Applied Electrostatic Precipitation

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Applied Electrostatic Precipitation

Edited by

K. R. PARKER Consultant in Air Pollution Control

Sutton Coldfield, West Midlands, UK

BLACKIE ACADEMIC & PROFESSIONAL An Imprint of Chapman & Hall

London· Weinheim . New York· Tokyo· Melbourne· Madras

Publisbed by Blackie Academic & Professional, an imprint of Cbapman & Hall, 2-6 Boundary Row, London SE18HN, UK

Chapman & Hall, 2-6 Boundary Row, London SEI8HN, UK

Chapman & Hall GmhH, Pappelallee 3, 69469 Weinheim, Germany

Chapman & Hall USA, 115 Fifth Avenue, New York NY 10003, USA

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Chapman & Hall India, R. Seshadri, 32 Second Main Road, CIT East, Madras 600035, India

First edition 1997

© 1997 Chapman & Hall Softcover reprint oftbe bardcover 1 st edition 1997

Typeset in 1O/12pt Times by Doyle Graphics, Tullamore, Ireland

ISBN-13:978-94-010-7193-2 001: 10.1 007/978-94-009-1553-4

e-ISBN-13 :978-94-009-1553-4

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A catalogue record for this book is available from the British Library Library of Congress Catalog Card Number: 96-83827

@) Printed on acid-free text paper, manufactured in accordance with ANSI/NISO Z39.48-1992 (Permanence of Paper).

Contents

List of contributors xiii Preface xv

1 Why an electrostatic precipitator? 1 K.R. PARKER

1.1 Introduction 1.2 Control system characteristics 2 1.3 Control operating principles 4

1.3.1 Inertial separation 4 1.3.2 Wet scrubbers 4 1.3.3 Fabric filter 5 1.3.4 Electrostatic precipitation 6

1.4 Summary of control system properties 9

2 Milestones in the history of precipitation 11 K.R. PARKER

2.1 Precipitator installations 11 2.1.1 Early investigations and developments 11 2.1.2 Full-scale precipitator developments 13

2.2 Development of electrical supplies 20 2.2.1 Rectifier types 20 2.2.2 Primary control systems 22 2.2.3 Automatic control systems 22

References 23

3 Basic and theoretical operation of ESPs 25 c. RIEHLE 3.1 General remarks 25 3.2 Ion production 29

3.2.1 Principles 29 3.2.2 Corona initiation field strength 31 3.2.3 Corona onset voltage 33 3.2.4 Current-voltage relationship 36 3.2.5 Electrical field distribution 44

3.3 Particle charging 52 3.3.1 Charging process 52 3.3.2 Cochefs charging model 52 3.3.3 Time dependence and saturation charge 54

3.4 Particle migration 55 3.4.1 Equation of motion 55 3.4.2 Theoretical migration velocity 57

VI CONTENTS

3.5 Measuring and modelling particle separation 59 3.5.1 Grade efficiency and total efficiency 59 3.5.2 Laminar model 62 3.5.3 Deutsch model 62 3.5.4 Flow field and particle trajectories 76 3.5.5 Diffusivity models 82

3.6 Deposition 85 3.7 Removal 86 References 87

4 Mechanical design considerations for dry precipitators 89 F. KNUTTSEN and K.R. PARKER

4.1 Introduction 89 4.2 Discharge electrodes 89 4.3 Discharge electrode mounting 92 4.4 Collectors 94 4.5 Casings 97 4.6 HT insulators 100 4.7 Rapping 102 4.8 Hoppers 108 4.9 Electrical clearances 110 References 111

5 Aerodynamic factors affecting performance 113 L. LIND

5.1 Introduction 113 5.2 Turbulence and secondary flow 113

5.2.1 Historical resume 113 5.2.2 Turbulence 118 5.2.3 Secondary flow 122 5.2.4 Numerical flow model 126

5.3 Gas velocity 127 5.4 Gas distribution 129

5.4.1 Standards 130 5.4.2 Residence time 131 5.4.3 Space charge 134 5.4.4 Re-entrainment 136 5.4.5 Erosion 137 5.4.6 Sneakage and sweepage 137 5.4.7 Optimal distribution 138

