An experimental study of particle-bubble interaction and attachment in flotation

4 ACKNOWLEDGEMENTS . 6 TABLE OF CONTENTS . 7 LIST OF ABBREVIATIONS . 10 LIST OF ILLUSTRATIONS . 11 LIST OF TABLES . 13 Chapter 1: Introduction to particle-bubble interaction . 14 1.1 Overview . 14 1.2 Interest in studying the topic . 15 1.3 Motivation . 15 1.4 Purpose and objectives . 16 Chapter 2: Flotation process . 18 2.1 Description . 18 2.2 History of flotation . 19 2.3 Types of flotation . 21 2.4 Steps in the process . 22 2.4.1 Collision . 24 8 2.4.2 Attachment . 26 2.4.3 Stability . 30 2.5 Industrial applications . 32 2.6 Flotation efficiencies . 35 Chapter 3: Experimental . 36 3.1 Particles and fluid . 36 3.2 Particle treatments . 37 3.2.1 Treatment 1: Low hydrophobicity . 37 3.2.2 Treatment 2: Smooth hydrophobic . 39 3.2.3 Treatment 3: Rough hydrophobic . 41 3.2.4 Treatment 4: Superhydrophobic particles . 43 3.2.5 Treatment 5 . 44 3.3 Particle characterization . 45 3.4 Bubbles . 47 3.5 Cameras and lenses . 48 3.6 Experimental set up . 49 3.7 Triggering system . 51 3.8 Conducting experiments . 53 3.8. 1 Alignment and calibration . 54 3.8. 2 Release of bubbles . 55 Chapter 4: Data analysis and results . 57 9 4.1 Image processing . 57 4.2 Particle and bubble aggregates . 61 4.3 Particle-bubble interaction analysis . 62 4.3.1 Influence of relative distance . 62 4.3.2 Influence of bubble size and treatment . 70 4.3.3 Influence of surface roughness . 72 4.4 Terminal velocities . 73 4.4.1 Influence of bubble size . 74 4.4.2 Terminal velocity model . 74 4.5 Attachment and detachment . 76 4.6 Collision efficiency comparison . 79 Chapter 5: Discussion and conclusions . 81 5.1 Ideal bubble size . 81 5.2 Terminal velocity . 82 5.3 Collision description . 83 5.4 Future work . 84 BIBLIOGRAPHY . 86 APPENDICES . 89 10 LIST OF ABBREVIATIONS KAUST King Abdullah University of Science and Technology TPC Triple phase contact TPCL Triple phase contact line 11 LIST OF ILLUSTRATIONS Figure 2.1: Zones around the bubble. 25 Figure 2.2: Forces acting on the particle. 29 Figure 2.3: Forces acting on the TPCL of a particle-bubble aggregate. 31 Figure 3.1: Treated particles and slides. 45 Figure 3.2: Experimental arrangement diagram. 50 Figure 3.3: Image of the experimental arrangement. 51 Figure 3.4: Arrangements for the triggering system. 52 Figure 3.5: A cropped image used to find the pixel correlation. 54 Figure 4.1: A video frame with its binary image. 57 Figure 4.2: Ellipse fitted to a bubble shape. 59 Figure 4.3: Trajectories of a particle, a bubble, and an aggregate. 60 Figure 4.4: Particle-bubble aggregates of rough hydrophobic particles. 61 Figure 4.5: Particle-bubble aggregates with superhydrophobic particles. 62 Figure 4.6: Relative distance and aggregate force balance. 63 Figure 4.7: Cartesian coordinate system showing both cameras. 64 Figure 4.8: Rough hydrophobic particle interactions with rb ≈ 0.22 mm. 65 Figure 4.9: Rough hydrophobic particle interactions with rb ≈ 0.32 mm. 66 Figure 4.10: Rough hydrophobic particle interactions with rb ≈ 0.7 mm. 67 Figure 4.11: Rough hydrophobic particle interactions with rb ≈ 1.4 mm. 67 Figure 4.12: Superhydrophobic particle interactions with rb ≈ 0.2 mm. 68 12 Figure 4.13: Superhydrophobic particle interactions with rb ≈ 0.31 mm. 69 Figure 4.14: Superhydrophobic particle interactions with rb ≈ 1.07 mm. 70 Figure 4.15: Critical radius for two particle types with varying bubble size. 71 Figure 4.16: Relative positions of the interactions for smooth particles. 72 Figure 4.17: Relative positions of the interactions for rough particles. 73 Figure 4.18: Terminal velocity of the particle-bubble aggregates. 74 Figure 4.19: Satellite bubble generation during the expansion of the TPCL. 76 Figure 4.20: Water droplet inside a bubble of a particle-bubble aggregate. 77 Figure 4.21: Droplet generation inside the bubble from a dimple. 78 Figure 4.22: Bubble pinch-off from a particle. 79 Figure 4.23: Predicted and observed collision efficiency. 80