LSE-listed Rainbow Rare Earths reports that work has started on the preliminary economic assessment (PEA) for its Phalaborwa rare earths project, in Limpopo.
The PEA will compare a conventional route to produce a cerium-depleted mixed rare earths carbonate against an alternative flow sheet that bypasses the carbonate stage and delivers three higher-value products, comprising neodymium-praseodymium oxide, terbium oxide and dysprosium oxide.
The results of the PEA will then guide the direction for development of a prefeasibility study.
Independent test work carried out to date has confirmed that the phosphogypsum at Phalaborwa is amenable to direct leaching with sulphuric acid for extraction of the contained rare earths.
The resultant pregnant leach solution, after acid recovery, will be a suitable feedstock for purification and separation of the valuable rare earths.
CEO George Bennett says the company has long believed that the real value in Rainbow’s business model would come from developing an integrated mine-to-metal producer, which is capable of realising the full value of the underlying rare earth oxides for stakeholders and developing a responsible, independent Western supply chain.
“Owing to the unique nature of Phalaborwa, with the rare earths contained in a ‘cracked’ chemical form, we are already able to progress to the downstream beneficiation process by producing a mixed rare earth carbonate, rather than a mineral concentrate.”
The scope of the PEA has been enlarged from the original plan to include a downstream processing step, as an alternative to the original flow sheet, which proposed the production of a mixed rare earth carbonate.
The additional processing step is possible at Phalaborwa owing to the fact that the rare earths contained in the phosphogypsum are in a “cracked” chemical form, the miner says in a statement.
Further downstream processing to separate and purify individual oxides is anticipated to deliver several benefits compared with a traditional flow sheet, including the enhanced flow sheet being expected to be capable of delivering a higher-value product, delivering the full value of the separated rare earth metal oxides.
By comparison, Rainbow’s Gakara project, in Burundi, produces a high-grade mineral concentrate, which has been sold to China for further downstream beneficiation or processing, realising about 30% of the contained rare earths metal oxide value.
The traditional flow sheet at Phalaborwa will produce a mixed rare earth carbonate, realising about 60% to 65% of the contained metal oxide value, compared with 100% of the metal oxide value Rainbow would achieve by going further downstream to produce separated individual oxides as a per the enlarged PEA scope of work.
Also, another benefit of the unconventional flow sheet is that capital and operating expenditure cost savings are expected compared with the initial traditional flow sheet to produce a mixed rare earth carbonate for further processing in a dedicated separation facility.
In addition, the unconventional flow sheet will result in only the high-value rare earths being separated and recovered, including neodymium, praseodymium, terbium and dysprosium – which represent 95% of the Phalaborwa rare earths basket value.
This enables Rainbow to capture the full benefit of additional value from downstream processing, without superfluous capital and operating expenditure which would be needed to separate all the individual rare earth elements present in the stacks.
The outcome of a successful trade-off study will enable Phalaborwa to deliver the increased value of the separated rare earth oxides through a single, low capital-intensity processing plant at the project site.
Bennett adds that, owing to Rainbow’s strong technical team, which worked alongside him at MDM Engineering on a number of feasibility studies for rare earths projects, Rainbow has the internal knowledge and experience to identify this opportunity for a single processing flow sheet.
This flow sheet will produce individual rare earth oxides with a lower capital intensity than a traditional approach, he adds.