Fluidized Bed Combustion (Mechanical Engineering (Marcell Dekker))

Fluidized Bed Combustion 8 Foreword 10 Preface 12 Contents 17 Table of Contents -1 CHAPTER 1: DEVELOPMENT OF FLUIDIZED BED COMBUSTION BOILERS 24 1.1. Problems of modern energy production and the requirements posed for coal combustion technologies 24 1.2. Development of FBC technology—background 28 1.3. A short review of FBC history 29 1.4. Development of FBC technology in Yugoslavia 33 1.5. Bubbling fluidized bed boilers—the state-of-the-art 35 1.6. The features of first generation FBC boilers 37 1.7. Reasons for circulating FBC boiler development 43 1.8. Basic principles and description of circulating FBC boilers 44 1.9. Characteristics of second generation FBC boilers 47 1.10. Circulating fluidized bed combustion boilers—the state-of-the-art 49 1.11. Application of the FBC boilers for energy production 52 References 55 Table of Contents -1 CHAPTER 2: HYDRODYNAMICS OF GAS-SOLID FLUIDIZATION 60 2.1. Basic definitions and properties of the particulate solids 61 2.1.1. Physical properties of the particulate solids 62 2.1.2. Geometrical characteristics of the particulate solids 63 2.1.3. Hydrodynam ic properties of solid particles 73 2.2. Onset and different regimes of gas-solid fluidization 78 2.2.1. Different possible states of the gas-solid mixtures 78 2.2.2. Fluidization regimes 83 2.2.3. Relative gas-particle velocity 91 2.3. The bubbling fluidized bed 92 2.3.1. General characteristics and macroscopic behavior of the bubbling fluidized bed 92 2.3.2. Minimum fluidization velocity 96 2.3.3. Bed expansion 104 2.3.4. Particle elutriation from fluidized bed 111 2.3.5. Bubbles in a fluidized bed 119 2.3.6. Gas and particle mixing in fluidized bed 131 2.4. Mathematical modelling of the fluidized bed 151 Nomenclature 156 Greek symbols 158 Dimensionless criterial numbers 159 References 159 Table of Contents -1 CHAPTER 3: HEAT AND MASS TRANSFER IN FLUIDIZED BEDS 169 3.1. Heat transfer processes in bubbling fluidized bed combustion boiler furnaces 169 3.2. Heat transfer between gas and solid particles in bubbling fluidized beds 172 3.3. Heat and mass transfer between fuel particles and a bubbling fluidized bed 177 3.3.1. Mass transfer between fuel particles and bubbling fluidized beds 178 3.3.2. Heat transfer between fuel particles and bubbling fluidized bed 182 3.4. Apparent conductive heat transfer in bubbling fluidized beds 187 3.5. Heat transfer between fluidized bed and surface 190 3.5.1. Mechanisms of bed-to-surface heat transfer 190 3.5.2. Heat transfer to immersed surfaces—experimental results 194 3.5.3. Influence of geometrical parameters on heat transfer 207 3.5.4. Radiative heat transfer in the fluidized bed 211 3.5.5. Modelling of heat transfer processes to immersed surfaces 214 3.6. Heat transfer to the walls of the fluidized bed combustion boiler furnace 217 Nomenclature 222 Greek symbols 223 Dimensionless criterial numbers 224 References 226 Table of Contents -1 CHAPTER 4: FUNDAMENTAL PROCESSES DURING COAL COMBUSTION IN FLUIDIZED BEDS 233 4.1. Characteristic features of combustion in fluidized beds 234 4.1.1. Combustion conditions in fluidized beds 234 4.1.2. Physical processes during coal particle combustion in fluidized beds 236 4.1.3. Parameters influencing combustion in the fluidized bed 239 4.2. Coal as combustible matter 241 4.2.1. Classification of coals 241 4.2.2. Coal petrography 246 4.2.3. Chemical structure of organic matter in coal 247 4.2.4. Chemical structure of mineral matter in coal 250 4.2.5. Porosity of coal and char particles 250 4.2.6. Coal characteristics that influence the combustion process 251 4.3. Fragmentation of coal particles in fluidized beds 254 4.3.1. Primary fragmentation 255 4.3.2.Secondary fragmentation 257 4.3.3. Attrition of char particles 258 4.4. Devolatilization and combustion of volatile matter 262 4.4.1. Volatile matter yield and composition 263 