La gazéification de la biomasse permet d’obtenir un gaz de synthèse riche en CO et H2 utilisable pour la production d’électricité, de biocarburants ou de composés chimiques. Ce procédé permet de palier à l’épuisement des ressources fossiles. L’utilisation de boues d’épuration comme ressources de biomasse assurerait à ce type de déchets organiques une valorisation énergétique. Cependant, les boues contiennent une forte charge minérale (entre 30 et 50% massique). Cette fraction est composée d’une vingtaine d’oxyde notamment la silice, la chaux et l’oxyde de phosphore, P2O5 (plus de 15%).Les boues sont des systèmes complexes très peu étudiés jusqu'à présent. Il est donc nécessaire de connaitre le comportement en température des inorganiques afin de mesurer leur impact lors du processus de gazéification et de se prémunir contre les risques de corrosion et de pollution du gaz liés à leur présence. - Dans un premier temps, les températures de liquidus de deux fractions minérales de boues ont été déterminées. Il s’avère que celles-ci, comprises entre 1257°C et 1358°C, sont dans la plage opératoire d’un gazéifieur à lit entrainé. De plus, une étude menée sur le binaire SiO2-P2O5 a permis d’améliorer les bases de données thermodynamiques. - Dans un second temps, les études thermodynamiques et cinétiques de volatilisation du phosphore ont mis en évidence le faible relâchement en température du phosphore grâce à la formation de phases réfractaires associant l’oxyde de phosphore et la chaux tel que Ca3(PO4)2 et Ca9Fe(PO4)7. La volatilité des inorganiques des boues est inférieure à 0.5% massique. - Enfin, l’interaction entre les inorganiques liquides et plusieurs céramiques réfractaires a été étudiée, par des essais de corrosion statique et dynamique. Un matériau, constitué d’alumine et d’oxyde de chrome, s’est révélé être un excellent candidat pour le garnissage du réacteur de gazéification. / Synthesis gas can be obtained by biomass gasification. It is composed of CO and H2 and can be used for the production of electricity, organic coumpounds and biofuels. The use of sewage sludges allows exploiting this kind of waste as biomass resources. However, sewage sludges contain a large percentage of minerals (30 to 50 % wt) composed of at least 20 different oxides including silica, lime and phosphorous oxide, P2O5 (15 % wt of the minerals). Mineral matters of sludges are complex and not well known. So, it is necessary to study their behaviour in function of temperature to understand their impact during gasification process and avoid gas pollution and corrosion of the ceramic refractories. Firstly, liquidus temperatures of two different mineral matters were determined. The result shows that these temperatures, between 1257 and 1358°C, are in the operating range of the gasifier. Thus, a study of the binary system SiO2-P2O5 had enabled to enhance thermodynamic databases. Secondly, thermodynamic and kinetic studies, confirmed the low release of P2O5 in function of temperature due to the formation of refractory compounds like Ca3(PO4)2 and Ca9Fe(PO4)7. Release of inorganics from the sludge is less than 0.5 % wt. Finally, interaction between slag and different ceramic refractories was studied. Static and dynamic trials were performed to choose the most resistant ceramic refractory. One of them composed of alumina and chrome oxide proved to be a good choice to build the gasifier wall.

