Improving coarse particle flotation using the HydroFloat™ (raising the trunk of the elephant curve)

The copper sulfide processing flowsheet has remained virtually untouched for decades and follows a logical progression - crush, grind, float, regrind and refloat to produce a final copper concentrate. This well-defined and proven method of copper sulfide processing has served the industry well for over a century and is based on the particle size range for which conventional flotation is most effective. Work by numerous experts has shown that mechanical flotation works well for a limited size range, from approximately 15 to 150 pm, and is best presented in the well-recognized "elephant curve." Particles outside this critical size range are typically lost in industrial operations and rejected to tailings due to inherent constraints associated with the physical interactions that occur in the pulp and froth phases of conventional flotation equipment. The underlying mechanisms responsible for the decline in flotation recovery of very fine and very coarse particles have been extensively discussed in the technical literature. For coarser particles, low recovery is typically attributed to both turbulence and buoyancy constraints. To overcome these inherent limitations found in conventional flotation cells, Eriez has developed and successfully implemented a technology, the HydroFloat'', that combines the aspects of fluidized-bed separation and flotation. More recently, this same technology has been demonstrated in sulfides for recovering coarse value from concentrator tails. Other efforts have shown the positive benefit that can be derived from implementation within the concentrator itself. This paper will discuss the theory of operation of fluidized-bed flotation and data from various applications are presented.