Preface ....................................................... XIX
About the Editors ............................................. XXI
List of Contributors .......................................... XXV
List of Abbreviations ........................................ XXIX
List of Symbols ............................................ XXXIII
Synopsis Volume 4 ........................................... XLIII
1 Overview of Solid Fuels, Characteristics and Origin .......... 1
Toby С Bridgeman, Jenny M. Jones, and Alan Williams
1.1 Origin of the Solid Biomass and Fossil Fuels ............ 1
1.1.1 Formation of Coal ................................ 1
1.1.2 Origin of Biomass Fuels .......................... 3
1.1.3 Peat ............................................. 4
1.1.4 Derived Fuels and Waste or Opportunity Fuels ..... 4
1.2 Availability and Resource Base of the Fossil and
Biomass Fuels ........................................... 5
1.2.1 Coal ............................................. 5
1.2.2 Biomass .......................................... 6
1.2.3 Peat ............................................. 6
1.2.4 Waste Materials .................................. 6
1.3 Methods of Characterizing Solid Fuels ................... 7
1.3.1 Proximate and Ultimate Analyses of Coals or
Biomass .......................................... 7
1.3.2 Calorific Value .................................. 8
1.3.3 Ash Composition .................................. 9
1.3.4 Ash Fusibility ................................... 9
1.3.5 Physical Properties ............................. 10
1.4 Physical and Chemical Properties of the Solid Fuels .... 10
1.4.1 Ultimate Analysis and Heating Value ............. 11
1.4.2 Proximate Analysis .............................. 11
1.4.3 Ash ............................................. 12
1.4.4 Classification .................................. 19
1.4.5 Reactivity of Solid Fuels ....................... 20
1.5 Handling and Preparation of the Fuels Prior to Use
1.5.1 Coal ............................................ 24
1.5.2 Biomass ......................................... 26
References .................................................. 29
2 Overview of Solid Fuels Combustion Technologies ............. 31
Despina Vamvuka
2.1 Introduction ........................................... 31
2.2 Coal Characteristics Affecting Combustion Processes
2.2.1 Coal Structure and Petrographic Composition ..... 32
2.2.2 Organic Elements and Sulfur Content ............. 33
2.2.3 Moisture and Volatile Matter Contents ........... 33
2.2.4 Calorific Value ................................. 34
2.2.5 Agglomeration Properties ........................ 34
2.2.6 Ash Content and Composition ..................... 34
2.2.6.1 Effect on Ash Softening Temperature .... 34
2.2.6.2 Effect on Slag Viscosity ............... 35
2.2.6.3 Effect on Fouling ...................... 35
2.3 Conventional Coal Combustion Technologies .............. 36
2.3.1 Stokers ......................................... 37
2.3.1.1 Spreader Stokers ....................... 38
2.3.1.2 Chain Grate Stokers .................... 39
2.3.1.3 Vibrating Grate Stokers ................ 39
2.3.1.4 Underfeed Stokers ...................... 39
2.3.2 Pulverized-Coal Furnaces ........................ 40
2.3.2.1 Dry-Bottom Furnaces .................... 42
2.3.2.2 Wet-Bottom Furnaces .................... 43
2.3.3 Cyclone Furnaces ................................ 45
2.4 Advanced Clean Coal Technologies ....................... 46
2.4.1 Fluidized-Bed Combustion ........................ 46
2.4.1.1 AFBC Process ........................... 47
2.4.1.1.1 Process and Key Issues ...... 47
2.4.1.1.2 Current Status and
Experience .................. 49
2.4.1.1.3 Future
Developments ..... 50
2.4.1.2 PFBC Process ........................... 52
2.4.1.2.1 Process and Key Issues ...... 52
2.4.1.2.2 Current Status and
Experience .................. 54
2.4.1.2.3 Future Developments ......... 55
2.4.2 Supercritical Coal Combustion ................... 56
2.4.2.1 Process and Key Issues ................. 56
2.4.2.2 Current Status and Experience .......... 57
2.4.2.3 Future Developments .................... 58
2.4.3 In Situ Emissions Control Technologies .......... 58
2.4.3.1 SOx Control Technologies ............... 58
2.4.3.2 NOx Control Technologies ............... 59
2.4.3.3 Near-Zero CO2 Emissions Technologies ... 62
2.5 Biomass Characteristics Affecting Combustion
Processes .............................................. 63
2.5.1 Moisture Content ................................ 63
2.5.2 Ash Content and Composition ..................... 63
