Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1983 Coal cleaning by froth flotation Choon Han Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Chemical Engineering Commons Recommended Citation Han, Choon, "Coal cleaning by froth flotation " (1983). Retrospective Theses and Dissertations. 8476. https://lib.dr.iastate.edu/rtd/8476 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. INFORMATION TO USERS This reproduction was made from a copy of a document sent to us for microfilming. 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Zeeb Road Ann Arbor, Ml 48106 8407075 Han, Choon COAL CLEANING BY FROTH FLOTATION Iowa State University PH.D. 1983 University Microfilms I nternsticn â! 300 N. zeeb Roaa, Ann Arbor, Mi 48106 PLEASE NOTE: In all cases this material has been filmed in the best possible way from the available copy. Problems encountered with this document have been identified here with a check mark V . 1. Glossy photographs or pages 2. Colored illustrations, paper or print 3. Photographs with dark background 4. Illustrations are poor copy 5. Pages with black marks, not original copy 6. Print shows through as there is text on both sides of page 7. Indistinct, broken or small print on several pages 8. Print exceeds margin requirements 9. Tightly bound copy with print lost in spine 10. Computer printout pages with indistinct print 11. Page(s) lacking when material received, and not available from school or author. 12. Page(s) seem to be missing in numbering only as text follows. 13. Two pages numbered . Text follows. 14. Curling and wrinkled pages 15. Other University Microfilms international Coal cleaning by froth flotation by Choon Han A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY Major: Chemical Engineering Approved: Signature was redacted for privacy. In Charge of Major Work Signature was redacted for privacy. For the Maj« Department Signature was redacted for privacy. For the Gradip^ College Iowa State University Ames, Iowa 1983 ii TABLE OF CONTENTS Page NOMENCLATURE v ABSTRACT viii INTRODUCTION 1 LITERATURE REVIEW 8 Theoretical Background of Froth Flotation 9 Flotation Reagents 13 Collectors 15 Frothers 21 Regulators 25 Activators 27 Depressants 29 Floatability of Coal and Pyrite 30 Flotation Characteristics of Iowa Coal 32 Variables of Coal Flotation 34 Particle size 34 Flotation reagents 36 Pulp density 38 Pulp pH 39 Agitator speed 39 Separation of Pyrite from Coal 40 Wet oxidation pretreatment 41 Ultrasonic vibration 44 Chemical comminution 46 Micro-bubble flotation 48 Kinetics of Coal Flotation 51 EXPERIMENTAL CONDITIONS 54 Experimental Apparatus and Procedures 54 Froth flotation test 54 Chemical pretreatment step 56 Micro-bubble flotation test 58 Other equipment 60 iii Page Materials Used 61 Coal 61 Chemical reagents and oils 62 Analysis and Calculations 63 THEORETICAL MODELING AND ANALYSIS 65 Analysis of Bubble-Particle Attachment 65 Attachment of bubbles to spherical surfaces 66 Attachment of bubbles to flat surfaces 81 Kinetic Modeling 88 EXPERIMENTAL RESULTS AND DISCUSSION 94 Flotation Characteristics of Iowa Coals 94 Effect of frother concentration 94 Effect of alkali concentration 98 Effect of wet oxidation pretreatment 106 Effect of collector dosage 109 Effect of oil in an alkaline pulp 113 Effect of oil with wet oxidation pretreatment 117 Effect of stepwise addition of oil 120 Two-stage flotation 122 Three-stage flotation 131 Agitator speed 136 Air rate 138 Conditioning time 140 Flotation rates 141 Flotation of Selected Appalachian Coals 144 Size Reduction and Degree of Liberation 152 Size effect 153 Degree of liberation 162 Chemical comminution 164 Ultrasonic vibration 170 Micro-bubble Flotation 174 Micro-bubble flotation phenomena 175 Results of micro-bubble flotation 178 Application of Kinetic Models 180 iv Page CONCLUSIONS AND RECOMMENDATIONS 192 Conclusions 192 Flotation characteristics of Iowa and Appalachian coals 192 Size reduction and degree of liberation 194 Micro-bubble flotation 195 Flotation kinetics 196 Recommendations 197 LITERATURE CITED 198 ACKNOWLEDGEMENTS 207 APPENDIX A. EXPERIMENTAL CONDITIONS AND RESULTS OBTAINED FOR FROTH FLOTATION OF COALS 208 APPENDIX B. COMPUTER PROGRAMMING FOR KINETIC MODELS OF FROTH FLOTATION OF COALS 223 NOMENCLATURE 2 Â contact area between an air bubble and a particle, cm . surface area of an air bubble, cm2 . 2 AQJ maximum contact area between an air bubble and a particle, cm . 2 Ag interfacial area between an air bubble and water, cm . a air phase. a"*" activity of a positive potential-determining ion in the solution, a^ activity of a positive potential-determining ion at PZC. a~ activity of a negative potential-determining ion in the solution. a~ activity of a negative potential-determining ion at PZC. a^ acceleration, cm./sec^. b radius of contact between an air bubble and a particle, cm. C concentration of particles in a pulp, g./cu. cm. Cg initial concentration of particles in a pulp, g./cu. cm. C^^ bulk contraction of ions, mole/cu. cm. E surface energy, erg/cm . in terfacial energy before the bubble-particle attachment, erg. Ej interfacial energy after the bubble-particle attachment, erg. Fg attachment force for a large air bubble, dyne. Fg attachment force for a small air bubble, dyne. Fgm limit of attachment force, dyne. F|j buoyant force of a gas bubble, dyne. Fg force of gravity, dyne. F^g total gravity force acting on n' particles, dyne, f correlation factor between r and r*. vi G(t) fraction recovered from the floatable and valuable material at time, t. g gas phase. h height of the truncated air bubble, cm. k flotation rate constant, ^. min. 1 liquid phase. M amount of material which remains unfloated. m maximum number of particles to be adsorbed on an air bubble, n flotation rate order. n' number of particles to be adsorbed on an air bubble. P(x) mass fraction of the valuable component of size, x. P^(x) mass density distribution of the floatable and valuable component of size, X. total fraction of the valuable component in the feed. total fraction of the valuable component which can be floatable over a very long time. R(x) mass fraction of the valuable component of size, x which can be floatable over a very long time. R' radius of a spherical particle, cm. Rm radius of the smallest air bubble, cm. radius of the largest spherical particle, cm. r radius of a small air bubble, cm. r' radius of a truncated air bubble, cm. r^j radius of an adsorbed ion, cm. floatability of a particle of size, x. vii s solid phase. o T absolute temperature, K. total mass fraction recovery. t time, min. V volume of the flotation pulp, cm. W(x) overall particle size distribution Wg adsorption work required to bring the potential determining ion from the bulk solution to the Stern phase, erg. AW work of adhesion of an air bubble on a spherical surface, erg. AW' work of adhesion of an air bubble on a flat surface, erg. w water phase. X particle size, cm. valence of a positive potential-determining ion. Z~ valence of a negative potential-determining ion. 7 rg adsorption density on the Stem layer, mole/cm". Y surface tension, dyne/cm. 5 closest distance of approach of counter ion to solid surface, cm. Ç potential at the shear plane, volts. 0 contact angle, degrees. p density, g./cu. cm. (|) adsorption potential, volts. ipg potential at the Stem plane, volts. surface potential, volts. viil ABSTRACT A number of experiments were conducted to determine the flotation characteristics of Iowa coals in which various conditions were applied to study the effect of different parameters such as frother dosage, oily collectors, pyrite depressants, and various combinations of these reagents.