Petr A. Nikrityuk is an associate professor at the Department of Chemical and Materials Engineering, University of Alberta (UofA), Canada. Before taking his current position at UofA, Petr Nikrityuk was the head of the research group Interphase Phenomena within the Center for Innovation Competence VIRTUHCON at the Technische Universitat Bergakademie Freiberg (TUBAF), Germany. He studied mechanical engineering at the Moscow Aviation Institute (MAI), where he obtained his PhD on the topic of mathematical modeling of thermal processes. Before taking his research group leader position in Freiberg, Petr Nikrityuk worked as software developer in the field of computational fluid dynamics and as a post doc fellow in the Institute for Aerospace Engineering at the Dresden University of Technology. Bernd Meyer is the Director of the Department of the Energy Process Engineering and Chemical Engineering at the Technische Universitat Bergakademie Freiberg (TUBAF), Germany. Having obtained his academic degrees from TUBAF, he spent most of his career working in research and development in gasification and power plant technologies before taking up the appointment as a professor at TUBAF, Chair of Energy Process Engineering and Thermal Waste Treatment (EVT). He has been a member of the Saxonian Academy of Sciences, and Rector of the TUBAF since 2008. Prof. Meyer is author and coauthor of more than 90 patents in the field of gasification and related technologies.

• Preface xiList of Contributors xvAcknowledgments xviiRecommended Reading xixCoal Gasification: Basic Terminology xxi1 Modeling of Gasifiers: Overview of Current Developments 1Petr A. Nikrityuk, Thomas Förster, and Bernd Meyer1.1 Numerical Modeling in Engineering 11.1.1 The Role of Direct Numerical Simulation (DNS) in Particulate-Flow Modeling 3Summary 61.2 CFD-based Modeling of Entrained-Flow Gasifiers 61.2.1 Mainstream Computational Submodels 81.2.1.1 Particle Conversion 91.2.1.2 Turbulence–Chemistry Interaction 121.2.2 Review of CFD-related Works 131.2.2.1 Noncommercial Software 131.2.2.2 Commercial Software 14Summary 171.3 Benchmark Tests for CFD Modeling 171.3.1 British Coal Utilization Research Association Reactor (bcura) 181.3.2 Brigham Young University Reactor (BYU) 191.3.3 Pressurized Entrained-Flow Reactor (PEFR) 22References 242 Gasification of Solids: Past, Present, and Future 29Martin Gräbner2.1 Introduction 292.2 Historical Background 302.3 Types of Gasification Reactors 332.4 Trends in Gasifier Development 362.5 Derived Challenges for Research 40References 403 Modeling of Moving Particles: Review of Basic Concepts and Models 43Sebastian Schulze, Robin Schmidt, and Petr A. Nikrityuk3.1 Introduction 433.2 Soft-Sphere Model 473.2.1 Numerical Implementation 483.2.1.1 Contact Forces 483.2.1.2 Collision Parameters 493.2.1.3 Contact Detection 503.2.1.4 Time Integration 523.2.2 Validation Cases 533.2.2.1 Free-Falling Particle 533.2.2.2 Analytic Solution for the Free-falling Particle 543.2.2.3 Slipping Sphere on a Rough Surface 553.2.3 Illustrative Examples 563.2.3.1 Breaking Dam Problem 563.2.3.2 Rotating Drum 573.2.3.3 Generation of Fixed Beds 583.3 Hard-Sphere Model 593.3.1 Governing Equations 603.3.2 Collision Treatment in Dense Particulate Systems 623.3.3 2D Formulation of Hard-Sphere Collisions 633.3.4 Illustration of Hard-Sphere Models 653.3.5 Conclusions 68Nomenclature 68References 704 c d and Nu closure Relations for Spherical and NonSpherical Particles 73Kay Wittig, Andreas Richter, and Aakash Golia4.1 Literature Review 734.2 Model Description 744.2.1 Numerical Scheme and Discretization 754.3 Code and Software Validation 784.4 Porous Particles 814.4.1 