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Flowsheet selection paying off in pilot phase

15th January 2016

By: Nadine James

Features Deputy Editor

  

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ASX-listed development company Peak Resources – which has started piloting beneficiation at its Tanzania-based Ngualla pilot plant – is so far “well-pleased” with its flowsheet selection, which allows for lower operating costs and the potential improvement of the leach recovery process, says MD Darren Townsend.

“We are focused on establishing Ngualla as a low-cost, long-term supplier of rare earths for magnet metals used in green and new technology applications,” he points out, predicting that the project will be the real value driver for the company in this market.

The selection and piloting of the beneficiation flowsheet and the completion of the pilot plant that became operational in November 2015 are integral to the bankable feasibility study (BFS), as they validate the project’s viability.

Moreover, the flowsheet has assisted in developing a multiple- stage, selective leach process that can eliminate a majority of gangue minerals, as well as cerium, Townsend adds.

Removing cerium first enables Peak to concentrate on recovering the high-value magnet metals praseodymium and neodymium, which are used in the clean energy and electronics industries. In terms of volume, cerium represents more than 45% of the composition of the rare earths Peak intends to mine in Tanzania.

“Cerium is a lossmaking rare earth . . . eliminating it early in the process [enables us to] reduce the amount of acid we use. In addition, a smaller treatment plant will be required to treat the ore, thereby reducing costs,” he explains.

Townsend admits that choosing this specific process “was not always on the cards, but is something Peak has aggressively pursued as an alternative, owing to the drop in cerium prices”.

He notes that Molycorp’s 1980s Mountain Pass project, in California, used a similar flowsheet, commenting that, while the elimination of cerium will undoubtedly benefit Peak, it might not be viable for other rare earths miners, particularly because Ngualla has unique and advantageous mineralisation.

“Let’s not forget that in 2010/11, the price of cerium was substantially higher than it is now, so there was deliberate action to design plants to produce this material. Though this is no longer the case, ore compositions differ and not all orebodies can be treated in this way.”

BFS Update
Peak has successfully completed the infill, water supply and geotechnical drilling programmes, which, according to Townsend, “have confirmed and improved the definition of high-grade mineralisation near surface”.

This information will be fed into an updated orebody model, in addition to providing engineers with parameters for designing the pit walls, tailings dam and foundations for the process plant.

“We have [established] a pilot plant for our beneficiation process and this will be followed by a pilot leach plant, which is scheduled to start in the first quarter of [2016].”

These pilot plants, combined with the earlier results from Peak’s 2013 solvent extraction pilot plant, will provide all the design parameters for the process plant work to be completed for the BFS.

“In parallel with this, offtake discussions and permitting will continue. We aim to provide updates that reflect the improved process route’s impact on the operating and capital costs of the project in the first quarter of 2016.”

Peak intends to complete the BFS by the end of this year and will decide on the construction schedule prior to the end of 2017. Plant commissioning and first production are expected in 2018/19. The company expects to employ about 150 people once processing operations start officially.

The project has not experienced any major delays, though Townsend does note that, owing to market conditions and the wait for regulatory approvals, the BFS funding was not formalised until February 2015. “This, combined with the beneficiation breakthrough [the cerium rejection flowsheet], delayed the start of the BFS.”

However, he reiterates that the high-grade beneficiation and cerium rejection flowsheet resulted from this delay.

The BFS is well funded and subject to meeting further milestones. Peak has secured a further A$10-million from private-equity investor Appian Capital Advisory and World Bank emerging market development institution the International Finance Corporation.

Nonetheless, Peak continues to interact with several banks, keeping them updated on Ngualla so that it is well placed to organise the debt portion of its funding when required.

In the short term, Peak aims to “successfully complete the process pilot plants, continue permitting the project and deliver a [high-]quality BFS”, Townsend elaborates.

While Peak is focused on Ngualla, the company might consider other critical metals in the future once the project is sufficiently advanced.

Edited by Tracy Hancock
Creamer Media Contributing Editor

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