4.4.2. Control processes and kinetics of devolatilization 276 4.4.3. Devolatilization time in fluidized beds—experimental results 287 4.4.4. Ignition and combustion kinetics of volatile matter 292 4.5. Volatile matter combustion in fluidized beds 297 4.5.1. High volatile coal combustion in real conditions 297 4.5.2. Coal particle behavior during the devolatilization process in fluidized beds 298 4.5.3. Distribution and combustion of volatile matter in fluidized beds 302 4.5.4. Modelling of volatile matter distribution and combustion in fluidized beds 306 D. Release and combustion of volatiles 307 G. Combustion above the bed 307 4.6. Char combustion 308 4.6.1. Kinetics of heterogeneous chemical reactions on the surface of carbon (char) particles 310 4.6.2. Chemical reactions and control processes during carbon (char) particle combustion 314 4.6.3. Carbon (char) particle burning models 319 4.6.4. Mathematical modelling of single char particle combustion in a fluidized bed 324 4.6.5. Char combustion kinetics in fluidized beds—experimental results 334 (a) Char burn-out time 344 (b) Chemical reactions in char particle combustion in fluidized beds 347 (c) Char combustion rate 349 (d) Kinetic parameters 353 4.6.6. Temperature of burning particles in a fluidized bed 355 4.7. Mathematical modelling of processes in solid fuel combustion in fluidized bed boilers 361 Nomenclature 373 Greek symbols 376 Dimensionless criterial numbers 376 References 377 Table of Contents -1 CHAPTER 5: FLUIDIZED BED COMBUSTION IN PRACTICE 388 5.1. Purpose and basic concept of devices for solid fuel combustion in fluidized bed 388 5.1.1. Furnaces for production of hot gases or hot air 388 (a) Purpose and applications 388 (b) Basic parameters and requirements 389 (c) Basic problems 390 (d) Some construction solutions 390 5.1.2 Industrial boilers with bubbling fluidized bed combustion 392 (a) Purpose and applications 392 (b) Basic parameters and requirements 394 (c) Basic problems in design 395 (d) Basic designs of industrial bubbling FBC boilers 395 5.1.3. Bubbling fluidized bed combustion boilers for electricity production 415 (a) Purpose and application 415 (b) Basic parameters and requirements 417 (c) Basic design problems 418 (d) Basic design solutions for large power bubbling FBC boilers 419 5.1.4. Choice of boiler concept-problems and the choice of basic parameters 423 5.2. The purpose and description of auxiliary systems in FBC boilers 432 5.3. Efficiency of solid fuel combustion in the FBC boilers 445 5.3.1. Influence of fuel properties 447 5.3.2. Influence of combustion regime parameters 452 5.3.3. Influence of furnace design 455 5.4. Load control in FBC boilers 458 5.5. Erosion of heat transfer surfaces immersed into the fluidized bed 460 5.6. Ash sintering during combustion in fluidized bed 467 5.7. Niche markets for bubbling FBC (written by Dr. E.J.Anthony) 469 Coal from small local mines 469 Biomass fuels 470 Pulping and deinking sludges 471 Municipal solid wastes 471 Hazardous and special wastes 472 High-sulphur pitch 473 Nomenclature 474 Greek symbols 474 References 475 Table of Contents -1 CHAPTER 6: INVESTIGATION OF COAL SUITABILITY FOR FLUIDIZED BED COMBUSTION 483 6.1. Effects of fuel characteristics on the design and FBC boiler concept and its operational behavior 483 6.2. ITE-IBK methodology for investigation of solid fuel suitability for combustion in fluidized beds 485 6.2.1. Principles of the ITE-IBK methodology 486 6.2.2. Description of the ITE-IBK methodology 491 6.2.3. Characteristics of the investigated fuels 495 6.2.4. Determination of the start-up temperature 500 6.2.5. Effects of fuel characteristics on fuel behavior during combustion in fluidized beds 508 6.3. Justification of the application of laboratory furnace investigation results in designing industrial boilers 517 Nomenclature 519 Greek symbols 520 References 520 Table of Contents -1 CHAPTER 7: HARMFUL