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 eddy impaction ash deposition model derived and validated in this document predicts eddy impaction rates as a function of turbulence intensity, boundary layer thickness, and gas velocity. The experimental apparatus introduces small particles (200 nm, 25 µm, and 500 µm diameter) into a gas stream flowing through a horizontal pipe (Re 2,300-8,000). The particles deposit on the pipe wall and the total mass of impacted particles provides a measure of collection efficiency. Experimental results indicate deposition velocity increases with Reynolds number, consistent with eddy impaction theory and based on increased turbulent energy. Eddy impaction also increases with particle size at fixed Reynolds number, again consistent with theory.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21373号 / 工博第4532号 / 新制||工||1706(附属図書館) / 京都大学大学院工学研究科化学工学専攻 / (主査)教授 前 一廣, 教授 河瀬 元明, 教授 佐野 紀彰 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Askackumulering i dieselpartikelfilter är ett välkänt problem som resulterar i ett förhöjt mottryck och påverkad prestanda hos fordonet. Däremot ges sällan uppmärksamhet åt filtrets katalytiska aktivitet och hur det påverkas vid förekomst av avgasföroreningar. Syftet med denna studie är att undersöka effekten av aska på filtrets katalytisk aktivitet och dess förmåga att oxidera föroreningar som är skadliga för miljön och människors hälsa. Dessutom utvärderas askbeläggningsmetoden varpå filtren laboratoriskt åldras med olika typer, samt varierande mängder, av aska för att försöka simulera åldring i fält. Filtrens ytegenskaper karakteriserades genom analys med optisk mikroskopi, SEM-EDS och XRF. Den katalytiska aktivitet undersöktes i en SCAT-rigg, varpå oxidationstester av NOx och C3H8 utfördes. Det färska och fältåldrade jämfördes med de laboratorieåldrade filtren som dopats med 22 g/L respektive 47 g/L CaSO4 samt ett filter dopat med 79 g/L aska. Den katalytiska aktiviteten för laboratorieåldrade filtren liknande det färska filtret. Det fältåldrade filtret hade däremot låg katalytisk aktivitet för oxidation av NO och nästan helt deaktiverat för oxidation av C3H8. I det åldrade filtret och det laboratorieaskabelagda filtren visade EDS att elementen Ca och S hade väl matchade deponeringsregioner på filterkanalytan, vilket indikerade förekomst av CaSO4. Den mikroskopiska analysen indikerade också att båda proverna hade homogen fördelning av aska på filterkanalytan. Trots likheten i de fysiokemiska egenskaperna hos filterkanalytan hos det fältåldrade och laboratorieaskbelagda filtren hade de signfikant olika resultat vid test av katalytisk aktivitet. Deaktiveringen av det åldrade filtret kan ha orsakats av andra typer av åldringsmekanismer. Den valda metoden är inte adekvat för att efterlikna åldring i fält. Ytterligare studier krävs för att utvärdera metoden och effekterna av aska på den katalytiska aktiviteten / Accumulation of ash on the Catalytic Diesel Particulate Filter (CDPF) is a well-known problem that results in elevated back pressure and affected vehicle performance. However, attention is seldom paid to the catalytic performance of the filter, and how it is affected by impurities from the exhaust. The objective of this study is to address the effect of ash on the catalytic performance of CDPF to oxidise pollutants that are harmful to the environment and human health. In addition, evaluating the feasibility to laboratory age CDPFs with different loads and compositions using the dip-coating method to simulate field aged filters. The filter characterisation was analysed by Optical Microscopy, Scanning Electron Microscopy (SEM) with Electron dispersive X-ray Spectroscopy (EDS), and X-ray Fluorescence (XRF). The catalytic performance was investigated based on NOx and C3H8 oxidation tests in a Synthetic Catalyst Activity Test (SCAT) rig. A fresh and field aged filter was compared with laboratory aged filters prepared with coatings of 22 g/L and 47 g/L CaSO4, and 79 g/L ash , respectively. The catalytic activity to oxidise NO and C3H8 was unaffected by the ash deposits in the laboratory aged filters, showing similar activity as the fresh filter. While the field aged filter had low catalytic performance to convert NO and was almost completely deactivated for the oxidation of C3H8. EDS mapping for the field aged filter and the laboratory ash coated sample showed that the elements Ca and S were present and had well-matched regions of deposit, respectively, indicating that CaSO4 was present. The microscopic analysis also indicated that both samples had a homogeneous distribution of ash on the filter channel surface. Despite the similarity in the physicochemical properties of the filter channel surface(field aged filter and the laboratory ash coated sample) the catalytic activity had significantly different results. This study suggests that the deactivationof the field aged filter might be caused by other types of ageing mechanism. The laboratory ageing by dip-coating is seen as a non-applicable method to simulate field aged filters. Further studies are required to evaluate both the method and the effects of ash on the catalytic activity.