Geometry Assumptions 814.4.2 Heat and Fluid Flow Past Porous Particles 824.4.3 Drag and Nusselt Numbers for Porous Particles 854.5 Nonspherical Particles 884.5.1 Heat and Fluid Flow of Particles Oriented in the Flow Direction 884.5.2 Flow Characteristics of Particles at Different Angles of Attack 914.5.3 Influence of Particle Orientation on Drag Forces and Heat Transfer 954.5.3.1 Drag Forces 954.5.3.2 Heat Transfer 964.5.3.3 Drag Forces and Nusselt Relations for Two Rotations 974.5.4 Discussion 1004.5.5 Conclusion 100References 1015 Single Particle Heating and Drying 105Robin Schmidt, Kay Wittig, and Petr A. Nikrityuk5.1 Nonporous Spherical Particle Heating in a Stream of Hot Air 1055.1.1 State of the Art 1055.1.2 Problem and Model Formulation 1075.1.2.1 Linear Model 1085.1.3 Illustration of Results and Subgrid Model 1095.1.4 Semiempirical Two-Temperature Subgrid Model 1145.2 Heating of a Porous Particle 1165.2.1 Problem and Model Formulation 1175.2.2 Porosity 1185.2.3 Results of Simulations 1195.2.3.1 Conclusion 1235.2.4 Appendix: Analytical Model 1235.3 Spherical Particle Drying in a Stream of Hot Air 1245.3.1 CFD-based Drying Model 1255.3.2 Subgrid Models 1275.3.2.1 Standard Model 1275.3.2.2 New Model 1275.3.3 Illustration and Validation of Models 1315.3.3.1 Results: CFD-Based Model 1315.3.3.2 Validation of Subgrid Model 1355.4 Conclusions 138References 1396 Unsteady Char Gasification/Combustion 143Dmitry Safronov6.1 Introduction 1436.2 Modeling Approach 1456.2.1 Governing Equations 1466.2.2 Initial Conditions and Boundary Conditions 1486.2.3 Reaction Kinetics and Transport Properties 1516.2.4 Evolution of Pore Structure and Interface Tracking 1526.3 Numerics and Code Validation 1536.3.1 Results and Discussion 1556.3.1.1 Oxidation Behavior of Porous Particles 1566.3.1.2 Details Inside the Particle 1576.3.1.3 Effect of Ambient Gas Composition 1576.3.1.4 Effect of Initial Particle Size and Ambient Gas Temperature on the Oxidation Regime 1586.4 Advice for Beginners 1606.5 Analytical Models 1626.5.1 One-Film Model 1626.5.2 Two-Film Model 1656.5.3 Chemically Reacting Porous Particle 166Nomenclature 167References 1687 Interface Tracking During Char Particle Gasification 171Frank Dierich and Kay Wittig7.1 Interface and Porosity Tracking for a Moving Char Particle 1717.1.1 Introduction 1717.1.2 Model and Governing Equations 1727.1.2.1 Setup 1727.1.2.2 Governing Equations in the Gas Phase 1737.1.2.3 Governing Equations in Porous Particles 1747.1.2.4 Boundary Conditions at the Particle Surface 1757.1.2.5 Reaction Kinetics 1757.1.2.6 Change of Porous Structure and Particle Shape 1767.1.2.7 Transport Properties 1777.1.3 Numerics 1787.1.4 Results and Discussion 1807.2 3D Interface Tracking for a Porous Char Particle in the Kinetic Regime 1927.2.1 Problem Description 1927.2.2 Porous Particle Description 1947.2.3 Internal Surface Reconstruction 1967.2.4 Results 1977.3 Conclusions 200References 2018 Pseudo-Steady-State Approach for Carbon Particle Combustion/Gasification 205Matthias Kestel, Dmitry Safronov, Andreas Richter, and Petr A. Nikrityuk8.1 Particle-Resolved CFD Simulations: Spherical Particles 2058.1.1 Review of the Literature 2058.1.2 Setup and Model Formulation 2078.1.3 Governing Equations 2108.1.4 Boundary Conditions 2118.1.5 Numerics and Software Validation 2128.1.5.1 Validation against Analytical Solution 2138.1.5.2 Validation against Experiments I: Laminar and Turbulent Regimes 2148.1.5.3 Validation against Experiments II: The impact of Particle Porosity 2178.1.6 Results: The Impact of Re on the Oxidation Regimes 2198.2 Particle-Resolved CFD Simulations: Nonspherical Particles 2258.2.1 Introduction 2258.2.2 Shapes