5.5 Model testing 139 5.6 Computational fluid dynamics 142 5.7 Field testing 148 5.8 Dust build-up and wear 149 References 150

6 The physical and chemical properties of particles and their effect on performance 153 K. PORLE and K.R. PARKER

6.1 Particle size and shape 153 6.1.1 Particle sizing 154 6.1.2 Particle shape and structure 160

6.2 Optical properties 6.3 Agglomeration 6.4 Cohesivity

CONTENTS

6.5 Particle electrical resistivity 6.6 Chemical compositon and reactivity References

7 Performance design considerations c. COTTINGHAM

7.1 Introduction 7.2 What are we trying to achieve? 7.3 Assessment of the process

7.3.1 Typical assessment 7.4 Plate spacing 7.5 Configuring the ESP 7.6 Conclusions References

8 Electrical operation of precipitators V. REYES

8.1 Introduction 8.2 Precipitator performance and electrical energization

8.2.1 Examples 8.3 Corona suppression and space charge effects

8.3.1 Electrical characteristics with air load 8.3.2 Characteristics with dust load

8.4 High tension sectionalization 8.5 Traditional DC energization

8.5.1 Basic principles 8.5.2 High voltage power supply ratings 8.5.3 Influence of the linear inductor

8.6 Intermittent energization 8.6.1 Basic principles 8.6.2 Comparison with traditional DC energization 8.6.3 Collection efficiency

8.7 Automatic voltage control and instrumentation 8.7.1 Introduction 8.7.2 Instrumentation 8.7.3 Basic control principles 8.7.4 Spark detection and voltage recovery 8.7.5 Back-corona detection and corona power control

8.8 Pulse energization 8.8.1 Introduction 8.8.2 Electrical configuration 8.8.3 Main features of pulse energization 8.8.4 Power consumption 8.8.5 Collection efficiency 8.8.6 Applications 8.8.7 Summary

8.9 Supervisory computer control 8.9.1 Stand-alone computer 8.9.2 Supervisory computer control via a gateway unit 8.9.3 Advanced control functions

Appendix 8A Appendix 8B References

VB

161 162 163 166 172 178

180

180 180 181 182 185 186 190 191

192

192 192 194 195 196 196 199 201 202 206 208 210 211 212 214 217 217 217 220 223 226 230 230 231 235 238 239 240 241 241 243 244 245 246 247 248

VlJI CONTENTS

9 Precipitator sizing methods and models of electrostatic precipitators e. PAULSON and M. REA

Editor's note

250

250

9A Precipitator sizing methods e. PAULSON

252

9A.1 Theoretical considerations 9A.1.1 Basic dust-collection equation for gas in a duct 9A.1.2 Electrostatic precipitation 9A.1.3 Improvement of the Deutsch equation 9A.1.4 Factors affecting electrostatic precipitation

9A.2 Practical considerations 9A.2.1 Interpretation of test results

9AJ Precipitator modelling 9AJ.1 Mathematical modelling 9AJ.2 Practical testing

References to 9A

9B Models of electrostatic precipitators M.REA

252 252 254 255 258 265 265 274 274 275 278

280

9B.l Basic concept 280 9B.1.1 The Deutsch equation 281 98.1.2 Charging of particles and the modified Deutsch equation 284

9B.2 The modern approach to computer modelling 285 98.2.1 Early models 285 98.2.2 Model by Caiiadas et al. [5] 286 98.2J Modelling at Padova university [6] 288

References to 9B 291

10 Sampling and analysis for particles and heavy metals in gas streams 292 G.B. NICHOLS and E.B. DISMUKES

10.1 Sampling and analysis 10.2 Heavy metals

10.2.1 General considerations 10.2.2 Sampling methods for multiple types of heavy metals 10.2.3 Sampling methods for mercury alone 10.2.4 Metal analysis in the laboratory 10.2.5 Prospects for real-time monitoring

