Frothers are used in flotation to aid generation of small bubbles, but little is known about the mechanisms that take place in the flotation machine to produce such an effect. Coalescence prevention is the common explanation, although the exact mechanism is obscure and almost no attention has been paid to a frother effect on bubble break-up, the other possible mechanism. This thesis presents a technique to study the effect of frothers on bubble coalescence at the generation stage (at a capillary tube) and a technique to study the effect of frothers on bubble coalescence and break-up in a turbulent field. The first technique is based on the sound bubbles emit when they form and coalesce. The sound signal was linked to bubble formation and coalescence events using high-speed cinematography. The technique has a resolution capable of detecting coalescence events that occur within 1-2 ms. The second technique allows discriminating between coalescence and break-up and is based on the exposure of a mono-size distribution of bubbles to a turbulent field generated by a three-bladed axial flow impeller. Analysis of bubble size distributions after contact with the turbulent field gives the coalescence and break-up fraction. The results show frothers reduce coalescence and alter the bubble size distribution of bubbles generated by break-up. / In the course of high-speed imaging an effect of frother on bubble shape and motion after formation was detected. Analysis of this forms the third major component of the work. A dependence of velocity on bubble aspect ratio is shown, which is in line with recent literature.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.111911 |
| Date | January 2008 |
| Creators | Kracht Gajardo, Willy Andrés, 1979- |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Mining and Materials Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 003131233, proquestno: AAINR66574, Theses scanned by UMI/ProQuest. |
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