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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

An experimental investigation of the urea-water decomposition and selective catalytic reduction (SCR) of nitric oxides with urea using V2O5-WO3-TiO2 catalyst.

Johar, Jasmeet Singh 01 November 2005 (has links)
Two flow reactor studies, using an electrically heated laminar flow reactor over Vanadia based (V2O5-WO3/TiO2) honeycomb catalyst, were performed at 1 atm pressure and various temperatures. The experiments were conducted using simulated exhaust gas compositions for different exhaust gases. A quartz tube was used in order to establish inert conditions inside the reactor. The experiments utilized a Fourier transform infrared (FTIR) spectrometer in order to perform both qualitative and quantitative analysis of the reaction products. Urea-water solution decomposition was investigated over V2O5-WO3/TiO2 catalyst over the entire SCR temperature range using the temperature controlled flow reactor. The solution was preheated and then injected into pure nitrogen (N2) stream. The decomposition experiments were conducted with a number of oxygen (O2) compositions (0, 1, 10, and 15%) over the temperature range of 227oC to 477oC. The study showed ammonia (NH3), carbon-dioxide (CO2) and nitric oxide (NO) as the major products of decomposition along with other products such as nitrous oxide (N2O) and nitrogen dioxide (NO2). The selective catalytic reduction (SCR) of nitric oxide (NO) with urea-water solution over V2O5-WO3/TiO2 catalyst using a laboratory laminar-flow reactor was investigated. Urea-water solution was injected at a temperature higher than the vaporization temperature of water and the flow reactor temperature was varied from 127oC to 477oC. A FTIR spectrometer was used to determine the concentrations of the product species. The major products of SCR reduction were NH3, NO and CO2 along with the presence of other minor products NO2 and N2O. NO removal of up to 87% was observed. The aim of the urea-water decomposition experiments was to study the decomposition process as close to the SCR configuration as possible. The aim of the SCR experiments was to delineate the effect of various parameters including reaction temperature and O2 concentration on the reduction process. The SCR investigation showed that changing parameter values significantly affected the NO removal, the residual NH3 concentration, the temperature of the maximum NO reduction, and the temperature of complete NH3 conversion. In the presence of O2, the reaction temperature for maximum NO reduction was 377?C for ratio of 1.0.
2

Performance and emissions study of diesel and waste biodiesel blends with nanosized CZA2 of high oxygen storage capacity

Pimenidou, Panagiota, Shanmugapriya, N., Shah, N. 29 November 2018 (has links)
Yes / In this work, the effect of the nanosized CZA2 (cerium-zirconium-aluminium) on the performance and emissions in a two- cylinder indirect injection (IDI) diesel engine, was studied. CZA2 was dispersed in diesel (D100) and waste cooking oil and tallow origin biodiesel-diesel blends (B10, B20, B30) and tested at different engine loads and constant speed. The nanocatalyst (CZA2) increased the brake specific fuel consumption (BSFC) and decreased the brake thermal efficiency (BTE, %) of all tested fuels, at all loads, except B20 at the lowest load. CZA2 reduced nitrogen oxides (NOx) from D100 at low and high engine loads, as well as carbon monoxide (CO) and unburned hydrocarbons (HC) at medium and high tested loads. The dispersion of CZA2 promoted the combustion of the biodiesel blends by almost eliminating HC while reducing NOx and CO emissions at various loads. Thermogravimetric analysis (TGA) coupled with Attenuated Total Reflectance- Fourier Transform Infrared (ATR-FTIR) spectroscopy revealed that the addition of CZA2 in diesel and biodiesel under pyrolysis and oxidation conditions resulted in the presence of saturated species like ketones and final oxidation products such as CO2, supporting their improved combustion and emissions’ reduction in the engine tests.
3

Redukce NOx ve spalinch / NOx reduction in flue gas

Rumnek, 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.
4

Snižování oxidů dusíku z proudu spalin na speciálních filtračních materiálech / Reduction of nitrogen oxides in flue gas on special filter materials

