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.

Tato diplomová práce se zabývá předehřevem spalovacího vzduchu a jeho vlivem na parametry spalovacího procesu. V teoretické části je zpracován přehled nejčastějších znečišťujících látek z průmyslového spalování. Je popsána aktuálně platná relevantní legislativa v Evropské unii a jsou porovnány její implementace do národní legislativy v České republice a v Německu. Dále je provedena klasifikace hořáků z hlediska různých kritérií a rešerše předchozí práce v oblasti předehřevu spalovacího vzduchu. Na zkušebně hořáků byla provedena experimentální studie dvou různých hořáků na zemní plyn při konstantním tepelném příkonu 750 kW se spalovacím vzduchem předehřátým až na 250 °C. Výsledky odhalily pozitivní vliv předehřevu na účinnost spalování. Množství emisí NOx a CO naopak rostlo s teplotou spalovacího vzduchu.

This diploma thesis deals with selected abatement techniques of nitrogen oxides (NOx) developed for large combustion plants. The first part describes selected NOx, their properties and explains the formation during combustion. Furthermore, there is an analysis of current legal legislation regulating the issue of emission limits. The third part presents selected primary and secondary measures that are widely used. The emphasis is placed on the description of selective catalytic (SCR) and non-catalytic reduction (SNCR). Finally, the basic design of these technologies for model combustion equipment is performed. The consumption of reducing medium and the volume of the catalyst for the mentioned techniques are calculated here. The estimate of selected operating and investment costs is a part of the basic scheme.

Transport, whose intensity year by year increase, has assuredly influence on air quality. This issue solution will be focused especially on localities burden with transport in urban areas. The contribution of transport to increased values of air pollution will be evaluated with regards to meteorological conditions. Background stations from Czech Hydrometeorological Institute categorization will be chosen such as comparative sites. Pollutants emitted from traffic such as particulate matter, nitrogen oxides and carbon monoxide will be observed except meteorological conditions.

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%.