Effect of slurry rheology on gas dispersion in a pilot-scale mechanical flotation cell |
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Authors: | N.Z.P. Shabalala M. Harris L.S. Leal Filho D.A. Deglon |
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Affiliation: | aCentre for Minerals Research, Department of Chemical Engineering, University of Cape Town, Private Bag Rondebosch, Cape Town 7700, South Africa;bDepartment of Mining and Petroleum Engineering, University of São Paulo, São Paulo, Brazil |
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Abstract: | This paper investigates the effect of slurry rheology on gas dispersion in a 100 l pilot-scale Batequip mechanical flotation cell. The study is conducted using Kaolin, Bindura nickel and Platreef slurries. All three ores display typical non-Newtonian rheological behaviour. The slurry yield stress and viscosity increase exponentially with solids concentration. Bubble size and gas hold-up vary from 0.60 to 1.10 mm and 2% to 15%, respectively. At low/moderate solids concentrations, bubble size and gas holdup display characteristic trends, as noted in numerous literature studies. At high solids concentrations, both bubble size and gas holdup decrease significantly, which is an unexpected finding. This is attributed to the formation of a ‘cavern’ of slurry around the impeller, due to the very high slurry yield stresses. This ‘cavern’ results in the generation of small bubbles in the impeller zone, but poor dispersion of these bubbles throughout the cell, resulting in low gas hold-ups. |
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Keywords: | Froth flotation Flotation machines Flotation bubbles Rheology |
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