Tesi: "Pulverized"

1

Tinkham, Kevin Michael. "Surface studies of pulverized fuel ash". Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.278875.

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2

Messig, Danny. "Numerical simulation of pulverized coal combustion". Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2017. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-228707.

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Die Arbeit befasst sich mit der Flamelet Modellierung für die Verbrennung von Kohlenstaub. Dabei liegt der Fokus sowohl auf der detaillierten Betrachtung der Gasphasenchemie als auch auf der Interaktion der Kohle mit der Gasphase. Ziel der Arbeit ist die Entwicklung einer Methode für die Simulation großtechnischer Kohlestaubfeuerungen. Die energetische Umsetzung von Kohle läuft in drei wesentlichen Schritten ab: Verdampfung der Feuchtigkeit, Ausgasung der Kohle (Pyrolyse) und schließlich der Koksabbrand. Da die Struktur der Kohle als fossiler Brennstoff hoch komplex ist, existieren viele prädiktive, rechenaufwändige Modelle zur Beschreibung dieser Prozesse [1–4]. Diese Modelle können nicht direkt in numerischen Strömungssimulationen genutzt werden, dienen aber zur Kalibrierung einfacherer kinetischer Modelle. Diese in der Arbeit angewendete Prozedur wird in [5] beschrieben. Zur detaillierten Beschreibung des Abbaus der entstehenden höheren Kohlenwasserstoffe werden in der Simulation große Reaktionsmechanismen benötigt. Die Benutzung solcher Mechanismen ist mit großen Rechenzeiten verbunden und daher bleibt deren Anwendbarkeit auf einfache Anwendungsfälle beschränkt. Der Vorteil der Flamelet Modellierung besteht darin, dass unter bestimmten Voraussetzungen der komplette thermo-chemische Zustand, bestehend aus Temperatur, Druck und Zusammensetzung, mit nur wenigen charakterisierenden Kontrollvariablen abgebildet werden kann. Durch Vorgabe und Variation der Kontrollvariablen können diese Zustände mittels kanonischer Flammenkonfigurationen vorberechnet und in sogenannten Flamelettabellen abgespeichert werden. Für das klassische Flamelet / Fortschrittsvariablen Modell [6] wird der thermo-chemische Zustand über Mischungsbruch und Fortschrittsvariablen parametriert, dabei bestimmt der Mischungsbruch den Anteil an Brenn- stoff im Gemisch und die Fortschrittsvariable den Fortschritt der chemischen Reaktion. Die Kontrollvariablen werden in der numerischen Simulation transportiert, an Stelle der Energie- und Speziesgleichungen. Dies stellt für große Mechanismen eine dramatische Reduktion der zu lösenden Gleichungen dar. Der thermo-chemische Zustand ergibt sich per Look-up aus den Flamelettabellen. Im Zuge der Verbrennung trockener Kohle werden zwei Brennstoffe durch Pyrolyse und Koksabbrand freigesetzt. Für die Flamelet Modellierung bedeutet dies entsprechend je einen Mischungsbruch für Pyrolysegas und Produkte aus dem Koksabbrand. Neben der Fortschrittsvariablen wird ebenfalls die Enthalpie der Gasphase als Kontrollvariable benötigt aufgrund des intensiven Wärmeaustauschs zwischen Kohle und Gasphase. In der Arbeit erfolgt die Vorstellung der benötigten Transportgleichungen sowie die Beschreibung verschiedener Methoden zur Integration nicht-adiabater Zustände in Flamelettabellen. Dabei unterscheiden sich die vorgestellten Tabellierungstrategien hauptsächlich in der betrachteten Verbrennungsart. IV Erfolgt die Mischung von Brennstoff und Oxidationsmittel erst in der untersuchten Flammenkonfiguration, spricht man von Diffusionsflammenstrukturen; sind beide schon gemischt, so entstehen Vormischflammenstrukturen. Die Detektion solcher Strukturen erfolgt in der Arbeit anhand einer Flammenstrukturanalyse mittels Flammenmarker. Die prinzipielle Übertragbarkeit des Flamelet / Fortschrittsvariablen Modells auf turbulente Kohlestaubfeuerung wurde von Watanabe [7] gezeigt, jedoch ist die Bewertung der eingesetzten Flamelet Modellierung in Grobstruktursimulationen nicht ohne weiteres möglich. Deshalb werden zur Verifizierung der entwickelten Tabellierungstrategie in der Arbeit einfache Flammenkonfigurationen betrachtet, die es erlauben, direkte Chemielösungen mit den Lösungen der tabellierten Chemie zu vergleichen. Für den entsprechenden Vergleich erfolgt die Vorstellung zweier Analysen. Bei der a priori Analyse wird der thermo-chemische Zustand der detaillierten Lösung mit dem tabellierten Zustand verglichen. Für den Look-up werden dabei die Kontrollvariablen der direkten Chemiesimulation benutzt. Die a posteriori Analyse ist der Vergleich einer voll gekoppelten Rechnung unter Benutzung der Tabellierungstrategie mit der zugehörigen detaillierten Rechnung. Die erste untersuchte Konfiguration stellt eine Gegenstromanordnung mit vorgewärmter Luft und Kohlebeladung dar. Die Hauptergebnisse dieser rein numerischen Studie wurden bereits veröffentlicht [8] und es konnte die erfolgreiche Applikation der vorgestellten Tabellierungstrategie in dieser Anordnung für Tabellen basierend auf Diffusionflammenstrukturen gezeigt werden. Für die Validierung der detaillierten Rechnungen erfolgt die Nutzung experimenteller Daten [9, 10] für magere Methan-Sauerstoff-Stickstoff Mischungen in Staupunktströmungen. Es zeigt sich, dass diese Konfigurationen stark von den vorgemischten Gasflammen dominiert werden und somit Tabellen basierend auf Vormischflammenstrukturen einzusetzen sind. Die entwickelte Tabellierungsmethode ist in der Lage, auch diese Flammenstrukturen abzubilden. Abschließend wird numerisch eine Parametervariation hinsichtlich Einlassgeschwindigkeit und Kohlebeladung vorgestellt, um die Robustheit und breite Anwendbarkeit der entwickelten Tabellierungstrategie aufzuzeigen. Zusammenfassend konnte mittels Flammenstrukturanalyse für jede vorgestellte Konfiguration der zu verwendende Typ der Tabelle bestimmt werden. In den untersuchten Konfigurationen führte deren Anwendung zu einer guten Übereinstimmung mit den detaillierten Rechnungen. Damit legt diese Arbeit den Grundstein für weiterführende Betrachtung zur Simulation großtechnischer Kohlestaubfeuerungen.