References

292 298 298 300 302 302 303 303

11 The commissioning of electrostatic precipitators 305 D.A. STYLER and J.e. WESTBURY

11.1 Introduction 11.2 Mechanical commissioning

305 306

CONTENTS IX

11.2.1 Construction stage 306 11.2.2 Post construction stage 319 11.2.3 Cold commissioning 323 11.2.4 Hot commissioning 326

11.3 Electrical commissioning 326 11.3.1 An overview 326 11.3.2 Managers and commissioning 326 11.3.3 Familiarity revisited 327 11.3.4 The programme - who writes the programme and when? 327 11.3.5 Monitoring 329

11.4 Process commissioning 339 11.4.1 Hot commissioning 340 11.4.2 Back to the real world! 348

12 Dry type precipitator applications 349 K. PORLE and K.R. PARKER

12.1 Introduction 349 12.2 Power generation industry 349

12.2.1 Bituminous coals 350 12.2.2 Anthracite coals 353 12.2.3 Subbituminous coals 354 12.2.4 Brown coals 355 12.2.5 Lignites 356 12.2.6 Oil-based fuels 356

12.3 The cement industry 359 12.3.1 Wet process manufacture 359 12.3.2 Semi-wet processing 360 12.3.3 Dry process production plant 360 12.3.4 Alkali bypass plant 363 12.3.5 Clinker cooler precipitators 363 12.3.6 Cement mill precipitators 364

12.4 General steam-raising plant 365 12.4.1 Moving grate combustors (chain grate, reciprocating

and cyclic beds) 366 12.4.2 Fluidised bed units 366

12.5 Biomass-fired steam-raising plants 367 12.5.1 Wood chip combustion 368 12.5.2 Chicken litter, etc. 368 12.5.3 Municipal wastes 368

12.6 Iron and steel works 369 12.6.1 Sinter plants 369 12.6.2 Pelletising plants 372 12.6.3 Steel making 372 12.6.4 Operations involving the casting of hot metal 375

12.7 Non-ferrous industries 375 12.7.1 Copper and nickel recovery 376

12.8 Aluminium smelting 378 12.9 Paper and pulp industry 379

12.9.1 Bark firing 379 12.9.2 Cellulose pulp production 379 12.9.3 Lime sludge burning 380 12.9.4 Magnesium sulphate burning 380

12.10 Conclusions 381 References 381

x CONTENTS

13 The wet electrostatic precipitator: design and a pplica tions 382 K.R. PARKER

13.1 Introduction 382 13.2 Design considerations 383

13.2.1 Dust deposition and removal 383 13.3 Discharge electrodes 386 13.4 HT insulators 387 13.5 Casing/hopper design 387 13.6 Water treatment 390 13.7 Materials of construction 391 13.8 Electrical energisation 393 13.9 Typical applications of wet precipitators 394

13.9.1 Applications in the iron and steel making fields 394 13.9.2 Applications in the chemical industries 397 13.9.3 Applications following acid gas scrubbers 398 13.9.4 Incineration-type processes 399 13.9.5 HAC discharges 400 13.9.6 Glass manufacturing 400 13.9.7 Other applications 400

14 The mist precipitator: design and applications 402 K.R. PARKER

14.1 Introduction 402 14.2 Applications of mist precipitators 407

14.2.1 Collection of sulphuric acid mist 407 14.2.2 Gas detarring 411 14.2.3 Collection of radioactive particles 415 14.2.4 Other mist precipitator applications 416

14.3 Conclusions 417

15 Upgrading of existing precipitator efficiencies 418 K.R. PARKER and H. KRIGMONT

15A Modifications/changes to existing plant 418 15A.l Assessment of required performance improvement 419 15A.2 Performance improvement modification options 421 15A.3 Alternative solutions 423

