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.

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. <b>Keywords:</b>air staging, fuel staging, boiler, furnace,computational fluid dynamics, numerical simulation, pollutants,physical modeling, pulverized fuel combustion. / NR 20140805

Soot in coal combustion simulations is often ignored due to its computational complexity, despite significant effects on flame temperature and radiation. In this research, a 40 kW oxy-coal combustion system is modeled using Large Eddy Simulations (LES) and a semi-empirical monodisperse coal soot model. Simulation results are compared to experimental measurements of temperature, species concentrations, and soot concentration. Cases where soot is modeled are compared with cases where soot is neglected to determine the accuracy benefits of modeling soot. The simulations were able to replicate experimental results within an acceptable level of error. Including soot in the simulations did not consistently increase accuracy for the simulation setup and modeling assumptions used in this research.

This master‘s thesis deals with denitrification of brown coal-fired boiler of electric power plant. First chapters describe technical characteristics of the boiler and possible measurements which would lead to lowering NOx emissions. In order for boiler to meet emission standards valid from 1.1.2016 flue gas treatment by selective catalytic reduction is proposed. Main part of the thesis is thermal calculation of the boiler with modifications necessary in order to apply SCR. The aim of calculation is to determine flue gas exit temperature and temperature at catalyst area in order to assess the suitability of proposed modifications.

Nearly half of the electrical power produced in the United States is generated with coal. Coal power is inexpensive and reliable, but coal combustion releases harmful pollutants including NOx and SOx into the atmosphere if not controlled. CO2, a greenhouse gas, is also released during coal combustion and may contribute to global warming. A promising technology enabling carbon capture is oxy-coal combustion. During oxy-combustion, coal is burned in an atmosphere of O2 and recycled flue gas to eliminate nitrogen which makes up the majority of air-combustion flue gas. Oxy-combustion flue gas is mainly composed of CO2 and H2O. H2O can be condensed out of the gas, and the CO2 can then be captured and permanently stored relatively easily. The composition of the gas inside an oxy-fired boiler will be different due to the absence of nitrogen and the recycling of flue gas. Corrosive sulfur and chlorine gas species concentrations will be higher, and CO and NOx concentrations will be effected. An understanding of the differences in gas concentrations is critical to oxy-combustion boiler design. Four different pulverized coals were combusted in a reactor under staged and unstaged oxy-combustion conditions with warm recycled flue gas (420°F) to simulate conditions in an oxy-fired coal boiler. The gas composition was measured in the reducing and oxidizing zones for staged combustion, and in the same locations, 57 cm and 216 cm from the burner, for unstaged combustion. The results were compared to the results from similar staged air-combustion experiments using the same coals and burner. CO concentrations were higher for staged oxy-combustion compared to air-combustion, and the increase was more substantial for lower rank coals. H2S concentrations in the reducing regions were also higher, and the fraction of gas phase sulfur measured as H2S was higher for oxy-combustion. SO2 concentrations were 2.9 to 3.8 times as high as air-combustion concentrations. The measured conversion of coal sulfur to SO3 was lower for oxy-combustion, and ranged from 0.61% to 0.98%. The average fraction of coal sulfur measured in the gas phase was 84%, 80%, and 85% for staged oxy-combustion, unstaged oxy-combustion, and staged air-combustion respectively. HCl concentrations were 2.8 to 3.1 times higher in the staged oxy-combustion oxidizing zone, and a smaller fraction of coal chlorine was measured in the reducing zone. On average 70.8%, 79.5%, and 71.1% of the coal chlorine was measured as HCl for staged oxy-combustion, unstaged oxy-combustion, and staged air-combustion respectively. The fractions of coal chlorine and sulfur measured in the gas phase for staged combustion were not significantly affected by combustion media. Some staged oxy-combustion NO concentrations were lower than air-combustion concentrations while others were slightly higher, and NO emission rates were much lower due to recycling NO through the burner.

