This thesis deals with the evaluation of emissions of NOx and CO formed during the combustion process when the burner utilizing fuel staging and internal flue gas recirculation is used. In the theoretical part the NOx formation mechanisms and methods used to suppress their formation are described. This is followed with the currently valid legislation in the Czech Republic in terms of the emission limits for NOx and CO in stationary sources. In the work, combustion tests were performed at the burners testing facility at UPEI BUT. The tests revealed that the most important parameters, which influence the NOx formation, are fuel staging, increasing combustion air excess and the utilization of new equipment that induces the flue gas to be drawn back into the burner. The equipment is installed in the burner’s air channel. The dependence of flue gas temperature, heat flux to the combustion chamber’s section walls and in-flame temperatures distribution in the horizontal symmetry plane of the combustion chamber on various parameters were investigated. The parameters included the geometry of the equipment for flue gas recirculation, primary/secondary ratio, geometry of nozzles for secondary fuel supply, tangential orientation of these nozzles towards the burner axis, and the excess of combustion air.

The main aim of the work was the investigation of the effect of operational parameters of the combustion process (combustion air excess, primary fuel ratio) and burner constructional parameters (the pitch angle of secondary nozzles, tangential orientation of secondary nozzles towards the axis of the burner) on the formation of NOx and CO, flue gas temperature, the shape, dimensions and stability of the flame, in-flame temperatures in the horizontal symmetry plane of the combustion chamber and the amount of heat extracted from the hot combustion gases in the combustion chamber’s shell. Experimental activities were carried out in the laboratory of the Institute of Process and Environmental Engineering, which is focused on burners testing. The combustion tests were performed with the experimental low-NOx type burner, namely the two-gas-staged burner. Mathematical model developed based on the experimental data describes the dependency of NOx on the operating parameters of the combustion process and burner constructional parameters. The model shows that increasing air excess and increasing angle of tangential orientation of the secondary nozzles reduce the formation of NOx. The temperature peaks in the horizontal symmetry plane of the combustion chamber decreases with increasing combustion air excess. The thermal load to the combustion chamber’s wall along the length of the flame was evaluated for selected settings. It was validated that the thermal efficiency of is reduced when higher air excess is used.

<p>SO₂ and NO_x (NO+NO₂) are important trace gases in the atmosphere as they adversely affect air quality and are precursors to sulfate and nitrate aerosols in the atmosphere. However, there are significant uncertainties in the emission inventories and the atmospheric chemistry processes of both gases. Addressing these uncertainties will help us to 1) better regulate their emissions from anthropogenic activities, 2) understand the formation mechanism of aerosol pollution events, during which rapid accumulation of nitrate and sulfate aerosols are commonly observed, and 3) better constrain the impact of SO₂, NO_x, sulfate aerosols and nitrate aerosols to the global radiation balance. Stable isotopes of nitrogen and sulfur are useful tools in understanding both the origins and chemistry of SO₂ and NO_x since different emission sources usually display distinct sulfur and nitrogen isotopic compositions, and different SO₂ and NO_xoxidation pathways fractionate sulfur and nitrogen isotopes differently. In this dissertation, five studies are conducted to 1) use sulfur isotopes to investigate the sources and chemistry of atmospheric sulfur, and 2) improve our understanding of the isotopic fractionation processes associated with the atmospheric chemistry of reactive nitrogen. </p><p>Using stable sulfur isotopes, we first analyzed the sources of sulfate aerosols collected at Baring Head, New Zealand and atmospheric deposition at the Atacama Desert. At Baring Head, we found that the secondary sulfate, i.e., sulfate formed from atmospheric oxidation of SO₂, is mainly observed in fine aerosols (<1 µm) while the sulfate in coarse aerosols (>1 µm) is mostly sea salt sulfate. 73-77% of the secondary sulfate is sourced from biogenic emissions by ocean phytoplankton, and the rest is originated from anthropogenic activities. The sulfate deposition across the Atacama Desert, on the other hand, is a mixture of sea salt sulfate (only near the coast), anthropogenic SO₂ emissions, local soil, and lake salts. Then, sulfur isotopes were used to investigate the formation chemistry of sulfate aerosols collected during a strong winter haze episode in Nanjing, China, where the sources of SO₂ were well-understood. We found that, although the sources of sulfur remain unchanged during the haze episode, the sulfur isotopic compositions of sulfate vary significantly, suggesting isotopic fractionation occurred during the formation of sulfate aerosols. We interpreted the variation using a Rayleigh distillation model to evaluate the contribution of sulfate formation pathways. The model suggested that the Transition Metal Ion catalyzed O₂ oxidation pathway contributed 49±10% of the total sulfate production, while the O₃/H₂O₂ oxidations accounted for the rest. </p><p>Next, we conducted experiments in an atmospheric simulation chamber to determine the isotopic fractionations between NO and NO₂. This isotopic fractionation is controlled by a combination of two factors: 1) the equilibrium isotopic exchange between NO and NO₂ molecules, and 2) the kinetic isotope effects of the NO_x photochemical cycle, namely the Leighton Cycle Isotope Effect (LCIE). Our experiments showed that the fractionation factor during the isotopic exchange is 1.0289±0.0019, and the fractionation factor of LCIE is 0.990±0.005. A model was constructed to assess the relative importance of the two factors, showing the isotopic exchange should be the dominant factor when NO_x >20 ppb, while LCIE should be more important at low NO_x concentrations (<1 ppb) and high rates of NO₂photolysis. Last, we quantified the overall nitrogen isotopic fractionation during the formation of nitrate aerosols collected at Baring Head, New Zealand. Our results showed that significant and variable (0-15‰) isotopic fractionations occurred during the formation of nitrate aerosols. The isotopic fractionation factors are lower in the summer and higher in the winter, which is mainly caused by seasonal variations in nitrate formation pathways. </p><p>Overall, this dissertation first applied stable sulfur isotopes in aerosol samples collected in different environments, demonstrating that isotopes are excellent tools in identifying the origins and chemistry of atmospheric sulfur. Then, we investigated the isotopic fractionation processes during the atmospheric nitrogen chemistry, which can be useful for future studies aimed at understanding the origins and chemistry of atmospheric nitrogen using stable nitrogen isotopes.</p>

