An acoustic technique for measurement of bubble solids mass loading – (a) Fundamental study of single bubble

This paper investigates a promising acoustic emission (AE) technique for estimating solids mass loading on pulp bubbles, with potential for on-line monitoring of attached solids in industrial flotation cells. It is observed that the coating of solids on a bubble surface results in a decrease in the fundamental (Minnaert) AE resonance frequency. Analytical models are derived to relate the resonance frequency of a loaded bubble to its size, attached solids mass loading and geometrical covering of particles. The AE resulting from induced pulsations of a solids loaded bubble is measured and linked with high-speed photographic recordings of the oscillations. These experiments have been performed for the attachment of a monolayer, multilayer and cluster of particles onto a gas bubble. The efficacy of the monitoring approach for these types of solids loading is demonstrated and a comparison is made of the sophistication of modelling necessary for adequate prediction of attached solids mass loading.

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► Analytical models are proposed for the resonance frequency of a loaded bubble.
► An active acoustic technique is applied to measure the resonance frequency.
► Monolayer bubble loading can be estimated from loaded/unloaded resonance frequency.
► The developed technique can measure single bubble loading to ∼0.1 mg accuracy.
► The proposed methodology is especially applicable to systems with small bubbles..