Scale-up in froth flotation: A state-of-the-art review

Abstract

Abstract Froth flotation has been one of the most important and widely used methods to concentrate minerals since its introduction over a hundred years ago. Over the last few decades, in order to process more mineral while reducing capital costs, flotation equipment has become exponentially larger. The increase in tank volume, however, has brought new challenges in the operation and design of industrial flotation tanks. This review analyses the literature on flotation tank scale-up for the first time, contrasting several techniques and approaches used in both historical and state-of-the-art research. The study of flotation scale-up is crucial for the optimisation of industrial plant performance and the maximisation of laboratory-scale research impact. While important advances in our understanding of flotation have been achieved, large flotation tank design and scale-up has, to a large extent, remained in-house know-how of manufacturing companies. This review of the literature relevant to flotation tank scale-up has resulted in a new classification, dividing the scale-up literature into two main areas of study, namely “Kinetic scale-up” and “Machine design scale-up”. This review indicates that current scale-up rules governing the design of flotation tanks focus mainly on pulp zone kinetic parameters and neglect the effects on the froth zone, despite the importance of froth stability and mobility in determining flotation performance. Froth stability and mobility are closely linked to the distance the froth needs to travel, which increases with tank diameter. Although including internal elements, such as launders and crowders, has been the industrial solution for enhancing froth transport and recovery in larger tanks, the design and scale-up of these elements have not been thoroughly studied. Gaps in our knowledge of flotation are discussed in the context of addressing the scale-up problem, considering froth transport and froth stability. Addressing these gaps will pave the way for the design and operation of large flotation tanks of enhanced performance.