This study examines the potential of electrification in reducing greenhouse gas emissions and air pollution from passenger cars in a short- to mid-term time perspective. Using Stockholm County as a case study, this has been done in a three-step process by modeling the relative change in emissions between 2019 and 2030. Firstly, four scenarios have been created for 2030, each of which state the number of gasoline cars, diesel cars, PHEVs and EVs in use on a municipality-level. Secondly, for each scenario, the movement of traffic has been modeled on a car-by-car basis using the Scaper/MATSim transportation model at KTH. Thirdly, using emission factors from HBEFA, an emission model for 17 pollutants has been created for the modeling of hot emissions, cold start emissions, evaporation losses and non-exhaust emissions. Compared to 2019 emission levels, with EVs and PHEVs accounting for 64.5 % of the car fleet, the optimistic scenarios suggest that emissions of CO2, NMHC and NOx could decrease by up to 43.6, 63.5 and 84.7 %, respectively, by 2030. Besides electrification, for NMHC and NOx, these emission reductions are largely a result of technological improvements of combustion vehicles. Conversely, emissions of particulate matter (PM10 and PM2.5) are projected to increase by up to 45.6 % in the optimistic scenarios. Roughly corresponding to the increase in the total driving distance, this increase can be attributed to the lower cost of driving of electric cars and the projected population increase of 15.5 %.

Indiana University-Purdue University Indianapolis (IUPUI) / In order to conform to pollutant-control regulations and minimize NOx emissions, modern household boilers and central heating systems are moving toward premixed combustors. These combustors have been successful with regards to emissions along with efficiency. However, their implementation has been associated with acoustical instability problems that could be solved through precise optimization in design rather than trial and error experimentation. This thesis introduces an experimental apparatus, which is designed to investigate the acoustic instability problem at the flame level. The goal is an experimental determination of the flame transfer function and comparison of the experimental data with a theoretical model of the flame. An experimental procedure is designed to diagnose the origins of the combustion instabilities by measurement of the flame transfer function. This research is carried out in three steps. The first step is to understand the acoustic instability problem through study of the theoretical models of the flame transfer function and selection of a model, which is most functional in industrial applications. A xiii measurement technique for the flame transfer function is developed according to the required accuracy in measurements, repeatability, and configurability for a wide range of operating conditions. Subsequently, an experimental apparatus is designed to accommodate the flame transfer function measurement technique. The components of the acoustic system are carefully sized to achieve precise measurement of the system parameters such as flows, pressures, and acoustic responses, and the apparatus is built. The apparatus is operated to measure the flame transfer function at several operating conditions. The experimentally measured flame transfer function is compared with a theoretical model for further verification. The experimental apparatus provides an improved assessment of the acoustic instability problem for industrial applications.