2.5.3 Particle Size ................................... 64
2.6 Industrial Biomass Combustion Systems .................. 64
2.6.1 Fixed Bed Systems ............................... 65
2.6.1.1 Grate Furnaces ......................... 65
2.6.1.2 Underfeed Stokers ...................... 69
2.6.2 Fluidized Bed Systems ........................... 71
2.6.2.1 Bubbling Fluidized Bed ................. 71
2.6.2.2 Circulating Fluidized Bed .............. 72
2.6.3 Dust Combustion Systems ......................... 74
2.7 Outlook ................................................ 75
2.8 Summary ................................................ 76
References .................................................. 78
3 Solid Biomass Combustion .................................... 85
Amit Suri and Masayuki Horio
3.1 Introduction ........................................... 85
3.2 Solid Biomass Fuels .................................... 88
3.2.1 Variety of Biomass Fuels ........................ 88
3.2.2 Characterization of Biomass Fuels ............... 92
3.2.2.1 Chemical Analysis ...................... 92
3.2.2.2 Ash Characterization ................... 95
3.2.2.3 Ash Behavior ........................... 99
3.2.2.4 Bulk Density and Energy Density ....... 102
3.2.2.5 Hardness .............................. 103
3.3 Principle of Solid Biomass Combustion ................. 104
3.3.1 Drying and Pyrolysis of Wood ................... 105
3.3.2 Effect of Heating Rate and Temperature on
Products of Pyrolysis .......................... 107
3.3.3 Ignition, Combustion, and Extinction ........... 108
3.3.4 Kinetics ....................................... 110
3.3.4.1 Volatiles Combustion .................. 110
3.3.4.2 Char Combustion ....................... 112
3.3.4.3 Effect of Shape Factor during
Combustion ............................ 113
3.3.5 Gaseous Emissions .............................. 114
3.3.5.1 Nitrogen Oxides (NOx) ................. 114
3.3.5.2 Nitrous Oxide (N20) ................... 117
3.3.5.3 Sulfur Oxides (SOx) ................... 118
3.3.5.4 Hydrogen Chloride (HC1) ............... 118
3.3.5.5 Heavy Metals and Dioxins .............. 118
3.4 Combustion and Conversion Technologies ................ 120
3.4.1 Large-Scale Boilers ............................ 120
3.4.1.1 Fixed Bed Combustion Systems .......... 122
3.4.1.1.1 Grate Furnaces ............. 122
3.4.1.1.2 Stoker Furnaces ............ 123
3.4.1.2 Fluidized Bed Combustion .............. 124
3.4.1.2.1 Circulating Fluidized
Bed ........................ 125
3.4.1.2.2 Bubbling Fluidized Bed ..... 126
3.4.1.3 Entrained Bed Furnace ................. 127
3.4.2 Small-Scale Boilers ............................ 128
3.4.2.1 Classical Cooking Stoves .............. 128
3.4.2.2 Fireplace Heaters ..................... 128
3.4.2.3 Pellet Burners ........................ 128
3.4.2.4 Charcoal Combustion ................... 129
3.5 Ash Behavior in Different Combustion Systems .......... 131
3.5.1 Ash Behavior in Grate Furnaces ................. 131
3.5.2 Ash Behavior in FBCs ........................... 133
3.6 Outlook ............................................... 135
3.7 Summary ............................................... 136
References ................................................. 136
4 Small-Scale Biomass Combustion ............................. 141
Matthias Gaderer, Florian Volz, and Robert Kunde
4.1 Introduction and Summary .............................. 141
4.2 Biomass Fuels ......................................... 142
4.3 Biomass Combustion Techniques ......................... 143
4.3.1 Combustion Process ............................. 143
4.3.2 Manually Operated Systems ...................... 144
4.3.2.1 Log Wood Combustor Systems ............ 144
4.3.2.1.1 Updraft Combustion with
Complete Combustion ........ 144
4.3.2.1.2 Updraft Combustion with
Top-Burnout ................ 145
4.3.2.1.3 Downdraft Combustion with
Bottom or Lateral
Burnout .................... 146
4.3.2.2 Log Wood Fired Heating Systems ........ 147
4.3.2.2.1 Fireplace .................. 147
4.3.2.2.2 Stoves ..................... 149
4.3.2.2.3 Tile Stove, Heat-Storing
Stoves ..................... 150
4.3.2.2.4 Central Heating Boilers .... 151
4.3.3 Automatically Fed Combustors ................... 153
4.3.3.1 Combustion Concepts for
Automatically Fed Firing Systems ...... 156
4.3.3.1.1 Underfed Firing ............ 156
4.3.3.1.2 Horizontally Fed Furnace
Systems or So-called
Stokers .................... 157
4.3.3.1.3 Drop-Shaft Firing .......... 158
4.3.3.2 Automatically Operated Wood Chip and
Pellet Heating Systems ................ 158