Synfuel from gasification of coal, biomass, and/or petroleum coke is an alternative to natural gas in land-based industrial gas turbines. However, carryover fine particulate in the syngas may lead to a considerable amount of deposition on turbine blades, which reduces component life and system performance. Deposition experiments on film-cooled turbine components were performed in an accelerated test facility to examine the nature of flyash deposits near film cooling holes. Experimental results indicate that deposition capture efficiency decreased with increased blowing ratio. Shaped holes exhibited more span-wise coverage than cylindrical holes and effectively reduced deposition. The TBC layer increased surface temperature, resulting in increased deposition. Coupons with close hole spacing exhibited a more uniform low temperature region downstream and less deposition. Capture efficiencies for small particles were lower than for large particles, especially at low blowing ratios. The trench increased cooling effectiveness downstream, but did not reduce overall collection efficiency of particulates because the trench also acted as a particulate collector. In the numerical computations using a CFD code (FLUENT), the standard k-ω turbulence model and RANS were employed to compute flow field and heat transfer. A Lagrangian particle method was utilized to predict the ash particulate transport. User-defined subroutines were developed to describe and predict particle deposition rates on the turbine blade surface. Small particles had a greater tendency to stick to the surface. As the surface temperature rose above the transition temperature, large particles dominated the excessive deposition due to the high delivery rate. Backside impingement of coolant improved the overall cooling effectiveness. Experiments and CFD modeling results suggest that clean coolant dominated the initial deposition process by blowing off the particles and preventing particles from impacting on the surface. Initial deposits formed between coolant channels. Subsequent deposition occurred on top of initial deposits, due to increasing deposit surface temperature, which led to the formation of distinct ridges between coolant paths.

In the late 1970s and early 1980s, the grassroots environmental movement brought national attention to the issues related to inequities in environmental quality. Previous research addressing these environmental inequities has progressively increased and advanced methodologically. However, the arguments and focus have been primarily limited to examining the socio-demographics in an ongoing debate of race and class. This thesis extends past the methodological stalemate focusing on the application of Geographic Information Systems (GIS) using survey data in an environmental justice case study of a community in south Florida. This approach examines the social, health and environmental impacts of a Superfund site on a low income, minority community. Using geo-coded survey (N=223) and environmental data (ash deposition patterns), this thesis employs path analysis to test the hypothesis that exposure matters. The exposure matters hypothesis suggests exposure (perceived, self-reported and actual) is a significant predictor of physical and psychological health. Results discuss significant findings, and then compare them with previous disaster and trauma-related research and present directions for future research.

The presented doctoral thesis “Fly ash impact in forest ecosystems in Northeastern Germany - an assessment and regionalization approach” intends to (a) test if the field assessment of ferrimagnetic susceptibility can be used as cost efficient method to get information on fly ash deposition impacted chemical site properties. (b) develop a regionalization approach to bridge the gap from plot-wise assessed data to spatial management information. The thesis is a follow-up of extensive research activities by the Institute for Soil Science and Site Ecology on industrial deposition in Dübener Heide and Upper Lusatian region which started in the early 1960ies and were intensified from the middle of the 1990ies on. A central topic of these research activities was the assessment of the impact of fly ash deposition on chemical soil properties. A major challenge was to transfer the assessed chemical characteristics from plot to region and to aggregate the measured values to provide an information basis, which can be used for a site potential and risk oriented forest management. This challenge was picked up by the joint research