Novel application of X-ray characterisation techniques in froth flotation for the study of bubble clusters

Abstract

Froth flotation is commonly used to upgrade minerals. Bubbles are used to carry valuable particles out of a slurry into the froth phase to a launder. The pursue of energy saving in grinding has led to the emergence of coarse flotation technologies. Evidence points to the crucial role of bubble clusters to lift coarse particles effectively. However, little is known about their formation and behaviour except from what can be gathered from the photographic method. This study demonstrates the capability of X-ray computed tomography (X-ray CT) to study the morphology of bubble clusters. The method is able to distinguish individual particles and how they are positioned on bubbles. In addition, X-ray particle image velocimetry (X-ray PIV) was initially employed on a 2-phase system (air and water) to determine its suitability for tracking bubbles and eventually bubble clusters. X-ray PIV could effectively be used to track the mean velocity of bubbles in all sections of a foam column. It was possible to estimate the composition (i.e., liquid holdup) within the column. It is believed that both methodologies will provide insights into the morphology of bubble clusters as well as their behaviour in the pulp, in the froth, and at the pulp/froth interface.