Os ânions inorgânicos nitrato (NO3-) e nitrito (NO2-) por muito tempo foram considerados produtos finais inertes do metabolismo do óxido nítrico (NO) e constituintes indesejáveis da dieta. Entretanto, é crescente o interesse das potenciais reações que podem se processar em meio fisiológico e, que envolvem especialmente o íon nitrito mediadas por complexos de metais de transição. Ferro-heme presente em proteínas como a mioglobina podem formar complexos porfirínicos com NO, gerando espécies que podem atuar principalmente como catalisadores em diversas vias biológicos importantes. Complexos com NOx coordenado a ferro-heme estão envolvidos tanto no processo da cura da carne (pigmentação da carne), como em processos redox, nos quais são capazes de oxidar substratos indiretamente pela produção de espécies reativas ou diretamente por reações de transferência de átomo de oxigênio (TAO). Os lipídeos, constituintes celulares fundamentais na composição de membranas e lipoproteínas, podem servir como substratos para essas reações e, sua oxidação pode ocasionar danos ao organismo. Tióis, importantes antioxidantes e constituintes de proteínas, também podem participar desse tipo de reações e, conseqüentemente gerar danos ao organismo. Considerando que o mecanismo e os parâmetros cinéticos e termodinâmicos destas reações ainda não foram completamente estabelecidos para explicar a vasta funcionalidade destes complexos, o presente projeto de pesquisa visa proporcionar um melhor conhecimento das reações redox envolvendo NOx e mediadas por porfirinas de ferro em alimentos e sistemas biológicos. / For long time, the anions nitrate (NO3-) and nitrite (NO2-) were considered inert end products of nitric oxide (NO) metabolism and undesirable constituents of the diet. Currently, there is an increasing interest for potential reactions which may occur in physiological conditions involving specially the nitrite ion and mediated by transition metal complexes. Heme NOx iron complexes are involved in meat curing process (meat pigmentation) and are able to oxidize substrates indirectly generating reactive species or directly by oxygen atom transfer reactions (OAT). Lipids, fundamental cellular constituents of membranes and lipoproteins, and thiols, important antioxidants and protein constituents, may serve as substrates to OAT and their oxidation may promote damage to the organism Considering that the mechanism and kinetic and thermodinamic parameters of these reaction have not yet been fully elucidated to explain the varied functionality of these complexes, the present research project aim to bring a better understanding of redox reactions involving NOx mediated by iron porphyrins in foods and biological systems. Thiols, important antioxidants and protein constituents, may serve as substrates to OAT and their oxidation may promote damage to the organism. The present work aims to bring a better understanding of the mechanism, kinetic and thermodynamic parameters of the reaction involving nitrite mediated by iron-porphyrins in food and biological systems.

Control of pollutants and emissions has become a major factor in the design of modern combustion systems. The “Liquid Hydrogen Fueled Aircraft - System Analysis” project funded in 2000 by the European Commission can be seen as such an initiative. Within the framework of this project, the Aachen University of Applied Sciences developed experimentally the “Micromix” hydrogen combustion principle and implemented it successfully in the Honeywell APU GTCP 36-300 gas turbine engine. Lowering the reaction temperature, eliminating hot spots from the reaction zone and keeping the time available for the formation of NOx to a minimum are the prime drivers towards NOx reduction. The “Micromix” hydrogen combustion principle meets those requirements by minimizing the flame temperature working at small equivalence ratios, improving the mixing by means of Jets In Cross-Flow and reducing the residence time in adopting a combustor geometry that provides a very large number of very small diffusion flames. In terms of pollutant emissions, compared to the unconverted APU, an essential reduction in emitted NOx was observed, stressing the potential of this innovative burning principle.<p>The objective of this thesis is to investigate the “Micromix” hydrogen combustion principle with the ultimate goal of an improved prediction during the design process. Due to the complex interrelation of chemical kinetics and flow dynamics, the “Micromixing” was analyzed first. Stereoscopic Particle Image Velocimetry was used to provide insight into the mixing process. A “simplified” set-up, that allowed to investigate the flow characteristics in great detail while retaining the same local characteristics of its “real” counterparts, was considered. The driving vortical structures were identified. To further investigate the physics involved and to extend the experimental results, numerical computations were carried out on the same “simplified” set-up as on a literature test case. In general, a number of physical issues were clarified. In particular, the interaction between the different vortical structures was looked into, and a kinematically consistent vortex model is proposed. After demonstrating the development of the mixing, the “cold flow” study was extended to a single injector. The double backward-facing step injector geometry was addressed experimentally and numerically. At design geometry, the flow appeared to behave single backward-facing like, with respect to the first gradation. In terms of varying step configurations, the flow was seen to be dependent on the periodic perturbation arising from the graded series of backward-facing steps. During the second part of the investigation, the “hot flow” was analyzed. Considering combustor similar operating conditions, a test burner was experimented on an atmospheric test rig. NOx emissions were traced by exhaust gas analysis for different working conditions. Particular flame patterns, such as a regular attached flame as well as lifted flames were observed. In parallel with the experimental work, numerical computations on a pair of opposite injectors, permitted to classify the combustion regime and the main factors involved in the NOx formation. Accordingly, NOx emission enhancing design changes are proposed. Finally, the demanding computational effort, worthy of acceptance for academic purposes, is found not agreeable as future design tool and improvements to speed up the design process are projected.<p> / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

