Abstract
Samples of the feed, underflow and overflow from water-based separations conducted using a continuous REFLUXTM Classifier involving inclined channels with a 3 mm spacing have been fractionated. Another REFLUXTM Classifier operating in a semi-batch configuration using a dense fluidising medium of lithium heteropolytungstates (LST) was used to determine the density distributions of the three streams. The partition surface of the separator was quantified, and the technique was validated against sink/float data for a −300 + 38 µm chromite ore separation. It was found that the LST flow fractionation determined the D50 with remarkable accuracy across the entire size range, with the Ep values also very good above 75 µm. For water-based continuous separations involving a gold ore covering the size range −1.0 + 0.090 mm, the D50 varied with particle size to the power −0.22 and the Ep remained relatively constant at approximately 170 kg/m3 for each of the narrow particle size ranges. These results were consistent with the partition surface validated based on the much finer size range of the higher density chromite ore. The performance of the continuous system was then modelled, with the results shown to agree well with separations conducted on the feed. This approach has been developed as an alternative to using the sink/float test, thus offering a new option with both a lower cost and minimal health and environmental risk. The findings from this study can in turn be used to assess the amenability of a given ore to gravity pre-concentration.
Highlights
Successful recovery and concentration of valuable minerals from gangue requires adequate liberation of the minerals for separation
This paper extends the initial findings presented at a recent conference [21], by introducing a comprehensive dataset in order to expand the particle size range, and in turn produce a robust partition surface
The technique was first validated against sink/float data for a −300 + 38 μm chromite ore separation, conducted in a REFLUXTM Classifier with 3 mm inclined channels [17]
Summary
Successful recovery and concentration of valuable minerals from gangue requires adequate liberation of the minerals for separation. The run-of-mine ore often undergoes several orders of magnitude size reduction through crushing and grinding before the valuable mineral is recovered and concentrated, typically at a P80 of around 75 μm. The energy required for comminution increases significantly as the P80 decreases. Rather than accepting the reality of higher operating costs due to increasingly lower grade ores and finer liberation sizes, one option is to implement pre-concentration strategies which target the removal of liberated gangue at the coarsest size possible, a concept referred to as coarse particle or early gangue rejection. The aim is to selectively reject gangue prior to fine grinding and downstream concentration without compromising the recovery of the valuable metal.
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