15A.3.1 Electrical 423 15A.3.2 Mechanical changes 423

15B Precipitator improvements achieved by changing the electrical resistivity of the particulates 425 158.1 Change of temperature/relative humidity of the gases 425 158.2 Flue gas additives to improve performance 426 References to 15A and 15B 428

CONTENTS xi

15C Theory, principles of operation, equipment and applications of flue gas conditioning 429 15C.1 Introduction 429 15C.2 Electrical resistivity 430

15C.2.1 Prediction of fly ash resistivity 432 15C.2.2 Resistivity effects in ESPs 433

15C.3 Flue gas conditioning 436 15.C.3.1 Conditioning by sulfur trioxide 437 15C.3.2 Ammonia conditioning 445 15C.3.3 Dual flue gas conditioning 452 15C.3.4 Balance of plant impact 453

15C.4 Flue gas conditioning equipment 454 15C.4.1 S03 FGC systems 454 15C.4.2 Ammonia FGC systems - design features 461 15C.4.3 ESP power consumption 462 15C.4.4 Mixing requirements 463

15C.5 Application of flue gas conditioning in converting hot-side fly ash precipitators to cold-side operation 463 15C.5.1 Introduction 463 15C.5.2 Flue gas conditioning 465 15C.5.3 Installation design 466 15C.5.4 FGC operation 468 15C.5.5 Economics 469 15C.5.6 Conclusions 471

15C.6 FGC systems - optimization 471 15C.6.1 General 472 15C.6.2 Theoretical approach 472 15C.6.3 Procedural approach 474 15C.6.4 Statistical approach 475 15C.6.5 Rapper adjustments 480 15C.6.6 Data collection 481

15C.7 Conclusions 481 References to 15C 481

16 Possible future developments in the field of electrostatic precipitation 483 K.R. PARKER, c. RIEHLE and H. KRIGMONT

16A Electrical developments 487 16A.1 High frequency power conversion or switched

mode power supplies 487 16A.2 Nanosecond pulse operation and acid gas control 490 References to 16A 491

16B Use of natural sulphur dioxide as a feed stock for flue gas conditioning systems: flue gas conditioning today and tomorrow 492 16B.1 Background 492 16B.2 'Native' or 'internal' feed stock FGC technologies 494

xii CONTENTS

168.2.1 'Slip-stream' FGC systems 494 168.2.2 In-duct FGC systems 495

168.3 In-situ gas conditioning (lGC) approach 496 168.3.1 Variable exposed area IGC system 496 168.3.2 Variable catalyst temperature IGC system 497

168.4 Variable flow IGC system 498 168.5 Catalyst selection 499 References to 168 500

16C High temperature/high pressure precipitators for advanced power generation systems 501 16C.l Fundamentals 503 16C.2 Voltage and current 505 16C.3 Particle charging 509 16C.4 Particle migration 510 16C.5 Grade efficiency 513 16C.6 Open questions 515

16C.6.l Electrical resistivity 515 16C.6.2 Mechanical stability of material 515 16C.6.3 Rapping 515 16C.6.4 Electrical insulation 516 16C.6.5 Emptying of hoppers 516 16C.6.6 Electrical power consumption 516

16C.7 Symbols 516 References to 16C 517

16D Computer sizing of precipitators 518

Index 519

Contributors

C. Cottingham

E.B. Dismukes

F. Knuttsen

H. Krigmont

L. Lind

G. Nichols

K.R. Parker

C. Paulson

K.Porie

M.Rea

V. Reyes

C. Riehle

D.A. Styler

J.C. Westbury

Lodge Sturtevant Ltd, George Street Parade, Birmingham, B3 1 QQ, UK

Grady Nichols Enterprises Inc., 400 Kiowa Street, Montevallo, AL 35115, USA

ABB Flakt Industri AB, S-35187, Vaxjo, Sweden

Allied Environmental Technology, One Pacific Plaza, 7755 Center Avenue, Suite 1100, Huntingdon Beach, CA 92647, USA