4.3.3.2.1 Stoves for the Combustion
of Wood Pellet ............. 158
4.3.3.2.2 Central Heating Boilers
for Wood Pellet and Wood
Chips ...................... 160
4.4 Emissions ............................................. 165
4.5 Electricity Production and Combined Heat and Power .... 167
References ................................................. 168
5 Coal Combustion ............................................ 171
Monika Kosowska-Golachowska
5.1 Introduction .......................................... 171
5.2 Description of Combustion of a Single Coal Particle ... 172
5.2.1 Heating and Drying ............................. 172
5.2.2 Ignition of Volatiles .......................... 174
5.2.3 Devolatilization and Volatile Combustion ....... 175
5.2.4 Char Combustion ................................ 179
5.2.4.1 Mechanisms of Combustion of Non-
Porous Char ........................... 180
5.2.4.2 Mechanisms of Combustion of Porous
Char .................................. 181
5.2.4.3 Burning Rate .......................... 182
5.2.4.4 Time of Char Combustion ............... 182
5.2.5 Fragmentation of a Coal Particle ............... 182
5.3 Experimental Research into Combustion of a Single
Coal Particle ......................................... 184
5.3.1 Test Apparatus ................................. 185
5.3.2 Test Procedure ................................. 186
5.3.3 Coals Tested ................................... 186
5.3.4 Thermal Fragmentation of Coal .................. 186
5.3.4.1 Effect of Coal Type ................... 187
5.3.4.2 Effect of Particle Diameter ........... 191
5.3.4.3 Influence of Bed Temperature .......... 191
5.3.5 Evolution of Coal Structure during
Combustion ..................................... 192
5.4 Mathematical Model of Primary Fragmentation ........... 198
5.4.1 Coal Heating ................................... 199
5.4.2 Volatile Release ............................... 201
5.4.3 Volatile Transport ............................. 202
5.4.4 Primary Fragmentation .......................... 202
5.4.5 Results of Numerical Simulations ............... 203
5.4.6 Verification of the Model ...................... 206
5.5 Applications of Coal Combustion in Industry ........... 209
5.6 Outlook ............................................... 211
5.7 Summary ............................................... 212
References ................................................. 213
6 Pulverized Coal-Fired Boilers .............................. 217
Hai Zhang and Junfu Lu
6.1 Introduction .......................................... 217
6.1.1 PC Combustion and PC Fired Boiler .............. 217
6.1.2 Physical Properties of PC Particles ............ 220
6.1.3 Conventional Layout of a PC Boiler ............. 221
6.1.4 Heating Surfaces and Water-Vapor Path in a PC
Boiler ......................................... 223
6.1.5 Heat Transfer Calculation Procedure of a PC
Boiler ......................................... 224
6.2 Some Theories ......................................... 226
6.2.1 Theoretical Air and Coefficient of Excess
Air ............................................ 226
6.2.2 Heat Balance and Efficiency of a PC Boiler ..... 227
6.2.3 Ignition of PC Particles ....................... 229
6.2.4 Char Combustion ................................ 232
6.2.5 NOx Formation Mechanisms ....................... 232
6.2.5.1 Thermal NO ............................ 233
6.2.5.2 Fuel NO ............................... 234
6.3 PC Fired Furnace ...................................... 235
6.3.1 Furnace Layout and Firing Type ................. 235
6.3.2 Cross-Section Heat Release Rates Selection ..... 237
6.3.3 Volumetric Heat Release Rates Selection ........ 238
6.3.4 Empirical Heat Transfer Calculation in the
Furnace ........................................ 238
6.3.4.1 General Introduction .................. 238
6.3.4.2 Heat Input to the Furnace ............. 239
6.3.4.3 Emissivity of the Flame and the
Furnace ............................... 240
6.3.4.4 Empirical Heat Transfer Calculation
in the Furnace ........................ 241
6.4 PC Fired Burners ...................................... 243
6.4.1 General Introduction ........................... 243
6.4.2 Arrangement of Burners ......................... 244
6.4.3 Low NOx burners (LNB) .......................... 247
6.4.4 Examples of LNBs ............................... 248
6.4.4.1 Boat-Shaped Bluff-Body Burner ......... 248
6.4.4.2 Double PA Channel Burner .............. 248
6.4.4.3 DRB Burner ............................ 249
6.4.4.4 WR Burner ............................. 250
