Boiler for Power and Process

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Boiler for Power and Process

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Contents

List of Figures …………………………………………………………………………………………………. xvii
List of Tables …………………………………………………………………………………………………xxxiii
Preface ……………………………………………………………………………………………………………… xli
Acknowledgments ……………………………………………………………………………………………. xlv
Author ……………………………………………………………………………………………………………xlvii
Structure of this Book ……………………………………………………………………………………… xlix
Conversion of Units ……………………………………………………………………………………………. lv
Preamble ………………………………………………………………………………………………………….lxiii
Section I: Boiler Fundamentals
1 Boiler Basics ………………………………………………………………………………………………..3
1.1 Introduction …………………………………………………………………………………………………….3
1.2 Classifi cation of Boilers ……………………………………………………………………………………3
1.2.1 Defi nition of a Boiler……………………………………………………………………………..3
1.2.2 Classifi cation…………………………………………………………………………………………3
1.3 Boiler Specifi cations ………………………………………………………………………………………..7
1.3.1 Steam Flow or Evaporation or Boiler Output…………………………………………7
1.3.2 Types of Pressures ………………………………………………………………………………..9
1.3.3 Outlet Temperatures ……………………………………………………………………………..9
1.3.4 Feed Water Temperature …………………………………………………………………….. 10
1.3.5 Fuels …………………………………………………………………………………………………… 10
1.4 Scope of Boiler Plant ……………………………………………………………………………………… 11
1.4.1 Inputs and Outputs …………………………………………………………………………….. 11
1.4.2 Boiler Package …………………………………………………………………………………….. 13
1.4.3 Boiler Island ……………………………………………………………………………………….. 13
1.5 Heat Balance for Boiler Effi ciency …………………………………………………………………. 14
1.5.1 Energy Balance in Boiler …………………………………………………………………….. 14
1.5.2 Boiler Effi ciency Calculations …………………………………………………………….. 14
1.5.3 Effect of Ambient Conditions on Boiler Effi ciency and Design …………… 15
1.5.4 Breakup of Losses ………………………………………………………………………………. 16
1.5.5 Typical Effi ciency Calculation ……………………………………………………………..20
1.6 Performance Testing of Boilers ………………………………………………………………………20
1.6.1 Input–Output Method ………………………………………………………………………… 21
1.6.2 Heat Loss Method ………………………………………………………………………………. 21
1.6.3 Calculation of Effi ciency from Performance Test Results …………………….23
1.6.4 New 1998 Boiler Performance Test Code …………………………………………….. 24
1.6.5 Performance Testing of Waste Heat Recovery Boilers ………………………….25
1.6.6 Performance Testing of Heat Recovery Steam Generators …………………..25
1.7 Boiler Evaluation ……………………………………………………………………………………………27
1.8 Boiler Design for Optimum Performance ………………………………………………………28
1.8.1 Stack Loss Reduction …………………………………………………………………………..29
1.8.2 Unburnt Loss Reduction ……………………………………………………………………..30
1.8.3 Radiation Loss Reduction ……………………………………………………………………30
1.8.4 Fan Power Reduction …………………………………………………………………………..30
1.8.5 Feed Pump Power Reduction ……………………………………………………………… 31
1.9 Designing to Boiler Codes …………………………………………………………………………….. 31
1.9.1 Basics of Boiler Pressure Part Design …………………………………………………..34
1.10 Capturing Basic Design Data ………………………………………………………………………… 37
Further Readings …………………………………………………………………………………………………..40
2 Heat and Flow …………………………………………………………………………………………… 41
2.1 Introduction ………………………………………………………………………………………………….. 41
2.2 Steam and Water Properties …………………………………………………………………………. 41
2.2.1 Boiling/Evaporation ……………………………………………………………………………42
2.2.2 Laws for Steam and Water …………………………………………………………………..42
2.2.3 Density ……………………………………………………………………………………………….42
2.2.4 Heat Distribution at Various Pressure Levels ……………………………………..43
