Gravity separation of ultra-fine iron ore in the REFLUX™ Classifier

The REFLUX™ Classifier is a recently developed water-based gravity separation technology that is already being used worldwide to beneficiate particles above 0.100 mm in size. This paper reports tests performed on an ultra-fine iron ore with nominal top size of 0.106 mm, but with 59 wt-% being below 0.038 mm in size. The REFLUX™ Classifier consists of a set of parallel inclined channels positioned above a vertical fluidised section. The Boycott effect generates a powerful throughput advantage and using narrow channels gives a high shear rate which generates a hydrodynamic lift force that helps to selectively re-suspend and elutriate the lower-density particles. The iron ore feed had a head grade of 35 wt-% Fe_T. At a low feed solids mass flux of 1.5 t m⁻²h⁻¹, the REFLUX™ Classifier produced high-grade products at a high recovery. Overall a grade of 66.1 wt-% Fe_T with Fe recovery of 80 wt-% could be achieved in a single-stage separation. Within the 0.020–0.038 mm size fraction, grades of 68.8 wt-% Fe_T were achieved with iron recoveries of 94.7 wt-%. Excellent recoveries of up to 57.0 wt-% were achieved even for the −0.020 mm size fraction.