6.4.4.5 PM Burner and Vertical Rich/Lean ...... 250
6.4.4.6 Louver Damper Burner and Bias
Combustion ............................ 251
6.4.4.7 In-Furnace HTAC Burner ................ 251
6.5 Outlook .......................................... 253
6.6 Summary .......................................... 254
References ................................................. 254
7 Modeling Moving and Fixed Bed Combustion ................... 257
Bemhard Peters and Harald Raupenstrauch
7.1 Introduction .......................................... 257
7.1.1 Combustion Characteristics of an Individual
Particle ....................................... 257
7.1.2 Combustion Characteristics of a Fixed or
Moving Bed ..................................... 258
7.1.3 Conversion Regimes ............................. 259
7.1.4 Classification of Model Approaches ............. 260
7.2 Modeling Approach ..................................... 262
7.2.1 Conversion ..................................... 262
7.2.1.1 Drying ................................ 263
7.2.1.2 Pyrolysis and Devolatilization ........ 263
7.2.1.3 Gasification and Combustion ........... 265
7.2.2 Transport of Fuel Particles .................... 266
7.2.3 Gas Flow ....................................... 267
7.3 Applications .......................................... 268
7.3.1 Conversion ..................................... 268
7.3.1.1 Drying ................................ 268
7.3.1.2 Pyrolysis and Devolatilization ........ 269
7.3.1.3 Gasification and Combustion ........... 271
7.3.1.3.1 Grate: Optimal Conditions
for Fuel Ignition and
Optimal Primary Air Load ... 272
7.3.2 Transport on a Grate and in a Rotary Kiln ...... 277
7.3.2.1 Grate ................................. 277
7.3.2.2 Rotary Kiln ........................... 279
7.4 Outlook ............................................... 279
7.5 Summary ............................................... 280
References ................................................. 280
8 Waste Combustion, MSW, Sewage Sludge, Hazardous, Grate
and Rotary Kiln ............................................ 285
Helmut Seifert and Jürgen Vehlow
8.1 Introduction .......................................... 285
8.2 Objectives of Thermal Waste Treatment ................. 285
8.3 Basic Processes for Thermal Waste Treatment ........... 286
8.4 Waste Incineration Processes .......................... 287
8.5 Incineration of Municipal Solid Waste ................. 288
8.5.1 Generation and Quality of Municipal Solid
Waste .......................................... 288
8.5.2 Management of Municipal Solid Waste ............ 289
8.5.3 Grate-Based Waste Incinerators ................. 289
8.5.3.1 Elements and Design of Grate
Furnaces .............................. 291
8.5.3.2 Grate Types ........................... 292
8.5.3.3 Travelling Grates ..................... 292
8.5.3.3.1 Roller Grates .............. 292
8.5.3.3.2 Reciprocating Grates ....... 293
8.5.3.4 Fundamentals of Fuel Technology ....... 295
8.5.3.4.1 Waste Characteristics ...... 295
8.5.3.4.2 Specific Combustion
Parameters ................. 297
8.5.3.4.3 Design of a Grate Fired
Furnace .................... 299
8.6 Material Partitioning Inside the Furnace .............. 300
8.7 Air Pollution Control ................................. 301
8.7.1 Flue Gas Quality ............................... 301
8.7.2 Air Emission Regulations ....................... 302
8.7.3 Process Stages ................................. 304
8.7.4 Particle Removal ............................... 304
8.7.5 Chemical Gas Cleaning .......................... 305
8.7.5.1 Wet Scrubbing ......................... 306
8.7.5.2 Dry Scrubbing ......................... 307
8.7.5.3 NOx Abatement ......................... 308
8.7.5.4 Control of Dioxins .................... 308
8.7.6 Quality of Emissions ........................... 309
8.8 Solid Residues ........................................ 310
8.8.1 Mass Flows in a Waste Incinerator .............. 310
8.8.2 Management of Bottom Ashes ..................... 311
8.8.2.1 Characterization ...................... 311
8.8.2.2 Pretreatment for Utilization .......... 311
8.8.2.3 Utilization and Environmental
Compatibility ......................... 311
8.9 Management of Boiler and Filter Ashes and APC
Residues .............................................. 313
8.9.1 Boiler and Filter Ashes ........................ 313
8.9.2 APC Residues ................................... 315
8.10 Hazardous Waste Combustion in Rotary Kiln Furnaces .... 315
8.11 Sewage Sludge Incineration in Fluidized Bed
Furnaces .............................................. 316
