Improved density fractionation of minerals in the REFLUXᵀᴹ classifier using LST as a novel fluidising medium

A hydrodynamic fractionation technique utilising the REFLUXᵀᴹ Classifier has previously been developed as an alternative to the sink/float technique. Although proven effective on low-density coal samples over a wide range of particle sizes using water or glycerol solutions as a fluidising medium, application of this technique to minerals has proven challenging due to the smaller variation in the buoyant weight force of the particles. This paper reports a step change in fractionation performance for dense minerals in a semi-batch REFLUXᵀᴹ Classifier using a non-hazardous dense liquid as the fluidising medium, i.e. an aqueous solution of lithium heteropolytungstates (LST). In this work, the REFLUXᵀᴹ Classifier fractionation produced using (i) LST (ρ_f ≈ 2400 kg/m³) and (ii) 70 wt% glycerol and water fluidising media in a system of inclined channels with a 6 mm perpendicular spacing were validated against sink/float data for a -2.0 + 0.090 mm sulfide gold ore sample. It has been found that the dense liquid promotes shear induced inertial lift at much lower shear rates, significantly improving the density-based fractionation performance of the system to align very strongly with the sink/float result. Conversely, both the water and glycerol solution were found to produce poor results.