project “ENFORCHANGE” (FKZ 0330634 K, German Federal Ministry of Education and Research). The presented thesis was carried out in the frame of this project during the period 2005 - 2009. The thesis was conceived as cumulative work, which includes ten papers in total. Five articles are published in peer-reviewed journals (ISI listed, 1 paper still in revision), and five are part of books or conference proceedings. • Chapter 1 “Introduction” gives an overview on the motivation, idea and structure of the thesis. • In chapter 2 “Aims and Scope of the presented work” information on the background and frame of the study within the project ENFORCHANGE is given. • Chapter 3 “Background and State of the Art” deals with the history of fly ash deposition in the model region Dübener Heide. • Chapter 4 “Material and Methods” gives information on fly ash and presents the spatial assessment design and the hereon based approaches for up-scaling and correlation of magnetic susceptibility with selected chemical characteristics. • Chapter 5 “Results” presents results of the spatial modeling and linear regression based approach to use ferrimagnetic susceptibility for predicting the contents of selected base cations, selected acid and heavy metal cations and Black Carbon. • Chapter 6 “Discussion and Conclusions” compares the assumptions and findings in the different articles, discusses contradictory findings and open questions and provides a comprehensive evaluation of the outcomes. Final conclusions are drawn and an outlook is given. A key finding of the thesis is that the industrial complex Bitterfeld was the most important source of fly ash deposited in the model region Dübener Heide. The power plant Zschornewitz plays only a minor role contrary to the research hypothesis formulated in ENFORCHANGE. Related to the targets of the thesis, spatial variation of magnetic susceptibility was predicted with high precision by a multiple linear regression model. A slightly differing set of model parameters  according to their explanatory value for three selected depth levels  improved the prediction quality. The selection of the parameters supported understanding the major drivers for magnetic particle deposition, storage, and vertical displacement in the forest soils. Humus layer (depth level 6-10 cm), horizontal distance to Bitterfeld and soil type (Podzol, semi-terrestrial sites) were the most important variables. These variables point to a slowed-down humus dynamic, which causes the accumulation of fly ash in the humus layer. In depth level 11 – 15 cm, variables such as “aspect” gain in importance, which describe the exposure against the major wind direction and thus indicate the probability and of deposition. For the mineral horizon (depth level 21-25 cm), exposition and especially stand properties are most important. The latter gives evidence for the intensity of deposition caused by surface roughness. Therefore, the variables “coniferous” and “mixed” stands were highly relevant for the model. Variable correlations between mass susceptibility and selected base cations, acid cations and heavy metals have been found. When using a linear regression model, a prediction of Ca and Mg and of Mn was possible. The model performance was lower for Fe, Al, Cd and Black Carbon. A possible reason was the use of different plot types: the assessment of magnetic susceptibility and chemical soil properties was well harmonized at the ENFORCHANGE plots considering the sampling material and sampling location. A comparable harmonization could not be achieved at a number of monitoring plots, which were included into the analysis to broaden the data base. Comparing the results from the linear regression model based prediction with the results achieved by multiple regression based spatial modeling lead to the conclusion that the mul¬tiple regression approach is more promising: by using other model parameters such as orographic, climatic or stand parameters together with magnetic susceptibility, the prediction quality of the deposed agents could be improved and small scale variations in nutrient potentials and risks driven by fly ash deposition could be better recognized and made available for forest management decisions. / Die vorgelegte Doktorarbeit “Fly ash impact in forest ecosystems in Northeastern Germany - an assessment and regionalization approach” (Flugascheeinträge in Waldökosysteme in Nordostdeutschland  ein Erfassungs- und Regionalisierungsansatz) verfolgte die Ziele (a) zu testen, ob sich die Erfassung der ferrimagnetischen Suszeptibilität eignet, um