Maximizing recovery, grade and throughput in a single stage Reflux Flotation Cell

Abstract

The Reflux Flotation Cell (RFC) utilises the Boycott Effect to decouple the overflow water flux from the gas flux, permitting in principle high product grade and recovery at a vastly higher volumetric feed flux. This study investigated this relationship between concentrate grade, recovery, and volumetric feed throughput using a single flotation stage and feed fluxes spanning 1–9 cm/s, well beyond that used in conventional flotation. Coal flotation tailings and hydrocyclone overflow provided convenient representations of “binary” feeds for the experiments, constituting liberated hydrophobic and hydrophilic particles. The results demonstrated robust recoveries through the preservation of the gas to feed flux ratio with increasing feed flux, while minimising the gas flux strengthened the capacity to maintain high product grade using inverted fluidization water as the wash water. Remarkably, a high product grade (low product ash%) was maintained over the extreme feed flux range by ensuring a net downwards flux of wash water delivered through the upper fluidized bed of bubbles. Coal Grain Analysis (CGA), an optical imaging technique, identified the maceral composition of the feed particles and validated, with close agreement, the RFC steady state separation performance. Indeed, under continuous operation the RFC data demonstrated an overall positive shift in performance relative to that of the standard tree flotation curve. The findings showed strong preservation of product grade and recovery using a single RFC stage, over a seven-fold increase in the feed flux relative to conventional flotation systems.