The first stage of Lithium Australia’s SiLeach® pilot plant trial at ANSTO’s minerals piloting facility in New South Wales has ended with the production of a lithium-pregnant liquor from lepidolite feed.
Stage two of the pilot will see this liquor processed into lithium chemicals, according to Lithium Australia Managing Director Adrian Griffin.
LIT’s SiLeach process is a halide-accelerated, sulphuric acid digestion system, operated at atmospheric pressure. No roasting is required, significantly reducing the energy footprint when compared with conventional lithium extraction technology. The process also significantly benefits from a range of potential by-product credits.
During stage one of the SiLeach trial, which ran from August 6-16, the plant operated in continuous mode for five days, processing lepidolite concentrate at approximately 4 kg/h through leach, pre-neutralisation and impurity removal stages.
Preliminary data indicate lithium extraction in the leach circuit peaked at 97.5% and averaged 94% for the duration of the trial, according to LIT. Acid addition was 1,300 kg/t and fluorspar addition was 180 kg/t of concentrate feed.
“Leach results exceeded target, supporting the opportunity for concentrate grind size and reagent optimisation during design of the proposed large-scale pilot plant (LSPP, pictured),” the company said.
Operation of the multi-stage impurity removal circuit confirmed the expected rejection of aluminium fluoride (AlF3) in the first stage and encouraged further investigation into the feasibility of recovering an AlF3 by-product from this residue.
The lithium-rich liquor produced during stage one of the trial met purity targets and will be processed through to lithium chemicals in stage two of the trial, due to commence today (September 10). At that stage, calcium and fluorine will be removed and a lithium phosphate produced as a final product.
“Run in an integrated manner, the trial successfully demonstrated continuous operation of Lithium Australia’s proprietary SiLeach process, including full recycle of intermediate process streams.”
The company announced in July it was commencing the first of a two-stage pilot, with the concentrate used as feed for the trial prepared in Perth, Western Australia, under the supervision of Independent Metallurgical Operations. This consisted of lepidolite recovered from mine waste.
Samples of the pregnant solution have been provided to multiple vendors in order to complete solid/liquid separation test work, as well as confirm equipment selection and sizing and support cost estimation for the SiLeach LSPP front-end engineering and design study currently being conducted by CPC Project Design.