Cattle biomass (CB) has been proposed as a renewable, supplementary fuel for co-firing and reburning. Reburning coal with CB has the potential to reduce NOx and Hg emissions from coal fired systems. The present research focuses on three areas of combustion: 1) Biomass reburning experiments are conducted to determine the optimum operating conditions for the NOx reduction using blends of coal and CB as reburn fuels. 2) Since CB contains higher ash contents compared to coals, the fouling behavior is also investigated under the transient and short-time operation. 3) Finally CB contains higher Cl compared to coals, which oxidizes Hg to HgCl2. To understand the Hg oxidation behavior, a fundamental study of Hg oxidation in coal combustion is conducted using a plug flow reactor (PFR). The main parameters investigated are types of the reburn fuel, reburn equivalence ratios (ERRBZ), O2 concentrations in the reburn gas, injection angles of the reburn fuel, cross-sectional geometries of the reburn nozzles, symmetric and asymmetric reburn injections, reburn heat inputs, baseline NOx concentrations, and presence and absence of the heat exchangers (HEX). The results of reburning show that CB is a very effective fuel in NOx reduction, and the extent of NOx reduction is strongly dependent to the ERRBZ. The optimum conditions of the boiler operation for biomass reburning are as follows: ERRBZ = 1.1, 45° upward circular reburn nozzles, 12.5% O2 in the reburn gas, symmetric injection, and presence of HEXs. To make an effective reburn process, the baseline NOx concentrations must be higher than 230 g/GJ (0.5 lb/mmBTU) and the reburn heat input higher than 20%. The results of ash fouling show the presence of ash in the hotter region of the furnace seems to promote heat radiation thus augmenting the heat transfer to the HEX. The growth of the layer of ash depositions over longer periods typically lowers overall heat transfer coefficients. The addition of HCl to Hg containing gases in the PFR significantly increases Hg oxidations. The addition of NO inhibited the overall reaction and shifted the reaction temperature higher while the addition of O2 promoted Hg oxidations and lowered the reaction temperature. For heterogeneous cases, the use of the VWT catalyst promotes the reduction of Hg0 and shifted the reaction temperatures lower than those for homogeneous cases.

The emissions of nitrogen oxides (NOx) are a serious environmental problem due to its relationship with the formation of smog, acid rain and because they are dangerous for human and animal health. These gases are produced in high quantities in diesel engines used for automotive applications, and different strategies are being used to reduce them, among which are the Selective Catalytic Reduction (SCR) systems. For its operation, it is necessary a supply of ammonia as NOx reducing agent, but the inefficiency at low temperatures of the systems used nowadays has led to the conception of the solid ammonia storage units (ASS). Unfortunately, the materials currently used, i.e. metal halides, do not meet the ammonia supply requirements at low temperatures and have problems of swelling and agglomeration. In order to find a material with better properties for its application as an ammonia sorbent material, MgCl2 composites with different carbon materials (graphite, graphene, and SWCNTs) were prepared by direct mixing and wet impregnation methods, and characterized in this work. Despite the decrease of total storage capacity, improvements were found in thermal stability and mass retention, as well as in sorption and desorption kinetics, making these materials a first result towards the improvement of the solid ammonia storage units.