Stricter requirements on the reduction of Nitrogen Oxides (NOx) in the emissions of heavy-duty diesel vehicles drives development for more efficient aftertreatment systems. An ammonia covered catalyst is one of the most successful technologies in reducing NOx by converting it into the harmless byproducts water and nitrogen. The ammonia injection control is however difficult due to nonlinearities and the impact of external exhaust parameters. The ammonia coverage ratio depends heavily on the surface temperature of the catalyst and a rapid increase in surface temperature would lead to a rapid decrease in ammonia storage capabilities. If the storage capabilities decrease below the current level of stored ammonia, the excess ammonia will flow into the exhaust and convert to NOx, an undesired phenomenon due to the cost of and the pollution caused by the ammonia released, often referred to as ammonia slip. This issue is further amplified by the fact that the problem is asymmetric, that is injected ammonia cannot be actively removed but has to be reduced by the reaction with the NOx present in the exhaust. As such, it is very important to keep the level of ammonia storage ratio low enough to avoid slipping but at the same time sufficiently high to obtain a satisfactory NOx conversion efficiency. These two issues are the main reasons why feedback control has proven to be difficult to implement to solve the dosing problem. As one has to store a lot of ammonia in order to obtain a satisfactory conversion of NOx, one often cannot react to rapid temperature increases in the catalyst. As such, one often experiences a lot of ammonia slip during these scenarios. In this report it is shown that utilizing predicted parameters of the exhaust in a model predictive controller reduces the ammonia consumption by 38% while also improving the tracking of the NOx conversion reference by 5.5%. / Strängare krav på minskning av kväveoxider (NOx) i utsläpp från tunga dieselfordon driver utvecklingen för ett mer effektivt efterbehandlingssystem. En ammoniakbelagd katalysator är en av de mest framgångsrika tekniker för att minska NOx genom att omvandla det till de ofarliga biprodukterna vatten och kväve. Injeceringen av ammoniak är dock svår att reglera på grund av olinjär dynamik och påverkan av externa avgasparametrar. Täckningsgraden av ammoniak beror starkt på yttemperaturen hos katalysatorn, där en ökning av temperaturen skulle leda till en minskad lagringskapacitet av ammoniak. Om lagringskapaciteten minskar under nuvarande täckningsgraden av ammoniak kommer överskottet av ammoniak att frigöras och strömma ut ur katalysatorn tillsammans med avgaserna och omvandlas till NOx, ett oönskat fenomen på grund av kostnaden för och de föroreningar som orsakas av ammoniaken. Detta problem förvärras av det faktum att problemet är asymmetriskt, dvs injicerad ammoniak kan inte aktivt avlägsnas utan måste reduceras genom att reagera med de befintliga NOx som finns i avgaserna. Därav är det väldigt viktigt att täckningsgraden av ammoniak hålls tillräckligt lågt för att undvika att ammoniaken frigörs men samtidigt tillräckligt hög för att erhålla den önskade omvandlingen av NOx. Dessa två problem är de främsta anledningarna till att reglering med återkoppling har visat sig vara svårt att implementera för att lösa doseringsproblemet. Eftersom det krävs en hög täckningsgraden av ammoniak för att få en önskvärd omvandling av NOx hinner en ofta inte korrigera för snabba temperaturökningar i katalysatorn. Det frigörs därför mycket av den lagrade ammoniaken under dessa scenarier. I denna rapport demonstreras att användandet av predikterade avgasparametrar i en modell prediktiv kontroller minskar ammoniakförbrukningen med 38% samtidigt som den önskade NOx omvandlingen förbättrades med 5.5%.

Black carbon (BC) and polycyclic aromatic hydrocarbons (PAHs) are two atmospheric pollutants produced by motor vehicles using carbonaceous fuels. As a part of the Mexico City Project, measurements of BC, PPAHs and many other gas- and particle-phase emissions were measured in Mexico City using a mobile laboratory during the Mexico City Metropolitan Area field campaign in April 2003 (MCMA-2003). The main goal of this research is to estimate emissions of BC and particulate PAHs (PPAHs) for Mexico City's vehicle fleet. The emissions of gas-phase pollutants such as carbon monoxide (CO), total nitrogen oxides (NOy) and volatile organic compounds (VOC) are also estimated. The mobile lab has previously been used to chase vehicles and measure their emissions, but analysis has traditionally focused on determining emission factors of individual vehicles associated with specific chasing events. The laboratory continuously samples ambient air from an inlet at the front of the van, and it is always "seeing" exhaust plumes from the vehicles around it while driving through traffic. We have developed an algorithm that automatically identifies the exhaust plume measurement points, which are then used as the basis for calculation of emission factors. In the nearly 90 hours of on-road sampling during the field campaign, we have identified ~30,000 exhaust measurement points. The large sample size enables us to estimate fleet-average emission factors and thus the emission inventory. Motor vehicles are estimated to emit annually 1,960 tons of BC, 56.2 tons of PPAHs, 1,320,000 tons of CO, 125,000 tons of NOy and 2440 tons of VOCs. The spatial and temporal patterns of BC and PPAHs in different locations with in MCMA are also studied. / Master of Science