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3

Mescher, Ann M. "Flame structures in a pulverized coal combustor /". The Ohio State University, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487862399449444.

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4

Karlsen, Torill Marie. "The erosive characteristics of South African pulverized coals". Master's thesis, University of Cape Town, 1985. http://hdl.handle.net/11427/22642.

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5

Misra, Mahendra Kumar. "Modeling of pulverized-coal flames in plug flow furnaces /". The Ohio State University, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487685204970189.

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6

Gallagher, Neal Benjamin. "Alkali metal partitioning in a pulverized coal combustion environment". Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/185896.

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Fouling, slagging, corrosion, and emission of submicron particulate from pulverized coal combustors have been linked to vapor alkali. Size segregated fly ash samples extracted from a 17 kW down-fired pulverized coal combustor showed strong evidence of alkali vaporization. The fraction of sodium in sizes smaller than 0.65 μm (f(8A)) showed a correlation with acid soluble sodium divided by total silicates in the parent coal. Addition of silicates to coal reduced f(8A) for sodium. Potassium existing primarily in the mineral matter, did not show a similar correlation, but f(8A) for potassium did correlate with f(8A) for sodium. Bench scale experiments indicated potassium does not vaporize in the presence of Na or Cl alone, but requires both, and was only released when sodium was captured. Additional of sodium acetate to coal increased f(8A) for potassium. Equilibrium calculations, experiment, and modelling of sodium capture by silicates during pulverized coal combustion identified several important mechanisms governing alkali behavior. The mode of occurrence of alkali in the parent coal dictates its ability to vaporize, its release kinetics, and its sate as it diffuses to the char surface. Other species such as chlorine, sulfur, moisture, and other metals influence alkali stability in the vapor, its reactivity, and its condensation characteristics. Char oxidation can influence alkali vaporization, and capture by affecting included silicate surface area. Sodium reaction with silicates captures from 70 to over 95% of total sodium for typical coals. Silicate additive appears to be a viable technique for reducing the fraction of alkali in the vapor during combustion.

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7

Seames, Wayne Stewart. "The partitioning of trace elements during pulverized coal combustion". Diss., The University of Arizona, 2000. http://hdl.handle.net/10150/284196.

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The environmental impact resulting from the release of trace elements during coal combustion is an important issue for the coal-fired electric utility industry. Trace elements exit the combustor by partitioning between the flue gas and the fly ash particles. A comprehensive study has been conducted to investigate the mechanisms governing the partitioning of trace elements during pulverized coal combustion. The behavior of seven trace elements (arsenic, selenium, antimony, cobalt, cesium, thorium, and cerium) in six pulverized coals were studied under commercially relevant conditions in a well-described laboratory combustion environment. The partitioning of trace elements is governed by the extent of volatilization during combustion, the form of occurrence in the flue gas, and the mechanisms controlling vapor-to-solid phase transformation to fly ash particle surfaces. The most common vapor-to-solid phase partitioning mechanism for semi-volatile trace elements is reaction with active fly ash surfaces. Trace elements that form oxy-anions upon volatilization (e.g. arsenic, selenium, antimony) will react with active calcium and iron cation fly ash surface sites. Trace elements that form simple oxides upon volatilization (e.g. cobalt, cesium) will react with active aluminum oxy-anion fly ash surface sites. The maximum combustion temperature affects the availability of active calcium and iron surface sites but not aluminum sites. Sulfur inhibits the reactivity of oxy-anions with iron surface sites. For coals with high sulfur contents (>1 wt % as SO₂), volatilized trace elements that form oxy-anions will partition by reaction with calcium surface sites if sufficient sites are available. For coals with low sulfur contents, volatilized trace elements that form oxy-anions, will partition by reaction with iron surface sites. Volatilized trace elements that form oxy-anions will not partition by reaction if the coal sulfur content is high and the calcium content is low (<3 wt% as CaO). Transition metals (e.g. cobalt) may form simple oxides, oxy-anions or both upon volatilization. An appreciable fraction of trace elements with limited volatility (e.g. cobalt, thorium, cerium, cesium) will volatilize. These will partition back to the solid phase by homogeneous nucleation or surface reaction depending upon the post-combustion conditions present.

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8

Ogden, Gregory E. "Pulverized coal combustion: Flame attachment and nitrogen oxide emissions". Diss., The University of Arizona, 2002. http://hdl.handle.net/10150/289822.

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To fully utilize coal as a long-term energy source, pollution prevention technologies must be developed to mitigate the negative environmental and health impacts of coal combustion. NOₓ emissions are of particular concern due to their role in forming ground-level ozone, photochemical smog, fine particulates and acid rain. A systematic evaluation of near-flame aerodynamics was conducted to determine how burner operating parameters and oxygen partial pressure influence flame attachment and coal ignition, two properties essential for proper low NOₓ burner operation. A laboratory scale (17kW) 2m tall, 0.5m diameter electrically heated furnace and axial burner with adjustable secondary combustion air annuli and primary fuel jets were used in the study. Transport air oxygen partial pressure (PO₂), coal particle size distribution, primary and secondary jet velocity, and wall temperature were varied independently to determine the effect of each variable on flame attachment and NOₓ. NOₓ emissions from the furnace were similar to those from full-scale tangentially-fired boilers. The tendency for flame attachment increased with velocity ratio (Θ), wall temperature, PO₂, and coal fines. Θ's greater than 1 were required for stable combustion. Increasing Θ reduced flame standoff distances and NOₓ for always-detached flames. NOₓ increased with Θ for always-attached flames. Increasing PO₂ reduced NOₓ by up to 50% by promoting flame attachment. However both oxygen enrichment and increasing fines had little impact on NOₓ for always-attached and always-detached flames. Wall temperature and excess air in leakage were the dominant variables affecting NOₓ. Furnace exhaust oxygen levels increased when operating under a slight vacuum with corresponding increases in NOₓ. Emissions for detached flames increased with wall temperature 3 times faster than attached flames. Emissions data obtained from the furnace under slight positive furnace pressure increased linearly with wall temperature. A novel dual flame was produced at high Θ and reduced PO₂ consisting of one flame attached to the burner and one stabilized 18" below the burner. This configuration is similar to staged combustion but without separate over-fire air. Emissions from the dual flame were significantly below those observed from conventional Type-O attached and detached flames.

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9

Bool, Lawrence E. III. "The partitioning of iron during the combustion of pulverized coal". Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/186374.