This study utilized Cu-catalysts to catalyze a NO reduction reaction using CH4 as a reductant. Due to CH4 being a weak reductant and is easily affected by O2 concentration, we undertook a series experiments with O2 concentration and promoters, so that we could better understand their influence. The experiment conditions were as follows : reaction temperature between 150¢J- 800¢J¡Fa catalysts weight of 0.5 g¡F total gas flow rate of 1000 ml/min¡Frelative humidity at 0.9 %¡Fan O2 concentration between 0 - 6%¡Fand CH4 concentration between 1000 - 10000 ppm. First, we sorted out the best metal carriers and calcining temperature, from this we decide to use £^-Al2O3 as a carrier with a calcining temperature under 500¢Jto produce our catalysts. During the O2 concentration experiment, when the inflow O2 concentration was below 1% (including 0% O2), Cu-catalysts reduce NO above 550¢J.The conversion reached a rate of 95 % at a temperature of 750¢J¡Fwhen the oxygen concentration was between 3% and 6% O2, catalysts reacted within 300 - 500¢J with NO converting to NO2¡Fat a concentration between 1.5% and 2% O2, NOx underwent reduction at 750¢J,and NOx conversion raised from 0 % to above 90%. Therefore in analyzing the experiment results, it shows that NOx will reduce violently when the O2 concentration is below 0.7% and while using CH4 as a reductant. This result was also apparent in O2 concentrations between 1.5 % and 2%. In the experiments of M/O ratio (the ratio of CH4 and O2 inflow), we found M/O ratio was not a deciding factor within the reaction mechanics, furthermore the limiting factor of O2 concentration decreases under 0.7%¡Fin addition it was also found that adding large amounts of CH4 could quicken the reduction process. Lastly, a mass balance was performed, which had a result over 70 %. In the experiments where Y¡BLa¡BSr¡BCo were added as promoters to the Cu-catalysts, we found that Cu-La/£^-Al2O3¡BCu-Sr/£^-Al2O3 and Cu-Co/£^-Al2O3 can accelerate O2 depletion. Henceforth, it is possible to deduce promoters will be a useful method in solving O2 limiting. In the comparison of metals loading methods, we found no difference in activity using separate-impregnation and co-impregnation methods, whereas in the BET and SEM co-impregnation experiments, there was a larger surface-area and dispersion.

The reaction mechanism for the Selective Catalytic Reduction (SCR) of NO by NH3 on V2O5 surface was simulated by means of density functional theory (DFT) calculations performed at B3LYP/6-31G** level. As the initiation reaction, ammonia activation on V2O5 was investigated. Coordinate driving calculations showed that ammonia is adsorbed on Br&oslash / nsted acidic V-OH site as NH4 + species by a nonactivated process with a relative energy of -23.6kcal/mol. Vibration frequencies were calculated as 1421, 1650, 2857 and 2900cm-1 for the optimized geometry, in agreement with the experimental literature. Transition state with a relative energy of -17.1kcal/mol was also obtained. At the end of the Lewis acidic ammonia interaction calculations, it was observed that ammonia is hardly adsorbed on the surface. Therefore, it is concluded that the SCR reaction is initiated more favorably by the Br&oslash / nsted acidic ammonia adsorption. As the second step of the SCR reaction, NO interaction with the preadsorbed NH4 + species was investigated. Accordingly, NO interaction results in the formation of gas phase NH2NO molecule with a relative energy difference of 6.4kcal/mol. For the rest of the reaction sequence, gas phase decomposition of NH2NO was considered. Firstly, one of the hydrogen atoms of NH2NO migrates to oxygen. It then isomerizes in the second step. After that, the reaction proceeds with the isomerization of the other hydrogen. Finally, a second hydrogen atom migration to the oxygen leads to the formation of N2 and H2O. Total relative energy for this reaction series was obtained as -60.12kcal/mol, in agreement with the literature.

