Universiẗat, Diss., 2001--Heidelberg.

Cette étude présente la caractérisation de catalyseurs deNOx ou deN2O en termes d’une relation structure-propriétés. Ceci afin de comprendre les interactions intervenant entre les catalyseurs et les espèces gazeuses présentes dans le système étudié et d’aider à la formulation de ces matériaux. Cette modélisation est réalisée par l’approche LSER (Linear Solvation Energy Relationship), qui permet de mettre en avant les interactions (polaire, acido-basique…) entrant en jeu lors du processus d’adsorption de composés à la surface des matériaux. Ces études montrent que l’approche LSER permet de suivre l’évolution de la surface des catalyseurs après différents traitements comme l’ajout de phases actives. La comparaison des affinités catalyseur-composés gazeux permet de mettre en avant les différences observées au niveau des équations LSER, principalement pour l’évolution de la polarité, la basicité et l’acidité, paramètres qui sont fortement impliqués lors de l’adsorption d’aromatiques, d’alcools ou d’eau par exemple. Cette méthode permet également de mettre en avant certaines étapes clefs des différents processus d’élimination des NOx ou N2O, étapes qui varient en fonction du processus, tel que la forte adsorption des réducteurs sur le catalyseur pour le deNOx charbon alors que le même effet entraine des performances plus faibles dans le cas du deN2O. La méthode LSER, qui constitue une approche thermodynamique, ouvre une voie et est un moyen supplémentaire dans la compréhension des phénomènes intervenants dans les processus de catalyse deNOx et deN2O ; et montre que les phénomènes d’adsorption ne sont pas, selon les cas, prépondérants dans les performances des catalyseurs / This study presents the characterisation of deNOx and deN2O catalysts in terms of structure-properties relationship in order to understand the different interactions involved between catalysts and gaseous species present in the system and to contribute to the formulation of these materials. The LSER modelisation (Linear Solvation Energy Relationship) allows us to prove the interactions involve during the adsorption process of compounds at the surface. The evolution of the catalyst’s surface after different treatments is following by the LSER approach. The comparison of the affinity proves the differences observed in the LSER equations: especially the polarity, basicity and acidity terms, implicated in aromatics, alcohol and water adsorption. This method shows differences between different steps in the processes of NOx and N2O elimination (as the strong adsorption of reducers on the catalyst for the coal-deNOx, whereas the same effect involves weaker performances in the case of the deN2O. The LSER method which consists in a thermodynamic approach, is a new useful technique for the understanding of the phenomenon involved in the deNOx and deN2O catalysis processes. It also demonstrates that the adsorption processes are not so important in the catalysts performances

Afin de limiter les rejets de polluants dans l’atmosphère par les véhicules, les normes Euro ont été mises en place en Europe à partir des années 1990. Ces normes sont de plus en plus strictes. Par exemple, pour les cas des poids lourds, le maximum d’émission des NOx a été divisé par cinq lors du passage Euro V (2009) à Euro VI (2014). Parallèlement à cela, certaines flottes captives de poids lourds roulent au 100 % biodiesel. Or, ce carburant contient des minéraux (Na, K, P) qui peuvent interagir avec la ligne de dépollution des gaz d’échappement.Dans ces travaux, l’étude a porté sur l’impact de Na et P déposés séparément ou simultanément sur des catalyseurs de réduction catalytique sélective des oxydes d’azote par l’ammoniac (NH3-SCR) à base de zéolithe Ferrierite (FER) contenant du cuivre.En mettant en relation les activités catalytiques en NH3-SCR et les différentes caractérisations mises en œuvre avant et après ajout des minéraux, il a été conclu que l’ajout de sodium entrainait une perte d’activité à basse température (< 300 °C) liée à l’empoisonnement des sites acides du catalyseur, et que la perte d’activité à haute température (> 450 °C) est liée à la formation de CuO. Cette formation de CuO est due à un échange entre le cuivre et le sodium lors de l’empoisonnement par voie aqueuse. Pour l’empoisonnement au phosphore, la désactivation à basse température (< 300 °C) apparait liée à une interaction entre le cuivre et le phosphore. Cette interaction entraine une augmentation de la température de réduction du cuivre. L’ajout simultané de sodium et phosphore entraine une désactivation des catalyseurs plutôt similaire à celle du phosphore qu’à celle du sodium. / In order to decrease the air pollution due to vehicles, European legislation have been implemented since the 90’s. The European norm are stricter. For example, the NOx emissions limit for trucks were divided by five between Euro V (2009) and Euro VI (2014). In parallel, some trucks use exclusively 100 % biodiesel. Unfortunately, biodiesel contains some minerals (Na, K, P) with can interact with the exhaust gas post-treatment system.This work presents the impact of Na and/or P deposits on Selective Catalytic Reduction catalysts with dedicated to the NH3-SCR process, based on copper/Ferrierite (FER).By combining the results of NH3-SCR catalytic activity and characterisations before and after adding minerals, the main parameters of deactivation were highlighted. Sodium deactivation at low temperature (< 300 °C) is due to the decrease of acidity. The deactivation at high temperature (> 450 °C) is due to the formation of copper oxide when sodium was added in water. This formation of CuO results of an exchange of Na and Cu in the exchange positions of the zeolite. Phosphorous addition mainly leads to a catalytic deactivation at low temperature (< 300 °C), the deactivation seems to be link to Cu-P interaction. This interaction leads to the increase of the reduction temperature of copper. Overall, the simultaneous addition of sodium and phosphorous leads to a decrease of catalytic activity similar to the one with phosphorous alone.

