Principles of Powder Technology

Transcription

1 Principles of Powder Technology Edited by M. J. Rhodes University of Bradford, UK JOHN WILEY & SONS Chichester New York Brisbane Toronto Singapore

2 Contents List of Contributors Preface ix xi Chapter 1 Powder Processing The Overall View 1 D. Geldart 1.1 Introduction Academic and industrial research needs 2 Bibliography 7 Chapter 2 Characterizing the Single Particle 9 A. E. Hawkins 2.1 Introduction Particle density " 2.3 The microscope Sampling Size measurement IK 2.6 Particle shape Worked examples Problems 30 References 31 Chapter 3 Characterization of Powders Introduction Sampling Particle size measurement -W) 3.4 Distributions of other particle properties Problems with answers ' 1(^ Notation 67 References ^ Chapter 4 Mixing and Segregation in Powders 71 J. C. Williams 4.1 Introduction The statistics of solids mixing The segregation of paniculate materials 76

3 vi CONTENTS 4.4 The selection of mixers The specification of mixer performance The mixing of cohesive paniculate materials Conclusions Worked examples 87 Notation 89 Acknowledgment 89 References 90 Chapter 5 The Storage and Flow of Powders 91 /. C. Williams 5.1 Introduction Types of storage hoppers Disadvantages of core flow hoppers Advantages of mass flow hoppers Disadvantages of mass flow hoppers Characterizing the flowability of paniculate materials The analogy between hopper design and soil mechanics The prediction of stresses inside the hopper The third stage of the hopper design procedure 1( Flow factor charts Other types of mass flow hopper Time consolidation Filling and emptying hoppers Problems 117 Bibliography 118 Chapter 6 Gas Fluidization 119 D. Geldart 6.1 Introduction Particle and powder properties Minimum fluidization velocity and bed pressure drop Slugging fluidized beds and bubble rise velocities Bed expansion Entrainment from fluidized beds Heat transfer Fluid bed chemical reactors Applications Worked example: design of a fluidized bed heater 136 Notation 140 References 142 Chapter 7 Pneumatic Conveying 143 M. J. Rhodes 7.1 Introduction Dilute-phase and dense-phase transport Dilute-phase conveying Dense-phase conveying Matching the system to the powder 162

4 CONTENTS vii 7.6 Worked example: design of dilute-phase system Problems 167 Notation 168 References 169 Chapter 8 Solid-Gas Separation Introduction and principles General characteristics of gas cleaners Aero-mechanical dry separators Aero-mechanical wet separators (scrubbers) Electrostatic precipitators Filters Problems with answers 190 Notation 191 References 192 Chapter 9 Size Enlargement 193 N. G. Stanley-Wood 9.1 Introduction Particle-particle bonding Bonding by mechanical force Size enlargement (methods and equipment) 207 References 225 Chapter 10 Size Reduction 227 M. H. Prior, H. Prem and M. J. Rhodes 10.1 Introduction Particle failure and product behaviour Models predicting energy requirements for size reduction processes Prediction of the product size distribution Material properties and selection criteria for the size reduction process Stressing mechanisms Crushers and roll mills Impact, jet and classifier mills Ball, rod and related mills Miscellaneous size reduction machines Wet size reduction Industrial comminution systems Wear and wear protection Summary Worked example Problems 295 References 296 Chapter 11 Explosion and Fire Hazards of Powders 299 K. N. Palmer 11.1 Introduction 29V 11.2 Characteristics of dust explosions 300

5 viii CONTENTS 11.3 Explosibility tests and their application Sources of ignition and their avoidance Fires in powders Explosion protection Application to industrial processes Worked examples 330 References 333 Chapter 12 Health Risks of Fine Powders 335 E. King 12.1 Introduction Size of airborne dust Dust and the respiratory tree Other routes into the body Nature of risk to health Exposure related risk to health Air sampling techniques Air standards The control of risk to health Personal protective equipment (PPE) Use of controls Examples of dust control 363 Appendix 364 Glossary and acronyms 365 References 366 Chapter 13 Flow of Liquid-Solid Suspensions 367 H. Benkreira 13.1 Introduction Settling of suspensions Homogeneous suspensions Heterogeneous suspensions Conclusions 391 Notation 391 References 393 Chapter 14 Solid-Liquid Separation Introduction Pre-treatment of suspensions Equipment and principles Sizing and scale-up of equipment 419 Notation 477 References 477 Index 429