2.2.5 Steam/Rankine Cycle …………………………………………………………………………43
2.2.6 Steam and Water Properties ………………………………………………………………..45
2.2.7 Mollier Chart or Enthalpy–Entropy (H–s) Diagram ……………………………45
2.2.8 Temperature–Entropy (T–s) Diagram ………………………………………………….45
2.3 Heat Transfer …………………………………………………………………………………………………47
2.3.1 Heat Flow ……………………………………………………………………………………………47
2.3.2 Conduction …………………………………………………………………………………………48
2.3.3 Convection ………………………………………………………………………………………….50
2.3.4 Radiation …………………………………………………………………………………………….55
2.3.5 Combined Heat Transfer …………………………………………………………………….56
2.3.6 Extended Surfaces ……………………………………………………………………………….57
2.4 Fluid Flow ……………………………………………………………………………………………………..59
2.4.1 Bernoulli’s Equation ……………………………………………………………………………60
2.4.2 Material Balance or Continuity Equation ……………………………………………60
2.4.3 Flow through Nozzles and Orifi ces …………………………………………………….60
2.4.4 Flow Coeffi cients ………………………………………………………………………………… 61
2.4.5 Resistance to Flow in Pipes ………………………………………………………………… 62
2.4.6 Air and Gas Duct Losses …………………………………………………………………….65
2.5 Circulation …………………………………………………………………………………………………….65
2.5.1 Principles of Circulation ……………………………………………………………………..65
2.5.2 Flow in Vertical and Horizontal Tubes ………………………………………………..65
2.5.3 Departure from Nucleate Boiling ……………………………………………………….66
2.5.4 Maintaining Nucleate Boiling …………………………………………………………….. 67
2.5.5 Types of Circulation …………………………………………………………………………… 70
2.5.6 Limits for Natural Circulation …………………………………………………………….73
2.5.7 Circulation Systems for Subcritical and Supercritical Pressures …………. 74
2.5.8 Boiler Feed Pumps ………………………………………………………………………………75
2.6 Combustion …………………………………………………………………………………………………..78
2.6.1 Stages of Combustion ………………………………………………………………………….78
2.6.2 Combustion Chemistry ………………………………………………………………………79
2.6.3 Combustion Air ………………………………………………………………………………….79
2.6.4 Heat of Combustion …………………………………………………………………………….80
2.6.5 Three Ts ………………………………………………………………………………………………82
2.6.6 Adiabatic Flame Temperature ……………………………………………………………..82
2.6.7 Specifi c Heats of Gas …………………………………………………………………………..82
2.6.8 Air and Gas Weights …………………………………………………………………………..82
viii Contents
2.6.9 Flue Gas Analysis ……………………………………………………………………………….87
2.6.10 Specifi c Volume of Flue Gases……………………………………………………………..89
2.7 Thermodynamic Cycles …………………………………………………………………………………90
2.7.1 Carnot Cycle ……………………………………………………………………………………….. 91
2.7.2 Rankine or Steam Cycle ……………………………………………………………………… 91
2.7.3 Brayton or Gas Turbine Cycle ………………………………………………………………92
2.7.4 Combined Cycle ………………………………………………………………………………….92
Further Readings …………………………………………………………………………………………..95
3 Fuels and Ash …………………………………………………………………………………………….97
3.1 Introduction …………………………………………………………………………………………………..97
3.2 Solid Fuels ……………………………………………………………………………………………………..98
3.2.1 Fossil Fuels ………………………………………………………………………………………….98
3.2.2 Waste Fuels ………………………………………………………………………………………. 110
3.3 Liquid Fuels ………………………………………………………………………………………………… 120
3.3.1 Fuel Oils……………………………………………………………………………………………. 120
3.4 Gaseous Fuels ………………………………………………………………………………………………125
3.4.1 Fossil Fuels ………………………………………………………………………………………..125
3.4.2 Waste or Manufactured Fuels …………………………………………………………… 128
3.5 Ash ……………………………………………………………………………………………………………… 132
3.5.1 Coal Ash …………………………………………………………………………………………… 132
3.5.2 Oil Ash ……………………………………………………………………………………………… 142
Further Readings ………………………………………………………………………………………… 143
4 Water Conditioning …………………………………………………………………………………. 145