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The presence of pyrite in coal has long been known to affect the slagging propensity of the coal when burned in industrial boilers. In particular it has been found that molten pyrite bonds very well to steel furnace tubes. In addition, it has been found that the amount of chemically bound iron greatly influences the slag contact angle and stickiness on steel heat transfer tubes. The goal of this research, which is part of a larger project headed by the PSI Technology Company to study mineral matter transformations during combustion, is to explore and model the mechanisms dominating the fate of iron during combustion. To achieve this goal a well characterized suite of coals was burned in a 17kW downfired laboratory combustor. Fly ash was extracted from the flue gas and size classified. These ash samples were then subjected to a number of analytical techniques including Atomic Absorption Spectroscopy (AA), Energy Dispersive X-Ray (EDX), Computer Controlled Scanning Electron Microscopy (CCSEM), Transmission Electron Microscopy (TEM), and Mossbauer Spectroscopy to determine the ash bulk composition and morphology. Of these techniques, Transmission Electron Microscopy and Mossbauer, were instrumental in determining the iron-silicate interactions during combustion. Utilizing the information gleaned from the fly ash analysis, and work in the literature, it was possible to propose a pathway for iron interactions during combustion. A mechanistic model was then proposed to quantify the competition between processes governing iron oxidation/crystallization and those promoting iron-silicate mixing/reaction. This model described the partitioning of iron between chemically bound and physically bound phases. By utilizing kinetic parameters from the literature and fundamental transport phenomena, this model was able to successfully correlate data from several coals burned under a range of combustion conditions. The model can also be used to quantify the effect of combustion modifications and fuel property changes on iron partitioning.

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10

Xia, Yunkai. "Dynamic property evaluation of frother". Morgantown, W. Va. : [West Virginia University Libraries], 2000. http://etd.wvu.edu/templates/showETD.cfm?recnum=1743.

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Thesis (M.S.)--West Virginia University, 2000.
Title from document title page. Document formatted into pages; contains x, 89 p. : ill. Vita. Includes abstract. Includes bibliographical references (p. 62-64).

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11

Ismail, Mostafa Mostafa Ahmed. "Char burn-out and flame stability in a pulverized fuel furnace". Thesis, Imperial College London, 1989. http://hdl.handle.net/10044/1/47486.

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12

Loehden, David Otto. "The formation of fouling and slagging deposits in pulverized coal combustion". Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/14685.

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13

Helble, Joseph John. "Mechanisms of ash particle formation and growth during pulverized coal combustion". Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14860.

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14

Bose, Arun Chand. "Pulverized coal combustion: Fuel nitrogen mechanisms in the rich post-flame". Diss., The University of Arizona, 1989. http://hdl.handle.net/10150/184635.

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Chemical kinetic mechanisms governing the fate of coal nitrogen in the fuel-rich stage of a pulverized-coal staged combustion process were investigated. Emphasis was on determination of the effects of coal rank, temperature and stoichiometric ratios on the speciation and rates of destruction of nitrogenous species and correlation of coal data by a unif1ed mechanism. The relative importance of homogeneous and heterogeneous mechanisms during post-flame interconversion reactions of the fuel nitrogen pool was quantified. Experiments with doped propane gas and a high- and low-grade coals, burned under a variety of conditions in a 2 Kg/h downflow combustor, yielded timeresolved profiles of temperature, major (H₂, CO, CO₂, O₂ and N₂), nitrogenous (NO, HeN and NH₃) and hydrocarbon (CH₄ and C₂H₂) species. These profiles allowed global mechanisms describing the speciation and destruction of fuel nitrogen species to be explored, using predictive models of increasing levels of sophistication. Fuel nitrogen speciation varied significantly from coal to coal and depended on stoichiometric ratio and temperature, which were varied independently. A general correlation describing the destruction rate of NO was derived from data. This rate, which was first-order in both NO and NH₃, was generally valid for all coals and all conditions examined. Fuel nitrogen interconversion reactions, especially destruction of NO and HeN, was predominantly homogeneous, but no single elementary reaction was controlling. Temperature quench down the combustor is the origin of OH equilibrium overshoot. Expressions for estimating the OH equilibrium overshoot as a function of the axial temperature decay along the combustor were derived both empirically and kinetically from fundamental considerations using data from doped propane gas runs. These expressions, together with available literature values of gas phase rate coefficients, could adequately describe the post-flame NO and HeN profiles of coal and gas runs. HeN profiles in the far postflame zone of the coal flames are strongly influenced by the slow release of nitrogen from the coal residue. This devolatilization plays a critical role in supplying the HeN that drives the multistep process converting fuel N into molecular nitrogen.

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15

Williams, Anthony Noel. "Assessment, development and validation of nitric oxide formation and destruction mechanisms for pulverized coal fired combustion /". St. Lucia, Qld, 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16492.pdf.

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16

Scotto, Mark Vincent 1960. "A mechanism for the oxidation and fragmentation of a char particle". Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276699.

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A mechanism for the oxidation and fragmentation of a char particle was developed. Qualitative agreement between the model simulations and experimental data observed in the literature, is found for the higher gas temperatures (1700K). However fundamental differences are found in the particle temperature histories and burnout times at low temperature (1250K). The role that fragmentation plays on the char particle history is incorporated into the model and the possible production of fine particulate through fragmentation is examined. A relatively large fraction of the mass of char available for fragmentation is produced early in the combustion history of the particle. Therefore, if this mechanism is important in the generation of fine particulate matter during char combustion, the simulations indicate that it would occur early in the combustion process. Due to the limited experimental data in the literature on the time resolved particle size distribution in the early stages of combustion, corroboration between model and experiment was not possible.

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17

Rech, Rene Lucio. "Desenvolvimento de equipamento para estudos de injeção de carvão pulverizado em alto-fornos siderúrgicos". reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/185240.