8.12 Alternative Processes for Thermal Waste Treatment ..... 317
8.13 Summary ............................................... 319
References ................................................. 319
9 Gasification and Pyrolysis of Coal ......................... 325
Adam Luckos, Mohammed N. Shaik, andjohan C. van Dyk
9.1 Introduction .......................................... 325
9.2 Fundamentals of Coal Gasification Technology .......... 326
9.3 Pyrolysis and Gasification Chemistry .................. 328
9.3.1 Pyrolysis ...................................... 328
9.3.2 Stoichiometry and Thermodynamics of
Gasification ................................... 331
9.3.3 Kinetics of Gasification Reactions ............. 333
9.4 Coal Gasification Technologies ........................ 334
9.4.1 Fixed-Bed Gasifiers ............................ 335
9.4.1.1 Fixed-Bed Dry-Bottom (FBDB) Process ... 336
9.4.1.2 British Gas/Lurgi Process ............. 338
9.4.2 Fluidized-Bed Gasifiers ........................ 339
9.4.2.1 High Temperature Winkler Process ...... 340
9.4.2.2 Kellogg Rust Westinghouse Process ..... 342
9.4.2.3 Kellogg Brown Root Transport
Gasifier .............................. 343
9.4.3 Entrained-Flow Gasifiers ....................... 345
9.4.3.1 Shell Coal Gasification Process ....... 345
9.4.3.2 Prenflo Gasification Process .......... 348
9.4.3.3 General Electric Coal Gasification
Process ............................... 350
9.4.3.4 Conoco-Phillips E-Gas Gasification
Process ............................... 351
9.4.3.5 Mitsubishi Heavy Industries Coal
Gasification Process .................. 352
9.4.3.6 Siemens Fuel Gasification
Technology ............................ 355
9.4.4 Other Gasification Technologies ................ 356
9.4.4.1 Opposed Multi-Burner (OMB)
Gasification Technology ............... 356
9.4.4.2 Pratt and Whitney Rocketdyne (PWR)
Gasification Technology ............... 357
9.4.4.3 Plasma Gasification ................... 357
9.4.4.4 Underground Coal Gasification ......... 357
9.5 Outlook ............................................... 358
9.6 Summary ............................................... 359
References ................................................. 359
10 Gasification of Biomass and Waste .......................... 365
Alberto Gómez-Barea and Bo Leckner
10.1 Introduction .......................................... 365
10.2 Biomass as a Fuel for Gasification .................... 366
10.2.1 Impact of Biomass Characteristics on Gasifier
Performance .................................... 366
10.2.2 Biomass Classification and Standardization ..... 368
10.2.3 Biomass Reliability ............................ 369
10.3 Thermochemistry of Biomass Gasification ............... 370
10.4 Gasification Technologies ............................. 373
10.4.1 Types of Gasifiers ............................. 373
10.4.1.1 Fixed-Bed Gasifiers ................... 374
10.4.1.2 Fluidized-Bed Gasifiers ............... 375
10.4.1.3 Entrained-Flow Gasifiers .............. 376
10.4.2 Direct and Indirect Gasification ............... 376
10.4.3 Pressured Gasification ......................... 378
10.5 Gas Requirements for Utilization ...................... 378
10.6 Gas Cleaning .......................................... 380
10.6.1 Dust Removal ................................... 380
10.6.2 Removal of Contaminants ........................ 381
10.6.2.1 Nitrogen .............................. 381
10.6.2.2 Chlorine .............................. 381
10.6.2.3 Alkalis ............................... 381
10.6.2.4 Sulfur ................................ 382
10.6.3 Tar Removal and Conversion ..................... 382
10.6.3.1 Secondary Methods ..................... 382
10.6.3.2 Primary Methods ....................... 384
10.6.4 State of the Art of Gas Cleaning Technology .... 386
10.7 Applications .......................................... 387
10.7.1 Direct Firing .................................. 387
10.7.1.1 Direct Firing for Thermal
Applications .......................... 387
10.7.1.2 Direct Firing in Stand-Alone Gas
Boiler for Electricity Production ..... 388
10.7.2 Co-Firing ...................................... 389
10.7.3 Power Production in Engines .................... 391
10.7.4 Biomass Gasification Integrated in Combined
Cycles ......................................... 392
10.7.5 Production of Liquids by Chemical Synthesis .... 393
10.7.6 Fuel Cell Applications ......................... 394
10.8 Summary and Outlook ................................... 395
References ................................................. 396