4.1 Introduction ………………………………………………………………………………………………… 145
4.2 Water and Boiler …………………………………………………………………………………………. 145
4.2.1 Effects of Water on Boilers ………………………………………………………………… 146
4.2.2 Types of Water ………………………………………………………………………………….. 147
4.2.3 Water Treatment ……………………………………………………………………………….. 147
4.2.4 Impurities in Water …………………………………………………………………………… 148
4.2.5 Water Terminology …………………………………………………………………………… 148
4.3 Deaeration and O2 Scavenging ……………………………………………………………………. 149
4.3.1 Deaeration ………………………………………………………………………………………… 150
4.3.2 O2 Scavenging ………………………………………………………………………………….. 153
4.4 Water and Steam Conditioning …………………………………………………………………… 154
4.4.1 Feed Water ………………………………………………………………………………………… 154
4.4.2 Boiler Water ……………………………………………………………………………………… 155
4.4.3 Boiler Water Conditioning ………………………………………………………………… 156
4.4.4 Sludge Conditioning …………………………………………………………………………. 158
4.4.5 Boiler Blowdown ………………………………………………………………………………. 158
4.4.6 After-Boiler Protection ……………………………………………………………………… 159
4.4.7 Chemical Dosing ………………………………………………………………………………. 159
4.5 Carryover ……………………………………………………………………………………………………. 161
4.5.1 Steam Separators ………………………………………………………………………………. 162
4.5.2 Silica in Boiler Water ………………………………………………………………………… 163
4.5.3 Loading of Steam Separators ……………………………………………………………. 163
4.5.4 Foaming and Priming ………………………………………………………………………. 164
4.5.5 Steam Purity Measurement ………………………………………………………………. 165
Further Readings ………………………………………………………………………………………… 166
Contents ix
5 Boiler Materials ………………………………………………………………………………………. 167
5.1 Introduction ………………………………………………………………………………………………… 167
5.2 Boiler Parts………………………………………………………………………………………………….. 167
5.3 Boiler Steels ………………………………………………………………………………………………… 168
5.3.1 Boiler Quality (BQ) Plates …………………………………………………………………. 169
5.3.2 Boiler Tubes ……………………………………………………………………………………… 170
5.3.3 Pipes …………………………………………………………………………………………………. 177
5.3.4 Pressure Castings and Forgings ……………………………………………………….. 178
5.4 Structural Steels ………………………………………………………………………………………….. 182
5.4.1 Structural Quality Tubes and Pipes ………………………………………………….. 182
5.4.2 High-Temperature Castings ……………………………………………………………… 183
5.5 Fundamentals of Metallurgy ………………………………………………………………………. 184
5.5.1 Classifi cation of Steels ………………………………………………………………………. 185
5.5.2 Effect of Alloying Elements on Steel Properties ……………………………….. 189
5.5.3 Heat Treatment Processes …………………………………………………………………. 189
5.5.4 Certain Terms in Heat Treatment as Relevant to Boiler Steels …………… 189
5.5.5 Corrosion ………………………………………………………………………………………….. 192
5.6 Properties of Steel in Brief …………………………………………………………………………… 195
5.6.1 Tensile Strength ………………………………………………………………………………… 195
5.6.2 Hardness ………………………………………………………………………………………….. 196
5.6.3 Toughness ………………………………………………………………………………………… 196
5.6.4 Fatigue Strength ……………………………………………………………………………….. 199
5.6.5 High-Temperature Properties ……………………………………………………………200
5.7 Bricks, Refractory, Insulation, and Lagging ………………………………………………… 201
5.7.1 Refractories ……………………………………………………………………………………….. 201
5.7.2 Various Types of Refractories …………………………………………………………….203
5.7.3 Insulation …………………………………………………………………………………………..207
5.7.4 Lagging ……………………………………………………………………………………………..208
5.8 Wear-Resistant Refractory Ceramic Materials ……………………………………………..209
Further Readings ………………………………………………………………………………………… 210
Section II: Boiler Parts and Auxiliaries
6 Heating Surfaces ……………………………………………………………………………………… 213
6.1 Introduction ………………………………………………………………………………………………… 213