kosteneffizient quantitative und / oder qualitative Informationen zu den eingetragenen Flugaschemengen und den in der Folge veränderten bodenchemischen Potenzialen zu erheben (b) zu testen, ob der Indikator „ferrimagnetische Suszeptibilität“ genutzt werden kann, um Informationen über Flugascheeinträge von der punktbezogenen Erfassung auf einen regionalen Maßstab hoch zu skalieren. Grundlage dieser Zielstellungen sind Forschungsarbeiten zu der Frage der langfristigen Wirksamkeit und ökologischen Bedeutung von Industrieexhalationen auf Waldökosysteme, die am Institut bereits in den 1960ziger Jahren begonnen wurden und verstärkt seit Mitte der 1990ziger Jahre fortgeführt wurden. Auf ihrer Basis wurde die Herausforderung eines kostengünstigen und flächenbezogenen Erhebungsansatzes identifiziert und formuliert. Die vorgelegte Arbeit ordnete sich in diese Forschungsarbeiten ein und führte sie im Rahmen des Verbundforschungsvorhabens ENFORCHANGE ((FKZ: 0330634 K, Bundesministerium für Bildung und Forschung) von 2005 - 2009 fort. Die Doktorarbeit ist als kumulative Arbeit angelegt, im Rahmen derer insgesamt 10 Publikationen zusammengefasst wurden. Davon sind 5 in internationalen Journalen bereits publiziert, akzeptiert oder in einem Fall in Begutachtung; 5 weitere Publikationen wurden ergänzend und auf speziellere Themen bezogen in Proceedings oder Buchbeiträgen publiziert. Die Arbeit gliedert sich in 5 Abschnitte: • Kapitel 1 (Einleitung) gibt einen kurzen Überblick zur Motivation und Struktur der Doktorarbeit. • In Kapitel 2 (Ziele und Rahmen der Arbeit) wird der Arbeitsansatz im Rahmen des Verbundforschungsvorhabens ENFORCHANGE vorstellt. • Kapitel 3 umfasst eine Auswertung von Veröffentlichungen zur Geschichte und den ökologischen Auswirkungen der Flugascheeinträge am Beispiel der Modellregion Dübener Heide. • In Kapitel 4 wird der methodische Ansatz der Arbeit vorgestellt, der von einem Vortest zur Eignung der Erfassung der magnetischen Suszeptibilität über die Ableitung eines flächigen Erhebungsansatzes bis hin zur Frage der Modellbildung und Korrelation mit chemischen Kenngrößen reicht. • Kapitel 5 beinhaltet die Ergebnisse der räumlichen Modellbildung und der Korrelation der magnetischen Suszeptibilität mit ausgewählten Basen-, Säure- und Schwermetallkationen sowie mit Schwarzem Kohlenstoff. • Kapitel 6 diskutiert, vergleicht und bewertet die Ergebnisse der den Veröffentlichungen zugrunde liegenden Studien und zieht ein abschließendes Resumé. Ein Schlüsselergebnis der vorgelegten Arbeit belegt, dass entgegen der ursprünglichen Arbeitshypothese des Projektverbundes ENFORCHANGE nicht das mehr als 100 Jahre alte Kraftwerk Zschornewitz die wesentliche Quelle für die Flugascheeinträge in der Modellregion Dübener Heide war, sondern der räumlich entfernter gelegene, aber deutlich größere Industriekomplex Bitterfeld. Bezogen auf die Zielsetzung der vorgelegten Arbeit, konnte mithilfe multipler Regressionsverfahren und auf Basis von Feldaufnahmen der ferrimagnetischen Suszeptibilität in einem regelmäßigen Stichprobenraster ein hoch auflösendes räumliches Modell gebildet werden. Unter Berücksichtigung weiterer Modellparameter, die schrittweise hinsichtlich ihres Erklärungswertes ausgewählt wurden, konnten mikrotopographische und vegetationsbedingte Informationen genutzt werden, um die räumliche Variabilität des magnetischen Signals differenziert darzustellen. Damit ergibt sich eine Planungsgrundlage, die die bisher genutzte, auf Waldschadensansprachen basierende Stratifizierung in Zonen unterschiedlicher Eintragsintensität mit Bezug zur Planungseinheit deutlich detaillierter untersetzt. Der Versuch, auf Flugascheeintragsmengen, respektive -vorräte zu schließen ließ sich hingegen auf Basis der verfügbaren Daten nicht umsetzen. Die Korrelationsbeziehungen der von Volumen- in den Massenbezug umgerechneten Suszeptibilität mit Basen-, Säure und Schwermetallkationen sowie Schwarzem Kohlenstoff fielen heterogen aus. Eine gute Vorhersage auf Basis eines linearen Regressionsmodells konnte für Ca, Mg und Mn getroffen werden, wohingegen die Modellqualität für Fe, Al sowie Cd und Schwarzen Kohlenstoff deutlich schlechter zu beurteilen war. Dies ergab sich zum einen aus der verfügbaren Datenbasis, die keine durchgängige Harmonisierung für die Erhebungen der Suszeptibilität und der chemischen Kennwerte erlaubte. Zum anderen geht diese Erkenntnis mit Ergebnissen aus der Regionalisierung einher, die einen Einbezug weiterer Modellparameter und die Nutzung multipler anstelle linearer Regressionsmodelle nahe legt.

No description available.