of Particles 2278.2.3 Results 2288.2.3.1 Integral Characteristics 2318.3 Conclusions 2358.4 Setup of Heterogeneous Reactions in ANSYS FLUENT 2358.4.1 Step 1: Species Transport Settings 2358.4.2 Step 2: Define Species and Mixtures 2368.4.3 Step 3: Define Reactions 2378.4.4 Step 4: Boundary Settings 238Nomenclature 239References 2409 Pore-Resolved Simulation of Char Particle Combustion/Gasification 243Andreas Richter, Matthias Kestel, and Petr A. Nikrityuk9.1 Introduction 2439.2 Model Assumptions and Chemistry 2459.2.1 Numerical scheme, discretization, and software validation 2489.3 Small Porous Particle: 90 μm 2499.3.1 Influence of Gas Temperature 2569.4 Large Porous Particle: 2 mm 2579.4.1 Small Reynolds Numbers 2579.4.2 Large Reynolds Numbers 2599.5 3D Simulations under Gasification Conditions 2649.6 Conclusions 267Nomenclature 267References 26810 Subgrid Models for Particle Devolatilization-Combustion-Gasification 271Sebastian Schulze, Robin Schmidt, and Petr A. Nikrityuk10.1 Subgrid Model for the Devolatilization/Combustion of a Moving Coal Particle 27110.1.1 State of the Art 27110.1.2 Model Formulation 27610.1.2.1 Semiglobal Chemical Reactions 28010.1.3 CFD-based Model 28110.1.4 Model Validation 28210.2 Novel Intrinsic Submodel for Gasification of a Moving Char Particle 29010.2.1 Model Formulation 29110.2.1.1 Total Carbon Consumption Rate 29210.2.1.2 Basic Equations 29310.2.2 CFD-based Model 29510.2.2.1 Numerics and Validation 29710.2.3 Model Performance 297Nomenclature 300References 30111 New Frontiers and Challenges in Gasification Technologies 305Alexander Laugwitz and Bernd Meyer11.1 Introduction 30511.2 Trends in Gasifier Design 30711.2.1 Advanced Fluidized-Bed Coal Gasifiers 30811.2.1.1 Fluidized Bed with Slag Bath 30911.2.1.2 Multistaged Spouted Bed with Slag Bath 31011.2.1.3 Internal Circulating Fast Fluidized-Bed Gasifier (INCI) 31111.2.1.4 Agglomerating Fluidized Bed with Internal Post Gasification 31411.2.2 Highly Loaded Compact Gasifiers 31511.2.2.1 Hybrid Wall Gasifier 31611.3 Future Gasifier Simulations 31911.3.1 Requirements of Proposed Future Gasifiers 31911.3.2 Additional Fundamental Aspects of Future Numerical Simulations 322References 325Index 329

Petr A. Nikrityuk is an associate professor at the Department of Chemical and Materials Engineering, University of Alberta (UofA), Canada. Before taking his current position at UofA, Petr Nikrityuk was the head of the research group Interphase Phenomena within the Center for Innovation Competence VIRTUHCON at the Technische Universitat Bergakademie Freiberg (TUBAF), Germany. He studied mechanical engineering at the Moscow Aviation Institute (MAI), where he obtained his PhD on the topic of mathematical modeling of thermal processes. Before taking his research group leader position in Freiberg, Petr Nikrityuk worked as software developer in the field of computational fluid dynamics and as a post doc fellow in the Institute for Aerospace Engineering at the Dresden University of Technology. Bernd Meyer is the Director of the Department of the Energy Process Engineering and Chemical Engineering at the Technische Universitat Bergakademie Freiberg (TUBAF), Germany. Having obtained his academic degrees from TUBAF, he spent most of his career working in research and development in gasification and power plant technologies before taking up the appointment as a professor at TUBAF, Chair of Energy Process Engineering and Thermal Waste Treatment (EVT). He has been a member of the Saxonian Academy of Sciences, and Rector of the TUBAF since 2008. Prof. Meyer is author and coauthor of more than 90 patents in the field of gasification and related technologies.

