plus haute température. La variation du gaz vecteur n'engendre pas d'effet significatif sur la décomposition du NH4NO3.La décomposition du nitrate d’ammonium formé in situ a été réalisée dans le but de se rapprocher des conditions du procédé NH3-SCR, où le nitrate d’ammonium se forme par l’interaction entre le NH3 et le NO2. La méthode expérimentale a été conçue pour maximiser la formation du nitrate d’ammonium selon les deux cas extrêmes pouvant être trouvés dans un système SCR : la saturation préalable du catalyseur en NH3 puis en NO2 (« NH3 experiment ») et l’inverse, saturation en NO2 puis NH3 (« NO2 experiment »). Dans ce cas plusieurs catalyseurs ont été préparés afin d’isoler certaines caractéristiques et évaluer leur impact. Les effets de la teneur en cuivre, du type de métal (Cu ou Fe), de la structure de la zéolite (CHA ou FER), de la méthode de préparation, de l’atmosphère de calcination et du gaz vecteur pendant la décomposition ont été étudiés. Les effets obtenus ont été corrélés avec les résultats de la caractérisation physicochimique des catalyseurs afin de déterminer les paramètres prépondérants des différences observées.La formation du N2O lors du « NH3 experiment » est toujours plus importante que celle obtenue dans le « NO2 experiment » et dépend fortement de la concentration en sites acides de Brönsted quelle que soit la structure de la zéolithe. En revanche, dans le « NO2 experiment », ce sont plutôt les espèces métalliques et sa localisation qui influencent la décomposition du nitrate d’ammonium. La taille des cristaux a aussi une influence. La méthode de préparation et l’atmosphère de calcination n’ont pas un effet très significatif. Le gaz vecteur influence seulement les émissions à haute température : la formation du N2O est plus importante en présence d’oxygène. / The thesis project focused on the study of the formation and elimination of N2O by copper-zeolite or iron-zeolite catalysts, used for selective catalytic reduction of NOx with ammonia (NH3-SCR). In the NOx reduction process the main N2O formation routes are the decomposition of the ammonium nitrate (NH4NO3) and the NH3 oxidation. Still, a literature review showed a more important contribution from the decomposition of ammonium nitrate. Therefore, the study was then concentrated on the decomposition of the ammonium nitrate in two axes: the decomposition of commercial NH4NO3 and the in situ formation followed by decomposition of ammonium nitrate.Besides, the catalysts used for this study, have been thoroughly characterized by different physicochemical techniques in order to, particularly, assess the concentration and deposition form of metals, the acidity and the size of the crystals.After performing the decomposition of commercial NH4NO3 without catalyst, the study has focused on the effect of interaction with a catalyst. The effect of the carrier gas, the hydrodynamic conditions and concentration of NH4NO3 were also studied.Under static conditions, i.e. without liquid NH4NO3 entrainment, the decomposition of the commercial ammonium nitrate mostly leads to N2O. In contrast, the reaction pathway under dynamic conditions depends on the deposition method of ammonium nitrate onto the catalyst. The solid aggregates in the outer surface of the catalyst decompose directly to N2O, especially when the liquid ammonium nitrate cannot be entrained by the carrier gas. The absence of a catalyst promotes the decomposition into nitrogen, formed by the interaction between the NH3 and HNO3 released upon the dissociation of NH4NO3. On the other hand, in the presence of a catalyst NH3 tends to adsorb and to be oxidized at higher temperatures. The carrier gas composition did not have a significant effect in the decomposition of NH4NO3.The decomposition of ammonium nitrate formed in situ was performed in order to get closer from what happens under SCR conditions, where the ammonium nitrate is formed by the interaction between NH3 and NO2. The experimental method was designed to maximize the formation of ammonium nitrate according to the two extreme conditions that may be found in a SCR system: firstly catalyst saturation by NH3 and then by NO2 (“NH3 experiment”) and then the reverse, saturation by NO2 and then by NH3 (“NO2 experiment”). In this study several catalysts were prepared in order to isolate certain characteristics and assess their impact. The effects of the copper loading, the type of metal (Cu and Fe), the structure of the zeolite (CHA or FER), the method of preparation, the calcination atmosphere and the carrier gas during decomposition were studied. These effects were correlated to the results of the physico-chemical characterization of the catalysts with the purpose of find the cause of the faced differences.The formation of N2O during the “NH3 experiment” is always greater than that obtained on the “NO2 experiment”, and strongly depends on the concentration of the Brönsted acid sites, regardless the zeolite structure. However, on the “NO2 experiment”, it is rather the metal species and its location that influence the decomposition of ammonium nitrate. The size of the crystals also has an influence. The preparation method and the calcination atmosphere do not have a significant effect. The carrier gas impacts on the high temperature emission: the formation of N2O is greater in the presence of oxygen.