Följande studie är gjord på uppdrag av Sjöfartsverket. I studien undersöktes hur en installation av ett Common Rail-system ombord på isbrytaren Ymer påverkat bränsleförbrukningen samt utsläppen av kväveoxider. Rådata som loggats ombord på Ymer har analyserat och bearbetat. Material och information från tillverkare, besättning samt teknisk chef på Sjöfartsverket, Albert Hagander har använts under studien. Tillsammans med uppmätta mätdata och tidigare gjord litteraturstudie stöds resultaten i studien. Det är ingen slump att system av Common Rail-typ redan är tillämpat inom de flesta branscher så som transport, personbilsindustri och jordbruk. Huvudsyftet med Common Rail är att minska bränsleåtgången samt minska utsläppen genom en renare och mer effektiv förbränning av bränslet.  Huvudsakligen undersöktes hur det nyinstallerade systemet påverkat bränsleförbrukningen och hur bränslebesparingen varierar med belastningen av maskinen. Vidare granskades hur utsläppen av kvävedioxider påverkats efter installationen. Problematiken med ökad NOx-produktion till följd av en högre förbränningstemperatur som Common Railsystemet medför diskuteras i rapporten. De resultat vi kommit fram till att en bränslebesparing kan göras ombord på Ymer genom att ersätta det gamla bränslesystemet med ett bränslesystem av Common Rail-typ. Vidare har installationen medfört andra förbättringar så som fartygsmaskinens reaktion på de många lastväxlingar som förekommer under isbrytning. / The following study has been carried out on behalf of Sjöfartsverket. The study examines how the installation of a common rail system on board the icebreaker Ymer affected fuel consumption and emissions of nitrogen oxides. The raw data logged on board Ymer was analyzed and processed. Materials and information from manufacturers, crew and the technical manager at the Swedish Maritime Administration, Albert Hagander have been used during the study. Together with measured data and previously made research study the findings of the study are supported. It is no coincidence that the system of the common rail type is already applied in most industries such as transport, car industry and agriculture. The main purpose of the Common Rail is to reduce fuel consumption and reduce emissions through cleaner and more efficient combustion of the fuel. We primarily examined how the newly installed system affected fuel consumption and the fuel savings will vary with the load of the machine. Furthermore, we examined how emissions of nitrogen oxides were affected after installation. The problem of increased NOx production due to a higher combustion temperature as the common rail system entails are discussed in the report. The result that was concluded was that fuel savings can be made on board Ymer by replacing the old fuel system with a common rail fuel type. Furthermore, the installation has brought other improvements such as ship machine's reaction to the many load changes that occur during icebreaking.

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

Dans cette étude, on s'est intéressé à la modélisation réduite et au contrôle d’organes intervenant dans la réduction des émissions de polluants des véhicules automobiles à basse consommation. Il s’agit des réacteurs catalysés de type « piège à NOx » et SCR, utilisés dans les architectures de post-traitement des gaz d’échappement des véhicules Diesel. Ces systèmes ont en commun la nécessité de contrôler les niveaux des émissions de polluants stockés sur les sites catalytiques et l’optimisation du fonctionnement du GMP en vue d’approcher les futures normes Euro et les nouvelles incitations sur les émissions de gaz à effet de serre.Le piège à NOx est un système catalytique dont la fonction première est de collecter les oxydes d’azote (NOx) des gaz d’échappement afin qu’ils ne soient pas rejetés dans l’environnement. Le réacteur SCR est un système catalytique qui utilise le principe de réduction sélective des NOx par l’ammoniac (NH3), initialment produit et délivré à partir d’un stock d’urée embarqué.La similitude des technologies a permis la mise en œuvre de méthodologies communes de modélisation cinétique et de réduction de modèles, basées sur l’étude thermochimique et cinétique des réseaux réactionnels. Après application aux systèmes respectifs de piège à NOx et SCR, nous avons obtenus des modèles réduits qui ont pu être identifiés, validés et appliqués à l’observation et au contrôle des niveaux de stock des polluants (respectivement NOx et NH3). / The purpose of this study is to develop mathematical reduced order models for components of low consumption motor vehicles : the lean NOx trap and the SCR catalysts, used in the exhaust of Diesel engines and involved in the reduction of pollutants in exhaust emissions. These systems have in common that they aim at controling the boundaries on pollutant emissions in order to achieve the forthcoming Euro standards and they allow the optimization of the aftertreatment systems to reduce greenhouse gases.The lean NOx trap catalyst aims at collecting the NOx in order to avoid the pollution of the environment and the SCR catalyst uses the selective reduction of the NOx by the ammonia (NH3), initially produced by an embedded urea system. The similarity between the two technologies allow the implementation of common methodologies for reduced order modeling of catalytic reactors based on thermochemical and kinetic studies. After application, respectively to the NOx trap and the SCR, we obtain reduced order models which were identified, validated and implemented for the control and diagnosis of the amount of stock of the pollutants (respectively NOx and NH3).