• Preface xiList of Contributors xvAcknowledgments xviiRecommended Reading xixCoal Gasification: Basic Terminology xxi1 Modeling of Gasifiers: Overview of Current Developments 1Petr A. Nikrityuk, Thomas Förster, and Bernd Meyer1.1 Numerical Modeling in Engineering 11.1.1 The Role of Direct Numerical Simulation (DNS) in Particulate-Flow Modeling 3Summary 61.2 CFD-based Modeling of Entrained-Flow Gasifiers 61.2.1 Mainstream Computational Submodels 81.2.1.1 Particle Conversion 91.2.1.2 Turbulence–Chemistry Interaction 121.2.2 Review of CFD-related Works 131.2.2.1 Noncommercial Software 131.2.2.2 Commercial Software 14Summary 171.3 Benchmark Tests for CFD Modeling 171.3.1 British Coal Utilization Research Association Reactor (bcura) 181.3.2 Brigham Young University Reactor (BYU) 191.3.3 Pressurized Entrained-Flow Reactor (PEFR) 22References 242 Gasification of Solids: Past, Present, and Future 29Martin Gräbner2.1 Introduction 292.2 Historical Background 302.3 Types of Gasification Reactors 332.4 Trends in Gasifier Development 362.5 Derived Challenges for Research 40References 403 Modeling of Moving Particles: Review of Basic Concepts and Models 43Sebastian Schulze, Robin Schmidt, and Petr A. Nikrityuk3.1 Introduction 433.2 Soft-Sphere Model 473.2.1 Numerical Implementation 483.2.1.1 Contact Forces 483.2.1.2 Collision Parameters 493.2.1.3 Contact Detection 503.2.1.4 Time Integration 523.2.2 Validation Cases 533.2.2.1 Free-Falling Particle 533.2.2.2 Analytic Solution for the Free-falling Particle 543.2.2.3 Slipping Sphere on a Rough Surface 553.2.3 Illustrative Examples 563.2.3.1 Breaking Dam Problem 563.2.3.2 Rotating Drum 573.2.3.3 Generation of Fixed Beds 583.3 Hard-Sphere Model 593.3.1 Governing Equations 603.3.2 Collision Treatment in Dense Particulate Systems 623.3.3 2D Formulation of Hard-Sphere Collisions 633.3.4 Illustration of Hard-Sphere Models 653.3.5 Conclusions 68Nomenclature 68References 704 c d and Nu closure Relations for Spherical and NonSpherical Particles 73Kay Wittig, Andreas Richter, and Aakash Golia4.1 Literature Review 734.2 Model Description 744.2.1 Numerical Scheme and Discretization 754.3 Code and Software Validation 784.4 Porous Particles 814.4.1 Geometry Assumptions 814.4.2 Heat and Fluid Flow Past Porous Particles 824.4.3 Drag and Nusselt Numbers for Porous Particles 854.5 Nonspherical Particles 884.5.1 Heat and Fluid Flow of Particles Oriented in the Flow Direction 884.5.2 Flow Characteristics of Particles at Different Angles of Attack 914.5.3 Influence of Particle Orientation on Drag Forces and Heat Transfer 954.5.3.1 Drag Forces 954.5.3.2 Heat Transfer 964.5.3.3 Drag Forces and Nusselt Relations for Two Rotations 974.5.4 Discussion 1004.5.5 Conclusion 100References 1015 Single Particle Heating and Drying 105Robin Schmidt, Kay Wittig, and Petr A. Nikrityuk5.1 Nonporous Spherical Particle Heating in a Stream of Hot Air 1055.1.1 State of the Art 1055.1.2 Problem and Model Formulation 1075.1.2.1 Linear Model 1085.1.3 Illustration of Results and Subgrid Model 1095.1.4 Semiempirical Two-Temperature Subgrid Model 1145.2 Heating of a Porous Particle 1165.2.1 Problem and Model Formulation 1175.2.2 Porosity 1185.2.3 Results of Simulations 1195.2.3.1 Conclusion 1235.2.4 Appendix: Analytical Model 1235.3 Spherical Particle Drying in a Stream of Hot Air 1245.3.1 CFD-based Drying Model 1255.3.2 Subgrid Models 1275.3.2.1 Standard Model 1275.3.2.2 New Model 1275.3.3 Illustration and Validation of Models 1315.3.3.1 Results: CFD-Based Model 1315.3.3.2 Validation