Submitted by Edileide Reis (leyde-landy@hotmail.com) on 2013-04-23T13:25:50Z No. of bitstreams: 1 Rodrigo Albuquerque.pdf: 737432 bytes, checksum: 3351ed8449f3bb0f3c8410fe64500d25 (MD5) / Made available in DSpace on 2013-04-23T13:25:50Z (GMT). No. of bitstreams: 1 Rodrigo Albuquerque.pdf: 737432 bytes, checksum: 3351ed8449f3bb0f3c8410fe64500d25 (MD5) Previous issue date: 2006 / Recentemente, o desenvolvimento de tecnologias eficientes visando à redução dos óxidos de nitrogênio, em regeneradores de unidades de craqueamento catalítico em leito fluidizado, tem se tornado uma grande preocupação, devido aos rigorosos limites de emissão impostos pela legislação ambiental. Como a maioria das refinarias utiliza promotores de combustão, os catalisadores de redução devem operar em presença de monóxido de carbono e devem ser capazes de remover ambos os poluentes. Os óxidos metálicos suportados têm sido considerados como substituintes apropriados para os catalisadores à base de metais nobres. Entre eles, o cobre tem sido apontado como uma espécie ativa muito atrativa para a reação. Além disso, observou-se que a adição de um segundo metal melhora o desempenho catalítico dos materiais e que o suporte desempenha um papel importante na reação. Considerando estes aspectos, neste trabalho foi estudada a influência de diferentes suportes (ZrO2, CeO2 e ZrO2 -CeO2), no desempenho de catalisadores à base de cobre e ferro na redução catalítica de óxidos de nitrogênio usando monóxido de carbono como agente redutor. Os suportes foram preparados por técnicas de precipitação e os metais foram impregnados a partir de soluções de acetato de cobre e nitrato de ferro, seguido de calcinação a 450ºC. As amostras foram caracterizadas por análise química, análise térmica diferencial, termogravimetria, difração de raios X, medida de área superficial específica, espectroscopia por reflectância difusa na região do ultravioleta e visível, espectroscopia no infravermelho por transformadas de Fourier de monóxido de carbono quimissorvido, redução por hidrogênio à temperatura programada e espectroscopia fotoeletrônica de raios X. Os catalisadores foram avaliados, na faixa de 150 a 500ºC, na redução do óxido nítrico com monóxido de carbono. Observou-se que o suporte à base de zircônio era constituído das fases tetragonal e monoclínica e o óxido de cério da fase cúbica. Foi observado que o cério estabilizava a fase tetragonal do óxido de zircônio no suporte misto. Em todas as amostras, as áreas superficiais específicas foram próximas a 100 m2.g-1. Os resultados de XPS mostraram que o estado de oxidação do cobre era função do suporte usado. Entretanto, independente do suporte utilizado, a adição de ferro modificou as propriedades químicas do cobre favorecendo a formação de espécies mais redutíveis na superfície do catalisador. Os catalisadores contendo os dois metais mostraram-se mais ativos, seguidos por aqueles contendo ferro e cobre. O desempenho superior do catalisador bimetálico suportado em óxido de cério foi atribuído à capacidade dos metais em facilitar o ciclo redox, que ocorre durante a reação de redução do óxido nítrico com monóxido de carbono. / Salvador

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Environmentally friendly and efficiently produced energy from sustainable and renewable resources is of great importance. Carbon dioxide (CO2) and nitric oxides (NOx) are the main emissions of air-breathing gas turbines in power plants. Gas turbines of the power generation industry are normally fueled with liquid fuels, natural gas or syngas in changing qualities. Syngas can be produced by gasification processes in IGCC power plants and consist of varying percentages of the main fractions hydrogen (H2) and carbon monoxide (CO). CO2 emissions can be reduced by a decrease of the CO-share and an increase of the hydrogen-share in the syngas fuel, and by using pre-combustion carbon capture and sequestration (CCS) technology. For low NOx, current gas turbine combustion chamber technologies require diluents, a rather low H2 content and modifications of the combustor hardware. A feasible solution for low NOx hydrogen and syngas combustion in gas turbines is the Micromix principle developed at Aachen University of Applied Sciences. The goal of this doctoral thesis is the research on a Micromix combustor with increased power densities fueled with hydrogen-rich syngas with about 90% by volume hydrogen, and going up to 100% hydrogen in the fuel. Test burner experiments are used to characterize the combustion and emission properties of a multitude of key drivers. Based on this optimization with a variety of scaled model test burners, a prototype dual-fuel hydrogen/syngas Micromix combustor is designed and integrated into the annular combustion chamber of an industrial gas turbine. In the gas turbine, the performance characteristics of the prototype-combustor are investigated under real operational conditions with hydrogen-rich syngas and pure hydrogen. / Doctorat en Sciences de l'ingénieur et technologie / info:eu-repo/semantics/nonPublished

The stringent regulations of emission levels from heavy duty vehicles create a demand for new methods for reducing harmful emissions from diesel engines. This thesis deals with the modelling of the nitrogen oxide (NOx) emissions from heavy duty vehicles using a selective catalyst as an aftertreatment system, utilising ammonia (NH3) for its reduction. The process of the selective catalytic reduction (SCR) is nonlinear, since the result of the chemical reactions involved depends on the load operating point and the temperature. The purpose of this thesis is to investigate different methods for nonlinear system identification of SCR systems with control applications in mind. The main focus of the thesis is on finding suitable techniques for effective NOx reduction without the need of over dosage of ammonia. By using data collected from a simulator together with real measured data, new black-box identification techniques are developed. Scaling and convergence properties of the proposed algorithms are analysed theoretically. Some of the resulting models are used for controller development using e.g. feedback linearisation techniques, followed by validation in a simulator environment. The benefits of nonlinear modelling and control of the SCR system are highlighted in a comparison with control based on linear models of the system. Further, a multiple model approach is investigated for simultaneous control of NOx and tailpipe ammonia. The results indicate an improvement in terms of ammonia slip reduction in comparison with models that do not take the ammonia slip into account. Another approach to NOx reduction is achieved by controlling the SCR temperature using techniques developed for LPV systems. The results indicate a reduction of the accumulated NOx.