Ce travail porte sur l'étude de la gazéification de biomasse en Réacteur à Flux Entrainé (RFE), dans le contexte du développement de procédés pour la production de biocarburants de deuxième génération. L'objectif de cette thèse est de modéliser les différents phénomènes qui régissent la conversion de la biomasse dans des conditions représentatives d'un RFE. La pyrolyse et la gazéification de particules de hêtre de taille comprise entre 315 et 415 µm ont été étudiées entre 800 et 1400°C en four à chute de laboratoire. L'influence de l'ajout de H2O, de CO2 et de O2 sur les produits de gazéification a été explorée, et les essais ont été simulés à partir d'un modèle 1D. L'ajout de H2O ou de CO2 permet de diminuer les rendements en char de manière significative. En phase gaz, l'influence principale de ces deux espèces est la modification de la composition en espèces majoritaires avec la réaction de gaz à l'eau. L'ajout de O2 a pour effet d'améliorer la conversion du carbone de la biomasse en gaz, et de réduire de manière significative la production de suies et de char. Le modèle, basé sur une chimie détaillée, permet de simuler ces essais de façon très satisfaisante sur toute la gamme de variation des conditions opératoires. La pyrolyse et la gazéification de particules de hêtre tamisées entre 1,12 et 1,25 mm a été étudiée en présence de O2. À 800, 1000 et 1200°C, la conversion de ces « grosses » particules est plus faible que celles des petites particules, mais à 1400°C la taille de particule n'a pas d'influence. Enfin, une étude expérimentale a été menée dans un RFE pilote pour étudier l'influence de la quantité de O2, de la taille de particule et de la pression sur la gazéification de particules de bois. Ces essais ont été simulés de façon satisfaisante en adaptant le modèle 1D. / The present work deals with biomass gasification in Entrained Flow Reactor (EFR) in the context of the development of new Biomass-to-Liquid processes. The objective of this study is to develop a comprehensive model to better understand the phenomena controlling biomass gasification in conditions representative of an EFR. Biomass pyrolysis and gasification of beech particles sieved between 315 and 450 µm have been studied between 800 and 1400°C in a drop tube furnace. The influence of H2O, CO2 and O2 addition on gasification products has been investigated and the tests have been simulated with a 1D model. The addition of H2O or CO2 leads to a significantly lower char yield. The main influence of these two oxidants in gas phase is the modification of major species composition with water gas shift reaction. With the addition of O2, the carbon conversion into gas is improved and the char and soot yields are significantly lower. The simulations are in very good agreement with the experimental results. Biomass pyrolysis and gasification of beech particles sieved between 1.12 and 1.25 mm have been studied in presence of O2. Between 800 and 1200°C the carbon conversion into gas is lower than with the smaller particles but at 1400°C the particle size has no influence. At last, the influence of O2 addition, particle size and pressure on biomass gasification has been studied in a pilot scale EFR. These experimental results have been satisfactorily simulated by adapting the 1D model.

Mit Hilfe eines variabel einsetzbaren Reaktornetzwerkmodells (RNM) wird in der vorliegenden Dissertation der Prozess der Vergasung von Brennstoffmischungen in der Fließbildsimulation beschrieben. Neben der Untersuchung von gestuften Prozessketten zur Veredelung von kohlenstoffhaltigen Energieträgern ist damit auch die differenzierte Analyse von Effekten während der Vergasung von binären und ternären Brennstoffmischungen möglich. Die Erstellung sowie Validierung des RNM wird anhand des PEFR-Vergasers, des SFGT-Vergasers und des Hybridwandvergaser vorgenommen. Die anschließende Analyse der Vergasung von Brennstoffmischungen zeigt, dass in ihren Eigenschaften sehr heterogene Brenn¬stoffmischungen Synergieeffekte bei der Vergasung hervorrufen. Diese sind in der Literatur schon oft beschrieben worden, eine systematische Analyse wird jedoch erst in der vorliegenden Dissertation durchgeführt. / Within this document the modeling and simulation of fuel blend gasification is investigated based on a variably applicable Reduced Order Model (ROM) developed for the flowsheet simulation of entrained-flow gasification reactors and processes. On one hand this enables the investigation of cascaded solid fuel conversion technologies and on the other hand effects during gasification of binary and ternary fuel blends are describable. The development as well as the validation of the ROM has been carried out for the SFGT gasifier, the PEFR gasifier and the hybrid-wall gasifier. The subsequent analysis of binary and ternary fuel blend gasification shows that fuel blends with very heterogeneous component properties induce synergy effects which have been reported in various peer review publications.