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A injeção de carvão pulverizado (pulverized coal injection - PCI) é uma técnica largamente utilizada nos altos-fornos pelas siderúrgicas brasileiras, seguindo uma tendência mundial, que busca reduzir o consumo específico de coque por tonelada de gusa e, em consequência, do custo do ferro gusa produzido. A combustão do carvão pulverizado ocorre sob pressões médias (de até 4 atm), temperaturas de chama elevadas (em torno de 2 000 °C), altas taxas de aquecimento (104 a 105 °C/s), tempo de residência muito curtos (inferiores a 40 ms), e é seguida pela gaseificação na presença de CO2. Como não existem métodos padronizados para a avaliação das características de combustão dos carvões para sua utilização em PCI, utilizam-se geralmente equipamentos de injeção de carvão em escalas laboratorial e de bancada, além plantas-piloto com este propósito. O objetivo principal deste trabalho é apresentar as etapas do desenvolvimento de um equipamento em escala de bancada realizado no Laboratório de Siderurgia da Escola de Engenharia da UFRGS (LASID-UFRGS), desde o projeto conceitual até a fase pré-operacional, e os resultados iniciais obtidos, para estudar as características de combustão dos carvões em condições bastante similares às que ocorrem nos altos-fornos. Os testes iniciais incluem a avaliação da combustão de um carvão brasileiro objetivando seu uso potencial em PCI, em substituição parcial de carvões importados para este fim. Optou-se por um projeto moderno, altamente automatizado, que inclui aquisição rápida de dados, com escala e conceito operacional adequados para estudos acadêmicos, de configuração vertical e que possibilitasse a operação no modo de injeção de uma amostra de carvão em pulso único, bem como uma adequação futura ao modo de injeção contínua de carvão. Algumas características relevantes do equipamento são a medição e aquisição ultrarrápida de dados termodinâmicos de pressão e temperatura em diversos pontos do sistema, permitindo o registro dos fenômenos transientes que ocorrem durante a combustão, a possibilidade de programação e controle de tempos, pressões e temperaturas para testes de combustão e de pirólise através de rotinas especialmente desenvolvidas para isto, bem como a coleta representativa dos produtos sólidos e gasosos resultantes da combustão para posterior análise. É ainda possível a filmagem da xvi combustão em modo ultrarrápido, permitindo correlacionar as imagens aos dados termodinâmicos registrados durante a combustão ao longo de um segundo, em intervalos de poucos milissegundos. Os resultados iniciais obtidos na fase pré-operacional demonstram o bom funcionamento do sistema, permitindo distinguir claramente a influência da variação de parâmetros operacionais como tipo de carvão, massa e de amostra injetada, pressão e temperatura de operação e composição dos gases oxidantes.
Pulverized coal injection (PCI) is a technique used in blast furnaces (BFs) by Brazilian steel industry, following a worldwide trend, to reduce coke consumption by ton of hot metal produced, and therefore reducing the overall cost. Burning of pulverized coal injected into tuyeres of BFs takes place under medium pressure (up to 4 atm), high flame temperatures (around 2 000 °C), very fast heating rates (104–105 °C/s) and very short residence times, less than 40 ms, followed by gasification in presence of CO2. Since there are no standard tests for evaluation of coal combustibility at PCI conditions, lab and bench scale coal injection rigs and pilot plants are usually employed for this purpose. This work shows the development steps of a bench-scale rig, built at the Iron and Steelmaking Laboratory of the School of Engineering - Universidade Federal do Rio Grande do Sul (LASID-UFRGS), from the conceptual design to the pre-operational step, as well as the initial results. This equipment permits to study the combustion characteristics of coals in conditions very close to those occurring in blast furnaces. Initial tests include the combustion evaluation of a Brazilian coal, aiming its potential usage for PCI, in partial substitution of imported coals for this purpose. The rig has a modern design and is highly automated. Its scale and operational concept is fitted for academic studies. It has a vertical configuration, to be operated with injection of a coal sample in a single pulse mode and is capable to be adjusted afterwards to continuous coal injection mode. Some relevant characteristics of the injection rig are: (1) the very fast measurement and acquisition of thermodynamic data of pressure and temperature in several points of the system, allowing the capture of transient phenomena occurring along the combustion process; (2) the possibility of programming and controlling time intervals, pressures and temperatures to perform combustion and pyrolysis tests, employing specially developed routines; and (3) the representative sample collection of solid and gaseous combustion products to be further analyzed. It is also possible to capture images of the combustion by a high-speed camera, allowing correlate the images, acquired during a time interval of one second, with the thermodynamic data collected in intervals of few milliseconds. xviii The good performance of the equipment was shown by the initial results obtained at the pre-operational phase. The experimental data clearly depicted the effect of operational parameters like coal type, injected sample mass, operational pressure and temperature, and oxidizing gas composition.

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18

Chu, L.-M. "The value of pulverized refuse fines for plant growth and land reclamation". Thesis, University of Liverpool, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233803.

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19

Salem, Mahmoud. "Investigation of materials based on pulverized fuel ash and sodium silicate solutions". Thesis, University of Greenwich, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303855.

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20

Graham, Karl Allen. "Submicron ash formation and interaction with sulfur oxides during pulverized coal combustion". Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13745.

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21

Mackrory, Andrew John. "A Mechanistic Investigation of Nitrogen Evolution in Pulverized Coal Oxy-Fuel Combustion". Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2640.pdf.

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22

Lokare, Shrinivas Sadashiv. "A mechanistic investigation of ash deposition in pulverized-coal and biomass combustion /". BYU ScholarsArchive, 2008. https://scholarsarchive.byu.edu/etd/1594.

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This investigation details the effects of fuel constituents on ash deposition through systematic experimental and theoretical analyses of fundamental particle experiments and a suite of fuels with widely varying inorganic contents and compositions. The experiments were carried out in the Multifuel Flow Reactor (MFR) at Brigham Young University. Fuels included several biomass fuels (straw, sawdust and mixtures of straw-sawdust with other additives such as Al(OH)3, CaCO3, etc.) and four commercially-used coals (Illinois#6, Powder River Basin – Caballo and Cordero, Blind Canyon, and Lignite – Beulah Zap). The data from the series of experiments quantitatively illustrate the effects of fuel properties, physical and/or chemical, on ash deposition rate mechanisms. In deposition investigation, the most significant deposition mechanisms in a general ash deposition model – inertial impaction, condensation and eddy impaction – were selected. In this PhD work, these three mechanisms are analyzed using simulation techniques such as Fluent and programming languages such as C++. The experimental data was collected for deposition rate measurements to provide a data set for the model validations except for eddy impaction. In this model analyses, the impaction efficiency model predictions from this work indicated lower impaction efficiencies than the traditional potential flow model presented by others (Israel 1983). The experimental data by others (Lokare 2003) and the data collected in this work support these predictions and present a new impaction efficiency correlation as a function of Stokes number. Similarly, the capture and condensation models perform well and are supported by the respective experimental data. The comprehensive ash deposition model predicts ash deposition rates within 10% of experimental data and is able to distinguish the role of various additives in recipe fuels combustion. As an additional results, NOX behavior of Illinois#6 and PRB (Caballo) in oxyfuel combustion show evidence of inherent NOX reducing feature of oxyfuel combustion.