6.2 Evaporator Surfaces …………………………………………………………………………………….. 214
6.2.1 Furnace …………………………………………………………………………………………….. 214
6.2.2 Boiler Bank (BB) ………………………………………………………………………………..222
6.3 Superheater and Reheater (SH and RH) ……………………………………………………….227
6.3.1 Superheater (SH) ……………………………………………………………………………….227
6.3.2 Reheater (RH) ……………………………………………………………………………………228
6.3.3 Superheater and Reheater Design Principles……………………………………..228
6.3.4 Superheater and Reheater Classifi cation ……………………………………………229
6.3.5 Tubes for Superheater and Reheater ………………………………………………….233
6.3.6 Tube Spacing and Gas Velocities ……………………………………………………….235
6.3.7 Tube Metal Temperatures ………………………………………………………………….236
6.3.8 Steam Temperature Control (STC) ……………………………………………………. 237
6.4 Back-End Equipment ……………………………………………………………………………………242
6.4.1 Airheater or Economizer? …………………………………………………………………. 243
x Contents
6.4.2 Airheater versus Economizer ……………………………………………………………. 243
6.4.3 Airheater and Economizer Arrangements …………………………………………244
6.5 Economizer …………………………………………………………………………………………………. 245
6.5.1 Classifi cation …………………………………………………………………………………….. 246
6.5.2 Tube and Fin Materials ……………………………………………………………………..250
6.5.3 Operating Concerns in Economizers ………………………………………………… 251
6.6 Airheater ……………………………………………………………………………………………………..253
6.6.1 Airheater Types …………………………………………………………………………………253
6.6.2 TAH versus RAH ………………………………………………………………………………255
6.6.3 Tubular Airheater ……………………………………………………………………………..255
6.6.4 Rotary Airheater ……………………………………………………………………………….259
6.6.5 Operational Concerns ………………………………………………………………………. 262
Further Readings …………………………………………………………………………………………265
7 Fabricated Parts ……………………………………………………………………………………….. 267
7.1 Introduction ………………………………………………………………………………………………… 267
7.2 Unheated Pressure Parts ……………………………………………………………………………… 267
7.2.1 Steam and Water Drums ……………………………………………………………………268
7.2.2 Downcomers, Supplies, and Risers …………………………………………………… 276
7.2.3 Integral Piping ………………………………………………………………………………….. 278
7.3 Draft Plant Items …………………………………………………………………………………………. 281
7.3.1 Flues, Ducts, Hoppers, and Casing ……………………………………………………. 282
7.3.2 Dampers ……………………………………………………………………………………………283
7.3.3 Expansion Joints ………………………………………………………………………………..286
7.3.4 Airfl ow Measuring Devices ……………………………………………………………….286
7.4 Structure ………………………………………………………………………………………………………289
7.4.1 Site Conditions …………………………………………………………………………………..289
7.4.2 Loads to be Supported by Structure …………………………………………………..290
7.4.3 External Loads on Structure ………………………………………………………………290
7.4.4 Boiler Expansion and Guides ……………………………………………………………. 291
7.4.5 Hot and Cold Structures …………………………………………………………………… 292
7.4.6 Top, Middle, or Bottom Support ………………………………………………………… 298
7.4.7 Bolted or Welded Construction ………………………………………………………….298
7.4.8 Rolled Beams or Built-Up Sections …………………………………………………….299
Further Readings …………………………………………………………………………………………………299
8 Boiler Auxiliaries ……………………………………………………………………………………. 301
8.1 Introduction ………………………………………………………………………………………………… 301
8.2 Fans …………………………………………………………………………………………………………….. 301
8.2.1 Fans in Boiler Plant …………………………………………………………………………… 301
8.2.2 Salient Aspects of Fans ……………………………………………………………………..302
8.2.3 Types of Fans …………………………………………………………………………………….303
8.2.4 Centrifugal Fans ……………………………………………………………………………….305
8.2.5 Axial Fans …………………………………………………………………………………………308
8.2.6 Fan Laws ………………………………………………………………………………………….. 310
8.2.7 Fan Selection …………………………………………………………………………………….. 311
