The Control of Boilers

Front Matter......Page 1
Preface to Second Edition......Page 3
Table of Contents......Page 5
2.2 The Basic Boiler......Page 11
2.3 Heat Recovery from the Flue Gases......Page 13
2.4 Boiler Types and Classifications......Page 17
2.5 Firetube Boilers......Page 18
2.6 Watertube Drum Boilers......Page 22
2.7 Watertube Once-through Boilers......Page 28
3.2 Input Related to Output......Page 30
3.3 Mass and Energy Balances Involved......Page 31
3.4 Efficiency Calculation Methods......Page 33
3.5 Boiler Control - The Process of Managing the Energy and Mass Balances......Page 34
4.1 Simple Feedback Control......Page 36
4.2 Feedforward-Plus-Feedback Control......Page 39
4.4 Ratio Control......Page 41
4.5 Some Fundamentals of Control System Application and Design......Page 42
4.7 Process Factors That Affect the Control System or Loop Application......Page 43
5.1 Gaseous Fuels - Their Handling and Preparation......Page 44
5.2 Liquid Fuels - Their Handling and Preparation......Page 45
5.3 Solid Fuels - Their Handling and Preparation for Firing......Page 50
5.4 Handling and Delivery of Solid Fuels......Page 51
5.5 Fuel Mixtures - Coal-Oil, Coal-Water......Page 53
5.6 Physical Combustion Requirements......Page 54
5.7 Combustion Chemistry and Products of Combustion......Page 56
5.8 Theoretical Air Requirements and Relationship to Heat of Combustion......Page 60
5.9 The Requirement of Excess Combustion Air......Page 62
6.1 Input/Output or Direct Method......Page 68
6.2 Heat Loss or Indirect Method......Page 70
7.1 Saturated Steam Moisture Elimination......Page 81
7.2 Steam Supply Systems......Page 82
7.3 Heat Energy and Water Storage......Page 83
8.2 Linking the Steam Pressure Change to Changes in Firing Rate......Page 86
8.3 Steam Pressure or Steam Flow Feedback Control......Page 89
8.4 Feedforward-Plus-Feedback - Steam Flow Plus Steam Pressure......Page 92
8.5 Load Sharing of Multiple Boilers......Page 96
8.6 Automatic Compensation for the Number and Size of Boilers Participating......Page 97
8.8 Energy Management by Boiler Load Allocation on a Least Cost Basis......Page 100
8.9 Energy Management Involving Cogeneration Networks......Page 102
9. Firing Rate Demand for Utility Boilers......Page 108
9.1 Matching Firing Rate Demand to Electrical Load Boiler-Turbine Coordination......Page 109
9.2 Boiler Load Measurement......Page 111
9.3 Unit Load Demand Development......Page 114
9.4 Boiler Following - Firing Rate Demand Development......Page 116
9.5 Turbine Following - Throttle Pressure Control with the Turbine Valves......Page 122
9.6 Boiler - Turbine Coordinated Control......Page 126
9.7 Sliding or Variable Pressure Control......Page 129
9.9 Digital Interlock and Tracking Control Modes......Page 130
10.2 Mechanisms for Control of Superheat Temperature......Page 132
10.3 Basic Steam Temperature Control Strategies......Page 137
10.4 Steam Temperature and Reheat Temperature Control Strategies......Page 140
10.5 A Reheat Temperature Control Arrangement for a Combustion Engineering Boiler......Page 142
10.6 The Corresponding Superheat Temperature Control for the Combustion Engineering Boiler......Page 145
10.7 Spray Water Sources - Steam and Water Flow Measurements......Page 147
10.9 Pumping and Firing Rate for Once-through Boilers......Page 149
10.10 Steam Temperature Control for Once-through Boilers......Page 153
11.2 Logic Diagramming for Motor Starting and Trip Protection......Page 158
11.2.1 Methods of Diagramming......Page 159
11.2.2 Typical Logic Presentation......Page 160
11.2.3 Implementation......Page 165
11.3 Digital Interlocks within the Control System......Page 166
11.4.1 Interlock Circuitry......Page 167
11.4.2 Boiler Hazards......Page 168
11.5 Limits and Runbacks......Page 169
12.2 Heating and Deaeration......Page 170
12.3 The Boiler Feedwater Pump......Page 173
12.4 The Flow Regulation System......Page 174
12.5 Shrink and Swell and Boiler Water Circulation......Page 176
12.6 Feedwater Chemical Balance and Control of Boiler Blowdown......Page 180
13.1 Measurement and Indication of Boiler Drum Level......Page 182
13.2 Feedwater Control Objectives......Page 184
13.3 Single-Element Feedwater Control......Page 187
13.4 Two-Element Feedwater Control......Page 191
13.5 Three-Element Feedwater Control......Page 195
13.6 Control Refinements and Special Control Problems......Page 197
13.7 Control of Feedwater for Once-through Boilers......Page 200
14.1 Draft Losses in Boilers......Page 203
14.2 Natural Draft and Forced Draft......Page 204
14.3 Pressure-Fired Boilers......Page 205
14.4 Balanced Draft Boilers......Page 207
14.5 Dampers and Damper Control Devices......Page 208