MATTER EMISSION FROM FBC BOILERS 524 7.1. Introduction 524 7.1.1. Combustion of coal and formation of harmful matter 525 7.1.2. Regulations on air protection 527 7.1.3. Air pollution in Yugoslavia 530 7.1.4. The role of FBC boilers in reduction of air pollution 531 7.2. Characteristics of the first generation industrial and demonstration FBC boilers in operation—SO2, NOx, CO, and particle emission 533 7.2.1. Design requirements for the first generation FBC boilers 534 7.2.2. Emission measured during operation of several characteristic first generation FBC boilers 535 7.2.3 Comparison of emissions from bubbling and circulating FBC boilers 536 7.3. Carbon-monoxide emission in bubbling fluidized bed combustion 538 7.4. Sulphur-dioxide emission in bubbling fluidized bed combustion 540 7.4.1. Physical and chemical processes controlling rate and degree of limestone sulphation during fluidized bed combustion 540 7.4.2 The effects of design and operating parameters on SO2 emission in fluidized bed combustion 546 7.4.3. Effects of limestone characteristics 553 7.4.4. Efficiency of limestone utilization 554 7.5. Emission of NOx and N2O in bubbling fluidized bed combustion 567 7.5.1. Nitrogen balance during coal combustion in FBC boilers 567 7.5.2. Mechanisms of N2O and NOx formation and destruction 572 7.5.3. Effects of coal characteristics on NOx and N2O formation 575 7.5.4. Effects of operating parameters 576 7.5.5. Measures for reduction of NOx and N2O emission in fluidized bed combustion 584 7.6. Emission of solid particles in fluidized bed combustion 586 7.6.1. Types and characteristics of solid combustion products from FBC boilers 586 7.6.2. Experience with baghouse filters 589 7.6.3. Experience in the application of electrostatic precipitators 590 Nomenclature 591 Greek symbols 591 References 591 Fluidized Bed Combustion......Page 8 Foreword......Page 10 Preface......Page 12 Contents......Page 17 Table of Contents......Page 0 1.1. Problems of modern energy production and the requirements posed for coal combustion technologies......Page 24 1.2. Development of FBC technology—background......Page 28 1.3. A short review of FBC history......Page 29 1.4. Development of FBC technology in Yugoslavia......Page 33 1.5. Bubbling fluidized bed boilers—the state-of-the-art......Page 35 1.6. The features of first generation FBC boilers......Page 37 1.7. Reasons for circulating FBC boiler development......Page 43 1.8. Basic principles and description of circulating FBC boilers......Page 44 1.9. Characteristics of second generation FBC boilers......Page 47 1.10. Circulating fluidized bed combustion boilers—the state-of-the-art......Page 49 1.11. Application of the FBC boilers for energy production......Page 52 References......Page 55 CHAPTER 2: HYDRODYNAMICS OF GAS-SOLID FLUIDIZATION......Page 60 2.1. Basic definitions and properties of the particulate solids......Page 61 2.1.1. Physical properties of the particulate solids......Page 62 2.1.2. Geometrical characteristics of the particulate solids......Page 63 2.1.3. Hydrodynam ic properties of solid particles......Page 73 2.2.1. Different possible states of the gas-solid mixtures......Page 78 2.2.2. Fluidization regimes......Page 83 2.2.3. Relative gas-particle velocity......Page 91 2.3.1. General characteristics and macroscopic behavior of the bubbling fluidized bed......Page 92 2.3.2. Minimum fluidization velocity......Page 96 2.3.3. Bed expansion......Page 104 2.3.4. Particle elutriation from fluidized bed......Page 111 2.3.5. Bubbles in a fluidized bed......Page 119 2.3.6. Gas and particle mixing in fluidized bed......Page 131 2.4. Mathematical modelling of the fluidized bed......Page 151 Nomenclature......Page 156 Greek symbols......Page 158 References......Page 159 3.1. Heat transfer processes in bubbling fluidized bed combustion boiler furnaces......Page 169 3.2. Heat transfer between gas and solid particles in bubbling