of Subgrid Model 1355.4 Conclusions 138References 1396 Unsteady Char Gasification/Combustion 143Dmitry Safronov6.1 Introduction 1436.2 Modeling Approach 1456.2.1 Governing Equations 1466.2.2 Initial Conditions and Boundary Conditions 1486.2.3 Reaction Kinetics and Transport Properties 1516.2.4 Evolution of Pore Structure and Interface Tracking 1526.3 Numerics and Code Validation 1536.3.1 Results and Discussion 1556.3.1.1 Oxidation Behavior of Porous Particles 1566.3.1.2 Details Inside the Particle 1576.3.1.3 Effect of Ambient Gas Composition 1576.3.1.4 Effect of Initial Particle Size and Ambient Gas Temperature on the Oxidation Regime 1586.4 Advice for Beginners 1606.5 Analytical Models 1626.5.1 One-Film Model 1626.5.2 Two-Film Model 1656.5.3 Chemically Reacting Porous Particle 166Nomenclature 167References 1687 Interface Tracking During Char Particle Gasification 171Frank Dierich and Kay Wittig7.1 Interface and Porosity Tracking for a Moving Char Particle 1717.1.1 Introduction 1717.1.2 Model and Governing Equations 1727.1.2.1 Setup 1727.1.2.2 Governing Equations in the Gas Phase 1737.1.2.3 Governing Equations in Porous Particles 1747.1.2.4 Boundary Conditions at the Particle Surface 1757.1.2.5 Reaction Kinetics 1757.1.2.6 Change of Porous Structure and Particle Shape 1767.1.2.7 Transport Properties 1777.1.3 Numerics 1787.1.4 Results and Discussion 1807.2 3D Interface Tracking for a Porous Char Particle in the Kinetic Regime 1927.2.1 Problem Description 1927.2.2 Porous Particle Description 1947.2.3 Internal Surface Reconstruction 1967.2.4 Results 1977.3 Conclusions 200References 2018 Pseudo-Steady-State Approach for Carbon Particle Combustion/Gasification 205Matthias Kestel, Dmitry Safronov, Andreas Richter, and Petr A. Nikrityuk8.1 Particle-Resolved CFD Simulations: Spherical Particles 2058.1.1 Review of the Literature 2058.1.2 Setup and Model Formulation 2078.1.3 Governing Equations 2108.1.4 Boundary Conditions 2118.1.5 Numerics and Software Validation 2128.1.5.1 Validation against Analytical Solution 2138.1.5.2 Validation against Experiments I: Laminar and Turbulent Regimes 2148.1.5.3 Validation against Experiments II: The impact of Particle Porosity 2178.1.6 Results: The Impact of Re on the Oxidation Regimes 2198.2 Particle-Resolved CFD Simulations: Nonspherical Particles 2258.2.1 Introduction 2258.2.2 Shapes of Particles 2278.2.3 Results 2288.2.3.1 Integral Characteristics 2318.3 Conclusions 2358.4 Setup of Heterogeneous Reactions in ANSYS FLUENT 2358.4.1 Step 1: Species Transport Settings 2358.4.2 Step 2: Define Species and Mixtures 2368.4.3 Step 3: Define Reactions 2378.4.4 Step 4: Boundary Settings 238Nomenclature 239References 2409 Pore-Resolved Simulation of Char Particle Combustion/Gasification 243Andreas Richter, Matthias Kestel, and Petr A. Nikrityuk9.1 Introduction 2439.2 Model Assumptions and Chemistry 2459.2.1 Numerical scheme, discretization, and software validation 2489.3 Small Porous Particle: 90 μm 2499.3.1 Influence of Gas Temperature 2569.4 Large Porous Particle: 2 mm 2579.4.1 Small Reynolds Numbers 2579.4.2 Large Reynolds Numbers 2599.5 3D Simulations under Gasification Conditions 2649.6 Conclusions 267Nomenclature 267References 26810 Subgrid Models for Particle Devolatilization-Combustion-Gasification 271Sebastian Schulze, Robin Schmidt, and Petr A. Nikrityuk10.1 Subgrid Model for the Devolatilization/Combustion of a Moving Coal Particle 27110.1.1 State of the Art 27110.1.2 Model Formulation 27610.1.2.1 Semiglobal Chemical Reactions 28010.1.3 