Introduction to Particle Technology

Martin Rhodes, PhD, is Professor Emeritus in the Department of Chemical and Biological Engineering, Monash University, Australia and has published extensively on particle technology. Jonathan Seville, PhD, is Professor of Formulation Engineering at the School of Chemical Engineering, University of Birmingham, UK. Formerly editor of the journal Powder Technology, he has published several books on particle technology. He is past President of the Institution of Chemical Engineers and a Fellow of the Royal Academy of Engineering.

• About the Authors xiPreface to the Third Edition xiiPreface to the Second Edition xiiiPreface to the First Edition xivAcknowledgements xviiAbout the Website xviiiIntroduction xix1 Particle Analysis 11.1 Particle Size 11.2 Description of Populations of Particles 41.3 Conversion Between Distributions 41.4 Describing the Population by a Single Number 71.5 Equivalence of Means 91.6 Common Methods of Displaying Size Distributions 111.6.1 Normal Distribution 111.6.2 Log-normal Distribution 111.7 Methods of Particle Size Measurement 121.7.1 Image Analysis 131.7.2 Light Scattering 131.7.3 Dynamic Light Scattering 151.7.4 Scanning Mobility Particle Sizer 151.7.5 Other Methods 161.8 Surface Area Measurement 171.8.1 Adsorption Isotherms 171.8.2 The BET Technique 171.9 Sampling 191.10 Worked Examples 19Test Yourself 28Exercises 292 Mechanical Properties of Particles 322.1 Introduction to Material Properties 332.2 Particle–Particle Contact for Elastic Materials 362.3 Contact in the Presence of Surface Forces 382.3.1 Cohesion and Adhesion 382.3.2 Surface Roughness and Contamination 412.3.3 Comparison of Cohesion with Particle Weight 412.3.4 Measurement of Cohesion and Adhesion 422.4 Friction 432.5 Impact and Bounce 452.5.1 Impacts in the Normal Direction 452.5.2 Oblique Impacts 472.6 Liquid Bridges 472.7 Worked Examples 52Test Yourself 54Exercises 543 Motion of Particles in a Fluid 563.1 Single Particles in a Fluid 563.1.1 Motion of Single Solid Particles in a Fluid 563.1.2 Particles Falling Under Gravity Through a Fluid 593.1.3 Effect of Boundaries on Terminal Velocity 633.1.4 Unsteady Motion 643.1.5 Further Reading 653.1.6 Worked Examples on the Motion of Single Particles in a Fluid 66Test Yourself – Single Particles in a Fluid 743.2 Settling of a Suspension of Particles 753.2.1 Introduction 753.2.2 Settling Flux as a Function of Suspension Concentration 773.2.3 Sharp Interfaces in Sedimentation 793.2.4 The Batch Settling Test 803.2.5 Relationship Between the Height–Time Curve and the Flux Plot 833.2.6 Worked Examples on Settling of a Suspension of Particles 85Test Yourself – Settling of a Suspension Particles 92Exercises – Single Particles in a Fluid 92Exercises – Settling of a Suspension of Particles 954 Discrete Element Method Modelling 1024.1 Introduction 1024.2 Principles – The “Hard-Sphere” and “Soft-Sphere” Approaches 1044.3 Updating Particle Positions –‘Time-Stepping’ 1074.4 Contact Detection 1094.5 Contact Modelling 1104.5.1 Linear Spring–Dashpot Model 1114.5.2 Hertzian Model 1124.5.3 Elastoplastic Models 1124.5.4 Cohesive Models 1134.6 Coupling with Computational Fluid Dynamics (CFD–DEM) 1144.7 Calibration 1154.8 Modelling