11 Fluidized Beds ............................................. 399
Zbigniew Bis
11.1 Introduction .......................................... 399
11.2 Theory ................................................ 401
11.2.1 Average Particle Size .......................... 404
11.2.2 Parameters of a Bed of Solids .................. 405
11.2.3 Critical Fluidization Velocities ............... 407
11.2.4 Structure of Fluidized Bed ..................... 413
11.2.5 Heat Transfer in Fluidized Bed ................. 418
11.3 Application in Industry ............................... 420
11.3.1 Introduction ................................... 420
11.3.2 Fundamental Rules in Designing and Operating
the Fluidized Bed Boilers ...................... 422
11.4 Outlook ............................................... 428
11.5 Summary ............................................... 431
References ................................................. 432
12 Modeling of Circulating Fluidized Bed Combustion ........... 435
Wei Wang and Jinghai Li
12.1 Introduction .......................................... 435
12.2 Fluid Dynamics ........................................ 437
12.2.1 Moving Packed Bed .............................. 437
12.2.2 Bubbling Fluidization .......................... 438
12.2.3 Fast Fluidization .............................. 438
12.2.3.1 Axial Voidage Profile ................. 439
12.2.3.2 Lateral Voidage Profile ............... 441
12.2.3.3 Meso-Scale Structure .................. 441
12.2.3.4 EMMS Model and Extensions ............. 441
12.2.3.5 Gas and Solids Mixing ................. 445
12.3 Heat and Mass Transfer ................................ 445
12.3.1 Particle-Fluid Heat/Mass Transfer .............. 446
12.3.1.1 Classical Correlations ................ 446
12.3.1.2 Heat/Mass Transfer with Meso-Scale
Structures ............................ 447
12.3.2 Bed-to-Wall Heat Transfer ...................... 449
12.4 Reaction Kinetics ..................................... 451
12.4.1 Devolatilization ............................... 452
12.4.2 Char Combustion ................................ 453
12.4.3 Pollutant Emission ............................. 455
12.5 Modeling Approaches ................................... 456
12.5.1 Lumped Parameter Model ......................... 456
12.5.2 1D/1.5D Model .................................. 456
12.5.3 Multi-D Model .................................. 457
12.5.4 CFD Model ...................................... 457
12.6 Multiscale CFD Modeling of Combustion ................. 458
12.6.1 Governing Equations for Multiphase Flow and
Reactions ...................................... 458
12.6.1.1 Continuity Equation for Phase j (j =
1, 2.. .N) ............................ 458
12.6.1.2 Momentum Equations for Gas Phase (g)
and Solid Phase (s) ................... 459
12.6.1.3 Mass Conservation Equations for Gas
and Solid Components .................. 462
12.6.1.4 Energy Conservation Equations ......... 464
12.6.2 An Example of Simulation ....................... 464
12.7 Summary and Prospects ................................. 466
References ................................................. 466
13 Agglomeration in Fluidized Bed Combustion: Mechanisms,
Detection, and Counteraction ............................... 471
J. Ruud van Ommen and Weigang Lin
13.1 Introduction .......................................... 471
13.2 Mechanisms of Agglomeration in a Fluidized Bed ........ 472
13.2.1 Hydrodynamics .................................. 472
13.2.2 Chemical Reactions and Transportation of
Sticky Compounds ............................... 474
13.3 Fuel Ash Measurement Methods .......................... 476
13.4 Agglomeration Detection Based on Process
Measurements .......................................... 477
13.4.1 Detection Methods Based on Pressure
Measurements ................................... 477
13.4.2 Detection Methods Based on Acoustic
Emissions ...................................... 479
13.4.3 Detection Methods Based on Temperature ......... 480
13.4.4 Detection Methods Based on Gas-Phase Alkali
Concentrations ................................. 480
13.4.5 Detection Methods Based on Other Measurement
Sources ........................................ 481
13.5 Agglomeration Counteraction Strategies and
Technologies .......................................... 481
13.6 Summary ............................................... 483
References ................................................. 485
14 Ash-Forming Matter and Ash-Related Problems ................ 493
Maria Zevenhoven, Patrik Yrjas, and Mikko Hupa