Mit Hilfe eines variabel einsetzbaren Reaktornetzwerkmodells (RNM) wird in der vorliegenden Dissertation der Prozess der Vergasung von Brennstoffmischungen in der Fließbildsimulation beschrieben. Neben der Untersuchung von gestuften Prozessketten zur Veredelung von kohlenstoffhaltigen Energieträgern ist damit auch die differenzierte Analyse von Effekten während der Vergasung von binären und ternären Brennstoffmischungen möglich. Die Erstellung sowie Validierung des RNM wird anhand des PEFR-Vergasers, des SFGT-Vergasers und des Hybridwandvergaser vorgenommen. Die anschließende Analyse der Vergasung von Brennstoffmischungen zeigt, dass in ihren Eigenschaften sehr heterogene Brenn¬stoffmischungen Synergieeffekte bei der Vergasung hervorrufen. Diese sind in der Literatur schon oft beschrieben worden, eine systematische Analyse wird jedoch erst in der vorliegenden Dissertation durchgeführt.:Nomenklatur XIV 1 Einleitung 1 2 Grundlagen 3 2.1 VERGASUNG 3 2.1.1 Vergasungsreaktionen 3 2.1.2 Vergasungskennzahlen 4 2.1.3 Modellierung der Vergasung 6 2.2 CO-VERGASUNG 8 2.2.1 Brennstoffe 8 2.2.2 Großtechnische Anwendung 8 2.2.3 Experimentelle Arbeiten 10 2.2.4 Modellierung und Simulation 13 2.2.5 Synergieeffekte 13 2.3 STOFFGEFÜHRTE PROZESSKETTE 15 2.4 BRENNSTOFFAUSWAHL UND BRENNSTOFFEIGENSCHAFTEN 16 2.5 ABLEITUNG DER AUFGABENSTELLUNG UND METHODIK 19 3 Entwicklung des Reaktornetzwerkmodells 22 3.1 MODELLIERUNGSUMGEBUNG 23 3.2 THERMODYNAMISCHE ZUSTANDSGLEICHUNG 23 3.3 STOFFDATENBANK 24 3.4 STRÖMUNGSBEDINGUNGEN IM FLUGSTROMREAKTOR 25 3.4.1 Zonenmodell 25 3.4.2 Verweilzeitverhalten 29 3.5 PARTIKELMODELL 31 3.6 MODELLIERUNG DER REAKTORZONEN 35 3.6.1 Nahbrennerzone (Zone I) 35 3.6.2 Jetzone (Zone II) 36 3.6.3 Rezirkulationszone (Zone III) 41 3.6.4 Auslaufzone (Zone IV) 41 3.6.5 Wasserquench (Zone V) 41 3.7 REGELMECHANISMEN 42 3.7.1 Regelung der Aschefließtemperatur 42 3.7.2 Regelung des Kohlenstoffumsatzgrades 46 3.7.3 Regelung der maximalen Reaktoraustrittstemperatur 47 3.7.4 Kombinierte Regelung 47 3.8 LÖSUNGSALGORITHMEN UND KONVERGENZVERHALTEN 48 4 Validierung des Reaktornetzwerkmodells 51 4.1 REAKTORNETZWERKMODELL PEFR-VERGASER 51 4.1.1 Aufbau des PEFR-RNM 51 4.1.2 Validierung des PEFR-RNM 54 4.2 REAKTORNETZWERKMODELL SFGT-VERGASER 61 4.2.1 Aufbau des SFGT-RNM 61 4.2.2 Validierung des SFGT-RNM 62 4.3 REAKTORNETZWERKMODELL HYBRIDWANDVERGASER 74 4.3.1 Beschreibung der Technologie Hybridwandvergaser 74 4.3.2 Aufbau des Hybridwandvergaser-RNM 75 4.3.3 Validierung des Hybridwandvergaser-RNM 78 5 RNM-Analyse der Vergasung von Brennstoffmischungen 85 5.1 VORÜBERLEGUNGEN 85 5.1.1 Festlegung der Randbedingungen 85 5.1.2 Thermische Vergaserleistung 86 5.1.3 Simulationsdauer und Automatisierung 87 5.2 AUSWERTUNG DER RNM-ANALYSE VON BRENNSTOFFMISCHUNGEN 89 5.2.1 RNM-Analyse BSM-BRP (binär) im SFGT-Vergaser 89 5.2.2 RNM-Analyse BSM-BRP (ternär) im SFGT-Vergaser 95 5.2.3 RNM-Analyse BSM-ibi (binär) im SFGT-Vergaser 100 5.2.4 RNM-Analyse BSM-ibi (ternär) im