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.

<p>Waste appears to be a low-cost fuel compared to biofuel. This Masters thesis was conducted for Vattenfall Utveckling AB and deals with how waste in the fuel affects the performance of a SCR-catalyst. Different mechanisms of deactivation were surveyed, focusing on the poisoning mechanism. A literature study was carried out, which was used as a reference when analysing the results.</p><p>Small samples (9x2x2 cm, 64 pieces) cut out from a full-scale unused honeycomb catalyst were exposed up to 1500h in two different combustion plants, Johannes in Gävle (co-combustion) and Högdalen in Stockholm (waste-combustion). The activity was measured mainly at 300°C but also at 250, 350, 375 and 400°C. SEM/EDS-analysis (about 20 samples) and wet chemical analysis (about 20 samples + 2 fly-ash samples) was then performed on the samples. A sample from each boiler was sent for BETanalysis.</p><p>The results from the analysis above were compared to earlier studies conducted on bio-fuel plants in order to investigate what might have deactivated the catalyst samples. Also a small multivariate data analysis (MVDA) was performed. The results from the study show that the catalyst samples exposed in Johannes have slightly less than 60 % of the activity left after 1500h, for Högdalen only 20 % of the activity remains after 1500h. For Johannes when only firing biofuel the corresponding figure is 74 % and in a coal-fired boiler just over 80 % of the activity remains after 1500h. For catalysts with a higher initial activity the deactivation rate is slower. The main mechanism of deactivation is poisoning from alkali metals. In Johannes the poisoning is mainly due to water-soluble potassium. In Högdalen water-soluble potassium, sodium and acid soluble lead causes the deactivation. Potassium stands for just over half of the poisoning effect, sodium just over 1/3 and lead for less than 1/6. SEM/EDS-analysis shows that the potassium content is about 3 times higher the first centimetre from the inlet, than the rest of the sample. The difference in potassiumconcentration between the surface and the walls of the catalyst is rather small. The concentration of lead on the other hand was found to be constant along the catalyst, but the concentration on the surface is much higher than in the walls. Erosion, sintering and plugging have not been studied in detail. Erosion tends to be a bigger problem in Johannes than in Högdalen, probably due to the texture of the fly ash. It does not seem to be any risk of sintering where the test-bench was exposed. For Johannes plugging was estimated to affect around 25 % of the channels in the samples after 1000h of exposure. Solely exposure for fly ash wasn’t found to affect the activity significantly.</p> / <p>Avfall framstår som ett billigt bränsle jämfört med biobränsle. Detta examensarbete utfördes åt Vattenfall Utveckling AB och studerar hur prestanda för katalysatorn i en SCR-anläggning (för NOx-rening) påverkas vid inblandning av avfall i bränslet. Olika deaktiveringsmekanismer kartlades, med en tyngdpunkt på mekanismen förgiftning. Även en litteraturstudie genomfördes, för att användas som referens vid resultatanalysen.</p><p>Små provbitar (9x2x2 cm, 64 stycken) utsågade ur en fullskalig oanvänd honeycombkatalysator exponerades upp till 1500h i två anläggningar, Johannes i Gävle (sameldning) samt Högdalen i Stockholm (avfallseldning). Aktiviteten mättes, därefter gjordes SEM/EDS-analyser (cirka 20 prov) och våtkemiska analyser (cirka 20 prov + 2 stycken flygaska). Ett prov från varje panna skickades på BET-analys. Analyserna ovan jämfördes med tidigare studier utförda på biobränsleeldade anläggningar för att ta reda på vad som kan ha deaktiverat katalysatorerna. Även en mindre multivariat dataanalys (MVDA) utfördes.</p><p>Resultat från studien är bland annat att katalysatorproven exponerade i Johannes har knappt 60 % av aktiviteten kvar efter 1500h, för Högdalen är motsvarande siffra runt 20 %. Det kan jämföras med 74 % för Johannes om bara biobränsle eldas och drygt 80 % för katalysatorer i en koleldad panna efter samma exponeringstid. Katalysatorer med en högre begynnelseaktivitet deaktiverades långsammare. Den huvudsakliga deaktiveringsmekanismen är alkaliförgiftning. I Johannes beror förgiftningen främst av vattenlösligt kalium. I Högdalen sker förgiftningen sannolikt av både vattenlösligt kalium och natrium, samt syralösligt bly. Av förgiftningen i Högdalen står kalium för lite drygt hälften, natrium för drygt 1/3 och blyet för resten. SEM/EDS-analyserna visade att kalium finns i cirka 3 gånger så hög koncentration den första centimetern från inloppet på proverna för att sedan bli ganska konstant. Det är ingen större skillnad i kaliumkoncentration på ytorna eller i väggarna. För bly är koncentrationen mer jämn i längdled, men i väggarna avsevärt lägre halter än på ytorna. Erosion, sintring och igensättning har inte studerats utförligt. Vad som kan sägas är att erosionen verkar vara ett större problem i Johannes än i Högdalen, troligen på grund av annan textur på flygaskan. Det verkar inte föreligga någon risk för sintring vid platsen för exponeringen. Igensättningen uppskattades i Johannes till 25 % av kanalerna i proverna efter 1000h exponering. Exponering för enbart flygaska i 500h påverkade inte aktiviteten signifikant.</p>