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23

LINAK, WILLIAM PATRICK. "THE EFFECT OF COAL TYPE, RESIDENCE TIME AND COMBUSTION CONFIGURATION ON THE SUBMICRON AEROSOL COMPOSITION AND SIZE DISTRIBUTION FROM PULVERIZED COAL COMBUSTION (STAGED, FLYASH, SPECIES ENRICHMENT)". Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/188070.

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Pulverized samples of Utah bituminous, Beulah (North Dakota) low Na lignite, Beulah high Na lignite and Texas (San Miguel) lignite coals were burned at a rate of 2.5 kg/hr in a laboratory furnace under various (overall fuel lean) combustion conditions. Particle size distributions (PSD) and size segregated particle filter samples were taken at various positions within the convection section. Temperature and gas concentrations were measured throughout. The evolution of the submicron PSD within the convection section for the four coals was similar, although the location of the initial particle mode at the convection section inlet varied with coal type. While staged (.8/1.2) combustion of the Utah bituminous coal had a variable effect on the volume of submicron aerosol produced, staged combustion of two of the three lignites (Beulah low Na and Texas) caused a definite increase in the submicron aerosol volume. Vapor enhancement due to a localized reducing atmosphere, which would effect coals of higher ash volatility or higher inherent ash content, is thought to explain this behavior. Depressed combustion temperatures associated with the high moisture content of the Beulah high Na lignite are thought to offset the effects of staging. Increased combustion temperatures (through oxygen enrichment) caused staged volume increases for the Beulah high Na lignite. Combustion temperatures are a controlling factor even at more extreme staging conditions. Chemical analysis of the size segregated particle samples show the trace elements, As, Pb, Zn and the major elements, Na and K to be enriched in the submicron aerosol. Auger depth profiles show these small particles to be comprised of a core enriched in Fe, Si, Ca and Mg and surface layers enriched in Na and K. These results point to a mechanism of homogeneous nucleation of low vapor pressure species followed by successive layering of progressively more volatile species. Volatile species are enriched in the submicron aerosol due to the large surface areas provided. Modeling efforts show that while coagulation may be the dominant mechanism to describe the aerosol evolving within the convection section, it cannot be used solely to predict the PSD. Another mechanism, presumably surface area dependent growth (condensation) must be included.

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24

Oshinowo, Olanrewaju Malcolm. "Flow modifying screens in turbulent flows, an application to pulverized coal-fired boilers". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ27707.pdf.

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25

Schaffel-Mancini, Natalia [Verfasser]. "Ecological evaluation of the pulverized coal combustion in HTAC technology / Natalia Schaffel-Mancini". [Clausthal-Zellerfeld] : [Univ.-Bbibliothek], 2009. http://d-nb.info/997066938/34.

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26

Kang, Shin-Gyoo. "Fundamental studies of mineral matter transformation during pulverized coal combustion : residual ash formation". Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13746.

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27

Dedy, Eka Priyanto. "Efficient Pretreatment Technology and Ash Handling for Co-firing Pulverized Coal with Biomass". Kyoto University, 2018. http://hdl.handle.net/2433/235093.

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28

Chan, Kwok-wong, e 陳國煌. "The study of utilization of pulverized fuel ash in road construction in Hong Kong". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1993. http://hub.hku.hk/bib/B31232966.

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29

Borgert, Kyle James. "Oxyfuel Carbon Capture for Pulverized Coal: Techno - Economic Model Creations and Evaluation Amongst Alternatives". Research Showcase @ CMU, 2015. http://repository.cmu.edu/dissertations/523.

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Abstract (sommario):

Today, and for the foreseeable future, coal and other fossil fuels will provide a major portion of the energy services demanded by both developed and developing countries around the word. In order to reduce the emissions of carbon dioxide associated with combustion of coal for electricity generation, a wide range of carbon capture technologies are being developed. This thesis models the oxyfuel carbon capture process for pulverized coal and presents performance and cost estimates of this system in comparison to other low-carbon fossil fuel generators. Detailed process models for oxygen production, flue gas treatment, and carbon dioxide purification have been developed along with the calculation strategies necessary to employ these components in alternative oxyfuel system configurations for different types of coal-fired power plants. These new oxyfuel process models have been implemented in the widely-used Integrated Environmental Control Model (IECM) to facilitate systematic comparisons with other low-carbon options employing fossil fuels. Assumptions about uncertainties in the performance characteristics of gas separation processes and flue gas duct sealing technology, as well as plant utilization and financing parameters, were found to produce a wide range of cost estimates for oxyfuel systems. In case studies of a new 500 MW power plant burning sub-bituminous Powder River Basin coal, the estimated levelized cost of electricity (LCOE) 95% confidence interval (CI) was 86 to 150 [$/MWh] for an oxyfuel system producing a high-purity [99.5 mol% CO2] carbon dioxide product while capturing 90% of the flue gas carbon dioxide. For a CoCapture oxyfuel system capturing 100% of the flue gas CO2 together with all other flue gas constituents, the estimated LCOE 95% CI was 90 to 153 [$/MWh] (all costs in constant 2012 US Dollars). Using the IECM, an oxyfuel system for CO2 capture also was compared under uncertainty to an existing amine-based post-combustion capture system for a new 500 MW power plant, with both systems capturing 90% of the CO2 and producing a high-purity stream for pipeline transport to a geological sequestration site. The resulting distribution for the cost of CO2 avoided showed the oxyfuel-based system had a 95% CI of 44 to 126 [$/tonne CO2] while the amine-based system cost 95% CI ranged from 50 to 133 [$/tonne CO2]. The oxyfuel cost distribution had a longer tail toward more expensive configurations but over 70% of the distribution showed the oxyfuel-based system to be ~10[$/tonne CO2] lower in cost compared to the amine-based capture system. An evaluation of several low-carbon generation options fueled by coal and natural gas further considered both direct and indirect greenhouse gas emissions. This analysis showed oxyfuel to be economically competitive with all capture system considered, and also indicated oxyfuel to be the preferred carbon capture technology for minimizing overall carbon intensity. Combined, these results suggest that oxyfuel is a promising carbon capture technology, and the only one which offers the unique ability to capture all the combustion gases to become a truly zero emission coal plant. Realization of the latter option, however, is contingent on the development of new regulatory policies for underground injection of mixed flue gas streams that is outside the scope of this thesis.