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Measurements and prediction of particulate number concentrations and their chemical composition over Yanbu Industrial City, Saudi ArabiaAl-Mahmodi, Jaafar Nasheed hameed January 2011 (has links)
Many recent studies have highlighted the substantial health-related impacts of particle number (PMno) rather than particle mass. The aim of this study is to determine the correlation of trace gases with PMno, to identify the chemical composition of particle different sizes and to predict the NOx and PMno over Yanbu Industrial City (YIC). Trace gases (NOx, SO2, H2S, O3, CO), PMno with diameter (7nm-10μm), traffic and meteorological parameters were measured at three sampling sites in YIC. The maximum PMno (333,971 cm-3) at downwind site#1 was about 2.5 times higher than that (123,842 cm-3) at upwind site#2 and about 1.2 times higher than that (263,572 cm-3) at downwind site#3. The average PMno distribution at downwind sites consisted of one distinguishable mode (nucleation mode<20nm) whereas the upwind site had two modes (the nucleation and the accumulation modes). The correlation of PMno with NO/NOx (r>0.7) are generally stronger than with NO2 at sites#1 and 2, whereas for site #3 the correlation between PMno with NO2/NOx are better than with NO. PMno has generally either weak or poor correlation with SO2 and CO, respectively. Particle samples of different sizes (7nm-10?m) were chemically analysed using an ion chromatograph (IC) for inorganic ions and inductively coupled plasma mass spectrometry (ICP-MS) for trace metals at site#3. The ionic analysis revealed that sulfate and ammonium was mainly present in particle of size < 0.38μm while nitrate and chloride was mainly present in particles of size > 0.38μm. Non-sea salt sulfate was dominant in all particle sizes compared to the marine sulfate which is minor. The total sulfate and nitrate contributed 50.3% and 24.4% of the total ionic mass respectively followed by chloride (13.3%) and ammonium (10.6%). The trace-metals analysis results indicated that Na represented more than 94% of the total mass and the contributions of the remaining metals (Al, Sr, Zn, V, Cr, Fe, etc) were about 6%. A further part of this study consisted of the coupling of the WRF/CALMET system with the CALPUFF model, which was applied to predict NOx and PMno concentrations. The WRF model was employed to generate the meteorological input data for CALMET. WRF predictions were evaluated with surface data and upper air profiles using RASS/SODAR and radiosondes. WRF tends to underestimate the surface temperature on average with biases of up to -3.4°C and also underestimates temperature profiles with average biases ranging between -2.7 and -5.2oC when compared to the RASS profiler, but with a lower bias (< -2.4°C) when compared to radiosonde profiles. The mean wind speed bias for the majority of the cases was close to the benchmark of ±0.5m/s, but the mean wind direction bias for half of the cases exceeded the benchmark of 10o. It was concluded that WRF predictions can be used for air dispersion modeling to produce reasonable outputs. NOx predictions by CALPUFF showed that the contribution of the traffic to the highest concentrations during the nighttime was up to 80%, but after sunrise the contribution from industries became higher (up to 70%). The highest predicted NOx concentration (~313μg/m3) was much lower than the national ambient standard (660μg/m3) and the community area is affected much by industries during mid-morning hours when the wind shifting from land breeze to sea breeze. The fractional bias (FB) ranged between -0.1 and 1.06 indicating that the model tends to under-predict the NOx observations. PMno predictions of two sizes (7-40nm and 7nm-10μm) were derived based on the NOx predictions. All FB values were ranged between -0.1 and 0.5. It was concluded that PMno predictions were generally better than those of the NOx due mainly to adding the background term (intercept) for the PMno predictions.
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Redukce NOx ve spalinch / NOx reduction in flue gasRumnek, Tom January 2010 (has links)
My master´s thesis deals with the problems of NOx abatement that are included in flue gas. The accent is put on flue gases treatment throug cloth filter or ceramic candles, where the deposited catalyst enables NOx reduction throug the method of selective cytalytic reduction. In thesis is also describe experimental unit which current remove gaseous pollutants (dioxin, VOC and NOX) and ash on catalytic cloth filter or catalytic ceramic candles. For experimental unit has been calculated pressure drop. Pressure drop has been calculated for nominal and maximal conditions for cloth filter and ceramic candle. Last part of thesis deals with compile a experimental schemes for different concentration of NO, flow and temperature of combustion.