Coal gasification and combustion can introduce contaminants in the solid or molten state depending on the gas clean up procedures used, coal composition and operating conditions. These byproducts when combined with high temperatures and high gas stream velocities can cause Deposition, Erosion, and Corrosion (DEC) of turbine components downstream of the combustor section. The objective of this dissertation is to use computational techniques to investigate the dynamics of ash deposition in a leading edge vane geometry with film cooling. Large Eddy Simulations (LES) is used to model the flow field of the coolant jet-mainstream interaction and the deposition of syngas ash in the leading edge region of a turbine vane is modeled using a Lagrangian framework. The three row leading edge vane geometry is modeled as a symmetric semi-cylinder with a flat afterbody. One row of coolant holes is located along the stagnation line and the other two rows of coolant holes are located at ±21.3° from the stagnation line. The coolant is injected at 45° to the vane surface with 90° compound angle injection. The coolant to mainstream density ratio is set to unity and the freestream Reynolds number based on leading edge diameter is 32000. Coolant to mainstream blowing ratios (B.R.) of 0.5, 1.0, 1.5, and 2.0 are investigated. It is found that the stagnation cooling jets penetrate much further into the mainstream, both in the normal and lateral directions, than the off-stagnation jets for all blowing ratios. Jet dilution is characterized by turbulent diffusion and entrainment. The strength of both mechanisms increases with blowing ratio. The adiabatic effectiveness in the stagnation region initially increases with blowing ratio but then generally decreases as the blowing ratio increases further. Immediately downstream of off-stagnation injection, the adiabatic effectiveness is highest at B.R.=0.5. However, in spite of the larger jet penetration and dilution at higher blowing ratios, the larger mass of coolant injected increases the effectiveness with blowing ratio further downstream of injection location. A novel deposition model which integrates different sources of published experimental data to form a holistic numerical model is developed to predict ash deposition. The deposition model computes the ash sticking probabilities as a function of particle temperature and ash composition. This deposition model is validated with available experimental results on a flat plate inclined at 45°. Subsequently, this model was then used to study ash deposition in a leading edge vane geometry with film cooling for coolant to mainstream blowing ratios of 0.5, 1.0, 1.5 and 2.0. Ash particle sizes of 5, 7, 10μm are considered. Under the conditions of the current simulations, ash particles have Stokes numbers less than unity of O(1) and hence are strongly affected by the flow and thermal fields generated by the coolant interaction with the main-stream. Because of this, the stagnation coolant jets are successful in pushing and/or cooling the particles away from the surface and minimizing deposition and erosion in the stagnation region. Capture efficiency for eight different ash compositions are investigated. Among all the ash samples, ND ash sample shows the highest capture efficiency due to its low softening temperature. A trend that is common to all particle sizes is that the percentage capture efficiency is least for blowing ratio of 1.5 as the coolant is successful in pushing the particles away from the surface. However, further increasing the blowing ratio to 2.0, the percentage capture efficiency increases as more number of particles are transported to the surface by strong mainstream entrainment by the coolant jets. / Ph. D.

The United States holds the world's largest estimated reserves of coal and is also a net exporter of it. Coal gasification provides a cleaner way to utilize coal than directly burning it. Gasification is an incomplete oxidation process that converts various carbon-based feedstocks into clean synthetic gas (syngas), which can be used to produce electricity and mechanical power with significantly reduced emissions. Syngas can also be used as feedstock for making chemicals and various materials. A Computational Fluid Dynamics (CFD) scheme has been used to simulate the gasification process for many years. However, many sub-models still need to be developed and improved. The objective of this study is to use the improved CFD modeling to understand the thermal-flow behavior and the gasification process and to provide guidance in the design of more efficient and cheaper gasifiers. Fundamental research has been conducted to improve the gasification sub-models associated with the volatile thermal cracking, water-gas-shift (WGS) reaction, radiation effect, low-rank-coal gasification, coal to synthetic-natural-gas (SNG), and ash deposition mechanisms. The improved volatile thermal cracking model includes H2S and COS contents. A new empirical WGS reaction model is developed by matching the result with experimental data. A new coal demoisturization model is developed for evaporating the inherent moisture inside the coal particles during low-rank-coal gasification. An ash deposition model has also been developed. Moreover, the effect of different radiation models on the simulated result has been investigated, and the appropriate models are recommended. Some improved model tests are performed to help modify an industrial entrained-flow gasifier. A two-stage oxygen feeding scheme and a unique water quench design are investigated. For the two-stage oxygen feeding design, both experimental data and CFD predictions verify that it is feasible to reduce the peak temperature and achieve a more uniform temperature distribution in the gasifier by controlling the injection scheme without changing the composition and production rate of the syngas. Furthermore, the CFD simulation can acceptably approximate the thermal-flow and reaction behaviors in the coal gasification process, which can then be used as a preliminary screening tool for improving existing gasifiers’ performance and designing new gasifiers.