Waste appears to be a low-cost fuel compared to biofuel. This Masters thesis was conducted for Vattenfall Utveckling AB and deals with how waste in the fuel affects the performance of a SCR-catalyst. Different mechanisms of deactivation were surveyed, focusing on the poisoning mechanism. A literature study was carried out, which was used as a reference when analysing the results. Small samples (9x2x2 cm, 64 pieces) cut out from a full-scale unused honeycomb catalyst were exposed up to 1500h in two different combustion plants, Johannes in Gävle (co-combustion) and Högdalen in Stockholm (waste-combustion). The activity was measured mainly at 300°C but also at 250, 350, 375 and 400°C. SEM/EDS-analysis (about 20 samples) and wet chemical analysis (about 20 samples + 2 fly-ash samples) was then performed on the samples. A sample from each boiler was sent for BETanalysis. The results from the analysis above were compared to earlier studies conducted on bio-fuel plants in order to investigate what might have deactivated the catalyst samples. Also a small multivariate data analysis (MVDA) was performed. The results from the study show that the catalyst samples exposed in Johannes have slightly less than 60 % of the activity left after 1500h, for Högdalen only 20 % of the activity remains after 1500h. For Johannes when only firing biofuel the corresponding figure is 74 % and in a coal-fired boiler just over 80 % of the activity remains after 1500h. For catalysts with a higher initial activity the deactivation rate is slower. The main mechanism of deactivation is poisoning from alkali metals. In Johannes the poisoning is mainly due to water-soluble potassium. In Högdalen water-soluble potassium, sodium and acid soluble lead causes the deactivation. Potassium stands for just over half of the poisoning effect, sodium just over 1/3 and lead for less than 1/6. SEM/EDS-analysis shows that the potassium content is about 3 times higher the first centimetre from the inlet, than the rest of the sample. The difference in potassiumconcentration between the surface and the walls of the catalyst is rather small. The concentration of lead on the other hand was found to be constant along the catalyst, but the concentration on the surface is much higher than in the walls. Erosion, sintering and plugging have not been studied in detail. Erosion tends to be a bigger problem in Johannes than in Högdalen, probably due to the texture of the fly ash. It does not seem to be any risk of sintering where the test-bench was exposed. For Johannes plugging was estimated to affect around 25 % of the channels in the samples after 1000h of exposure. Solely exposure for fly ash wasn’t found to affect the activity significantly. / Avfall framstår som ett billigt bränsle jämfört med biobränsle. Detta examensarbete utfördes åt Vattenfall Utveckling AB och studerar hur prestanda för katalysatorn i en SCR-anläggning (för NOx-rening) påverkas vid inblandning av avfall i bränslet. Olika deaktiveringsmekanismer kartlades, med en tyngdpunkt på mekanismen förgiftning. Även en litteraturstudie genomfördes, för att användas som referens vid resultatanalysen. Små provbitar (9x2x2 cm, 64 stycken) utsågade ur en fullskalig oanvänd honeycombkatalysator exponerades upp till 1500h i två anläggningar, Johannes i Gävle (sameldning) samt Högdalen i Stockholm (avfallseldning). Aktiviteten mättes, därefter gjordes SEM/EDS-analyser (cirka 20 prov) och våtkemiska analyser (cirka 20 prov + 2 stycken flygaska). Ett prov från varje panna skickades på BET-analys. Analyserna ovan jämfördes med tidigare studier utförda på biobränsleeldade anläggningar för att ta reda på vad som kan ha deaktiverat katalysatorerna. Även en mindre multivariat dataanalys (MVDA) utfördes. Resultat från studien är bland annat att katalysatorproven exponerade i Johannes har knappt 60 % av aktiviteten kvar efter 1500h, för Högdalen är motsvarande siffra runt 20 %. Det kan jämföras med 74 % för Johannes om bara biobränsle eldas och drygt 80 % för katalysatorer i en koleldad panna efter samma exponeringstid. Katalysatorer med en högre begynnelseaktivitet deaktiverades långsammare. Den huvudsakliga deaktiveringsmekanismen är alkaliförgiftning. I Johannes beror förgiftningen främst av vattenlösligt kalium. I Högdalen sker förgiftningen sannolikt av både vattenlösligt kalium och natrium, samt syralösligt bly. Av förgiftningen i Högdalen står kalium för lite drygt hälften, natrium för drygt 1/3 och blyet för resten. SEM/EDS-analyserna visade att kalium finns i cirka 3 gånger så hög koncentration den första centimetern från inloppet på proverna för att sedan bli ganska konstant. Det är ingen större skillnad i kaliumkoncentration på ytorna eller i väggarna. För bly är koncentrationen mer jämn i längdled, men i väggarna avsevärt lägre halter än på ytorna. Erosion, sintring och igensättning har inte studerats utförligt. Vad som kan sägas är att erosionen verkar vara ett större problem i Johannes än i Högdalen, troligen på grund av annan textur på flygaskan. Det verkar inte föreligga någon risk för sintring vid platsen för exponeringen. Igensättningen uppskattades i Johannes till 25 % av kanalerna i proverna efter 1000h exponering. Exponering för enbart flygaska i 500h påverkade inte aktiviteten signifikant.