FLS Miljo a/s, Ramsingsveg 30, DK2500, Valby, Denmark

Grady Nichols Enterprises Inc., 400 Kiowa Street, Montevallo, AL 35115, USA

17 Somerville Road, Sutton Coldfield, West Midlands, B73 6JD, UK

CISRO, Division of Coal & Energy Technology, PO Box 136, North Ryde, New South Wales 2113, Australia

ABB Flakt Industri AB, S-351 87, Vaxjo, Sweden

Dipartimento Di Ingegneria Elettrica, Universita Degli Studi Di Pavoda, Via Gradenigo 6/A, 35131 Padova, Italy

FLS Miljo a/s, Ramsingsveg 30, DK2500, Valby, Denmark

Bayer AG, R&D Department, Particle Technology & Fluid Dynamic Group, D51368 Leverkusen, Germany

Lodge Sturtevant Ltd, George Street Parade, Birmingham, B3 1 QQ, UK

Lodge Sturtevant Ltd, George Street Parade, Birmingham, B3 1 QQ, UK

Preface

Increased awareness of the effects of atmospheric pollution and ever tightening legislation have meant that electrostatic precipitators, which have been widely used to separate particulate matter from process gas streams, are now required to achieve collection efficiencies in excess of 99.9% for a number of applications. These changes have challenged the precipitation industry to consider how the equipment can be improved to meet the latest legislation, where control is now focusing on heavy metal and respirable size particulate discharges. In addition to achieving the increased performance at an economic cost, the emissions have to be maintained on a continuous basis, as failure to do so could have serious economic consequences to the plant operators.

These demands have meant that all aspects of technology, engineering and operational concerns have had to be examined, reviewed and in some instances completely modified to meet the present criteria. In spite of commercial precipitators being used for almost 100 years, it has only been in the past two to three decades that the system has changed from essentially a 'black box' art to a scientifically-based technology. Fluid-dynamics, electro-dynamics, solid state electronics and microprocessor disciplines are now the basis for current precipitation theory, design, etc., i.e. the currently accepted 'State of the Art'.

Although computational fluid dynamics and finite element analysis and other computer programs are now widely used by the industry, the sizing of a precipitator to satisfy a certain performance for a specific application is still very dependent on the supplier's knowhow and experience. The original 'black book' approach, although now taking the form of an extensive computerized data bank, is still the basis of sizing. In spite of a great deal of work being carried out using high speed computers and complex programming, there is a reluctance among the suppliers to use this ap­proach, although it is very useful for analysing the field data. This situation is likely to change over the next few years and undoubtedly future precipi­tator sizing will be computer generated.

Following a review of the early development of electrostatic precipitation, this volume, containing contributions by many of the world's leading experts in the field of electrostatic precipitation, covers the theory of precipitation from both fluid and electrodynamic standpoints, plus the basic practical designs and the gaseous and particulate features which impact on the precipitators' performance.

XVI PREFACE

To assist the non-specialist, Chapters 12, 13 and 14 cover the applications of dry, wet and mist type precipitators, including how the designs are modified to meet a specific duty and an examination of the major process factors which can affect performance. Chapter 11 gives a full description of plant commissioning and Chapter 10 plant testing, for both mass concen­tration measurements and elemental analysis in terms of particle sizing and chemical make-up. Finally, Chapter 15 shows how it may be possible to improve the performance of an under performing precipitator while Chapter 16 indicates where future developments in precipitation theory, design or application may lead.

As Editor, I am indebted to the publishers for their backing and to the following, without whose experience and expertise, the book could not have been complied - Clive Cottingham, Ed Dismukes. Filip Knuttsen, Henry Krigmont, Leif Lind, Grady Nichols, Colin Paulson, Kjell Porle, Massimo Rea, Victor Reyes, Claus Riehle, David Styler and John Westbury, together with their respective companies for allowing permission to use the material. I would also like to thank Sheila Shepherd for correcting the final manu­script, Ken Darby, who was my mentor and a source of inspiration for some 35 years, and my wife, Maureen, for her encouragement and support in the project.

K.R. Parker November 1996