Exploring the effects of salts on gas dispersion and froth properties in flotation systems

Quinn, Jarrett.; Quinn, Jarrett.

Thesis

Exploring the effects of salts on gas dispersion and froth properties in flotation systems

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Quinn, Jarrett.

Abstract

English

Several mineral flotation plants utilize process water with high soluble salt content. The processing of soluble minerals, the use of recycle streams, sea or well water give rise to this situation. It is unclear as to the overall effect on flotation response though there does seem to be evidence of bubble size reduction, increased froth stability and reduced reagent dosage. The present work aims to quantify the effects of salts commonly present in process water on gas dispersion (bubble size and gas holdup) and froth properties (solid and liquid overflow rates) and to compare to a typical frother, MIBC (methyl isobutyl carbinol). Three sets of experiments were run: 2-phase, 3-phase using talc and 3-phase using ore. All tests were run in a laboratory column. The salts examined in the 2-phase tests were NaCl, CaCl₂, Na₂SO₄, Na₂S₂O₃ and Al₂(SO₄)₃. Tests were conducted to determine the effects of salt type and concentration on gas holdup, bubble size distribution and foaming. The salts containing multivalent ions had a greater impact than did the monovalent ions, in keeping with the literature. A relationship between gas holdup and ionic strength was established. The effects of NaCl and MIBC on frothing and on solid and liquid overflow rates in 3-phase tests using 1%w/w talc were investigated. The results showed increased frothing and overflow rates upon the addition of NaCl, comparable to adding MIBC. Three-phase tests using ore (Falconbridge's Brunswick Mine) explored the effect of NaCl concentration. The results show reduction in bubble size and increased gas holdup in salt solutions comparable to those in the 2-phase tests. For each case, the concentration of MIBC giving equivalent gas holdup and frothing as the salt systems was determined. Proposed mechanisms for coalescence inhibition and froth stability in salt solutions are briefly reviewed in light of the current findings.

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