Concentration and Recovery of Positively Buoyant Cenospheres using an Inverted REFLUX Classifier A thesis submitted for the degree of Doctor of Philosophy By Ali Kiani July 2016 i The thesis contains no material which has been accepted for the award of any other degree or diploma in any university or other tertiary institution and, to the best of my knowledge and belief, contains no material previously published or written by another person, except where due reference has been made in the text. I give consent to the final version of my thesis being made available worldwide when deposited in the University’s Digital Repository**, subject to the provisions of the Copyright Act 1968. **Unless an Embargo has been approved for a determined period. I hereby certify that the work embodied in this thesis contains a published paper/s/scholarly work of which I am a joint author. I have included as part of the thesis a written statement, endorsed by my supervisor, attesting to my contribution to the joint publication/s/scholarly work. ……………………………………………………. Ali Kiani ……………………………………………………. Kevin Galvin ii Acknowledgements I would like to acknowledge the people who have contributed to the production of my dissertation. Most importantly, I would like to deeply thank my principal supervisor, Professor Kevin Galvin, for his valuable guidance, useful advice, understanding and great supports. Studying under his supervision, I had the chance to gain valuable experience and learn many useful skills for my future career and life. I would also like to thank my co-supervisor, Doctor James Zhou, who provided me with very useful hints and comments, encouragement and supervision. His understanding at my difficult time made him like a close friend for me. Doctor Simon Iveson had a great contribution to my thesis, as he always kindly listened and gave me encouragement and advice. I deeply appreciate his very useful comments in different stages of my study as well as his patience and time in reading my thesis. I am also greatly thankful to Mark Mason for his kindness, patience and help during my PhD. His support in the laboratory during my PhD was exceptional for me. Many thanks also to my colleagues, especially Jamie, Anthony and Kim for their friendship, communication and help. I am also very grateful to Professor Behdad Moghtaderi for helping me to keep my spirit up during my life in Australia. At last, but not least, I would like to thank my immediate family for their kind supports and love during my life and study. Special thanks go to my wife for her love, understanding, patience, help and kindness. This thesis was impossible to be accomplished without their supports. Finally, I would like to appreciate the financial supports including the scholarships from the University of Newcastle, and the grants provided by the Australian Research Council and Vecor Australia. iii Table of Contents List of Figures x List of Tables xix Abstract xxi Publications xxiv Awards xxv Nomenclature xxvi CHAPTER 1 INTRODUCTION 1 1.1 Aim of Thesis 2 1.2 Background 4 1.3 Thesis Objectives 7 1.4 Outlines of Thesis 8 CHAPTER 2 GRAVITY SEPARATION FUNDAMENTAL CONCEPTS 10 2.1 Introduction 11 2.2 Isolated particle settling in a fluid 11 2.2.1 Drag force 11 2.2.2 Particle terminal settling velocity 14 2.2.3 Other factors affecting the settling velocity 16 2.2.3.1 Particle shape and size 16 2.2.3.2 Particle surface roughness 19 2.2.3.3 Container walls 21 2.3 Hindered settling 21 2.3.1 Modified Stokes’ law 22 2.3.2 Richardson and Zaki equation 23 2.3.3 Other studies on hindered settling 24 2.4 Fluidization 27 iv 2.4.1 Packed bed 27 2.4.2 Fluidized beds 28 2.4.3 Density definitions in fluidization 32 2.4.4 Particle entrainment (elutriation) 33 2.5 Particle segregation and dispersion 34 2.6 Fine particle beneficiation technologies 38 2.6.1 Gravity separation methods 39 2.6.2 Particle size classification 40 2.6.3 Enhanced gravity separation methods 41 2.7 Summary 42 CHAPTER 3 BULK STREAMING MOTION AND INCLINED SETTLING 43 3.1 Introduction 44 3.2 Bulk streaming motion 44 3.2.1 Evidence for bulk streaming motion 44 3.2.2 Conditions for the development of bulk streaming motion 49 3.2.3 Similar phenomena to bulk streaming 54 3.2.3.1 Clustering and streaming in a gas-solid fluidized bed 54 3.2.3.2 Shear thinning behaviour of concentrated suspensions 55 3.3 Inclined settling 56 3.4 REFLUX™ Classifier 62 3.4.1 The Laskovski et al. correlation 65 3.4.2 Elutriation models for laminar high-shear flow in narrow channels 68 3.5 Combined effects of Inclined Settling and