CFD-based Model 28110.1.4 Model Validation 28210.2 Novel Intrinsic Submodel for Gasification of a Moving Char Particle 29010.2.1 Model Formulation 29110.2.1.1 Total Carbon Consumption Rate 29210.2.1.2 Basic Equations 29310.2.2 CFD-based Model 29510.2.2.1 Numerics and Validation 29710.2.3 Model Performance 297Nomenclature 300References 30111 New Frontiers and Challenges in Gasification Technologies 305Alexander Laugwitz and Bernd Meyer11.1 Introduction 30511.2 Trends in Gasifier Design 30711.2.1 Advanced Fluidized-Bed Coal Gasifiers 30811.2.1.1 Fluidized Bed with Slag Bath 30911.2.1.2 Multistaged Spouted Bed with Slag Bath 31011.2.1.3 Internal Circulating Fast Fluidized-Bed Gasifier (INCI) 31111.2.1.4 Agglomerating Fluidized Bed with Internal Post Gasification 31411.2.2 Highly Loaded Compact Gasifiers 31511.2.2.1 Hybrid Wall Gasifier 31611.3 Future Gasifier Simulations 31911.3.1 Requirements of Proposed Future Gasifiers 31911.3.2 Additional Fundamental Aspects of Future Numerical Simulations 322References 325Index 329

Petr A. Nikrityuk is an associate professor at the Department of Chemical and Materials Engineering, University of Alberta (UofA), Canada. Before taking his current position at UofA, Petr Nikrityuk was the head of the research group Interphase Phenomena within the Center for Innovation Competence VIRTUHCON at the Technische Universitat Bergakademie Freiberg (TUBAF), Germany. He studied mechanical engineering at the Moscow Aviation Institute (MAI), where he obtained his PhD on the topic of mathematical modeling of thermal processes. Before taking his research group leader position in Freiberg, Petr Nikrityuk worked as software developer in the field of computational fluid dynamics and as a post doc fellow in the Institute for Aerospace Engineering at the Dresden University of Technology. Bernd Meyer is the Director of the Department of the Energy Process Engineering and Chemical Engineering at the Technische Universitat Bergakademie Freiberg (TUBAF), Germany. Having obtained his academic degrees from TUBAF, he spent most of his career working in research and development in gasification and power plant technologies before taking up the appointment as a professor at TUBAF, Chair of Energy Process Engineering and Thermal Waste Treatment (EVT). He has been a member of the Saxonian Academy of Sciences, and Rector of the TUBAF since 2008. Prof. Meyer is author and coauthor of more than 90 patents in the field of gasification and related technologies.

• Preface xiList of Contributors xvAcknowledgments xviiRecommended Reading xixCoal Gasification: Basic Terminology xxi1 Modeling of Gasifiers: Overview of Current Developments 1Petr A. Nikrityuk, Thomas Förster, and Bernd Meyer1.1 Numerical Modeling in Engineering 11.1.1 The Role of Direct Numerical Simulation (DNS) in Particulate-Flow Modeling 3Summary 61.2 CFD-based Modeling of Entrained-Flow Gasifiers 61.2.1 Mainstream Computational Submodels 81.2.1.1 Particle Conversion 91.2.1.2 Turbulence–Chemistry Interaction 121.2.2 Review of CFD-related Works 131.2.2.1 Noncommercial Software 131.2.2.2 Commercial Software 14Summary 171.3 Benchmark Tests for CFD Modeling 171.3.1 British Coal Utilization Research Association Reactor (bcura) 181.3.2 Brigham Young University Reactor (BYU) 191.3.3 Pressurized Entrained-Flow Reactor (PEFR) 22References 242 Gasification of Solids: Past, Present, and Future 29Martin Gräbner2.1 Introduction 292.2 Historical Background 302.3 Types of Gasification Reactors 332.4 Trends in Gasifier