Large Systems 1184.9 Modelling Aspherical Particles 1194.10 Data Analysis and Visualization 1214.11 Validation 1234.12 Worked Examples 124Exercises 132Interactive Exercises 1325 Colloids, Aerosols and Fine Particles 1335.1 Introduction 1335.2 Brownian Motion 1345.3 Surface Forces 1365.3.1 van der Waals Forces 1375.3.2 Electrical Double-Layer Forces 1395.3.3 Adsorbing Polymers, Bridging and Steric Forces 1445.3.4 Net Interaction Force 1455.4 Effect of Surface Forces on Behaviour in Air and Water 1455.5 Influences of Particle Size and Surface Forces on Solid/Liquid Separation by Sedimentation 1485.5.1 Sedimentation Rate 1485.5.2 Sediment Concentration and Consolidation 1495.6 Gas–Solid Separation 1515.7 Suspension Rheology 1525.8 Influence of Surface Forces on Suspension Flow 1575.8.1 Repulsive Forces 1575.8.2 Attractive Forces 1585.9 Nanoparticles 1625.10 Worked Examples 163Test Yourself 166Exercises 1676 Packed Beds and Fluidized Beds 1706.1 Fluid Flow Through a Packed Bed of Particles 1706.1.1 Pressure Drop–Flow Relationship 1706.1.2 Further Reading 1746.1.3 Worked Examples 174Test Yourself – Fluid Flow through Packed Beds 1766.2 Fluidization 1766.2.1 Fundamentals 1766.2.2 Relevant Powder and Particle Properties 1796.2.3 Bubbling and Non-Bubbling Fluidization 1816.2.4 Classification of Powders 1836.2.5 Expansion of a Fluidized Bed 1876.2.6 Entrainment 1916.2.7 Heat Transfer in Fluidized Beds 1956.2.8 A Simple Model for the Bubbling Fluidized Bed Reactor 2016.2.9 High Velocity Fluidization 2056.2.10 Some Practical Considerations 2106.2.11 Applications of Fluidized Beds 2136.2.12 Worked Examples 220Test Yourself – Fluidization 226Exercises – Fluid Flow through Packed Beds 227Exercises – Fluidization 2287 Pneumatic Transport and Standpipes 2337.1 Pneumatic Transport 2337.1.1 Dilute Phase and Dense Phase Transport 2347.1.2 The Choking Velocity in Vertical Transport 2347.1.3 The Saltation Velocity in Horizontal Transport 2367.1.4 Fundamentals 2377.1.5 Design for Dilute Phase Transport 2407.1.6 Dense Phase Transport 2457.1.7 Matching the System to the Powder 2507.2 Standpipes 2517.2.1 Standpipes in Packed Bed Flow 2527.2.2 Standpipes in Fluidized Bed Flow 2527.2.3 Pressure Balance During Standpipe Operation 2557.2.4 Further Reading 2577.3 Worked Examples 258Test Yourself 263Exercises 2648 Separation of Particles from a Gas 2668.1 Gas Cyclones 2678.1.1 Flow Characteristics of Cyclones 2688.1.2 Efficiency of Separation of Cyclones 2688.1.3 Scale-up of Cyclones 2728.1.4 Range of Operation of Cyclones 2758.1.5 Some Practical Design and Operation Details of Cyclones 2768.2 Filtration 2798.3 Worked Examples 282Test Yourself 285Exercises 2869 Storage and Flow of Powders – Hopper Design 2889.1 Mass Flow and Core Flow 2889.2 The Design Philosophy 2909.2.1 Flow – No Flow Criterion 2919.2.2 The Hopper Flow Factor ff 2919.2.3 Unconfined Yield Stress σy 2919.2.4 Powder Flow Function 2929.2.5 Critical Conditions for Flow 2929.2.6 Critical Outlet Dimension 2939.2.7 Summary 2949.3 Shear Cell Test 2949.4 Analysis of Shear Cell Test Results 2969.4.1 Mohr’s Circle – in Brief 2969.4.2 Application of Mohr’s Circle to the Analysis of the Yield Locus 2979.4.3 Determination of σy and σc 2989.4.4 