La Réduction Catalytique Sélective des NOx par NH3 est un procédé efficace de dépollution des gaz. Cependant, pour une application sur véhicules Diesel, l'activité à basse température (175-250°C, phase de démarrage du véhicule) reste limitée. De plus, les catalyseurs de NH3-SCR sont sensibles au rapport NO2/NOx, avec un optimum pour NO2/NOx = 0,5. Or, à basse température, la proportion de NO2 est faible car le catalyseur d’oxydation (DOC) placé en amont est également peu actif. L'éthanol (EtOH) est un autre réducteur possible, principalement avec des catalyseurs Ag/Al2O3. Ce système présente également d'une activité limitée à basse température, bien que l'oxydation de EtOH s'accompagne de la formation de NO2. Dans ces travaux, l'association de EtOH et NH3 pour la SCR de NO sur catalyseur Ag/Al2O3 a été étudié. Un effet de synergie a été obtenu, avec un gain important d'activité à basse température. Ce gain ne provient pas directement d'une réaction entre NH3 et EtOH ou ses sous-produits d'oxydation (CH3CHO, CO…), ni uniquement grâce à la réaction entre NO2 (formé par réaction de NO avec EtOH) et NH3. La caractérisation des espèces adsorbées par IRTF et des tests de (H2+NH3)-SCR ont permis de conclure que les espèces H*, provenant de la déshydrogénation de l'éthanol, réagissent avec les NOx pour conduire à des espèces HNOx très réactives avec NH3.Finalement, la mise en œuvre d'un double-lit (2%Ag/Al2O3 + catalyseur de NH3-SCR), afin d'utiliser NH3, NO et NO2 restants, a permis d'obtenir une conversion NOx comprise entre 46 et 95% entre 175 et 250°C. Ce système permet donc une conversion des NOx élevée à basse température en s'affranchissant du NO2 procuré par le DOC. / The NOx Selective Catalytic Reduction is an efficient process for exhaust gas treatment. However, for Diesel vehicles, the activity at low temperature (175-250°C, starting phase of vehicles) remains limited. In addition, the NH3-SCR catalysts are sensitive to the NO2/NOx ratio, with an optimum for NO2/NOx = 0.5. Unfortunately, at low temperature, the proportion of NO2 is low because the oxidation catalyst (DOC) placed upstream is also weakly efficient.Ethanol (EtOH) is another possible reductant, mainly associated with Ag/Al2O3 catalysts. This system also has a limited activity at low temperature, although the oxidation of EtOH is accompanied by NO2 formation. In this work, the association of EtOH and NH3 for the SCR of NO on a Ag/Al2O3 catalyst was studied. A synergistic effect was obtained, with a high gain of conversion at low temperature. This gain neither results from a reaction between NH3 and EtOH or its oxidation by-products (CH3CHO, CO…), nor only by the reaction between NO2 (formed by reaction of NO with EtOH) and NH3. Characterization of adsorbed species by FTIR and (H2+NH3)-SCR experiments led to the conclusion that H* species, resulting from ethanol dehydrogenation, react with NOx to yield HNOx species highly reactive with NH3.Finally, in order to use the remaining NH3, NO and NO2, the use of a dual bed (2%Ag/Al2O3 + NH3-SCR catalyst) allowed a NOx conversion between 46 and 95% from 175 to 250°C. This system consequently allows a high NOx conversion at low temperature, avoiding the NO2 lack at low temperature (low DOC activity).