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30

Smith, Karl M. "The capture of COâ‚‚ from flue gas using adsorbents developed from pulverized fuel ash". Thesis, University of Nottingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440998.

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31

Chan, Kwok-wong. "The study of utilization of pulverized fuel ash in road construction in Hong Kong /". [Hong Kong] : University of Hong Kong, 1993. http://sunzi.lib.hku.hk/hkuto/record.jsp?B1339244X.

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32

Shen, Qiqing. "Rapid Pyrolysis of Raw and Pretreated Biomass under Conditions Pertinent to Pulverized Fuel Applications". Thesis, Curtin University, 2021. http://hdl.handle.net/20.500.11937/86933.

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Abstract (sommario):

This Ph.D. study investigates the rapid pyrolysis of biomass at high temperatures and the properties of derived char samples under various conditions. A novel drop-tube furnace was used to experimentally determine the accurate char yields after rapid pyrolysis at 1300°C, which is realized for the first time. Based on true char yield, the evolution of char properties was revealed, and the retention of inorganic species, the transformation of particle shape during rapid pyrolysis were quantified.

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33

Baranski, Jacek. "Physical and numerical modelling of flow pattern and combustion process in pulverized fuel fired boiler". Licentiate thesis, KTH, Materials Science and Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1533.

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Abstract (sommario):

This licentiate thesis describes development of modellingtools, experimental physical modelling and numerical modellingto simulate real combustion processes for advanced industrialutility boiler before and after retrofit.

The work presents extended study about formation,destruction and control of pollutants, especially NOx, whichoccur during combustion process.

The main aim of this work is to improve mixing process incombustion chamber. To do this, the optimization of placementand direction of additional air and fuel nozzles, the physicalmodelling technique is used. By using that method, it ispossible to obtain qualitative information about processes,which occur in the real boiler. The numerical simulationsverify the results from physical modelling, because duringmathematical modelling quantitative informations about flow andmixing patterns, temperature field, species concentration areobtained.

Two 3D cases, before and after retrofit, of pulverized fuelfired boiler at 125 MW output thermal power are simulated. Theunstructured mesh technique is also used to discretize theboiler. The number of grid was 427 656 before retrofit and 513362 after retrofit. The comparisons of results of numericalsimulation before and after retrofit are presented. The resultsfrom physical modelling and numerical simulation are alsoshown.

Results present that nozzles of additional air and fuel givea considerably better mixing process, uniform temperature fieldand CO2 mass fraction. The whole combustion chamber worksalmost as a "well stirred reactor", while upper part of boilerworks as a "plug flow reactor".

Differences between from measured of temperatures andpredicted temperatures are not too big, the maximum differenceis about 100 K. It seems, that calculated temperatures showgood agreement with measurement data.

The results illuminate the potential of physical andnumerical modelling methods as promising tools to deal with thecomplicated combustion processes, even for practicalapplication in the industry.

Keywords:air staging, fuel staging, boiler, furnace,computational fluid dynamics, numerical simulation, pollutants,physical modeling, pulverized fuel combustion.

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34

Shen, Yansong Materials Science &amp Engineering Faculty of Science UNSW. "Mathematical modelling of the flow and combustion of pulverized coal injected in ironmaking blast furnace". Awarded by:University of New South Wales. Materials Science & Engineering, 2008. http://handle.unsw.edu.au/1959.4/41108.

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Pulverized coal injection (PCI) technology is widely practised in blast furnace ironmaking due to economic, operational and environmental benefits. High burnout of pulverized coal in the tuyere and raceway is required for high PCI rate operation. A comprehensive review reveals that although there have been a variety of PCI models, there is still an evident need for a more realistic model for PCI operation in blast furnace. Aiming to build a comprehensive PCI model of a full-scale blast furnace, this thesis presents a series of three-dimensional mathematical models, in terms of model development, validation and application, in a sequence from a pilot-scale to a full-scale, from a simple to complicated geometry, from a coal only system to a coupled coal/coke system. Firstly a three-dimensional model of pulverized coal combustion is developed and applied to a pilot-scale PCI test rig. This model is validated against the measurements from two pilot-scale test rigs in terms of gas species composition and coal burnout. The gas-solid flow and coal combustion are simulated and analysed. The results indicate that the model is able to describe the evolutions of coal particles and provide detailed gas species distributions. It is also sensitive to various parameters and hence robust in examining various blast furnace operations. This model is then extended to examine the combustion of coal blends. The coal blend model is also validated against the experimental results for a range of coal blends conditions. The overall performance of a coal blend and the individual behaviours of its component coals are analysed. More importantly, the synergistic effect of coal blending on overall burnout is examined and the underlying mechanisms are explored. It is indicated that such synergistic effect can be optimized by adjusting the blending fraction, so as to compensate for the decreased burnout under high coal rate operation. The model provides an effective tool for the optimum design of coal blends. As a scale-up phase, the coal combustion model is applied to the blowpipe-tuyereraceway region of a full-scale blast furnace, where the raceway is simplified as a tube with a slight expansion. The in-furnace phenomena are simulated and analysed, focusing on the main coal plume. The effect of cooling gas conditions on combustion behaviours is investigated. Among the three types of cooling gas (methane, air, and oxygen), oxygen gives the highest coal burnout. Finally, a three-dimensional integrated mathematical model of pulverized coaVcoke combustion is developed. The model is applied to the blowpipe-tuyere-raceway-coke bed region of a full-scale blast furnace, which features a complicated raceway geometry and coke bed properties. The model is validated against the measurements in terms of coal burnout from a test rig and gas composition from a blast furnace, respectively. The model gives a comprehensive full-scale picture of the flow and thermo-chemical characteristics of PCI process. The typical operational parameters are then examined in terms of coal burnout and gas composition. It is indicated that the final burnout along the tuyere axis is insensitive to some operational parameters. The average burnout over the raceway surface can better represent the amount of unburnt coal particles entering the surrounding coke bed and it is also found to be more sensitive to the changes of most parameters. In addition, the underlying mechanisms of coal combustion are obtained. The coal burnout strongly depends on both oxygen availability and residence time. The existence of recirculation region gives a more realistic coal particle residence time and burnout. Compared with the fore-mentioned two models, this model is considered as a more comprehensive model of PCI operation for understanding the infurnace behaviours and provides more reliable information for the design of operational parameters.

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35

Ndibe, Collins [Verfasser]. "Characterization of torrefied fuels for direct co-firing in large pulverized fuel boilers / Collins Ndibe". Düren : Shaker, 2019. http://d-nb.info/1190525763/34.

