Effect of gas rate and impeller speed on bubble size in frother-electrolyte solutions. (December 2016)

• Record Type: Journal Article
• Authors: Sovechles, J.M.; Lepage, M.R.; Johnson, B.; Waters, K.E.
• Is Part Of: Minerals engineering. Volume 99(2016)
• Page Start: 133
• Page End: 141
• Publication Date: 2016-12
• Subjects: Bubble size -- Seawater -- Frother -- Salt -- Impeller speed -- Flotation; Mines and mineral resources -- Periodicals; Ressources minérales -- Périodiques; Mines and mineral resources; Periodicals; Electronic journals; 622
• DOI: 10.1016/j.mineng.2016.08.021
• Languages: English
• ISSNs: 0892-6875

Abstract

Highlights: Bubble size was determined for electrolyte-frother mixtures in a lab scale mechanical flotation cell. Bubble size decreased with the addition of frother to a sea salt solution, but increased when frother was added to NaCl. These different trends were assumed to be caused by various break-up or coalescence phenomena. Bubble coalescence was shown to mask the effect of frother on bubble break-up at low frother concentration. Differences in bubble size was highly dependent upon cell operating conditions. Abstract: In a flotation cell, bubble size is a function of both coalescence and breakup phenomena. Two phase tests, conducted in a conventional 5.5 L Denver mechanical flotation cell, studied the effect of impeller speed, gas flow rate and frother concentration on bubble size in various electrolyte-frother solutions. The addition of frother to a synthetic sea salt did reduce the measured bubble size (at certain mechanical conditions); whereas the effect of frother addition to NaCl was too small (when compared to measurement errors) to make significant conclusions. This led to more detailed CCC curves (0–50 ppm MIBC) for NaCl, NaCl + MgCl2, NaCl + CaSO4, and NaCl + KCl solutions, at constant electrolyte concentrations, to be conducted. They showed an increase in bubble size with the addition of MIBC. This was attributed to the saturation of frother at the air-water interface, reducing local surface tension gradients that help produce smaller bubbles. This occurrence is typically masked in traditional CCC curves due to the dominance of coalescence effects at low frother concentrations.