SFGT-Vergaser 102 5.3 DISKUSSION DER ERGEBNISSE AUS RNM-ANALYSE 106 5.4 BSM-DIAGRAMME FÜR VERGASERBETRIEB 109 5.4.1 BSM-Diagramme für SFGT-Vergaser 109 5.4.2 BSM-Diagramme für Hybridwandvergaser 112 6 Zusammenfassung und Ausblick 117 Literatur 121 Abbildungsverzeichnis 133 Tabellenverzeichnis 141 Anhang 145 / Within this document the modeling and simulation of fuel blend gasification is investigated based on a variably applicable Reduced Order Model (ROM) developed for the flowsheet simulation of entrained-flow gasification reactors and processes. On one hand this enables the investigation of cascaded solid fuel conversion technologies and on the other hand effects during gasification of binary and ternary fuel blends are describable. The development as well as the validation of the ROM has been carried out for the SFGT gasifier, the PEFR gasifier and the hybrid-wall gasifier. The subsequent analysis of binary and ternary fuel blend gasification shows that fuel blends with very heterogeneous component properties induce synergy effects which have been reported in various peer review publications.:Nomenklatur XIV 1 Einleitung 1 2 Grundlagen 3 2.1 VERGASUNG 3 2.1.1 Vergasungsreaktionen 3 2.1.2 Vergasungskennzahlen 4 2.1.3 Modellierung der Vergasung 6 2.2 CO-VERGASUNG 8 2.2.1 Brennstoffe 8 2.2.2 Großtechnische Anwendung 8 2.2.3 Experimentelle Arbeiten 10 2.2.4 Modellierung und Simulation 13 2.2.5 Synergieeffekte 13 2.3 STOFFGEFÜHRTE PROZESSKETTE 15 2.4 BRENNSTOFFAUSWAHL UND BRENNSTOFFEIGENSCHAFTEN 16 2.5 ABLEITUNG DER AUFGABENSTELLUNG UND METHODIK 19 3 Entwicklung des Reaktornetzwerkmodells 22 3.1 MODELLIERUNGSUMGEBUNG 23 3.2 THERMODYNAMISCHE ZUSTANDSGLEICHUNG 23 3.3 STOFFDATENBANK 24 3.4 STRÖMUNGSBEDINGUNGEN IM FLUGSTROMREAKTOR 25 3.4.1 Zonenmodell 25 3.4.2 Verweilzeitverhalten 29 3.5 PARTIKELMODELL 31 3.6 MODELLIERUNG DER REAKTORZONEN 35 3.6.1 Nahbrennerzone (Zone I) 35 3.6.2 Jetzone (Zone II) 36 3.6.3 Rezirkulationszone (Zone III) 41 3.6.4 Auslaufzone (Zone IV) 41 3.6.5 Wasserquench (Zone V) 41 3.7 REGELMECHANISMEN 42 3.7.1 Regelung der Aschefließtemperatur 42 3.7.2 Regelung des Kohlenstoffumsatzgrades 46 3.7.3 Regelung der maximalen Reaktoraustrittstemperatur 47 3.7.4 Kombinierte Regelung 47 3.8 LÖSUNGSALGORITHMEN UND KONVERGENZVERHALTEN 48 4 Validierung des Reaktornetzwerkmodells 51 4.1 REAKTORNETZWERKMODELL PEFR-VERGASER 51 4.1.1 Aufbau des PEFR-RNM 51 4.1.2 Validierung des PEFR-RNM 54 4.2 REAKTORNETZWERKMODELL SFGT-VERGASER 61 4.2.1 Aufbau des SFGT-RNM 61 4.2.2 Validierung des SFGT-RNM 62 4.3 REAKTORNETZWERKMODELL HYBRIDWANDVERGASER 74 4.3.1 Beschreibung der Technologie Hybridwandvergaser 74 4.3.2 Aufbau des Hybridwandvergaser-RNM 75 4.3.3 Validierung des Hybridwandvergaser-RNM 78 5 RNM-Analyse der Vergasung von Brennstoffmischungen 85 5.1 VORÜBERLEGUNGEN 85 5.1.1 Festlegung der Randbedingungen 85 5.1.2 Thermische Vergaserleistung 86 5.1.3 Simulationsdauer und Automatisierung 87 5.2 AUSWERTUNG DER RNM-ANALYSE VON