This master's thesis deals with current situation of medical waste management in the Czech Republic and it also analyzes the quality of existing units for thermal treatment of the medical waste. In the second part of the thesis, available off-gas cleaning methods were described as well as the emission limits for waste incineration, which correspond to the legislative regulations effective in the Czech Republic. These emission limits are considered as input data for off-gas cleaning system design. In the main part of this thesis, two technological solutions of off-gas cleaning methods for Up-to-Date medical waste incineration unit were designed. The unit is designed for energy utilization of 1400 tons of medical waste accumulated during one year in a regional hospital of model region. From given input parameters, two appropriate apparatus concepts were created. After that, both concepts were evaluated either form energetic point of view as well as from material one. From these evaluations, key apparatuses of both concepts were designed which provided necessary design dimensions for further investment price estimation of each individual key apparatus. In the conclusion of this thesis, the best solution of an off-gas cleaning method was picked according to the comparison of operating and investment costs.

Thermal processing of wastes is a metod, when during combustion occur reduction of wastes till 10% previous volume. The main advantage of this method is possibility to heat utilization for heat and electric production. Through thermic process develops range of pollutants (NOx, CO, SO2, HCl, HF, PCDD/F) that had to be remove from off-gas or reduced to enviromental values in agreement with laws in force [16]. For this purpose are combustion units equip with range of devices for removing this pollutans. The main task of this diploma thesis is selectoin of ctirical device in term of pressure drops. The value of pressure drop stands significant part in proposition of efficiecy off-gas fan. In increase or decrease total pressure drop consumption of electrical energy of off-gas fan is rising or going down. Change of consumption in total classification is projecting in energy utilization rate of waste where is determinate if it stands of energy utilizatoin or just incineration. In first part of diploma thesis are described in detail availability methods of off-gas cleaning where is described their principle, advanteges, disadvatages and comparison of effectivity. In second part of diploma thesis is made example model about influnce technology on value of total pressure drop. There were chosen two technologies for removing dioxins (technology of catalytic filtration REMEDIA and DeNox/DeDiox). For both technologies were made detailed analysis of pressure drops single components of these technologies. Attainment results were compared and rated with one another. For analysis these two methods were designed mathematical process in software Maple 9.5.

This diploma thesis deals with the issue of nitrogen oxides emissions in exhaust gases and possibilities of their reduction. The task of the thesis was analysis of systems for NOX reduction by contemporary diesel engines, design and construction of NOX reduction device for given diesel engine, then verify functionality of this system compiled from commercially available components. In the last part of thesis available measurements will be made with an analysis of achieved results.