OD6 project · Western Australia
Splinter Rock REE
Western Australia. Australia's largest and highest-grade clay-hosted rare earths deposit.
Splinter Rock REE Project
The Splinter Rock project is located approximately ~150km by road northeast of Esperance. The rare earth element (REE) mineralisation at the Splinter Rock Project occurs in the weathered profile (in-situ regolith) adjacent to Booanya granitic basement rocks which are enriched in REE.
The strong enrichments in REE distinguishes Booanya granites from all other granite groups in the Esperance area. CSIRO have been engaged to use cutting edge exploration tools to assist OD6 in targeting the most likely areas of significant REE mineralisation.
Four significant prospect areas have been identified at Splinter Rock, being: Scrum, Centre, Flanker and Prop. The prospects contain amongst the thickest and highest grades of clay hosted REE’s in Australia. The thickness, area and density of the clays show the massive potential scale of REE at Splinter Rock. An updated mineral resource estimate of 682 Mt @ 1,338 TREO at 1,000 ppm cut-off grade was announced in May 2024.
Highlights include:
- High grade indicated MRE at the stand-out Inside Centre prospect of 119Mt at 1,632 ppm TREO with 23% Magnet Rare Earth Oxides (MagREO) with near surface mineralisation up to 70m thick
- Less than 10% of targeted clay basin area included in the estimate, with on-going exploration to further expand the known mineralisation
- High value MagREO represent an average of ~23% of TREO grade
- Continued exploration prioritisation of ‘best of the best’ in terms of grade, MagREO content, thickness and metallurgical recovery
REE Processing Guide
OD6 metals is proposing the following innovative processing flowsheet to deliver rare earth products based on the test work completed to date.
- Heap Leach with Nanofiltration (NF), Ion Exchange (IX) and Impurity Removal (IR)
- ~75% Nd & Pr overall Recovery
- High-quality Mixed Rare Earth Carbonate (MREC) of ~56% TREO
- High-quality Mixed Rare Earth Hydroxide (MREH) of ~59% TREO
- Superior product quality with low levels of impurities (Al, Fe, P, Si)
- Extremely low uranium and thorium content (<0.001% U + Th)
- Optimised capital and operating cost drivers
Central to the flowsheet is the use of a site based chlor-alkali facility that utilises salt and water to produce two reagents, namely hydrochloric acid (HCl) and sodium hydroxide (NaOH). HCl is used to leach the rare earth elements, then NaOH is used to remove impurities, precipitate a mixed rare earth carbonate or hydroxide product (MREC/H) and neutralise the clays prior to in pit disposal.
Chlor-alkali Process and Vendor Information
The chlor-alkali process involves passing an electric current through high purity sodium chloride (NaCl or salt) brine to produce hydrogen, chlorine and caustic soda. The hydrogen and chlorine can then be combined into hydrochloric acid. The equations to create caustic soda (NaOH) and hydrogen chloride (HCl) are:
OD6 has obtained information from and held discussions with chlor-alkali electrolyser vendors and experts to determine if owning and operating a site based facility is a viable option. To date all indications are that this is likely to provide the lowest operating cost for a long term project that will form an integrated processing facility with storage tanks for HCl and NaOH to buffer any disruptions.
Based on the publicly available information associated with a BICHLORâ„¢ Electrolyser, plus informal discussion, the following key details are noted for a single chlor-alkali electrolyser:
- Power consumption is the major cost at 1,990 kWhr/te NaOH @ 6 kA/m².
- Normally allow for 350 days operation and 7 kA/m².
- Normally operate at 385mbarg, 90°C and 32wt% NaOH.
- Can produce up to 62ktpa HCl and 69ktpa of NaOH.
- Indicative pricing for a chlor-alkali electrolyser is approximately £3M each (A$5.7M).
- Multiple smaller electrolysers can be utilised to provide operation flexibility.
A chlor-alkali facility would also consist of the key production steps outlined in Figure 2 along with the associated equipment. Figure 3 also provides an example of scale of two operational electrolysers.
At an average consumption of 16 kg HCl / tonne of ore a single electrolyser based on the above information could provide sufficient reagents to treat ~4Mtpa of clay ore. The average acid consumption may potentially be lower based on the potential removal of coarse grained (>75 µm) material which is yet to be reported.
Given power being the main cost driver OD6 envisages that low-cost power supply would be sourced from an owned and operated hybrid power system consisting of solar, wind turbines, energy storage and gas or diesel powered generators. OD6 understands that a similar facility that is currently powering the Esperance township and surrounding areas is currently achieving a 70% renewable power penetration rate which is significant achievement that OD6 should aim to replicate.
On an owned and operated basis, utilising low cost power supply, OD6 has an aspiration target to achieve an operational reagent consumption cost that would be equivalent to about $5-6/t of processed clay ore, assuming sunk capital costs.
BICHLORâ„¢ Electrolyser | INEOS Electrochemical Solutions
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