Rainbow Rare Earths Ltd (LSE:RBW, OTC:RBWRF) said a seventy-day pilot test for the Phalaborwa development project in South Africa had confirmed concentrate recoveries at 66%.
A final separation stage pilot plant will further sort the concentrate into rare earth oxides, with this work ongoing in Florida.
The separation of two key metals has now reached over 95% purity via an optimised first-stage chromatography step, with the process expected to reach the targeted purity of 99.5%
Other key findings from the pilot were a 50% reduction in the expected heating energy requirement while the first-stage impurity leach worked to the desired level.
As a result, the subsequent rare earths leach has been reduced from three stages in the PEA to two stages, while a continuous ion exchange ("CIX") pilot plant operation was conducted at Mintek to recover the rare earths in the impurity leach solution.
This CIX pilot plant delivered "excellent recovery, impurity rejection and rare earths upgrading", the statement added.
Dave Dodd, Rainbow’s technical director, said: The significant results, including lower leach temperatures, the reduced number of stages in the main rare earth leach, reduced thickener requirements and lower cost materials of construction, are expected to deliver capital and operating cost benefits compared to the base case scenario for these processes set out in the PEA.
"The excellent performance of the pilot CIX plant at Mintek, coupled with the very good rare earth group separation and 95% Nd/Pr purity achieved by the optimised first pass of ion chromatography work in Florida, auger well for the finalisation of the CIX/CIC process and validate Rainbow's use of CIX/CIC as our chosen rare earth recovery method.
George Bennett, CEO, added: "Whilst the pilot test work has taken longer to complete than originally planned, the positives of the additional time invested, in pursuing the optimisation opportunities identified on the primary pilot plant, cannot be underestimated from the point of view of confirming capital and operating costs for the Definitive Feasibility Study ("DFS") within the PEA guidelines.”
Work is continuing in both South Africa and the UA to finalise the pilot testing and the resulting optimisation opportunities, said the statement.
As part of the work to deliver the DFS in the second half of next year, Rainbow plans to release an interim report later this year to update the economics of the Phalaborwa project.
This will reflect the optimisations delivered from the pilot test work campaigns, footprinted against the preliminary economic assessment, and to allow for the commencement of project financing