Modern Mining August 2021

Key takeaways  The results of the PEA are expected by end-October 2021  The project comprises 38,3-million t of gypsum resulting from his- toric phosphate hard rock mining  Bosveld Phosphates has made available to the project the existing mothballed phosphoric acid plant infrastructure  The PEA will compare a conventional route to produce a cerium- depleted mixed rare earths carbonate versus an alternative flow sheet that bypasses the carbonate stage  Only the high value rare earths, representing 95% of the Phalaborwa rare earths basket value, will be separated and recovered “The price for NdPr oxide was about US$38 000 per tonne around April 2020 and is now at about US$95 000 per tonne. Forecast demand for permanent magnets is set to continue to grow strongly, driven by elec- tric vehicles and wind turbines which, in turn, are driven by legislation and world-wide emission reduction drives. “So, whether we like it or not, this is a structural change which is not going away.”  producing a mixed rare earth carbonate, rather than a mineral concen- trate,” says Bennett Progress To date, Rainbow Rare Earths has drilled out the two gypsum residue stacks at Phalaborwa and conducted full assays on the grade and rare earth basket, among others and Bennett notes an inferred Joint Ore Reserves Committee (JORC) resource of some 38-million t. “Secondly,” he says, “we have been doing metallurgical test work at ANSTO to optimise the process flow sheet which Sasol used successfully to build a pilot plant at Phalaborwa. That plant produced around 3 t of a cerium-depleted, mixed rare earth carbonate and a cerium oxide. This ongoing test-work was reported in the company’s Regulatory News Service (RNS) announcement, indicating recoveries of approximately 70% at ambient temperature through a sulphuric acid leach possibly improving further with increased temperature. “Due to the cracked nature of the gypsum, we can go straight down- stream without first producing a mixed rare earth concentrate, then cracking, and then going downstream to produce a mixed rare earths car- bonate. This will save a huge amount of Capex and Opex. “Due to the ANSTO test work results, we have been investigating separation technology in parallel and are doing a study to go all the way downstream producing separated rare earth oxides. In other words, we are not stopping at a mixed rare earths carbonate, as this would save further Capex and Opex and we will realise the full value of the price for separated rare earth oxides.” He says only three oxides, NdPr, Dy and Tb, need to be separated as these constitute 95% of the value of the rare earths basket at Phalaborwa. This further reduces capital and operating expenditure. “The PEA will definitely show a project that produces a mixed rare earth carbonate, but also could possibly go all the way to separated rare earth oxides, depending on the outcome of this parallel study.” Future outlook Bennett describes the outlook for rare earths as “very positive”, with prices once again rising strongly over the last few weeks in terms of NdPr, the two key rare earths needed in permanent magnets for electric vehicles, wind-turbines and consumer electronics, among others.

August 2021  MODERN MINING  19