8.2.8 Effi ciency and Power ………………………………………………………………………… 314
8.2.9 Fan Control ………………………………………………………………………………………. 315
8.2.10 Construction Features ………………………………………………………………………. 320
8.2.11 Two Modes of Fan Operation …………………………………………………………….322
Contents xi
8.2.12 Single Set and Two Sets of Fans ………………………………………………………. 324
8.2.13 Fan Erosion and Protection …………………………………………………………….. 324
8.2.14 Boiler Fans ………………………………………………………………………………………. 325
8.3 Dust-Collecting Equipment ………………………………………………………………………… 326
8.4 Mechanical Dust Collectors (MDCs) …………………………………………………………… 328
8.4.1 Multiclones ……………………………………………………………………………………….. 328
8.4.2 Large-Diameter Cyclones …………………………………………………………………. 331
8.5 Dry Electrostatic Precipitator (ESP) …………………………………………………………….. 332
8.5.1 Operating Principle of an ESP …………………………………………………………… 332
8.5.2 Components ………………………………………………………………………………………333
8.5.3 Features …………………………………………………………………………………………….333
8.5.4 Advantages ……………………………………………………………………………………….338
8.5.5 Limitations ………………………………………………………………………………………..338
8.5.6 Performance Parameters ……………………………………………………………………338
8.6 Fabric Filters (FFs) ………………………………………………………………………………………..341
8.6.1 Advantages of FF……………………………………………………………………………….342
8.6.2 Limitations of FF ……………………………………………………………………………….342
8.6.3 ESP versus FF ……………………………………………………………………………………343
8.6.4 Performance of FF ……………………………………………………………………………..343
8.6.5 Reverse Gas Filters …………………………………………………………………………….344
8.6.6 Pulse Jet Filters ………………………………………………………………………………….344
8.6.7 RGF versus PJF ………………………………………………………………………………….345
8.6.8 Bags for FF ………………………………………………………………………………………..345
8.7 Wet Scrubbers (WSs) ……………………………………………………………………………………346
8.7.1 Advantages of WS ……………………………………………………………………………..346
8.7.2 Limitations of WS ………………………………………………………………………………348
8.7.3 Application of WS ……………………………………………………………………………..348
8.7.4 Comparison of Different Dust Collectors by Performance …………………348
8.8 Valves and Mountings …………………………………………………………………………………349
8.8.1 Main Steam Stop Valve and Nonreturn Valve ……………………………………350
8.8.2 Start-Up Vent Valves …………………………………………………………………………. 352
8.8.3 CBD and IBD Valves ………………………………………………………………………….353
8.8.4 Safety Valves ……………………………………………………………………………………..353
8.8.5 Drain and Vent Valves ………………………………………………………………………356
8.8.6 Control Valves …………………………………………………………………………………..358
8.9 Soot Blowers ……………………………………………………………………………………………….. 361
8.9.1 Working Principle of Soot Blowers ……………………………………………………. 362
8.9.2 Types and Locations of Soot Blowers …………………………………………………363
8.9.3 Boiler Firing and Soot Blowers …………………………………………………………..363
8.9.4 Steam versus Air ……………………………………………………………………………….365
8.9.5 Types of Blowers ………………………………………………………………………………..365
8.9.6 Rotary AH Cleaning …………………………………………………………………………. 369
8.9.7 Water Lancing …………………………………………………………………………………… 369
8.9.8 SB Piping…………………………………………………………………………………………… 370
8.9.9 Acoustic or Sonic Soot Blowers …………………………………………………………. 370
8.10 Water-Level Indicators ………………………………………………………………………………… 371
8.10.1 Direct Water-Level Indicators ……………………………………………………………. 372
8.10.2 Remote Water-Level Indicators ………………………………………………………….. 376
Further Readings ………………………………………………………………………………………………… 378
xii Contents
Section III: Boilers and Firing
9 Industrial and Utility Boilers ………………………………………………………………….. 381
9.1 Water Tube Boilers for Industry and Power …………………………………………………. 381
9.1.1 Characteristic Features of Industrial Boilers ……………………………………… 381