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36

Looney, John H. "Evaluation of column flotation circuits for fine coal cleaning". Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06112009-063033/.

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37

Carpenter, William Cody. "Burner Design for a Pressurized Oxy-Coal Reactor". BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7506.

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The need for electric power across the globe is ever increasing, as is the need to produce electricity in a sustainable method that does not emit CO2 into the atmosphere. A proposed technology for efficiently capturing CO2 while producing electricity is pressurized oxy-combustion (POC). The objective of this work is to design, build, and demonstrate a burner for a 20 atmosphere oxy-coal combustor. Additionally, working engineering drawings for the main pressure vessel and floor plan drawings for the main pressure vessel, exhaust, and fuel feed systems were produced. The POC reactor enables the development of three key POC technologies: a coal dry-feed system, a high pressure burner, and an ash management system. This work focuses on the design of a traditional diffusion flame burner and the design of the main reactor. The burner was designed with the intent to elongate the flame and spread heat flux from the reacting fuel over a longer distance to enable low CO2 recycle rates. This was done by matching the velocities of the fuel and oxidizer in the burner to minimize shear between incoming jets in order to delay the mixing of the coal and oxygen for as long as possible. A spreadsheet model was used to calculate the jet velocities and sizes of holes needed in the burner, comprehensive combustion modeling was outsourced to Reaction Engineering International (REI) to predict the performance of burner designs. Using the guidance of the modeling results, a burner design was selected and assembled. The burner consists of a center tube where the primary fuel will flow, two concentric secondary tubes making an inner and an outer annulus, and eight tertiary lances. The burner and reactor are ready to be tested once issues involving the control system are resolved. Measurements that will be taken once testing begins include: axial gas and wall temperature, radiative heat flux, outlet gas temperature, and ash composition.

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38

Kleinhans, Ulrich Sebastian [Verfasser]. "Fly Ash Formation and Deposition during Pulverized Fuel Combustion: Numerical and Experimental Investigations / Ulrich Sebastian Kleinhans". München : Verlag Dr. Hut, 2017. http://d-nb.info/1135596417/34.

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39

Ngai, Yuen-yi Helen, e 魏婉儀. "Soil genesis and vegetation growth in pulverized fuel ash and refuse landfills capped by decomposed granite". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1998. http://hub.hku.hk/bib/B31219780.

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40

Cole, Robert Paul. "Ballistic Penetration of a Sandbagged Redoubt Using Silica Sand and Pulverized Rubber of Various Grain Sizes". Scholar Commons, 2010. http://scholarcommons.usf.edu/etd/3565.

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The basis of this work is to find how varying the grain size of materials contained in sandbags (sand and crumb rubber) effects the ballistic penetration of the projectiles from both the 7.62x39mm (308-short), and 9mm Luger cartridges. The sandbags were stacked in a pyramidal stacking configuration according to military specifications in order to simulate a section of a sandbag barrier or redoubt as would be seen on the battlefield. The projectiles were fired at the targets, and the velocity and penetration data was recorded. The results concern both military and civilian applications alike. The 7.62x39 round was found to experience more fragmentation as grain size increased, and was also found to have, on average, the least amount of penetration into the largest grains. The 9mm round was found to suffer negligible deformation in all of the various sizes of materials, and when fired at the two types of materials, showed a steady trend of decreasing penetration depth with increasing grain size. The sand had a wearing effect on the projectiles leaving them scared or fragmented and deformed while the rubber kept the rounds in pristine condition.

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41

Ngai, Yuen-yi Helen. "Soil genesis and vegetation growth in pulverized fuel ash and refuse landfills capped by decomposed granite /". Hong Kong : University of Hong Kong, 1998. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19471166.

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42

Messig, Danny [Verfasser], Christian [Akademischer Betreuer] Hasse, Christian [Gutachter] Hasse e Michael [Gutachter] Eiermann. "Numerical simulation of pulverized coal combustion / Danny Messig ; Gutachter: Christian Hasse, Michael Eiermann ; Betreuer: Christian Hasse". Freiberg : Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2017. http://d-nb.info/122106925X/34.

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43

Reeder, Todd A. "Corrosion-related Gas Measurements and Analysis for a Suite of Coals in Staged Pulverized Coal Combustion". BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2230.

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Eleven gas species, including CO, CO2, H2, H2O, H2S, HCl, NOX, O2, SO2, COS and SO3, were measured in a 150 kWth, staged, pulverized coal, down-fired combustor using a Fourier transform infrared (FTIR) spectrometer, gas chromatograph (GC), and a Horiba PG-250 5-gas analyzer. Additional gases such as HCN, NH3, CH4, and other hydrocarbons were also measured. Seven coals of varying rank and composition were investigated. Measurements were obtained in reducing (S.R. = 0.85) and oxidizing (S.R. = 1.15) conditions. In particular, sulfur- and chlorine-containing species including H2S, SO2, COS, SO3, and HCl are discussed. In the reducing zone, all four measured sulfur species were present although SO3 was only 1-3% of the total coal sulfur. A trade-off between SO2, H2S, and COS was clearly identifiable according to S.R. H2S and COS increased and SO2 decreased in highly reducing or high-CO regions. The total amount of sulfur in the measured species in the reducing zone was estimated to be about 65-80% of the total coal sulfur. The total amount of sulfur measured in the four gases increased linearly with coal sulfur in both the oxidizing and reducing zones for the seven coals considered. In the oxidizing zone, SO3 remained low (1-3% of total sulfur) with the only other measurable sulfur bearing species being SO2. Chlorine was found to be released in the reducing zone and form primarily HCl. As the HCl was transported into the oxidizing region, the chlorine remained as HCl. Measurement of HCl was difficult, making some of the data incomplete. The HCl concentration was found to be affected by the flow rate of gases into the sampling line and gas analyzers suggesting HCl is highly reactive and needs to be quenched rapidly or it will react during sampling. Several trends in the data were matched by equilibrium calculations including trends for H2S, COS and SO2 in both reducing and oxidizing conditions. SO3 did not match equilibrium although the amount of SO3 was proportional to the amount of sulfur in the coal. HCl, though consistent with cited literature for several coals, did not agree with equilibrium trends or values.

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44

Stimpson, Curtis K. "The Composition and Morphology of Coal Ash Deposits Collected in an Oxy-Fuel, Pulverized Coal Reactor". BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3225.

