METALLURGICAL TESTWORK HITS ITS 1ST MILESTONE AHEAD OF SCHEDULE DURING DEFINITE FEASIBILITY STUDY's WORK PROGRAM
· Report covers Sensor Based Sorting well ahead of schedule
The Company has received approval from Dorfner to provide the information directly from the Report: "FS Testwork for the
For the test work, samples were taken by
Sensor based sorting test work was conducted to reduce the host rock dilution and pre-concentrate the spodumene ore by rejecting host rock. It was applied to the fractions +8 -25 mm and +25 -70mm. Tests were carried out separately for the AHP and MHP type materials in both size fractions. The following sorting tests were carried out:
· Laser sorting tests on bulk samples (approx. 50 tons feed) including scavenger sorting
· XRT sorting tests as an alternative to laser sorting including scavenger sorting
· Laser sorting on recombined 80% (host rock) / 20 (ore) mix
Bulk Laser Sorting
The objective of the bulk laser sorting test work was to confirm the results of the previous test work and produce sorted product for the subsequent lab and pilot test work. In all tests a scavenger sorting was conducted, to recover any spodumene misplaced to the sorter rejects from the rougher stage.
Figure 1: Laser sorter: 3D model of Laser sorter (top) and Laser sorter test rig in Tomra's technical center used for fraction +25 mm
Based on the results of initial screening and laser sorting tests an overall mass balance for both, the MHP ore and the AHP ore sample, was estimated. In case of AHP ore (rougher sorting only) a mass reduction of 25.1 wt.-% of initial mass was realised by rejecting host rock during sensor based sorting. A lithium recovery of 93.1 wt.-% in sorted AHP ore was calculated. The sorted ore is the combined product after sorting of fraction +25 mm and fraction +8 -25 mm as well as fines -8 mm from the initial screening step. In addition, spodumene is pre-concentrated and lithium content increased from 1.0 wt.-% to 1.3 wt.-% Li2O after sorting. In the case of MHP ore (rougher sorting only) a mass reduction of 23.2 wt.-% of initial mass was realised by rejecting host rock during sensor based sorting. The lithium recovery was calculated to 92.5 wt.-% in the sorted MHP ore. Lithium content increased from 0.9 wt.-% in the initial head sample to 1.1 wt.-% Li2O after sorting. The results are comparable to the previous sorting results, where 92.0 wt.-% overall lithium recovery for MHP and 93.0 wt.-% for AHP were achieved.
When adding the scavenger sorting stage in the calculation, the overall lithium recovery in the sorted ore improves to 95.5 wt.-% for AHP ore and as well to 95.5 wt.-% for MHP ore.
The use of XRT sorting as an alternative to laser sorting was investigated. Although laser-based sorting provided excellent recovery and waste rock rejection in the testwork, it requires the ore to be pre-rinsed.
Figure 2: XRT sorter: 3D model of XRT sorter (top) and XRT sorter test rig in Tomra's technical center
Compared to the laser sorting the XRT sorting was significantly less selective. This is indicated by the reduced recovery in the rougher stage. The lithium recovery using XRT in the rougher product was in the range of 76.2 to 85.2 wt.-%, compared to 86.3 to 92.6 wt.-% using laser sorting at a similar product quality. In addition, a significant amount of lithium (8.4 to 20.6 wt.-%) and mass (6.3 to 23.5 wt.-%, for comparison 2.8 to 5.7 wt.-% in laser sorting) was separated in the scavenger product for recirculation to feed. Therefore, the laser sorting technology appears to be the preferred solution for sorting of the ore form the
Laser Sorting High Dilution
High dilution with host rock is expected with up to 80% (host rock content in sorter feed) when mining narrow veins during the life of mine. Therefore, laser sorting tests were conducted with a recombined sample with approx. 80% host rock dilution. A flow sheet with rougher, scavenger and cleaner sorting was tested.
The quality of the final product after sorting (cleaner product) is similar in quality as the products yielded after sorting of the samples as received (scavenger product). The lithium recovery in the cleaner product was in the range of 53.2 to 67.6 wt.-%. Significant amounts of lithium is also in the cleaner tailings and scavenger product (6.3 to 19.6 wt.-%). These two products are recirculated in the commercial process, therefore, most of the lithium in these products should be recoverable.
Lithium was analyzed in the host rock, which is not connected to spodumene but rather to lithium bearing minerals in the host rock (holmquistite), influencing the lithium recovery calculation for the 80/20 case. The source of lithium in the host rock is recommended to be investigated further and has to be taken into account when using the sorting results for further recovery estimations during engineering studies.
The information contained within this announcement is deemed by the Company to constitute inside information under the Market Abuse Regulation (EU) No. 596/2014
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