9.1.2 Characteristic Features of Utility Boilers ……………………………………………382
9.2 Industrial Boilers …………………………………………………………………………………………383
9.2.1 Boiler Classifi cation by Firing ……………………………………………………………383
9.2.2 Classifi cation by Number of Drums …………………………………………………. 393
9.2.3 Balanced Draft and Pressurized Firing …………………………………………….. 394
9.3 Utility Boilers ……………………………………………………………………………………………… 395
9.3.1 Small versus Large Utility Boilers …………………………………………………….. 395
9.3.2 Supercritical Boilers ………………………………………………………………………….. 396
9.3.3 Boiler Designs for Utilities…………………………………………………………………404
9.3.4 Features of Supercritical Boilers ………………………………………………………..408
9.3.5 Drum-Type or Supercritical Boiler? …………………………………………………… 415
9.3.6 Standard Plant Confi gurations for Supercritical Boilers ……………………. 416
Further Readings ………………………………………………………………………………………………… 416
10 Burner Firing …………………………………………………………………………………………… 417
10.1 Oil and Gas Firing …………………………………………………………………………………….. 417
10.2 Burners and Combustion…………………………………………………………………………… 418
10.2.1 Burner Size ……………………………………………………………………………………. 418
10.2.2 Burner Turndown …………………………………………………………………………. 419
10.2.3 Air Registers ………………………………………………………………………………….420
10.2.4 Excess Air for Oil and Gas Firing ………………………………………………….. 421
10.2.5 Combustion of Oil and Gas in Circular Burners…………………………….424
10.2.6 Atomizers ………………………………………………………………………………………425
10.2.7 Gas Burners ……………………………………………………………………………………432
10.2.8 Low NOx Burners …………………………………………………………………………..435
10.2.9 Igniters …………………………………………………………………………………………..438
10.2.10 Flame Monitors ………………………………………………………………………………440
10.3 Duct Burners ……………………………………………………………………………………………..441
10.4 Burner Management and Safety System …………………………………………………….444
10.5 Oil- and Gas-Fired Boilers ………………………………………………………………………….445
10.5.1 Package Boilers ………………………………………………………………………………446
10.5.2 Field-Erected Modular Boilers ……………………………………………………….453
Further Readings ………………………………………………………………………………………………… 461
11 Stoker Firing…………………………………………………………………………………………….463
11.1 Introduction ……………………………………………………………………………………………….463
11.2 Mechanical Stokers …………………………………………………………………………………….463
11.2.1 Grates and Stokers ………………………………………………………………………….466
11.2.2 CG versus TG …………………………………………………………………………………466
11.2.3 Using Same Grate for Mass and Spreader Burning ……………………….. 467
11.2.4 Moistening of Coal before Firing …………………………………………………… 467
11.2.5 Clinker ………………………………………………………………………………………….. 467
11.2.6 Coal Segregation ……………………………………………………………………………468
11.2.7 Coal Sizing …………………………………………………………………………………….468
Contents xiii
11.3 Mass Burning ……………………………………………………………………………………………. 471
11.3.1 Chain or Traveling Grates with Gravity Feeding …………………………… 471
11.3.2 RG and PG Grates …………………………………………………………………………. 473
11.4 Spreader Burning ……………………………………………………………………………………….475
11.4.1 Spreader Firing: CG and RG with Spreader Stokers ……………………….475
11.4.2 Spreader Firing with Dumping Grates ………………………………………….. 492
11.5 Stoker-Fired Boilers …………………………………………………………………………………… 495
11.5.1 Oil or Gas Firing in Stoker-Fired Boilers ……………………………………….. 497
11.5.2 Principles of Spreader Stoker-Fired Boiler Design …………………………. 498
11.5.3 Fuel Flexibility in Stokers ………………………………………………………………500
11.5.4 Biofuel Firing on Stokers ……………………………………………………………….. 501
Further Readings …………………………………………………………………………………………………504
12 Fluidized Bed Combustion ………………………………………………………………………505
12.1 Introduction ……………………………………………………………………………………………….505
12.2 FBC Fundamentals …………………………………………………………………………………….506