Sirový, 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.
5

Studies of urban air quality using electrochemical based sensor instruments

Popoola, Olalekan Abdul Muiz January 2012 (has links)
Poor air quality has been projected to be the world’s top cause of environmental premature mortality by 2050 surpassing poor sanitation and dirty water (IGBP / IGAC press release, 2012 ). One of the major challenges of air quality management is how to adequately quantify both the spatial and temporal variations of pollutants for the purpose of implementing necessary mitigation measures. The work described in this thesis aims to address this problem using novel electrochemical based air quality (AQ) sensors. These instruments are shown to provide cost effective, portable, reliable, indicative measurements for urban air quality assessment as well as for personal exposure studies. Three principal pollutants CO, NO and NO2 are simultaneously measured in each unit of the AQ instrument including temperature / RH measurements as well as GPS (for time and position) and GPRS for data transmission. Laboratory studies showed that the electrochemical sensor nodes can be highly sensitive, showing linear response during calibration tests at ppb level (0-160 ppb). The instrumental detection limits were found to be < 4 ppb (CO and NO) and < 1 ppb for NO2 with fast response time equivalent to t90 < 20 s. Several field studies were carried out involving deployment of both the mobile and static electrochemical sensor nodes. Results from some short-term studies in four different cities including Cambridge (UK), London (UK), Valencia (Spain) and Lagos (Nigeria) are presented. The measurements in these cities represent snapshot of the pollution levels, the stark contrast between the pollution level especially CO (mean mixing ratio of 16 ppm over 3 hrs) in Lagos and the other three cities is a reflection of the poor air quality in that part of the world. Results from long-term AQ monitoring using network of 46 static AQ sensors were used to characterise pollution in different environments ranging from urban to semi-urban and rural locations. By coupling meteorological information (wind measurements) with pollution data, pollution sources, and phenomena like the street canyon effect can be studied. Results from the long-term study also revealed that siting of the current fixed monitoring stations can fail to represent the actual air quality distribution and may therefore be unrepresentative. This work has shown the capability of electrochemical based AQ sensors in complementing the existing fixed site monitors thus demonstrating an emerging measurement paradigm for air quality monitoring and regulation, source attribution and human exposure studies.
6

Modélisation mathématique de la formation des NOx et de la volatilisation des métaux lourds lors de l'incinération sur grille d'ordures ménagères / Mathematical modelling of NOx formation and heavy metals volatilisation from MSW incineration on travelling grate

Asthana, Abhishek 06 May 2008 (has links)
Dans une optique de maîtrise du procédé d’incinération des ordures ménagères et de ses possibles émissions polluantes, nous avons développé un modèle mathématique qui simule un lit d’ordures ménagères en combustion sur une grille mobile. Ce modèle décrit la plupart des phénomènes physicochimiques et thermiques intervenant lors de l’incinération : séchage et pyrolyse de la charge, combustion et gazéification du carbone résiduel, transferts thermiques, effondrement du lit, brassage… Il intègre également une description des mécanismes de volatilisation des métaux lourds et de formation des NOx. La cinétique de départ des métaux lourds est modélisée en tenant compte des différentes étapes de transport (transfert externe, diffusion intraparticulaire, volatilisation) au moyen de l’approche des temps caractéristiques additifs. Dans le cas simulé du cadmium, la prédiction d’une volatilisation quasi-complète est conforme aux résultats de la littérature. Le sous-modèle NOx prend en compte les mécanismes de formation thermique, prompt, combustible, par l’intermédiaire de N2O, ainsi que les mécanismes de réduction homogène par recombustion et hétérogène par le carbone résiduel. Les calculs révèlent que prédominent la formation par le mécanisme combustible et la destruction par la réduction hétérogène. Enfin, le modèle de lit a été utilisé pour étudier l’influence des divers paramètres opératoires : température, débit et distribution d’air primaire, taille des particules de déchets, brassage et schéma de brassage. Les résultats sont présentés et discutés en détail. L’influence des conditions opératoires sur l’efficacité du procédé et sur les émissions de Cd et NOx est analysée / As a tool for controlling the Municipal Solid Waste (MSW) incineration process and its possible pollutant emissions, a mathematical model of the MSW bed burning on travelling grate of an incinerator was developed. The model describes most of the physico-chemical and thermal phenomena taking place in incineration like the drying and pyrolysis of the feed, combustion and gasification of char, oxidation of pyrolysis gases, heat transfer, bed shrinking, feed stirring, etc. Also described in the model are the mechanisms of Heavy Metals (HM) volatilization and NOx formation. Kinetics of HM release was modelled using the approach of additive reaction times accounting for the various transport mechanisms involved: external transfer, intra-particle diffusion and actual volatilization. In the case simulated, i.e. of Cd, almost total volatilization is predicted, which is confirmed by literature findings. The NOx sub-model takes into account most of the common mechanisms of formation like thermal, prompt, fuel, N2O intermediate and also NOx reduction by homogeneous reburning and heterogeneous reduction by char. Calculations show that NOx formation is predominated by the fuel mechanism and destruction by the heterogeneous reduction. Finally, the bed model was applied to study the influence of various operating parameters like flow rate, temperature and distribution of air under grates, waste particle size, feed stirring and the stirring scheme. The results are presented and discussed in detail and the influence of operating conditions on process efficiency and on emissions of Cd and NOx is analyzed
7

Experimental Characterisation of Real Driving Cycles in Diesel Passenger Vehicles under Different Environmental Conditions