Bulk Streaming Motion 72 3.6 The Potential for separating cenospheres from fly ash in an Inverted REFLUX™ Classifier 75 3.7 Summary 77 CHAPTER 4 FLY ASH AND CENOSPHERE CHARACTERIZATION 78 4.1 Introduction 80 v 4.2 Experimental 80 4.2.1 Experimental procedure 80 4.2.1.1 Cenosphere grade 80 4.2.1.2 Particle size 81 4.2.1.3 Particle density 82 4.2.1.4 Feed semi-batch fractionation 82 4.3 Results and Discussion 84 4.3.1 Morphology and compositions 84 4.3.2 Feed fractionation using the semi-batch REFLUX™ Classifier 86 4.3.3 Particle size and density 90 4.4 Conclusions 92 CHAPTER 5 PRELIMINARY EXPERIMENTS ON UPGRADING POSITIVELY BUOYANT PARTICLES USING AN INVERTED REFLUX™ CLASSIFIER 93 5.1 Introduction 95 5.2 Background 95 5.3 Experimental 96 5.3.1 Experimental equipment 96 5.3.2 Feed preparation 99 5.3.3 Experimental procedure 100 5.3.4 Samples analysis for grade and recovery 101 5.3.4.1 Gas pycnometry method 101 5.3.4.2 Sink-float separation method 102 5.3.5 Mass balance reconciliation technique 103 5.3.6 Particle size measurement 103 5.4 Results and Discussion 104 5.4.1 Model feed 104 5.4.1.1 Separation at different product fluxes 106 5.4.2 Fly ash feed 111 5.4.2.1 Separation at a high solids concentration 112 5.4.2.2 Zero-fluidization water effects 112 5.4.2.3 Effects of different operating conditions 114 5.4.2.3.1 Influence of fluidization rate 115 5.4.2.3.2 Influence of the feed rate 118 vi 5.4.2.3.3 Influence of the split ratio 125 5.4.2.4 Variation in recovery with particle size 126 5.4.2.5 Combined effects of product rate and fluidization rate 128 5.4.2.6 Density-based classification of cenospheres and fly ash in the IRC™ 129 5.5 Conclusions 130 CHAPTER 6 ENHANCED RECOVERY AND CONCENTRATION OF CENOSPHERES FROM FLY ASH PARTICLES IN THE INVERTED REFLUX™ CLASSIFIER 132 6.1 Introduction 134 6.2 Background 134 6.3 Experimental 138 6.3.1 Equipment 138 6.3.2 Methodology 138 6.3.3 Measurements 139 6.3.3.1 Sink-float experiments 139 6.3.3.2 The particle size distribution 140 6.3.3.3 Fly ash properties 141 6.4 Results and Discussion 142 6.4.1 The effects of the dense medium on the separation of positively buoyant cenospheres from fly ash in the IRC™ 143 6.4.2 Dense medium effects on the particles size classification in the IRC™ 146 6.4.3 Varying product split at the optimum feed pulp density 151 6.4.4 Effect of the feed throughput at the optimum feed pulp density 153 6.4.5 Grade-Recovery curve 155 6.5 Conclusions 156 CHAPTER 7 A PILOT SCALE STUDY OF CENOSPHERE RECOVERY AND CONCENTRATION IN THE INVERTED REFLUX™ CLASSIFIER 158 7.1 Introduction 160 7.2 Materials and Methods 160 7.2.1 Pilot scale Inverted REFLUX™ Classifier 160 7.2.2 Experimental procedure 162 vii 7.2.3 Data analysis 163 7.2.3.1 Grade and recovery 164 7.2.3.2 Particle size and density 164 7.3 Results and Discussion 165 7.3.1 Variation of the feed split ratio 166 7.3.2 Density and size classification of cenospheres and fly ash 172 7.3.3 Separation of cenospheres from fly ash at different feed throughputs 177 7.4 Conclusions 182 CHAPTER 8 MULTI-STAGE CONCENTRATION OF CENOSPHERES IN FLY ASH 184 8.1 Introduction 186 8.2 Experimental 186 8.2.1 Materials 186 8.2.2 Methods 186 8.2.3 Data analysis 187 8.3 Results and Discussion 189 8.3.1 Upgrading cenospheres from a low-grade fly ash feed 190 8.3.2 Upgrading cenospheres from a high-grade fly ash feed 191 8.3.2.1 Product grades and cenosphere recovery 192 8.3.2.2 Size and density of cenospheres in the multi-stage IRC™ process 198 8.4 Conclusions 202 CHAPTER 9 THE PERFORMANCE OF THE ONE-STAGE INVERTED REFLUX™ CLASSIFIER PROCESS IN SEPARATION OF CENOSPHERES FROM DIFFERENT FLY ASH FEEDS 203 9.1 Introduction 205 9.2 Experimental 205 9.3 Results and Discussion 206 9.4 Conclusions 212 viii CHAPTER 10 CONCLUSIONS AND RECOMMENDATIONS 213 10.1 Conclusions 214 10.2 Recommendations 218 Reference 220 Appendix A: IRC™ raw experimental and reconciled data and results (grade and recovery by the sink-float method) 234 Appendix B: IRC™ raw experimental data and results (grade and recovery by pycnometry) 269 Appendix C: Size distribution data and partition numbers 275 TM Appendix D: Double fractionation data obtained from the RC 316 Appendix E: The concentration induced enhancement obtained in Chapter 6, Runs 1-5 at different pulp densities 320 Appendix F: Three different models in predicting cenosphere hindered rise velocity in suspensions at different solids concentrations 321 Appendix G: Cumulative size distribution of cenospheres and fly ash in the preliminary and main feeds used in multi-stage study in Chapter 8.