En la actualidad, la industria del transporte es la encargada de satisfacer las necesidades logísticas del mundo. Los combustibles fósiles continúan siendo la principal fuente de energía de esta industria, y el motor Diésel, una de las tecnologías principales en la transformación de la energía química de estos combustibles en energía mecánica a través del proceso de combustión. Asociado a este proceso de transformación de la energía, un conjunto de efectos indeseados como las emisiones contaminantes o los gases de efecto invernadero han hecho movilizar a la comunidad científica. Dicha comunidad, ha realizado importantes esfuerzos en la investigación de soluciones limpias y eficientes que ayuden a minimizar los efectos indeseados del uso del motor Diésel. Sumado a los esfuerzos en la investigación, diferentes organizaciones gubernamentales han generado normativas que regulan estas emisiones contaminantes y la industria del motor ha reaccionado integrando soluciones tecnológicas que han hecho evolucionar la configuración original del motor Diésel. Debido a razones principalmente geopolíticas, el desarrollo económico a nivel mundial no se ha dado de manera homogénea, y en la actualidad, existe una disparidad global en cuanto a las exigencias en normativa de emisiones y la implementación de tecnologías para su control, siendo estas afectadas principalmente por sus costos. Es en este contexto donde se enmarca esta tesis doctoral, cuyo objetivo principal es el estudio de diferentes estrategias de inyección y de renovación de la carga como herramienta de control de emisiones en motores de encendido por compresión, teniendo en cuenta el costo de su integración. Se busca poder definir los límites de estas estrategias de bajo costo, determinando así su potencial real en la futura normativa de los mercados emergentes. Para abordar dicho objetivo, la tesis se ha desarrollado en tres etapas. En la primera, se ha realizado una aproximación teórico-experimental a las estrategias de inyección mediante modelado 3D-CFD y ensayos paramétricos en motor que permiten establecer como los parámetros de inyección responden al objetivo planteado. En la segunda etapa, se han estudiado las estrategias de renovación de la carga. Primero desde el modelado 1D para luego su posterior evaluación mediante su ensayo experimental en motor definiendo de esta manera las ventajas e inconvenientes de cada estrategia. En la tercera y última etapa, se han combinado todas las estrategias previamente estudiadas desde una aproximación experimental. De esta manera se puede alcanzar el objetivo de la tesis doctoral donde se ha comprobado la viabilidad de estas estrategias de bajo costo y se ha determinado su verdadero potencial como herramientas de control de las emisiones contaminantes. / En l'actualitat, la indústria del transport és l'encarregada de satisfer les necessitats logístiques del món. Els combustibles fòssils continuen sent la principal font d'energia d'aquesta indústria, i el motor Diésel, una de les tecnologies principals en la transformació de l'energia química d'aquests combustibles en energia mecànica a través del procés de combustió. Associat a aquest procés de transformació de l'energia, un conjunt d'efectes indesitjats com les emissions contaminants o els gasos d'efecte hivernacle han fet mobilitzar a la comunitat científica. Aquesta comunitat, ha realitzat importants esforços en la recerca de solucions netes i eficients que ajuden a minimitzar els efectes indesitjats de l'ús del motor Diésel. Sumat als esforços en la recerca, diferents organitzacions governamentals han generat normatives que regulen aquestes emissions contaminants i la indústria del motor ha reaccionat integrant solucions tecnològiques que han fet evolucionar la configuració original del motor Diésel. A causa de raons principalment geopolítiques, el desenvolupament econòmic a nivell mundial no s'ha donat de manera homogènia, i en l'actualitat, existeix una disparitat global quant a les exigències en normativa d'emissions i la implementació de tecnologies per al seu control, sent aquestes afectades principalment pels seus costos. És en aquest context on s'emmarca aquesta tesi doctoral, que