Redondo Puelles, Fernando 01 September 2023 (has links)
[ES] El futuro de los Motores de Combustión Interna en el sector de la automoción parece incierto, en cierta medida, debido a los cambios recientes en las normativas de homologación. Las regulaciones actuales han reducido considerablemente los límites de emisiones contaminantes , así como también han introducido pruebas más exigentes. La introducción de ciclos de conducción reales supuso un reto para los fabricantes de automóviles a la hora de homologar sus vehículos, ya que el tradicional y poco exigente ciclo de certificación del New European Driving Cycle (NEDC) ha sido sustituido por ciclos más severos como el World Light-Duty Test Cycle (WLTC) y Real Driving Emissions (RDE). Este estudio, en primer lugar, presenta una metodología para implementar ciclos RDE en un banco de ensayos de motores. Aun sabiendo que la esencia de la regulación RDE es evaluar las condiciones reales de conducción, reproducir los ciclos RDE en un banco de pruebas es de gran interés ya que las condiciones controladas y reproducibles que se pueden lograr en un laboratorio aportan información valiosa para entender el comportamiento del motor en conducción real, y por lo tanto contribuyen al desarrollo del motor. Este documento aplica la normativa más reciente de la Comunidad Europea y establece los pasos imprescindibles para realizar un ciclo RDE en un banco de pruebas de motores. En segundo lugar, gracias a que se ha demostrado la viabilidad de una sala de pruebas para realizar ciclos RDE, se han realizado diferentes ciclos RDE bajo diferentes solicitaciones dinámicas y condiciones externas como tempera- tura ambiente o temperatura del aire de admisión. Posteriormente, se analizó la emisión de contaminantes y el consumo de combustible con el fin de caracterizar los ciclos y condiciones de RDE. Además, se ha llevado a cabo una comparación de las emisiones y el consumo de combustible de las pruebas RDE frente a las obtenidas en las pruebas de estado estacionario, donde se encontraron discrepancias bastante bajas / [CA] El futur dels Motors de Combustió Interna al sector de l'automoció sembla incert, en certa mesura, a causa dels canvis recents a les normatives d'homologació. Les regulacions actuals han reduït considerablement els límits d'emissions contaminants i també han introduït proves més exigents. La introducció de cicles de conducció reals va suposar un repte per als fabricants d'automòbils a l'hora d'homologar els seus vehicles, ja que el tradicional i poc exigent cicle de certificació del New European Driving Cycle (NEDC) ha estat substituït per cicles més severs com el World Light-Duty Test Cycle (WLTC) i Real Driving Emissions (RDE). Aquest estudi, en primer lloc, presenta una metodologia per implemen- tar cicles RDE a un banc d'assajos de motors. Tot i saber que l'essència de la regulació RDE és avaluar les condicions reals de conducció, reproduir els cicles RDE en un banc de proves és de gran interès ja que les condicions controlades i reproduïbles que es poden aconseguir en un laboratori aporten informació valuosa per entendre el comportament del motor en conducció real, i per tant contribueixen al desenvolupament del motor. Aquest document aplica la normativa més recent de la Comunitat Europea i estableix els passos imprescindibles per fer un cicle RDE en un banc de proves de motors. En segon lloc, gràcies al fet que s'ha demostrat la viabilitat d'una sala de proves per fer cicles RDE, s'han realitzat diferents cicles RDE sota diferents sol·licitacions dinàmiques i condicions externes com ara temperatura ambient o temperatura de l'aire d'admissió. Posteriorment, es va analitzar l'emissió de contaminants i el consum de combustible per tal de caracteritzar els cicles i les condicions de RDE. A més, s'ha dut a terme una comparació de les emissions i el consum de combustible de les proves RDE davant de les obtingudes a les proves d’estat estacionari, on es van trobar discrepàncies força baixes- / [EN] The future of Internal Combustion Engines in the automotive sector seems uncertain, to some extent, due to the recent changes in type approval regulations. Current regulations have considerably reduced the engine pollutant emissions limits, as well as introduced more demanding testing conditions. The introduction of real driving cycles presented a challenging issue for car manufacturers when homologating their vehicles, since the traditional and undemanding New European Driving Cycle (NEDC) certification cycle has been replaced by more severe cycles such as World Light-Duty Test Cycle (WLTC) and Real Driving Emissions (RDE). This study, in the first place, presents a methodology for implementing RDE cycles in an engine test bench. Even knowing that the essence of RDE regulation is to assess actual driving conditions, reproducing RDE cycles in a test bench is of great interest since, the controlled and reproducible conditions that can be achieved in a laboratory lead to valuable information to understand engine behaviour in real driving conditions, and therefore contribute to engine development. This document applies the most recent European Community regulation and sets the essential steps to carry out an RDE cycle in an engine test bench. Secondly, as the feasibility of a test bench to perform RDE cycles has been proven, different RDE cycles have been performed under different dynamic solicitations and external conditions such as ambient or intake air temperatures. After that, the pollutant's emission and fuel mass consumption were analysed with the aim of characterising RDE cycles and conditions. Furthermore, a comparison of RDE test emissions and fuel consumption versus those obtained from steady-state tests has been carried out, where very small discrepancies were found. / Redondo Puelles, F. (2023). Experimental Characterisation of Real Driving Cycles in Diesel Passenger Vehicles under Different Environmental Conditions [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/196653

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