12.2.1 Fluidization ……………………………………………………………………………………506
12.2.2 Desulfurization ……………………………………………………………………………..509
12.2.3 Denitrifi cation ………………………………………………………………………………. 510
12.3 FBC Process: Pros and Cons ……………………………………………………………………… 511
12.3.1 Characteristics of FBC Boiler …………………………………………………………. 511
12.3.2 Advantages of FBC Boilers ……………………………………………………………. 512
12.3.3 Limitations of FBC Boilers …………………………………………………………….. 512
12.3.4 Thermal Effi ciency: Conventional versus FBC Boilers …………………… 513
12.4 Bubbling Fluidized Bed Combustion ………………………………………………………… 514
12.4.1 Process ………………………………………………………………………………………….. 514
12.4.2 Underbed versus Overbed Feeding ………………………………………………. 514
12.4.3 Bed Regulation for Part-Load Operation ………………………………………. 517
12.4.4 Bed Coil ………………………………………………………………………………………… 517
12.4.5 Deep versus Shallow Bed ……………………………………………………………… 518
12.4.6 Erosion in BFBC Boilers ………………………………………………………………… 519
12.4.7 Bed ………………………………………………………………………………………………… 519
12.4.8 Freeboard ……………………………………………………………………………………… 520
12.4.9 Ash Recirculation ………………………………………………………………………….. 520
12.4.10 Air Nozzles …………………………………………………………………………………… 521
12.4.11 Salient Process Parameters of BFBC Boilers ………………………………….. 521
12.4.12 Applications ………………………………………………………………………………….. 521
12.4.13 BFBC Boiler Design Principles ………………………………………………………. 523
12.4.14 BFBC Boiler Designs ……………………………………………………………………… 524
12.5 Circulating Fluidized Bed Combustion …………………………………………………….. 525
12.5.1 Process ………………………………………………………………………………………….. 525
12.5.2 Design Features of Classical or Hot Cyclone CFBC ………………………..530
12.5.3 CFBC Boilers …………………………………………………………………………………. 539
12.5.4 Cold Cyclone CFBC Boiler ……………………………………………………………..542
12.5.5 No-Cyclone U-Beam CFBC Boilers ………………………………………………..549
12.6 Utility Circulating Fluidized Bed Combustion Range Boilers …………………… 552
12.7 Ignifl uid Boilers …………………………………………………………………………………………554
Further Readings …………………………………………………………………………………………………558
xiv Contents
13 Pulverized Fuel Firing …………………………………………………………………………….. 559
13.1 Introduction ………………………………………………………………………………………………. 559
13.1.1 Main Features ……………………………………………………………………………….. 559
13.1.2 Advantages and Limitations …………………………………………………………. 561
13.2 Types of Firing ………………………………………………………………………………………….. 562
13.2.1 Indirect Firing ……………………………………………………………………………….. 562
13.2.2 Direct Firing ………………………………………………………………………………….563
13.3 Milling Plant ………………………………………………………………………………………………564
13.3.1 Suction and Pressurized Milling ……………………………………………………564
13.3.2 Feeders …………………………………………………………………………………………..565
13.3.3 Mills or Pulverizers ……………………………………………………………………….566
13.3.4 Coal Pipes ……………………………………………………………………………………… 587
13.4 Pulverized Firing Burners ………………………………………………………………………….589
13.4.1 Burner Light-Up and Low Load ……………………………………………………..590
13.4.2 Igniters ………………………………………………………………………………………….. 591
13.4.3 Flame Monitors and Burner Management System ………………………… 591
13.4.4 Burner Types …………………………………………………………………………………. 591
13.4.5 Circular Burners ……………………………………………………………………………. 591
13.4.6 Tangential Corner Burners ……………………………………………………………. 592
13.4.7 Circular versus Tangential Burners ………………………………………………. 594
13.4.8 Vertical Down-Shot Burners ………………………………………………………….. 594
13.4.9 Corner Firing ………………………………………………………………………………… 596
13.4.10 Low NOx PF Burners …………………………………………………………………….. 596
13.5 Pulverized Fuel Boilers ……………………………………………………………………………… 598
13.5.1 Design Principles ………………………………………………………………………….. 598