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Coal ash deposits were collected in a 160 kWth, down-fired oxy-coal reactor under staged and unstaged conditions for four different coals (PRB, Gatling, Illinois #6, and Mahoning). Concentration measurements of carbon, oxygen, sodium, magnesium, aluminum, silicon, phosphorus, sulfur, chlorine, potassium, calcium, titanium, chromium, manganese, iron, nickel, strontium, and barium were gathered from each deposit sample using scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS). Backscattered electron micrographs for each deposit sample were analyzed to gather morphological data. Particle size and shape were studied for each deposit collected. The average particle sizes of the particles in upstream deposits were much larger than the average particle sizes of the downstream deposits. The downstream deposits consisted primarily of spherical particles while the upstream deposits consisted of round, irregular polygonal, and porous particles. Deposit particles are believed to have deposited at all stages of burnout; those depositing early during pyrolysis may have continued to react after deposition. Element maps for the aforementioned elements were collected with SEM-EDS and analyzed to quantify both average composition and composition of individual particles. These values were compared to ASTM ash analyses performed for each coal and ash collected from the flue gas stream with a cyclonic particle separator. It was found that sulfur concentrations of deposits do not correlate with corresponding sulfur concentrations of the coal. Comparison of similar experiments performed with air-combustion show that oxy-combustion deposits contain about twice as much sulfur as air-combustion deposits when burning the same coal. Deposition propensity of each coal was also examined, and the PRB and Gatling coals were found to have a moderately high deposition propensity whereas the deposition propensity of the Mahoning and Illinois #6 coals was fairly low.

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45

Christ, Dominik Marek [Verfasser]. "The effect of char kinetics on the combustion of pulverized coal under oxyfuel conditions / Dominik Marek Christ". Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2014. http://d-nb.info/1058240560/34.

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46

Christ, Dominik [Verfasser]. "The effect of char kinetics on the combustion of pulverized coal under oxyfuel conditions / Dominik Marek Christ". Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2014. http://nbn-resolving.de/urn:nbn:de:hbz:82-opus-50655.

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47

Draper, Teri Snow. "Application of Two-Color Pyrometry to Characterize the Two-Dimensional Temperature and Emissivity of Pulverized-Coal Oxy-Flames". BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3206.

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Oxy-combustion is a developing technology that enables carbon dioxide (CO2) capture. Flame temperature and emissivity data were taken on a 150 kWth, pulverized-coal, burner flow reactor (BFR) that has been modified to run oxy-combustion with pure CO2 as simulated recycled flue gas. Data were taken at 78 conditions in which three parameters were varied, namely: the swirl angle of the fuel stream, the location of the oxidizer as it exited the burner, and the flow rate of diluent (pure CO2) added to the outer, secondary stream. At each condition, digital color images were obtained using a calibrated RGB camera. The images were used to determine lift-off length, temperature, and emissivity. The mathematical theory of two-color pyrometry and the calibration process used to measure the camera sensitivity is presented. The two most commonly used emissivity models in two-color pyrometry, the Hottel and Broughton and gray models, were investigated to determine which was the most appropriate for use in an oxy-coal flame. A significant difference of 7% in the temperature and 24% in the emissivity results were found when processing an image with the Hottel and Broughton and gray emissivity models. The Hottel and Broughton model was selected for processing, because the Hottel and Broughton model is more appropriate for soot which appeared to dominate flame emissions. Using the two-color data, several trends were documented. Flame temperature was seen to decrease with increasing CO2 flow rate. Within a given flame along the axial direction, temperature was seen to correlate with emissivity. As emissivity increased, flame temperature was seen to decrease. Many flames were lifted from the burner exit. Lift-off length was decreased and the flames became more attached by: 1) Increasing the amount of swirl given to the fuel stream, 2) Adding O2 to the center primary tube or 3) Decreasing the flow of secondary CO2. At higher center oxygen flow rates (above 8.5 kg/hr), the O2 jet velocity was large causing increased entrainment and mixing which degraded burner performance.

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48

Weidmann, Max [Verfasser], e Günter [Akademischer Betreuer] Scheffknecht. "About the flameless combustion of pulverized coal at the pilot scale : experiment and simulation / Max Weidmann ; Betreuer: Günter Scheffknecht". Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2018. http://d-nb.info/1169132987/34.

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49

van, Der Meer Willem Arie. "A thermofluid network-based methodology for integrated simulation of heat transfer and combustion in a pulverized coal-fired furnace". Doctoral thesis, Faculty of Engineering and the Built Environment, 2021. http://hdl.handle.net/11427/33045.

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Abstract (sommario):

Coal-fired power plant boilers consist of several complex subsystems that all need to work together to ensure plant availability, efficiency and safety, while limiting emissions. Analysing this multi-objective problem requires a thermofluid process model that can simulate the water/steam cycle and the coal/air/flue gas cycle for steady-state and dynamic operational scenarios, in an integrated manner. The furnace flue gas side can be modelled using a suitable zero-dimensional model in a quasi-steady manner, but this will only provide an overall heat transfer rate and a single gas temperature. When more detail is required, CFD is the tool of choice. However, the solution times can be prohibitive. A need therefore exists for a computationally efficient model that captures the three-dimensional radiation effects, flue gas exit temperature profile, carbon burnout and O2 and CO2 concentrations, while integrated with the steam side process model for dynamic simulations. A thermofluid network-based methodology is proposed that combines the zonal method to model the radiation heat transfer in three dimensions with a one-dimensional burnout model for the heat generation, together with characteristic flow maps for the mass transfer. Direct exchange areas are calculated using a discrete numerical integration approximation together with a suitable smoothing technique. Models of Leckner and Yin are applied to determine the gas and particle radiation properties, respectively. For the heat sources the burnout model developed by the British Coal Utilisation Research Association is employed and the advection terms of the mass flow are accounted for by superimposing a mass flow map that is generated via an isothermal CFD solution. The model was first validated by comparing it with empirical data and other numerical models applied to the IFRF single-burner furnace. The full scale furnace model was then calibrated and validated via detailed CFD results for a wall-fired furnace operating at full load. The model was shown to scale well to other load conditions and real plant measurements. Consistent results were obtained for sensitivity studies involving coal quality, particle size distribution, furnace fouling and burner operating modes. The ability to do co-simulation with a steam-side process model in Flownex® was successfully demonstrated for steady-state and dynamic simulations.

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50

Cantrell, Corey L. "Performance modeling of a pulverized coal boiler : a dissertation presented to the faculty of the Graduate School, Tennessee Technological University /". Click to access online version, 2007. http://proquest.umi.com/pqdweb?index=78&did=1445047991&SrchMode=1&sid=1&Fmt=6&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1255119231&clientId=28564.

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