BRENNSTOFFMISCHUNGEN 89 5.2.1 RNM-Analyse BSM-BRP (binär) im SFGT-Vergaser 89 5.2.2 RNM-Analyse BSM-BRP (ternär) im SFGT-Vergaser 95 5.2.3 RNM-Analyse BSM-ibi (binär) im SFGT-Vergaser 100 5.2.4 RNM-Analyse BSM-ibi (ternär) im SFGT-Vergaser 102 5.3 DISKUSSION DER ERGEBNISSE AUS RNM-ANALYSE 106 5.4 BSM-DIAGRAMME FÜR VERGASERBETRIEB 109 5.4.1 BSM-Diagramme für SFGT-Vergaser 109 5.4.2 BSM-Diagramme für Hybridwandvergaser 112 6 Zusammenfassung und Ausblick 117 Literatur 121 Abbildungsverzeichnis 133 Tabellenverzeichnis 141 Anhang 145

This project is primarily focused on improving the storage stability of bio-oils or pyrolysis oils by varying feedstock, reactor, and storage conditions. Pyrolysis oil is a complex medley of oxygenated chemicals (aliphatic and aromatic) that are well known to undergo unstable polymeric reactions (auto-catalyzed) if suitable additives are not utilized. These reactions can be severely detrimental to the long-term storage stability of pyrolysis oils. Hence, a detailed investigation was conducted in four phases namely: 1) pyrolysis oil production 2) additive prescreening 3) concentration optimization and 4) stability testing. During the first phase a lab-scale semi-continuous auger reactor is utilized to produce 16 pyrolysis oils. The reactor variables include pyrolysis temperature and vapor residence time. The feed stocks include pine wood, pine bark, oak wood, and oak bark. During the second phase a range of chemical additives (26) are prescreened to obtain three best performing additives. Anisole, glycerol, and methanol are consequently utilized to perform concentration optimization studies during the third phase. Viscosity, water content, and pH of pyrolysis oils are timely measured to assess the accelerated storage stability of pyrolysis oils during the phases 2-3. During the fourth phase, pyrolysis oils produced from three different reactor systems (lab-scale auger, large-scale auger, and entrained flow) were tested for their storage stability. Viscosity, water content, pH, density, and acid value are timely measured to assess the ambient and accelerated storage stability of pyrolysis oils during phase 4. Extrinsic variables such as light and filtration are utilized during the experimental testing of phase 4. The rheological data (Newtonian/non-Newtonian) enhanced the understanding of pyrolysis oil storage stability both qualitatively and quantitatively. The stability performance of a chemical additive is very much dependent on the concentration and its organic functional group. Consequently, alcohols fared above all the other functional groups in stabilizing the pyrolysis oils. Glycerol is observed to have special blending and homogenizing properties compared to all other additives. Feedstock seems to be the single most important factor affecting storage stability of pyrolysis oils. Consequently, pine wood resulted in the most stable pyrolysis oil whereas pine bark resulted in the least stable pyrolysis oil.