fluidized beds......Page 172 3.3. Heat and mass transfer between fuel particles and a bubbling fluidized bed......Page 177 3.3.1. Mass transfer between fuel particles and bubbling fluidized beds......Page 178 3.3.2. Heat transfer between fuel particles and bubbling fluidized bed......Page 182 3.4. Apparent conductive heat transfer in bubbling fluidized beds......Page 187 3.5.1. Mechanisms of bed-to-surface heat transfer......Page 190 3.5.2. Heat transfer to immersed surfaces—experimental results......Page 194 3.5.3. Influence of geometrical parameters on heat transfer......Page 207 3.5.4. Radiative heat transfer in the fluidized bed......Page 211 3.5.5. Modelling of heat transfer processes to immersed surfaces......Page 214 3.6. Heat transfer to the walls of the fluidized bed combustion boiler furnace......Page 217 Nomenclature......Page 222 Greek symbols......Page 223 Dimensionless criterial numbers......Page 224 References......Page 226 CHAPTER 4: FUNDAMENTAL PROCESSES DURING COAL COMBUSTION IN FLUIDIZED BEDS......Page 233 4.1.1. Combustion conditions in fluidized beds......Page 234 4.1.2. Physical processes during coal particle combustion in fluidized beds......Page 236 4.1.3. Parameters influencing combustion in the fluidized bed......Page 239 4.2.1. Classification of coals......Page 241 4.2.2. Coal petrography......Page 246 4.2.3. Chemical structure of organic matter in coal......Page 247 4.2.5. Porosity of coal and char particles......Page 250 4.2.6. Coal characteristics that influence the combustion process......Page 251 4.3. Fragmentation of coal particles in fluidized beds......Page 254 4.3.1. Primary fragmentation......Page 255 4.3.2.Secondary fragmentation......Page 257 4.3.3. Attrition of char particles......Page 258 4.4. Devolatilization and combustion of volatile matter......Page 262 4.4.1. Volatile matter yield and composition......Page 263 4.4.2. Control processes and kinetics of devolatilization......Page 276 4.4.3. Devolatilization time in fluidized beds—experimental results......Page 287 4.4.4. Ignition and combustion kinetics of volatile matter......Page 292 4.5.1. High volatile coal combustion in real conditions......Page 297 4.5.2. Coal particle behavior during the devolatilization process in fluidized beds......Page 298 4.5.3. Distribution and combustion of volatile matter in fluidized beds......Page 302 4.5.4. Modelling of volatile matter distribution and combustion in fluidized beds......Page 306 G. Combustion above the bed......Page 307 4.6. Char combustion......Page 308 4.6.1. Kinetics of heterogeneous chemical reactions on the surface of carbon (char) particles......Page 310 4.6.2. Chemical reactions and control processes during carbon (char) particle combustion......Page 314 4.6.3. Carbon (char) particle burning models......Page 319 4.6.4. Mathematical modelling of single char particle combustion in a fluidized bed......Page 324 4.6.5. Char combustion kinetics in fluidized beds—experimental results......Page 334 (a) Char burn-out time......Page 344 (b) Chemical reactions in char particle combustion in fluidized beds......Page 347 (c) Char combustion rate......Page 349 (d) Kinetic parameters......Page 353 4.6.6. Temperature of burning particles in a fluidized bed......Page 355 4.7. Mathematical modelling of processes in solid fuel combustion in fluidized bed boilers......Page 361 Nomenclature......Page 373 Dimensionless criterial numbers......Page 376 References......Page 377 (a) Purpose and applications......Page 388 (b) Basic parameters and requirements......Page 389 (d) Some construction solutions......Page 390 (a) Purpose and applications......Page 392 (b) Basic parameters and requirements......Page 394 (d) Basic designs of industrial bubbling FBC boilers......Page 395 (a) Purpose and application......Page 415 (b) Basic parameters and requirements......Page 417 (c) Basic design problems......Page 418 (d) Basic design solutions