The control of boilers

"This resource helps reduce boiler operating costs through a detailed, comprehensive, and applicable explanation of all aspects of boiler processes. It presents the basics of boiler control, the interrelationships of the process characteristics, and the dynamics involved. The 2nd Edition places significant emphasis on start-up, shut-down, flame monitoring, and safety interlock measures. Designed for professionals with a good understanding of boiler jargon, thermodynamics, control concepts, and math fundamentals."--Publisher's description 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 A basic text for beginners in the field of boiler control application. This edition (first in 1986) adds some basic information on the digital "starting up" phase of the operation in addition to the modulating "on-line" operation covered in the original edition, and extends the "on-line" aspects into the arena of the larger-capacity electric utility boilers. Annotation copyright Book News, Inc. Portland, Or. Aims to help users reduce boiler operating costs by offering a detailed explanation of all aspects of boiler processes. It presents the basics of boiler control, the interrelationships of process characteristics and the dynamics involved. This edition stresses startup, shutdown and safety matters.