Page 12 - Biomass Gasification, Pyrolysis And Torrefaction Practical Design and Theory

Contents xi

8.2 Fixed-Bed/Moving-Bed Gasifiers 251
8.2.1 Updraft Gasifiers 252
8.2.2 Downdraft Gasifiers 254
8.2.3 Crossdraft Gasifiers 258
8.3 Fluidized-Bed Gasifiers 259
8.3.1 Bubbling Fluidized-Bed Gasifier 259
8.3.2 Circulating Fluidized-Bed Gasifier 261
8.4 Entrained-Flow Gasifiers 268
8.4.1 Top-Fed Gasifier 270
8.4.2 Side-Fed Gasifier 271
8.4.3 Advantages of Entrained-Flow Gasifiers 272
8.4.4 Entrained-Flow Gasification of Biomass 272
8.5 Plasma Gasification 273
8.6 Process Design 274
8.6.1 Design Specification 275
8.6.2 Mass Balance 276
8.6.3 Energy Balance 282
8.7 Product Gas Prediction 287
8.7.1 Equilibrium Approach 287
8.8 Gasifier Sizing 289
8.8.1 Moving-Bed Gasifiers 289
8.8.2 Fluidized-Bed Gasifiers 292
8.9 Entrained-Flow Gasifier Design 299
8.9.1 Gasifier Chamber 300
8.10 Auxiliary Items 300
8.10.1 Position of Biomass Feeding Position 301
8.10.2 Distributor Plate 301
8.10.3 Bed Materials 301
8.11 Design Optimization 302
8.11.1 Process Optimization 303
8.12 Performance and Operating Issues 303
8.12.1 Gasification Efficiency 303
8.12.2 Operational Considerations 310
Symbols and Nomenclature 311

9. Hydrothermal Gasification of Biomass 315
9.1 Introduction 315
9.2 Supercritical Water 316
9.2.1 Properties of SCW 318
9.2.2 Application of SCW in Chemical Reactions 321
9.2.3 Advantages of SCW Gasification over Conventional
Thermal Gasification 322
9.3 Biomass Conversion in SCW 323
9.3.1 Gasification 323
9.3.2 Hydrolysis 324
9.3.3 SCW Oxidation 325
9.3.4 Scheme of an SCWG Plant 325