The effect of impeller-stator design on bubble size: Implications for froth stability and flotation performance

Abstract

The impeller in a mechanical flotation tank plays a key role in keeping particles in suspension, dispersing and breaking-up air bubbles, and promoting particle-bubble collision. However, the turbulent regime generated by the impeller can also affect the pulp-froth interface, destabilising the lower regions of the froth and affecting the overall flotation performance. The effects that pulp zone design modifications have on the froth are, however, poorly understood and have not been well-studied.In this work, we study the impact of impeller-stator design on the performance of a large laboratory-scale flotation tank. Two different impeller designs, with and without a stator, were assessed under a range of air flow rates to determine changes in pulp bubble size, froth stability, and metallurgical recovery. The results allow us to quantify, for the first time, the reduction in bubble size in a three-phase flotation system and the improvement in froth stability due to the use of a stator, and thus the enhancement in flotation performance. An inverse relationship is found between the pulp bubble size and froth stability. It is shown that the impeller designs that exhibited smaller bubble sizes resulted in higher froth stability values and also higher flotation recoveries. These findings provide insights into the links between pulp and froth zone phenomena, paving the way for improvements in flotation tank design that lead towards flotation optimisation.

From Microbubbles to Nanobubbles: Effect on Flotation

“…The flotation of mixed sulfides is a common application in mineral processing used for selective separation, also noting that the specific gravity of the minerals is different. The impeller in a mechanical flotation tank plays a key role in keeping particles in suspension, dispersing and breaking-up air bubbles, and promoting particle-bubble collision; however, the turbulent regime generated by the impeller can also affect the pulp-froth interface [12]. Hydration phenomena, associations, and interactions between collectors, air bubbles, and water-soluble mineral particles were also presented [13].…”

Gas Dispersion Characteristics in a Novel Jet-Stirring Coupling Flotation Device

“…The impeller rotational speed increases with increasing concentration. The increase of impeller speed is essentially due to the decrease of pressure difference caused by the measured space filled with most of the microbubbles, which directly causes the decrease of hydrostatic pressure and frictional resistance of the liquid medium on the stirring impeller, thus improving the turbulence of the flow field near the stirring impeller, which is beneficial to the improvement of particle-bubble collision mineralization efficiency. , …”

Frother Characterization Using a Novel Bubble Size Measurement Technique

“…When reporting bubble sizes, one of the most common metrics is the Sauter mean bubble diameter, which is calculated based on the volume to surface ratio of the bubbles, as illustrated in Equation ( 4) [20,21].…”

“…When reporting bubble sizes, one of the most common metrics is the Sauter mean bubble diameter, which is calculated based on the volume to surface ratio of the bubbles, as illustrated in Equation (4) [20,21]. The Critical Coalescence Concentration (CCC), which was defined as a concentration where bubbles cease to coalesce [13], was then determined.…”