el seu objectiu principal és l'estudi de diferents estratègies d'injecció i de renovació de la càrrega com a eina de control d'emissions en motors d'encès per compressió, tenint en compte el cost de la seua integració. Se cerca poder definir els límits d'aquestes estratègies de baix cost, determinant així el seu potencial real en la futura normativa dels mercats emergents. Per a abordar dita objectiva, la tesi s'ha desenvolupat en tres etapes. En la primera, s'ha realitzat una aproximació teòric-experimental a les estratègies d'injecció mitjançant modelatge 3D-CFD i assajos paramètrics en motor que permeten establir com els paràmetres d'injecció responen a l'objectiu plantejat. En la segona etapa, s'han estudiat les estratègies de renovació de la càrrega. Primer des del modelatge 1D per a després la seua posterior avaluació mitjançant el seu assaig experimental en motor definint d'aquesta manera els avantatges i inconvenients de cada estratègia. En la tercera i última etapa, s'han combinat totes les estratègies prèviament estudiades des d'una aproximació experimental. D'aquesta manera es pot aconseguir l'objectiu de la tesi doctoral on s'ha comprovat la viabilitat d'aquestes estratègies de baix cost i s'ha determinat el seu vertader potencial com a eines de control de les emissions contaminants. / Nowadays, the transport industry is responsible for accomplish the world's logistics requirements. Fossil fuels continue to be the main source of energy for this industry, and the Diesel engine, one of the main technologies in the transformation of the chemical energy of these fuels into mechanical energy through combustion. Associated with this process of energy transformation, a set of undesired effects such as pollutant emissions or greenhouse gases have challenged the scientific community that has made significant research efforts aiming clean and efficient solutions. Added to the scientific community efforts, different governmental organizations have created regulations in order to control these pollutant emissions and the engine industry has reacted by integrating technological solutions that have evolved the original configuration of the Diesel engine. Due mainly to geopolitical reasons, economic development worldwide has not occurred in a homogeneous manner, and currently, there is a global disparity regarding the requirements in emission regulations and the implementation of technologies for their control, mainly driven by their costs. It is in this framework where is set this doctoral thesis, with the main objective to study different injection and air management strategies as a tool for emission control in compression ignition engines, taking into account the cost of their integration. The aim is to be able to define the limits of these low-cost strategies, thus determining their real potential in the future regulations of emerging markets. To address this objective, the thesis has been developed in three stages. In the first one, a theoretical-experimental approach to the injection strategies has been carried out using 3D-CFD modeling and parametric engine tests which allow us to establish how the injection parameters help to reach the depicted thesis objective. In the second stage, the air management strategies have been studied. First, from the 1D modeling point of view in order to select the best option for this platform, and later to proceed with the experimental validation of this selection. Through the described approach is possible defining the advantages and disadvantages of each air management strategy. In the third and final stage, all previously studied strategies have been combined from an experimental approach. In this way, the evaluation of these cost-effective strategies has been defined and the fully potential as a tool for emissions control has been determined thus the objective of the doctoral thesis could be achieved. / Estepa Ruiz, D. (2018). Study of different fuel injection and air management strategies as a tool for emissions control in a compression ignition engine (Diesel engine) [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/113076 / TESIS

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