13.5.2 Fuel Flexibility ……………………………………………………………………………….602
13.5.3 Co-Firing of Fuels ………………………………………………………………………….603
13.5.4 Boiler Turndown ……………………………………………………………………………603
13.5.5 PF Boiler Layouts …………………………………………………………………………..603
13.5.6 PF Boiler Designs …………………………………………………………………………..604
Further Readings …………………………………………………………………………………………………609
14 Waste Gas Firing (Heat Recovery Steam Generators) ………………………………. 611
14.1 Introduction ………………………………………………………………………………………………. 611
14.2 Heat Recovery Steam Generators and Waste Heat Recovery Boilers ………….. 611
14.3 Gas Turbines ……………………………………………………………………………………………… 612
14.3.1 Gas Turbines for Power: Rapid Growth …………………………………………. 613
14.3.2 Defi nitions of Terms ……………………………………………………………………… 614
14.3.3 Basics …………………………………………………………………………………………….. 615
14.3.4 Cycles ……………………………………………………………………………………………. 617
14.3.5 Types …………………………………………………………………………………………….. 619
14.3.6 Manufacturers ………………………………………………………………………………. 620
14.3.7 Popular Models …………………………………………………………………………….. 621
14.3.8 Characteristics ………………………………………………………………………………. 623
14.3.9 Performance Enhancement ……………………………………………………………. 625
14.4 Heat Recovery Steam Generators ………………………………………………………………. 627
14.4.1 Conventional Boilers versus HRSGs ……………………………………………… 627
14.4.2 Standardized HRSG Designs: Not Possible …………………………………… 628
14.4.3 Demanding Design ……………………………………………………………………….. 629
Contents xv
14.4.4 Scope Issues ………………………………………………………………………………….. 629
14.4.5 Diverter Damper and Bypass Stack Assembly ……………………………….630
14.4.6 Fired HRSGs ………………………………………………………………………………….630
14.4.7 Design Aspects ……………………………………………………………………………… 631
14.4.8 Fins and Tubes ……………………………………………………………………………….635
14.4.9 Vertical and Horizontal HRSGs ……………………………………………………..640
14.4.10 System Confi gurations of Typical HRSGs ………………………………………645
14.4.11 Once-Through Steam Generators (OTSGs) ……………………………………..645
14.4.12 Performance Testing ………………………………………………………………………648
14.4.13 Layout of CCPP ………………………………………………………………………………648
Further Readings …………………………………………………………………………………………………650
Glossary ………………………………………………………………………………………………………….. 651
Appendix A: Boiler Calculations …………………………………………………………………….. 667
A.1 Introduction ……………………………………………………………………………………………….. 667
A.1.1 Combustion Calculations ………………………………………………………………… 667
A.1.2 Effi ciency Calculations ……………………………………………………………………. 675
A.1.3 Firing Equipment Selection ……………………………………………………………… 679
A.1.4 Preliminary Furnace Calculations ……………………………………………………680
A.1.5 Draft Plant Calculations ………………………………………………………………….. 681
A.1.6 Sizing of Valves and Mountings ……………………………………………………….686
A.1.7 Sizing of Pumps ……………………………………………………………………………….690
A.1.8 Sizing of Control Valves ………………………………………………………………….. 692
A.1.9 Sizing of Drives ……………………………………………………………………………….. 693
Further Readings ………………………………………………………………………………………………… 695
Appendix B: Table of Combustion Constants ………………………………………………….. 697
Appendix C: ASTM Standards Pertaining to Testing and Specification of
Coals and Oils ……………………………………………………………………………. 701
List of Calculations …………………………………………………………………………………………. 703
List of Symbols ……………………………………………………………………………………………….. 705
List of Acronyms …………………………………………………………………………………………….. 707
Design Guidelines …………………………………………………………………………………………. 711
Fuel and Ash Data …………………………………………………………………………………………… 713
Technology Comparisons ………………………………………………………………………………… 715
Important Descriptions …………………………………………………………………………………… 717
Index ……………………………………………………………………………………………………………….. 719