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Charakteristické parametry procesu spalování při využití vzduchu s obsahem kyslíku vyšším než 21 % / Characteristic parameters of oxygen-enhanced combustion processHudák, Igor January 2013 (has links)
Diplomová práce se zabývá spalováním zemního plynu při využití vzduchu s vyšším obsahem kyslíku (21–46 % kyslíku ve spalovacím vzduchu), tzv. kyslíkem obohaceným spalováním (OEC). Technologie OEC nalezla uplatnění v průmyslu, kde se jsou nároky na zvýšenou produktivitu, dosažení vyšší tepelné účinnosti, zlepšení vlastností plamene, snížení náklady, či zlepšení kvality výsledného produktu. Ačkoliv OEC přináší řadu výhod, je nutné zmínit i nevýhody jako: poškození zařízení, nestejnoměrné zahřívání, narušení plamene, zvýšené emise anebo zpětný zášleh plamene. Zkoušky proběhly na zkušebně hořáků, která umožňuje testovat hořáky nejen na plynná a kapalná paliva, ale i hořáky navržené pro kombinované spalování při maximálním výkonu hořáku 1 800 kW. Při zkouškách byl použit plynový „low-NOx“ hořák se stupňovitým přívodem paliva. V diplomové práci je popsán vliv obsahu kyslíku ve spalovacím vzduchu na emise oxidů dusíku (NOx), teplotu plamene, přenos tepla ze spalin do stěn spalovací komory, a také vlastnosti plamene, zvláště pak jeho stabilitu, tvar a rozměry. Zkoušky proběhly při výkonech 300 kW, 500 kW a 750 kW, přičemž pro výkon 750 kW proběhly testy jak při jednostupňové, tak dvoustupňové konfiguraci.
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Snižování oxidů dusíku z proudu spalin na speciálních filtračních materiálech / Reduction of nitrogen oxides in flue gas on special filter materialsSirový, Martin January 2013 (has links)
This thesis deals with the reduction of oxides of nitrogen (NOx) which are part of the exhaust gas combustion devices. The focus is on reduction of NOx by selective catalytic reduction (SCR) and catalyst filtration. The first part of this work deals with the formation of NOx, their hazards and related legislation. The following is an overview of the available technologies to reduce NOx in the flue gas and comparison of this methods. The following section describes the experimental catalytic filtration unit INTEQ II, where the first real experiment selective catalytic reduction of NOx with ammonia was realized. We have verified the operability of the experimental units and achieve up to 80% efficiency SCR. The final section describes the progress of the experiment and its results. It is recommended a few minor adjustments to improve stabile operation of unit INTEQ II.
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Etude expérimentale de l'influence des mélanges gazeux sur la combustion sans flamme / An experimental study of the influence of the aerodynamic mixing on flameless combustion regimeRottier, Christiane 02 March 2010 (has links)
Une étude expérimentale de l'influence des mélanges gazeux sur le régime de combustion sans flamme a été menée sur l'installation pilote du CORIA, en collaboration avec GDF SUEZ. La première partie de cette étude a été consacrée à la caractérisation détaillée de ce régime de combustion particulier au méthane pur avec et sans préchauffage de l'air comburant. Des mesures locales de température et concentrations d'espèces stables ont été réalisées à l'aide de thermocouples à fil fin et sonde de prélèvement. Une attention particulière a aussi été portée au développement et l'adaptation de techniques d'imagerie sur ce type de four : l'imagerie de chimiluminescence OH* pour la visualisation des zones de réaction et la PIV endoscopique afin d'obtenir des champs de vitesse de grandes dimensions malgré le fort confinement à haute température. L'analyse des résultats obtenus a permis de mettre en évidence le rôle principal de l'aérodynamique des jets turbulents de réactifs dans le four assurant l'obtention et la stabilisation de ce régime de combustion massivement diluée. Dans la seconde partie de cette étude, la faisabilité de l'utilisation d'hydrogène dans un four pilote fonctionnant en régime de combustion sans flamme a été démontrée. On retrouve toutes les caractéristiques intrinsèques à ce régime de combustion en termes de forte efficacité énergétique (lors du préchauffage de l'air) et très faibles émissions polluantes (CO et NOx) de ce régime massivement dilué, associé à la réduction des émissions de CO2 avec l'augmentation de la teneur en hydrogène dans le combustible. En fonctionnement à l'hydrogène pur et sans préchauffage de l?air, le four n?émet plus aucune espèce carbonée et quasiment pas de NOx ; on se rapproche d'un four à "zéro émission". / An experimental study of the influence of the aerodynamic mixing on flameless combustion regime has been carried out on the CORIA lab-scale facility with the collaboration of GDF SUEZ. A detailed characterisation of this innovating combustion mode, using pure methane as fuel, with and without air preheating is the first part of this study. Temperature and stable species concentrations measurements have been performed with fine wire thermocouple and sampling probe. Imaging techniques have been developed and adapted for in-furnace measurements: OH* chemiluminescence imaging for reaction zone visualization and endoscopic PIV in order to obtain large dimensions velocity fields in spite of the confinement. The results enable us to put in evidence the leading role of aerodynamic of the turbulent jets to ensure the stabilisation of this massive diluted combustion regime. The second part of this study concerns the use of hydrogen as fuel in the pilot furnace operating in flameless combustion regime. The main characteristics of this combustion regime have been found again: high efficiency and very low pollutant emissions (CO and NOx) associated to CO2 emissions reduction while increasing content of hydrogen in the fuel. With pure hydrogen and without air preheating, the furnace produces no carbon-species and nearly no NOx, condition close to a “zero-emission” furnace.
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