for large power bubbling FBC boilers......Page 419 5.1.4. Choice of boiler concept-problems and the choice of basic parameters......Page 423 5.2. The purpose and description of auxiliary systems in FBC boilers......Page 432 5.3. Efficiency of solid fuel combustion in the FBC boilers......Page 445 5.3.1. Influence of fuel properties......Page 447 5.3.2. Influence of combustion regime parameters......Page 452 5.3.3. Influence of furnace design......Page 455 5.4. Load control in FBC boilers......Page 458 5.5. Erosion of heat transfer surfaces immersed into the fluidized bed......Page 460 5.6. Ash sintering during combustion in fluidized bed......Page 467 Coal from small local mines......Page 469 Biomass fuels......Page 470 Municipal solid wastes......Page 471 Hazardous and special wastes......Page 472 High-sulphur pitch......Page 473 Greek symbols......Page 474 References......Page 475 6.1. Effects of fuel characteristics on the design and FBC boiler concept and its operational behavior......Page 483 6.2. ITE-IBK methodology for investigation of solid fuel suitability for combustion in fluidized beds......Page 485 6.2.1. Principles of the ITE-IBK methodology......Page 486 6.2.2. Description of the ITE-IBK methodology......Page 491 6.2.3. Characteristics of the investigated fuels......Page 495 6.2.4. Determination of the start-up temperature......Page 500 6.2.5. Effects of fuel characteristics on fuel behavior during combustion in fluidized beds......Page 508 6.3. Justification of the application of laboratory furnace investigation results in designing industrial boilers......Page 517 Nomenclature......Page 519 References......Page 520 7.1. Introduction......Page 524 7.1.1. Combustion of coal and formation of harmful matter......Page 525 7.1.2. Regulations on air protection......Page 527 7.1.3. Air pollution in Yugoslavia......Page 530 7.1.4. The role of FBC boilers in reduction of air pollution......Page 531 7.2. Characteristics of the first generation industrial and demonstration FBC boilers in operation—SO2, NOx, CO, and particle emission......Page 533 7.2.1. Design requirements for the first generation FBC boilers......Page 534 7.2.2. Emission measured during operation of several characteristic first generation FBC boilers......Page 535 7.2.3 Comparison of emissions from bubbling and circulating FBC boilers......Page 536 7.3. Carbon-monoxide emission in bubbling fluidized bed combustion......Page 538 7.4.1. Physical and chemical processes controlling rate and degree of limestone sulphation during fluidized bed combustion......Page 540 7.4.2 The effects of design and operating parameters on SO2 emission in fluidized bed combustion......Page 546 7.4.3. Effects of limestone characteristics......Page 553 7.4.4. Efficiency of limestone utilization......Page 554 7.5.1. Nitrogen balance during coal combustion in FBC boilers......Page 567 7.5.2. Mechanisms of N2O and NOx formation and destruction......Page 572 7.5.3. Effects of coal characteristics on NOx and N2O formation......Page 575 7.5.4. Effects of operating parameters......Page 576 7.5.5. Measures for reduction of NOx and N2O emission in fluidized bed combustion......Page 584 7.6.1. Types and characteristics of solid combustion products from FBC boilers......Page 586 7.6.2. Experience with baghouse filters......Page 589 7.6.3. Experience in the application of electrostatic precipitators......Page 590 References......Page 591 A realization of recent clean energy initiatives, fluidized bed combustion (FBC) has quickly won industry preference due to its ability to burn materials as diverse as low-grade coals, biomass, and industrial and municipal waste. Fluidized Bed Combustion catalogs the fundamental physical and chemical processes required of bubbling fluidized beds b Long periods of availability of cheap liquid and gaseous fuels have favorably affected industrial and technological development worldwide.