14.1 Analysis of Ash-Forming Matter ........................ 493
14.2 Release and Chemical Reactions of Ash-Forming
Matter ................................................ 500
14.2.1 Silicon ........................................ 502
14.2.2 Aluminum ....................................... 503
14.2.3 Iron ........................................... 504
14.2.4 Potassium and Sodium ........................... 505
14.2.5 Calcium and Magnesium .......................... 507
14.2.6 Sulfur ......................................... 510
14.2.7 Chlorine ....................................... 511
14.2.8 Phosphorus ..................................... 512
14.3 Deposit Formation ..................................... 513
14.4 Agglomeration and Sintering in Fluidized Bed
Conversion ............................................ 520
14.5 Corrosion ............................................. 524
14.6 Final Remarks ......................................... 527
References ................................................. 528
15 Ash Fouling of Boiler Tubes and Thermophysical Properties
of Deposits ................................................ 533
Arvo Ots
15.1 Introduction .......................................... 533
15.2 Types and Classification of Ash Deposits .............. 534
15.3 Formation of Ash Deposits ............................. 535
15.3.1 Forces Acting on a Ash Particle ................ 535
15.3.2 Sticking of Particles on the Surface ........... 537
15.3.3 Formation of Loose Deposits .................... 538
15.3.4 Formation of Bound Deposits .................... 542
15.4 Thermophysical Properties of the Ash Deposits ......... 546
15.4.1 Thermal Conductivity ........................... 546
15.4.2 Thermal Radiation Emissivity ................... 549
15.4.3 Influence of Emissivity on Heat Transfer ....... 550
15.5 Summary ............................................... 553
References ................................................. 553
16 Co-Firing Biomass with Coal in Fluidized Bed Combustion
Systems .................................................... 557
Nevin Selçuk and Zuhal Cogebakan
16.1 Introduction .......................................... 557
16.2 Comparison between Coal and Biomass Characteristics ... 558
16.3 Comparison between Combustion Characteristics of
Coal and Biomass ...................................... 561
16.4 Motivation Behind Co-firing ........................... 563
16.5 Co-firing Biomass with Coal ........................... 566
16.5.1 Combustion Efficiency .......................... 568
16.5.2 Emissions ...................................... 569
16.5.2.1 C02 and CO Emissions .................. 569
16.5.2.2 SO2 Emissions ......................... 570
16.5.2.3 NOx and N20 Emissions ................. 571
16.5.2.4 Trace Element Emissions ............... 573
16.5.3 Agglomeration and Ash Deposition ............... 573
16.6 Industrial and Utility-Scale Applications ............. 575
16.7 Outlook ............................................... 575
16.8 Summary ............................................... 577
References ................................................. 577
17 Co-utilization of Biomass Based Fuels in Pulverized Coal
Power Plants in Europe ..................................... 585
Panagiotis Grammelis, Michalis Agraniotis, and Emmanuel
Kakaras
17.1 Introduction .......................................... 585
17.2 Current Co-firing Techniques .......................... 586
17.3 Practical Considerations for Retrofitting a Coal-
Fired Unit to Co-firing Biomass ....................... 588
17.3.1 Fuel Availability .............................. 588
17.3.2 Plant Modifications ............................ 591
17.3.2.1 Biomass Handling, Storage, and Fuel
Preparation ........................... 591
17.3.2.2 Preparation of the Blended Fuel and
Modifications in the Coal Mills ....... 592
17.3.2.3 Impact of Co-firing on the Boiler
Performance ........................... 594
17.3.2.4 Impacts of Co-firing on Emissions ..... 595
17.3.3 Legislative Framework on Environmental
Issues ......................................... 596
17.3.4 Financial Evaluation ........................... 598
17.3.5 Societal Issues ................................ 599
17.4 Review on Co-firing Experience at European Level ...... 600
17.5 Research trends for Biomass Co-firing in Europe ....... 602
17.6 Conclusions ........................................... 605
References .................................................... 607
Index ......................................................... 609
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