Page 11 - Biomass Gasification, Pyrolysis And Torrefaction Practical Design and Theory

x Contents

5.6.5 Ablative Pyrolyzer 171
5.6.6 Rotating-Cone Pyrolyzer 171
5.6.7 Vacuum Pyrolyzer 172
5.7 Pyrolyzer Design Considerations 172
5.7.1 Production of Liquid Through Pyrolysis 172
5.8 Biochar 173
5.8.1 Potential Benefits of Biochar 175
Symbols and Nomenclature 176

6. Tar Production and Destruction 177
6.1 Introduction 177
6.2 Tar 177
6.2.1 Acceptable Limits for Tar 178
6.2.2 Tar Formation 180
6.2.3 Tar Composition 181
6.3 Tar Reduction 183
6.3.1 In Situ Tar Primary Reduction 184
6.3.2 Postgasification—Secondary Reduction of Tar 193

7. Gasification Theory 199

7.1 Introduction 199
7.2 Gasification Reactions and Steps 199
7.2.1 Gasifying Medium 200
7.3 The Gasification Process 200
7.3.1 Drying 201
7.3.2 Pyrolysis 203
7.3.3 Char Gasification Reactions 203
7.3.4 Char Combustion Reactions 208
7.3.5 Catalytic Gasification 210
7.3.6 Gasification Processes in Reactors 212
7.4 Kinetics of Gasification 218
7.4.1 Chemical Equilibrium 218
7.4.2 Char Reactivity 229
7.5 Gasification Models 232
7.5.1 Simulation Versus Experiment 232
7.5.2 Gasifier Simulation Models 233
7.6 Kinetic Model Applications 240
7.6.1 Moving-Bed Gasifiers 240
7.6.2 Fluidized-Bed Gasifiers 241
7.6.3 Entrained-Flow Gasifiers 244
Symbols and Nomenclature 246

8. Design of Biomass Gasifiers 249

8.1 Introduction 249
8.1.1 Gasifier Types 249