The objective of the presented diploma thesis is reduction of nitrogen oxides from the flue gas stream on catalyst under non-standart conditions. Emphasis is places on the description of selected pollutants in flue gas (especially nitrogen oxides), legislative requirements for air protection and technologies for removal of nitrogen oxides, expecially methods of selective catalytic and non-catalytic reduction. The practical part is devoted to the reduction of nitrogen oxides by selective catalytic reduction on a pilot plant INTEQ II in the laboratory NETME Center. The subject of interest is the determination of the NOx reduction efficiency depend on the temperature for selected catalyst. The end of the practical part pursues with comparison of measurement results and their evaluation.

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.

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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According to the World Health Organization, urban air pollution is a high public health priority due its linkage to cardio-pulmonary disease and association with increased mortality and morbidity (1, 2). Additionally, air pollution impacts climate change, visibility, and ecosystem health. The development of effective strategies for improving air quality requires accurate estimates of air pollutant emissions. In response to the need for new approaches to measuring emissions, we have designed a mobile Flux Lab for the Atmospheric Measurement of Emissions (FLAME) that applies a proven, science-based method known as eddy covariance for the direct quantification of anthropogenic emissions to the atmosphere. The mobile flux lab is a tool with novel, multifaceted abilities to assess air quality and improve the fidelity of emission inventories. Measurements of air pollutant concentrations in multiple locations at the neighborhood scale can provide much greater spatial resolution for population exposure assessments. The lab's mobility allows it to target specific sources, and plumes from these can be analyzed to determine emission factors. Through eddy covariance, the lab provides the new ability to directly measure emissions of a suite of air pollutants. We have deployed the FLAME to three different settings: a rural Appalachian town where coal transport is the dominant industry; schools in the medium-sized city of Roanoke, Virginia; and the large urban areas around Norfolk, Virginia, to measure neighborhood-scale emissions of air pollution. These areas routinely experience high ozone and particulate matter concentrations and include a diverse array of residential neighborhoods and industries. The FLAME is able to capture emissions from all ground-based sources, such as motor vehicles, rail and barge traffic, refuse fires and refueling stations, for which no direct measurement method has been available previously. Experiments focus on carbon dioxide (CO₂), the principal greenhouse gas responsible for climate change; nitrogen oxides (NOx), a key ingredient in ground-level ozone and acid rain; volatile organic compounds (VOCs), a second key ingredient in ozone and many of which are air toxics; and fine particulate matter (PM2.5), a cause of mortality, decreased visibility, and climate change. This research provides some of the first measurements of neighborhood-scale anthropogenic emissions of CO₂, NOx, VOCs and PM2.5 and as a result, the first opportunity to validate official emission inventories directly. The results indicate that a mobile eddy covariance system can be used successfully to measure fluxes of multiple pollutants in a variety of urban settings. With certain pollutants in certain locations, flux measurements confirmed inventories, but in others, they disagreed by factors of up to five, suggesting that parts of the inventory may be severely over- or underestimated. Over the scale of a few kilometers within a city, emissions were highly heterogeneous in both space and time. FLAME-based measurements also confirmed published emission factors from coal barges and showed that idling vehicles are the dominant source of emissions of air toxics around seven schools in southwest Virginia. Measurements from this study corroborate existing emission inventories of CO₂ and NOx and suggest that inventories of PM2.5 may be overestimated. Despite the tremendous spatial and temporal variability in emissions found in dense urban areas, CO₂ fluxes on average are very similar across the areas in this study and other urban areas in the developed world. Nevertheless, the high level of variability in spatial and temporal patterns of emissions presents a challenge to air quality modelers. The finding that emissions from idling vehicles at schools are likely responsible for creating hot spots of air toxics adds to the urgency of implementing no-idling and other rules to reduce the exposure of children to such pollutants. Ultimately, the results of this study can be used in combination with knowledge from existing emission inventories to improve the science and policies surrounding air pollution. / Ph. D.