Development 362.5 Derived Challenges for Research 40References 403 Modeling of Moving Particles: Review of Basic Concepts and Models 43Sebastian Schulze, Robin Schmidt, and Petr A. Nikrityuk3.1 Introduction 433.2 Soft-Sphere Model 473.2.1 Numerical Implementation 483.2.1.1 Contact Forces 483.2.1.2 Collision Parameters 493.2.1.3 Contact Detection 503.2.1.4 Time Integration 523.2.2 Validation Cases 533.2.2.1 Free-Falling Particle 533.2.2.2 Analytic Solution for the Free-falling Particle 543.2.2.3 Slipping Sphere on a Rough Surface 553.2.3 Illustrative Examples 563.2.3.1 Breaking Dam Problem 563.2.3.2 Rotating Drum 573.2.3.3 Generation of Fixed Beds 583.3 Hard-Sphere Model 593.3.1 Governing Equations 603.3.2 Collision Treatment in Dense Particulate Systems 623.3.3 2D Formulation of Hard-Sphere Collisions 633.3.4 Illustration of Hard-Sphere Models 653.3.5 Conclusions 68Nomenclature 68References 704 c d and Nu closure Relations for Spherical and NonSpherical Particles 73Kay Wittig, Andreas Richter, and Aakash Golia4.1 Literature Review 734.2 Model Description 744.2.1 Numerical Scheme and Discretization 754.3 Code and Software Validation 784.4 Porous Particles 814.4.1 Geometry Assumptions 814.4.2 Heat and Fluid Flow Past Porous Particles 824.4.3 Drag and Nusselt Numbers for Porous Particles 854.5 Nonspherical Particles 884.5.1 Heat and Fluid Flow of Particles Oriented in the Flow Direction 884.5.2 Flow Characteristics of Particles at Different Angles of Attack 914.5.3 Influence of Particle Orientation on Drag Forces and Heat Transfer 954.5.3.1 Drag Forces 954.5.3.2 Heat Transfer 964.5.3.3 Drag Forces and Nusselt Relations for Two Rotations 974.5.4 Discussion 1004.5.5 Conclusion 100References 1015 Single Particle Heating and Drying 105Robin Schmidt, Kay Wittig, and Petr A. Nikrityuk5.1 Nonporous Spherical Particle Heating in a Stream of Hot Air 1055.1.1 State of the Art 1055.1.2 Problem and Model Formulation 1075.1.2.1 Linear Model 1085.1.3 Illustration of Results and Subgrid Model 1095.1.4 Semiempirical Two-Temperature Subgrid Model 1145.2 Heating of a Porous Particle 1165.2.1 Problem and Model Formulation 1175.2.2 Porosity 1185.2.3 Results of Simulations 1195.2.3.1 Conclusion 1235.2.4 Appendix: Analytical Model 1235.3 Spherical Particle Drying in a Stream of Hot Air 1245.3.1 CFD-based Drying Model 1255.3.2 Subgrid Models 1275.3.2.1 Standard Model 1275.3.2.2 New Model 1275.3.3 Illustration and Validation of Models 1315.3.3.1 Results: CFD-Based Model 1315.3.3.2 Validation of Subgrid Model 1355.4 Conclusions 138References 1396 Unsteady Char Gasification/Combustion 143Dmitry Safronov6.1 Introduction 1436.2 Modeling Approach 1456.2.1 Governing Equations 1466.2.2 Initial Conditions and Boundary Conditions 1486.2.3 Reaction Kinetics and Transport Properties 1516.2.4 Evolution of Pore Structure and Interface Tracking 1526.3 Numerics and Code Validation 1536.3.1 Results and Discussion 1556.3.1.1 Oxidation Behavior of Porous Particles 1566.3.1.2 Details Inside the Particle 1576.3.1.3 Effect of Ambient Gas Composition 1576.3.1.4 Effect of Initial Particle Size and Ambient Gas Temperature on the Oxidation Regime 1586.4 Advice for Beginners 1606.5 Analytical Models 1626.5.1 One-Film Model 1626.5.2 Two-Film Model 1656.5.3 Chemically Reacting Porous Particle 166Nomenclature 167References 1687 Interface Tracking During Char Particle Gasification 171Frank Dierich and Kay Wittig7.1 Interface and Porosity Tracking for a Moving Char Particle 1717.1.1 Introduction 1717.1.2 Model and Governing Equations 