Gas dispersion in a laboratory Denver flotation cell was characterized by measuring the superficial gas velocity (Jg), bubble size (d b) and estimating the bubble surface area flux, Sb as a function of impeller speed, frother concentration (Dowfroth 250), and solids content (-30mum silica). The cell was operated by self-aspiration or forced air. The air flow rate was measured using a McMillan meter (self-aspiration) and a mass flow meter (forced air). The bubble size was measured by a photographic technique developed at McGill. From repeat experiments, the average relative standard deviation on Jg was ca. 2% and on db was ca. 13%. No effect of location on bubble size was found. / In self-aspiration mode Jg increased with impeller speed due to increased suction and decreased with increasing frother concentration and solids content. The effect of frother was attributed to increased recirculation of air as the bubble size was reduced. The effect of solids appears related to sedimentation. Bubble size increased with increasing impeller speed, which was attributed to the increase in Jg. Solids did not affect the bubble size. Bubble size decreased with frother most notably at low concentration then remained almost constant at high frother concentration. The critical coalescence concentration appeared to be close to 5 ppm for the present conditions. The bubble surface area flux Sb increased approximately linearly with impeller speed up to ca. 40s-1. / Using forced air the bubble size behaved as expected: it decreased with increasing impeller speed (due to higher shear) and decreasing Jg . The Sb ranged up to ca. 80s-1, higher than values quoted for a laboratory machine. To correspond more closely to industrial cells, operation with forced air is recommended. The use of higher impeller speeds than are commonly used in laboratory testwork will give more closely fit superficial gas velocity found in industrial plant practice.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.80007 |
| Date | January 2003 |
| Creators | Do, Sung-Su, 1970- |
| Contributors | Finch, J. A. (advisor), Gomez, C. O. (advisor) |
| 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 | Master of Engineering (Department of Mining, Metals and Materials Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 002094847, proquestno: AAIMQ98521, Theses scanned by UMI/ProQuest. |
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