14.6 Draft or Air Flow Control Using a Variable-Speed Fan......Page 213
14.7 Minimum Air Flow......Page 216
15.1 Measurement of Furnace Draft......Page 218
15.2 Furnace Draft Control Using Simple Feedback Control......Page 220
15.3 Furnace Draft Control Using Feedforward-Plus-Feedback Control......Page 221
15.4 Furnace Draft Control Using Push-Pull Feedforward-Plus-Feedback Control......Page 222
15.5 Protection against Implosion......Page 224
16.1 Differential Pressure Measurement of Air Flow......Page 229
16.2 Non-Inferential Methods of Air Flow Measurement......Page 234
16.3 Control of Air Flow......Page 236
16.4 Flue Gas Dew Point Control......Page 239
16.5 Soot Blowing......Page 243
17.1.2 Uses......Page 245
17.2.1 The \"in situ\" Point Sample Method......Page 246
17.2.2 Extractive or \"ex situ\" Method......Page 247
17.2.3 Light or Infrared Beam across the Stack......Page 248
17.2.4 Comparison Factors......Page 249
17.3.1 Selection of the Constituent Gas or Gases......Page 250
17.3.3 Quality of the Flue Gas Analysis Measurement for the Stated Purpose......Page 251
17.4 Flue Gas Analysis vs. Boiler Load......Page 252
17.5 PPM CO vs. PPM Total Combustible Gas......Page 254
17.6.1 Percent Oxygen as an Individual Control Index......Page 255
17.6.2 Total Combustible or Carbon Monoxide in the PPM Range as an Individual Control Index......Page 258
17.6.3 Trimming Control Based on a Combination of % Oxygen and PPM CO......Page 259
17.7 Limiting Factors in Reducing Excess Air......Page 262
18.1 Burners for Gaseous Fuel......Page 264
18.2 Pulverized Coal Burners......Page 268
18.3 Fuel Oil Burners......Page 271
19.1.1 The Spreader Stoker......Page 280
19.1.2 The Underfeed Stoker......Page 281
19.1.3 The Overfeed Stoker......Page 283
19.2 Special Stoker Control Problems......Page 286
20.1 Basic Cause of Furnace Explosions......Page 288
20.2 Boiler Purge Logic......Page 290
20.4 Main Gas Header Valve Management......Page 292
20.5 Gas Burner Management Logic......Page 293
20.6 Main Fuel Trip......Page 296
20.8 Reliability of Interlock Circuitry......Page 297
21.1 Single-Point Positioning Control......Page 299
21.2 Parallel Positioning Control......Page 303
21.3 Metering Control Systems......Page 305
21.4 Effects of Fuel Btu Variation......Page 316
22.1 The Coal Feeder......Page 321
22.2 The Pulverizer and Classifier......Page 324
22.3 The Primary Air Fan or Exhauster Fan and the Coal Drying System......Page 326
22.4 Pulverizer Control Systems......Page 329
22.5 Compartmented Windbox Pulverized Coal Boilers......Page 338
22.6 Start-up and Management of Pulverizers and Their Burners......Page 340
22.7 The Cyclone Furnace......Page 343
22.8 Start-up and Management of Cyclone Furnaces......Page 346
23.1 Coal Btu Compensation......Page 347
23.2 The Use of Multiple Pulverizers......Page 350
23.3 The Combustion Control System for Pulverized Coal as a Single Fuel......Page 351
23.4 Pulverized Coal in Combination with Liquid or Gaseous Fuels......Page 352
23.5 Compartmented Windbox Pulverized Coal Control Systems......Page 355
23.6 Control Systems for Cyclone Furnace Boilers......Page 357
24.1 Parallel Positioning Control Systems for Stoker-Fired Boilers......Page 361
24.2 Inferential Measurement of Combustion Conditions in Boilers......Page 363
24.3 Parallel Positioning Control Systems with Steam Flow/Air Flow Readjustment......Page 364
24.4 Series Ratio Control Systems for Stoker-Fired Boilers......Page 367
24.5 Applying Flue Gas Analysis Trim Control to Stoker-Fired Boilers......Page 369
24.6 Combustion Control for Combination of Stoker and Liquid or Gaseous Fuel Firing......Page 371
24.7 NFPA Purging and Interlock Requirements for Stoker-Fired Boilers......Page 374
25. Atmospheric Fluidized-Bed Boilers......Page 376
25.1 Bubbling Bed Fluidized-Bed Boilers......Page 377
25.2 Circulating Bed Fluidized-Bed Boilers......Page 379
25.3 NFPA Requirements for Atmospheric Fluidized-Bed Combustion System Boilers......Page 382
26.1 Complex Control Systems for Electric Utility Boilers Using Embedded Process Models......Page 383
26.2.1 Self-Tuning or Adaptive Tuning......Page 384
26.2.3 Computation of Unmeasurable Variables......Page 385
26.2.4 Cross Coupling......Page 386
26.2.5 Nonlinear Control......Page 387
26.4 A General Observation Relative to Boiler Modeling......Page 388
26.5 General Observations Relative to Boiler Control Application......Page 390
A......Page 392
B......Page 393
C......Page 395
D......Page 398
E......Page 399
F......Page 400
H......Page 403
I......Page 404
M......Page 405
N......Page 406
P......Page 407
R......Page 408
S......Page 409
T......Page 411
W......Page 413
Z......Page 414