The design and optimization of entrained flow gasifiers is conducted more and more via computational fluid dynamics (CFD). A detailed resolution of single coal particles within such simulations is nowadays not possible due to computational limitations. Therefore the coal particle conversion is often represented by simple 0-D models. For an optimization of such 0-D models a precise understanding of the physical processes at the boundary layer and within the particle is necessary. In real gasifiers the particles experience Reynolds numbers up to 10000. However in the literature the conversion of coal particles is mainly regarded under quiescent conditions. Therefore an analysis of the conversion of single particles is needed. Thereto the computational fluid dynamics can be used. For the detailed analysis of single reacting particles under flow conditions a CFD model is presented. Practice-oriented parameters as well as features of the CFD model result from CFD simulations of a Siemens 200MWentrained flow gasifier. The CFD model is validated against an analytical model as well as two experimental data-sets taken from the literature. In all cases good agreement between the CFD and the analytics/experiments is shown. The numerical model is used to study single moving solid particles under combustion conditions. The analyzed parameters are namely the Reynolds number, the ambient temperature, the particle size, the operating pressure, the particle shape, the coal type and the composition of the gas. It is shown that for a wide range of the analyzed parameter range no complete flame exists around moving particles. This is in contrast to observations made by other authors for particles in quiescent atmospheres. For high operating pressures, low Reynolds numbers, large particle diameters and high ambient temperatures a flame exists in the wake of the particle. The impact of such a flame on the conversion of the particle is low. For high steam concentrations in the gas a flame appears, which interacts with the particle and influences its conversion. Furthermore the impact of the Stefan-flow on the boundary layer of the particle is studied. It is demonstrated that the Stefan-flow can reduce the drag coefficient and the Nusselt number for several orders of magnitude. On basis of the CFD results two new correlations are presented for the drag coefficient and the Nusselt number. The comparison between the correlations and the CFD shows a significant improvement of the new correlations in comparison to archived correlations. The CFD-model is further used to study moving single porous particles under gasifying conditions. Therefore a 2-D axis-symmetric system of non-touching tori as well as a complex 3-D geometry based on the an inverted settlement of monodisperse spheres is utilized. With these geometries the influence of the Reynolds number, the ambient temperature, the porosity, the intrinsic surface and the size of the radiating surface is analyzed. The studies show, that the influence of the flow on the particle conversion is moderate. In particular the impact of the flow on the intrinsic transport and conversion processes is mainly negligible. The size of the radiating surface has a similar impact on the conversion as the flow in the regarded parameter range. On basis of the CFD calculations two 0-D models for the combustion and gasification of moving particles are presented. These models can reproduce the results predicted by the CFD sufficiently for a wide parameter range.

The design and optimization of entrained flow gasifiers is conducted more and more via computational fluid dynamics (CFD). A detailed resolution of single coal particles within such simulations is nowadays not possible due to computational limitations. Therefore the coal particle conversion is often represented by simple 0-D models. For an optimization of such 0-D models a precise understanding of the physical processes at the boundary layer and within the particle is necessary. In real gasifiers the particles experience Reynolds numbers up to 10000. However in the literature the conversion of coal particles is mainly regarded under quiescent conditions. Therefore an analysis of the conversion of single particles is needed. Thereto the computational fluid dynamics can be used. For the detailed analysis of single reacting particles under flow conditions a CFD model is presented. Practice-oriented parameters as well as features of the CFD model result from CFD simulations of a Siemens 200MWentrained flow gasifier. The CFD model is validated against an analytical model as well as two experimental data-sets taken from the literature. In all cases good agreement between the CFD and the analytics/experiments is shown. The numerical model is used to study single moving solid particles under combustion conditions. The analyzed parameters are namely the Reynolds number, the ambient temperature, the particle size, the operating pressure, the particle shape, the coal type and the composition of the gas. It is shown that for a wide range of the analyzed parameter range no complete flame exists around moving particles. This is in contrast to observations made by other authors for particles in quiescent atmospheres. For high operating pressures, low Reynolds numbers, large particle diameters and high ambient temperatures a flame exists in the wake of the particle. The impact of such a flame on the conversion of the particle is low. For high steam concentrations in the gas a flame appears, which interacts with the particle and influences its conversion. Furthermore the impact of the Stefan-flow on the boundary layer of the particle is studied. It is demonstrated that the Stefan-flow can reduce the drag coefficient and the Nusselt number for several orders of magnitude. On basis of the CFD results two new correlations are presented for the drag coefficient and the Nusselt number. The comparison between the correlations and the CFD shows a significant improvement of the new correlations in comparison to archived correlations. The CFD-model is further used to study moving single porous particles under gasifying conditions. Therefore a 2-D