A model to describe flotation performance based on physics of foams and froth image analysis

Ventura-Medina, E. and Cilliers, J.J. (2002) A model to describe flotation performance based on physics of foams and froth image analysis. International Journal of Mineral Processing, 67 (1-4). pp. 79-99. ISSN 0301-7516

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Abstract

A froth-based flotation description is developed that combines the physical structure and the kinetics of flowing froths. Foam physics indicates that bubbles have a polyhedral shape and consist of lamellae between bubbles and Plateau borders. Hydrophobic material is attached to bubbles in the lamellae, while both entrained hydrophobic and hydrophilic solids are in the Plateau borders, which form drainage channels where three lamellae meet. Further, hydrophobic solids that have become detached from the lamellae through coalescence or bursting also enter the Plateau borders. The flow rate of hydrophobic solids and liquid associated with the interbubble lamellae can be quantified by the total surface area of the overflowing froth and the thickness and solids concentration of the lamellae. These can be measured directly by dynamic image analysis and froth surface sampling. The amount of solids carried in the Plateau borders by the overflowing froth is determined by the concentration in, and volumetric flow rate of these channels. The Plateau borders volume depends on the channel length, determined by the bubble size, and the channel cross-sectional area, determined by the fraction of unbroken bubbles in the overflowing froth. These can also be obtained from image processing. Therefore, the total flow rate of hydrophobic and hydrophilic solids and liquid have two contributions, firstly from the interbubble lamellae, and secondly from the Plateau borders. Mass flow rate equations have been derived for each of these three components in terms of the measurable variables which allow the unknown solids concentrations in the Plateau borders to be estimated. Experimental data from an industrial flotation operation have been interpreted using the proposed model.