This thesis discusses findings gained through work with the NOx abatement system at Radford Facility and Army Ammunition Plant (RFAAP). Removal of harmful substances from flue-gas emissions has garnered increased priority in the chemical industry in preceding decades, as governmental restrictions on these substances become more stringent and as national awareness concerning environmental quality and resource utilization continues to grow. These reasons make the study of NOx abatement an important and challenging endeavor. This work concerns itself specifically with reduction of NOx in flue-gas emissions from stationary sources. First we present an overview of current technology and approaches to controlling NOx for stationary sources. Next, we focus in on one particular approach to control of NOx within the context of a case study of the technology used at the Radford Facility and Army Ammunition Plant. RFAAP employs a scrubber/absorber tower followed in series by a selective catalytic reduction (SCR) reaction vessel in their NOx abatement system. We use as the method of study computer simulations within ASPEN Plus, a process simulation software package for chemical plants. We develop three different models with which to characterize NOx abatement at RFAAP, a conversion model, an equilibrium model and a kinetic model. The conversion-reaction model approximates the absorption and SCR reactions with constant percentage extent-of-reaction values. Though useful for initial investigation and mass balance information, we find the conversion model's insensitivity to process changes to be unacceptable for in-depth study of the case of NOx absorption and SCR. The equilibrium-reaction model works on the assumption that all the reactions reach chemical equilibrium. For the conditions studied here, we find the equilibrium model accurately simulates NOx absorption but fails in the case of SCR. Therefore, we introduce a kinetic-reaction model to handle the SCR. The SCR reactions prove to be highly rate-dependant and the kinetic approach performs well. The final evolution of the ASPEN Plus simulation uses an equilibrium model for the absorption operation and a kinetic model for the SCR. We explore retrofit options using this combined model and propose process improvements. We end this work with observations of the entire project in the form of conclusions and recommendations for improving the operation of the NOx abatement system through process-parameter optimization and equipment-retrofit schemes. By leading the reader through the process by which we arrived at a successful and highly informative computer model for NOx absorption and SCR, we hope to educate the reader on the subtleties of NOx abatement by absorption and SCR. We attempt to break down the numerous complex processes to present a less daunting prospect to the engineer challenged with the application of current NOx removal technology. In addition, we introduce the reader to the power and usefulness of computer modeling in instances of such complexity. The model teaches us about the details of the process and helps us develop concrete information for its optimization. Ideally, the reader could use a similar approach in tackling related operations and not confine the usefulness of this thesis to NOx absorption and SCR. The audiences that we think would benefit from exposure to this thesis are the following: • Environmental engineers with a NOx problem; • Process engineers interested in optimization tools; • Design engineers exploring flue-gas treatment options; • Combustion engineer desiring to learn about SCR; • Chemists and mathematicians intrigued by the complexities of NOx absorption chemistry. / Master of Science

Como consecuencia de las exigentes legislaciones medioambientales actualmente en vigor, como las Euro Emission Standards en Europa, los investigadores e ingenieros se ven forzados a "re-desarrollar" el proceso de combustión diésel para hacerlo menos contaminante. Uno de los principales contaminantes y más dañinos para la salud son los óxidos de nitrógeno (NOx) que están principalmente compuestos por: monóxido de nitrógeno (NO), dióxido de nitrógeno (NO2) y trióxido de dinitrógeno (N2O3). Centrándose en los NOx generados en una combustión diésel, una de las técnicas más populares para mitigar su formación es mediante la dilución de la corriente oxidante con productos de la combustión, previamente generados. De este modo, al reducir la reactividad de la corriente oxidante se consigue una disminución considerable de la temperatura de combustión y por extensión de los NOx. Sin embargo, dicha técnica causa nuevas interacciones físico-químicas entre los hidrocarburos y los NOx así como principalmente un notable cambio en la estructura del chorro diésel. Es por ello necesario considerar las diferentes vías de formación de éstos para poder predecir su generación. El hecho de considerar las diferentes vías de formación implica un incremento considerable de los recursos computacionales destinados a realizar las simulaciones, siendo en algunos casos inviable. Es por ello que el objetivo principal de esta tesis consiste en: desarrollar herramientas capaces de tener en consideración todas estas vías sin incrementar de manera considerable el coste computacional. Para ello inicialmente se realiza una exhaustiva revisión bibliográfica en donde se repasan las diferentes herramientas desarrolladas para la predicción de los NOx y se analizan sus puntos débiles. Éstos radican en simplificaciones de dudosa validez, que solamente tienen efectos positivos a altas y no a bajas temperaturas, o bien procesos demasiado tediosos y complejos para caracterizar los diferentes estados de una combustión. Posteriormente se diseña una metodología capaz de satisfacer el objetivo principal, basada en tres estudios. El primero permite profundizar en el proceso de formación de este contaminante a través de estudiar el incremento de la proporción de NO2 en los NOx debido a la recirculación masiva de estos productos. Por otro lado, los otros dos consisten en desarrollar diversas herramientas predictivas centradas exclusivamente en el NO, ya que como se dedujo del estudio anterior el NO2 se forma principalmente a partir del NO a través de un proceso de enfriamiento. La primera de estas herramientas está basada en una correlación empírica que a modo de ecuación correctiva mejora la capacidad predictiva, especialmente en condiciones de recirculación masiva, del mecanismo más implementado mundialmente, mientras que la segunda se sustenta en tabular únicamente la velocidad de formación del NO y el NO en equilibrio en función de la temperatura y de la cantidad de oxígeno disponible inicialmente para reaccionar. Finalmente para poder llevar a cabo estos estudios y cumplir con el objetivo principal se hace uso de un software comercial cinético-químico Chemkin, en su versión Professional, que sirve tanto de herramienta desarrolladora como de referencia. / Redón Lurbe, P. (2013). Modeling of the nitrogen oxides formation process applicable to several diesel combustion modes [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/33183

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