1727.1.2.1 Setup 1727.1.2.2 Governing Equations in the Gas Phase 1737.1.2.3 Governing Equations in Porous Particles 1747.1.2.4 Boundary Conditions at the Particle Surface 1757.1.2.5 Reaction Kinetics 1757.1.2.6 Change of Porous Structure and Particle Shape 1767.1.2.7 Transport Properties 1777.1.3 Numerics 1787.1.4 Results and Discussion 1807.2 3D Interface Tracking for a Porous Char Particle in the Kinetic Regime 1927.2.1 Problem Description 1927.2.2 Porous Particle Description 1947.2.3 Internal Surface Reconstruction 1967.2.4 Results 1977.3 Conclusions 200References 2018 Pseudo-Steady-State Approach for Carbon Particle Combustion/Gasification 205Matthias Kestel, Dmitry Safronov, Andreas Richter, and Petr A. Nikrityuk8.1 Particle-Resolved CFD Simulations: Spherical Particles 2058.1.1 Review of the Literature 2058.1.2 Setup and Model Formulation 2078.1.3 Governing Equations 2108.1.4 Boundary Conditions 2118.1.5 Numerics and Software Validation 2128.1.5.1 Validation against Analytical Solution 2138.1.5.2 Validation against Experiments I: Laminar and Turbulent Regimes 2148.1.5.3 Validation against Experiments II: The impact of Particle Porosity 2178.1.6 Results: The Impact of Re on the Oxidation Regimes 2198.2 Particle-Resolved CFD Simulations: Nonspherical Particles 2258.2.1 Introduction 2258.2.2 Shapes of Particles 2278.2.3 Results 2288.2.3.1 Integral Characteristics 2318.3 Conclusions 2358.4 Setup of Heterogeneous Reactions in ANSYS FLUENT 2358.4.1 Step 1: Species Transport Settings 2358.4.2 Step 2: Define Species and Mixtures 2368.4.3 Step 3: Define Reactions 2378.4.4 Step 4: Boundary Settings 238Nomenclature 239References 2409 Pore-Resolved Simulation of Char Particle Combustion/Gasification 243Andreas Richter, Matthias Kestel, and Petr A. Nikrityuk9.1 Introduction 2439.2 Model Assumptions and Chemistry 2459.2.1 Numerical scheme, discretization, and software validation 2489.3 Small Porous Particle: 90 μm 2499.3.1 Influence of Gas Temperature 2569.4 Large Porous Particle: 2 mm 2579.4.1 Small Reynolds Numbers 2579.4.2 Large Reynolds Numbers 2599.5 3D Simulations under Gasification Conditions 2649.6 Conclusions 267Nomenclature 267References 26810 Subgrid Models for Particle Devolatilization-Combustion-Gasification 271Sebastian Schulze, Robin Schmidt, and Petr A. Nikrityuk10.1 Subgrid Model for the Devolatilization/Combustion of a Moving Coal Particle 27110.1.1 State of the Art 27110.1.2 Model Formulation 27610.1.2.1 Semiglobal Chemical Reactions 28010.1.3 CFD-based Model 28110.1.4 Model Validation 28210.2 Novel Intrinsic Submodel for Gasification of a Moving Char Particle 29010.2.1 Model Formulation 29110.2.1.1 Total Carbon Consumption Rate 29210.2.1.2 Basic Equations 29310.2.2 CFD-based Model 29510.2.2.1 Numerics and Validation 29710.2.3 Model Performance 297Nomenclature 300References 30111 New Frontiers and Challenges in Gasification Technologies 305Alexander Laugwitz and Bernd Meyer11.1 Introduction 30511.2 Trends in Gasifier Design 30711.2.1 Advanced Fluidized-Bed Coal Gasifiers 30811.2.1.1 Fluidized Bed with Slag Bath 30911.2.1.2 Multistaged Spouted Bed with Slag Bath 31011.2.1.3 Internal Circulating Fast Fluidized-Bed Gasifier (INCI) 31111.2.1.4 Agglomerating Fluidized Bed with Internal Post Gasification 31411.2.2 Highly Loaded Compact Gasifiers 31511.2.2.1 Hybrid Wall Gasifier 31611.3 Future Gasifier Simulations 31911.3.1 Requirements of Proposed Future Gasifiers 31911.3.2 Additional Fundamental Aspects of Future Numerical Simulations 322References 325Index 329