Made available in DSpace on 2016-04-26T20:27:32Z (GMT). No. of bitstreams: 1 Leticia Simonetti Garcia.pdf: 681999 bytes, checksum: 86abac5a9cbfd08222f675043aacfe62 (MD5) Previous issue date: 2008-06-19 / This paper focuses on the capital pulverization phenomenon in Brazilian corporations and the effects arising therefrom in terms of control power organization in the light of Law No. 6404, enacted on December 15, 1976 ( LSA Corporation Law), its possible consequences, and proposes feasible solutions for conflicts that may surface in this new scenario. For this purpose, control power in joint stock companies was analyzed according to the manner it is regulated in the LSA, its diverse classifications, characteristics, and outstanding implications, as well as the bodies within joint stock companies that are directly affected as a result of capital pulverization in corporations, the concepts that act as guidelines for corporate governance in Brazil and, finally, the company s social role. Based on these studies, control in corporations with pulverized capital was submitted to a critical examination in order to assess if existing legal rules and mechanisms in our laws are adequate for the new reality. The intention was to demonstrate with this thesis that capital pulverization will demand adjustments to LSA and/or to the regulations of the CVM (Securities and Exchange Commission) and of the differentiated markets of corporate governance regarding the diverse control implications in a joint stock company with pulverized capital so as to ensure legal security which is essential for the continuous growth of our capital market and, ultimately, for our economy / O presente trabalho tem como objeto investigar o fenômeno da pulverização do capital das companhias abertas brasileiras e os efeitos que essa pulverização acarreta em termos de organização do poder de controle à luz da Lei n. 6.404, de 15 de dezembro de 1976 ( LSA ), as suas eventuais conseqüências e propostas de possíveis soluções para os conflitos que podem emergir desse novo cenário. Para tanto, foram analisados o poder de controle na sociedade anônima tal como apresentado e regulado pela LSA, as suas diversas classificações, características e implicações mais marcantes, bem como os órgãos da sociedade anônima que sofrem diretamente impacto em decorrência da pulverização do capital das companhias abertas, os conceitos que norteiam a governança corporativa em nosso país e, finalmente, a função social da empresa. Com base nos referidos estudos, foi realizada uma análise crítica do controle nas companhias abertas de capital pulverizado de modo a avaliar a adequação das normas e mecanismos jurídicos existentes em nossa legislação à nova realidade que se apresenta. Pretendeu-se demonstrar com o desenvolvimento da presente tese que a pulverização do capital demandará ajustes na LSA e/ou nas regulamentações da CVM e dos mercados diferenciados de governança corporativa no tocante às diversas implicações do controle de uma sociedade anônima de capital pulverizado, a fim de garantir a segurança jurídica imprescindível ao contínuo desenvolvimento do nosso mercado de capitais e, em última análise, da nossa economia