Determination of δ from Shear Cell Tests 2989.4.5 The Kinematic Angle of Friction between Powder and Hopper Wall, ΦW 2999.4.6 Determination of the Hopper Flow Factor, ff 3009.5 Summary of Design Procedure 3049.6 Discharge Aids 3049.7 Pressure on the Base of a Tall Cylindrical Bin 3049.8 Mass Flow Rates 3079.9 Conclusions 3089.10 Worked Examples 309Test Yourself 314Exercises 31410 Mixing and Segregation 31910.1 Types of Mixture 31910.2 Segregation 32010.2.1 Causes and Consequences of Segregation 32010.2.2 Mechanisms of Segregation 32110.3 Reduction of Segregation 32410.4 Equipment for Particulate Mixing 32510.4.1 Mechanisms of Mixing 32510.4.2 Types of Mixer 32610.5 Analysis of Mixer Performance 32810.5.1 Simple V-Mixer 32810.5.2 Analysing More Complex Mixers 33110.6 Assessing the Mixture 33210.6.1 Quality of a Mixture 33210.6.2 Sampling 33310.6.3 Statistics Relevant to Mixing 33310.7 Worked Examples 335Test Yourself 340Exercises 34111 Particle Size Reduction 34311.1 Mechanisms of Particle Size Reduction 34411.1.1 Breakage 34411.1.2 Abrasion 34811.1.3 Stressing Mechanisms for Size Reduction 34811.2 Model Predicting Energy Requirement and Product Size Distribution 34911.2.1 Energy Requirement 34911.2.2 Prediction of the Product Size Distribution 35211.3 Attrition 35411.3.1 Sources of Attrition in Processes 35511.3.2 Measurement of the Degree of Attrition Within a Process 35511.3.3 Measurement Methods 35611.3.4 Energy Requirement for Attrition 35611.4 Types of Comminution Equipment 35711.4.1 Stressing Mechanism 35711.4.2 Particle Size 36211.4.3 Material Properties 36311.4.4 Carrier Medium 36411.4.5 Mode of Operation 36411.4.6 Combination with Other Operations 36411.4.7 Types of Milling Circuit 36411.5 Worked Examples 366Test Yourself 368Exercises 36912 Size Enlargement 37212.1 Introduction 37212.2 Crystallization 37312.2.1 Crystal Structure 37312.2.2 Solubility and Saturation 37412.2.3 Nucleation and Growth 37612.2.4 Crystallizer Design 37812.3 Granulation 37812.3.1 Introduction 37812.3.2 Granulation Rate Processes 38012.3.3 Simulation of the Granulation Process 38812.3.4 Granulation Equipment 39112.4 Tableting 398Further Reading 40112.5 Worked Examples 401Test Yourself 402Exercises 40313 Particulate Products 40513.1 Introduction 40513.2 Structure and Properties 40713.3 Dissolution and Dispersion 41213.4 Suspensions and Their Stability 41513.5 Some Industrial Product Sectors 41713.5.1 Pharmaceutical Dosage Forms 41713.5.2 Food 41913.5.3 Paint and Coatings 419Further Reading 422Test Yourself 422Exercises 42314 Health and Safety 42414.1 Fire and Explosion Hazards of Fine Powders 42414.1.1 Introduction 42414.1.2 Combustion Fundamentals 42614.1.3 Combustion in Dust Clouds 42814.1.4 Control of the Hazard 43314.1.5 Worked Examples 436Test Yourself on Fire and Explosion Hazards 44214.2 Health Effects of Fine Powders 44314.2.1 Introduction 44314.2.2 The Human Respiratory System 44314.2.3 Interaction of Fine Powders with the Respiratory System 44514.2.4 Pulmonary Delivery of Drugs 45014.2.5 Harmful Effects of Fine Powders 452Test Yourself on Health Effects of Fine Powders 454Exercises – Fire and Explosion Hazards 454Exercises – Health Effects of Fine Powders 456Notation 457References 461Index 468