axis-symmetric system of non-touching tori as well as a complex 3-D geometry based on the an inverted settlement of monodisperse spheres is utilized. With these geometries the influence of the Reynolds number, the ambient temperature, the porosity, the intrinsic surface and the size of the radiating surface is analyzed. The studies show, that the influence of the flow on the particle conversion is moderate. In particular the impact of the flow on the intrinsic transport and conversion processes is mainly negligible. The size of the radiating surface has a similar impact on the conversion as the flow in the regarded parameter range. On basis of the CFD calculations two 0-D models for the combustion and gasification of moving particles are presented. These models can reproduce the results predicted by the CFD sufficiently for a wide parameter range.:List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IX List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .XIII Nomenclature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XV Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . XIX 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1 1.1 State of the Art in Carbon Conversion Modeling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1.1 Combustion of Solid Particles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1.2 Gasification of Porous Particles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1.2 Classification of the Present Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 1.3 Overview of the Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7 2 Basic Theory and Model Formulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.1 Geometry and Length Scales of Coal Particles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9 2.2 Conditions in a Siemens Like 200 MW Entrained Flow Gasifier . . . . . . . . . . . . . . . . . . . . 11 2.2.1 Velocity Field . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 2.2.2 Temperature Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.2.3 Particle Volume Fraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19 2.3 Time Scales of the Physical Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2.4 Basic Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 2.5 Conservation Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 2.6 Gas Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26 2.7 Boundary Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 2.8 Numerics and Solution Strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30 2.9 Mesh and Domain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31 3 CFD-based Oxidation Modeling of a Non-Porous Carbon Particle . . . . . . . . . . . . . . . . . . . . .37 3.1 Chemical Reaction System for Combustion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37 3.1.1 Heterogeneous Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37 3.1.2 Homogeneous Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40 3.1.3 Comparison of the Semi-Global vs. Reduced Reaction Mechanisms for the Gas Phase . .41 3.2 Validation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .43 3.2.1 Validation Against an Analytical Solution of the Two-Film Model . . . . . . . . . . . . . . . . . .43 3.2.2 Validation Against Experiments I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 3.2.3 Validation Against Experiments II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .49 3.3 Influence of Ambient Temperature and Reynolds Number . . . . . . . . . . . . . . . . . . . . . . . .51 3.4 Influence of Heterogeneous Kinetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 3.5 Influence of Atmosphere . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61 3.6 Influence of Operating Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66 3.7 Influence of Particle Diameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .70 3.8 The influence of Particle Shape . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 3.9 Impact of Stefan Flow on the Boundary Layer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 3.9.1 Impact of Stefan Flow on the Drag Coefficient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83 3.9.2 Impact of Stefan Flow on the Nusselt and Sherwood Number . . . . . . . . . . . . . . . . . . . .85 3.10 Single-Film Sub-Model vs. CFD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90 3.11 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 4 CFD-based Numerical Modeling of Partial Oxidation of a Porous Carbon Particle . . . . . . . . . .99 4.1 Chemical Reaction System for Gasification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 4.1.1 Heterogeneous Chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100 4.1.2 Homogeneous Chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 4.2 Two-Dimensional Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 4.2.1 Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106 4.2.2 Influence of Reynolds Number and Ambient Temperature . . . . . . . . . . . . . . . . . . . . . .109 4.2.3 Influence of Porosity and Internal Surface . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . 120 4.3 Comparative Three-Dimensional Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 4.3.1 Geometry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .126 4.3.2 Results of the 3-D Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 4.4 Extended Sub-Model for Gasification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133 4.5 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .138 5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . .141 5.1 Summary of This Work . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . .141 5.2 Recommendations for Future Works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .145 6 Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 6.1 Appendix I: Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 6.2 Appendix II: Two-Film Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158 6.3 Appendix III: Sub-Model for the Combustion of Solid Particles . . . . . . . . . . . . . . . . . . . . 160 6.4 Appendix IV: Sub-Model for the Gasification of Porous Particles . . . . . . . . . . . . . . . . . . . 161