Dentre os atuais desafios do direito societário brasileiro, a estrutura da propriedade acionária das sociedades por ações de capital aberto e a identificação daqueles que as comandam merecem destaque. O aquecimento das transações realizadas via mercado de capitais e a consolidação dos segmentos especiais de governança corporativa no Brasil resultaram no chamado fenômeno de dispersão acionária, que evidenciou certa ruptura na tradicional estrutura de propriedade acionária exclusivamente concentrada, até então predominante nas companhias brasileiras. Diante desse cenário contrastante, de mudanças no perfil do poder de controle sobre as companhias brasileiras, o presente trabalho apresentará em seu capítulo terceiro, após breve análise das estruturas de capital identificadas em diferentes economias e de retrospectiva sobre a propriedade acionária das companhias brasileiras (a serem apresentadas em seu segundo capítulo), extensa pesquisa empírica realizada com o propósito de identificar a atual estrutura de propriedade acionária predominante entre as companhias brasileiras listadas no segmento especial do Novo Mercado da BMF&BOVESPA (Novo Mercado), e com o objetivo de averiguar a existência do chamado controle societário minoritário entre tais companhias, conforme detalhado nos apêndices desta dissertação. Referida pesquisa empírica representa, ainda, rico processamento da base de dados e informações divulgadas à Comissão de Valores Mobiliários (CVM) pelas companhias listadas no Novo Mercado, e serve de base para a avaliação da necessidade de eventuais mudanças nos conceitos adotados pelo Direito Societário pátrio, tendo em vista entendimento divergente identificado na doutrina e em julgados da CVM no âmbito da possibilidade de existência de um controle societário exercido por acionista ou grupo de acionistas não detentores da maioria do capital social votante, conforme detalhado no quarto capítulo deste estudo. Por fim, serão apresentadas, no quinto e último capítulo, as considerações finais à análise proposta, com destaque para as principais conclusões obtidas na elaboração dos capítulos terceiro e quarto descritos acima, dentre elas a existência do controle societário interno não majoritário (controle minoritário) entre companhias listadas no Novo Mercado, bem como os reflexos dessa constatação no âmbito da prática do Direito Societário. / Among the current challenges of the Brazilian Corporate Law, the structure of the capital ownership of the corporations and the identification of those who exercises control over it remains an important aspect to be taken into consideration when analyzing the main aspects of the Brazilian capital market. The heat up of the transactions carried out through the capital market, and the consolidation of the special corporate governance segments in Brazil resulted in the so called phenomenon of the dispersed ownership, which revealed a rupture from the traditional structure of extremely concentrated ownership, that was prevailing until now among the Brazilian corporations. Given such contrasting scenario of changes in the profile of corporate power over Brazilian corporations, these thesis, after describing, over its first two chapters, the structures of capital ownership existent in different economies and providing a retrospective on the capital ownership of Brazilian corporations, presents, in its third chapter, an extensive empirical research performed with the purposes of identifying the current structure of capital ownership prevailing among the Brazilian companies listed in the Novo Mercado, special segment of the Brazilian Exchange BMF&BOVESPA (the New Market), as well as ascertaining the existence of minority corporate control among such companies, as detailed in the appendixes hereto. The referred empirical research presents, furthermore, detailed data processing in connection with the information disclosed by such companies to the Brazilian Stock Exchange Commission, the Comissão de Valores Mobiliários (CVM), and is also used as basis for reviewing the need of eventual changes in the concepts embodied by the Brazilian Corporate Law, in view of the divergent understanding identified in the Brazilian doctrine and judgments issued by the CVM in connection with the existence of a corporate control exercised by a shareholder or group of shareholders owner of shareholding not representative of the majority of the voting capital stock, as detailed in the fourth chapter of these thesis. Finally, the fifth and last chapter of these study presents the final considerations in connection with the review proposed hereto, highlighting the main conclusions obtained through the elaboration of the third and fourth chapters described above, among them the existence of a not majority internal control (minority control) in companies listed in the New Market, as well as the effects of such conclusion in the light of the practice of corporate law.

Gas, liquid and powder flow in the lower part of a blast furnace is complex phenomena. In order to understand the aerodynamics of the blast furnace properly, these phenomena must be included in their advanced form. Previous studies have shown that the conditions of blast furnace resemble the cold model experiments which have been done in decreasing gas velocities. Also, the recent studies have shown that liquid flow in a blast furnace can be represented more realistically considering it discrete in nature. In the current study, both the phenomena have been considered along with the injection of powder through a nozzle while studying the fluid flow behaviour in a packed bed. The situation resembles the lower part of an ironmaking blast furnace. In this study, gas flow has been modelled using k-ε turbulent model and has been coupled with previously developed stress model to calculate the raceway size. Coal powder is treated as continuum and has been modelled in the similar way as gas flow. After this gas and powder flow model were coupled with previously developed discrete liquid flow model. Liquid flow model has been considered for structured bed only. The governing equations for gas phase were discretized. Finite Volume method was used for the solution. Co-located grid is used for the simulation. Blending of upwind difference scheme and central difference scheme (deferred correction approach) is used to achieve the stability of upwind scheme and accuracy of central difference scheme. Similar treatment was employed for powder phase. For the solution of volume fraction of powder, powder phase continuity equation was used along with pseudo time step scheme. Results obtained from gas and powder models have been validated against published experimental data. Similarly, gas-liquid flow results have been validated against published experimental data on gas-powder flow. Results obtained by gas-powder-liquid model could not be validated against any experimental or theoretical data as they are not available in the literature. The effect of various parameters on the fluid flow (gas/liquid/powder) behaviour have been studied like the effect of increasing and decreasing gas velocities, flow rates of liquid, gas and powder, size of powder and packing etc. It is found that the above mentioned phenomena have significant effect on the fluid flow behaviour in a packed bed.

Dentre os atuais desafios do direito societário brasileiro, a estrutura da propriedade acionária das sociedades por ações de capital aberto e a identificação daqueles que as comandam merecem destaque. O aquecimento das transações realizadas via mercado de capitais e a consolidação dos segmentos especiais de governança corporativa no Brasil resultaram no chamado fenômeno de dispersão acionária, que evidenciou certa ruptura na tradicional estrutura de propriedade acionária exclusivamente concentrada, até então predominante nas companhias brasileiras. Diante desse cenário contrastante, de mudanças no perfil do poder de controle sobre as companhias brasileiras, o presente trabalho apresentará em seu capítulo terceiro, após breve análise das estruturas de capital identificadas em diferentes economias e de retrospectiva sobre a propriedade acionária das companhias brasileiras (a serem apresentadas em seu segundo capítulo), extensa pesquisa empírica realizada com o propósito de identificar a atual estrutura de propriedade acionária predominante entre as companhias brasileiras listadas no segmento especial do Novo Mercado da BMF&BOVESPA (Novo Mercado), e com o objetivo de averiguar a existência do chamado controle societário minoritário entre tais companhias, conforme detalhado nos apêndices desta dissertação. Referida pesquisa empírica representa, ainda, rico processamento da base de dados e informações divulgadas à Comissão de Valores Mobiliários (CVM) pelas companhias listadas no Novo Mercado, e serve de base para a avaliação da necessidade de eventuais mudanças nos conceitos adotados pelo Direito Societário pátrio, tendo em vista entendimento divergente identificado na doutrina e em julgados da CVM no âmbito da possibilidade de existência de um controle societário exercido por acionista ou grupo de acionistas não detentores da maioria do capital social votante, conforme detalhado no quarto capítulo deste estudo. Por fim, serão apresentadas, no quinto e último capítulo, as considerações finais à análise proposta, com destaque para as principais conclusões obtidas na elaboração dos capítulos terceiro e quarto descritos acima, dentre elas a existência do controle societário interno não majoritário (controle minoritário) entre companhias listadas no Novo Mercado, bem como os reflexos dessa constatação no âmbito da prática do Direito Societário. / Among the current challenges of the Brazilian Corporate Law, the structure of the capital ownership of the corporations and the identification of those who exercises control over it remains an important aspect to be taken into consideration when analyzing the main aspects of the Brazilian capital market. The heat up of the transactions carried out through the capital market, and the consolidation of the special corporate governance segments in Brazil resulted in the so called phenomenon of the dispersed ownership, which revealed a rupture from the traditional structure of extremely concentrated ownership, that was prevailing until now among the Brazilian corporations. Given such contrasting scenario of changes in the profile of corporate power over Brazilian corporations, these thesis, after describing, over its first two chapters, the structures of capital ownership existent in different economies and providing a retrospective on the capital ownership of Brazilian corporations, presents, in its third chapter, an extensive empirical research performed with the purposes of identifying the current structure of capital ownership prevailing among the Brazilian companies listed in the Novo Mercado, special segment of the Brazilian Exchange BMF&BOVESPA (the New Market), as well as ascertaining the existence of minority corporate control among such companies, as detailed in the appendixes hereto. The referred empirical research presents, furthermore, detailed data processing in connection with the information disclosed by such companies to the Brazilian Stock Exchange Commission, the Comissão de Valores Mobiliários (CVM), and is also used as basis for reviewing the need of eventual changes in the concepts embodied by the Brazilian Corporate Law, in view of the divergent understanding identified in the Brazilian doctrine and judgments issued by the CVM in connection with the existence of a corporate control exercised by a shareholder or group of shareholders owner of shareholding not representative of the majority of the voting capital stock, as detailed in the fourth chapter of these thesis. Finally, the fifth and last chapter of these study presents the final considerations in connection with the review proposed hereto, highlighting the main conclusions obtained through the elaboration of the third and fourth chapters described above, among them the existence of a not majority internal control (minority control) in companies listed in the New Market, as well as the effects of such conclusion in the light of the practice of corporate law.

This master’s thesis deals with the issue of recirculating of flue-gas of pulverized coal-fired boiler. Part of the thesis are thermal calculations of mills for operational status with and without flue-gas recirculation and design of routes of recirculated flue-gas into the mills at the level of feasibility study.