Breakthrough Alternative High Purity Alumina (HPA) Metallurgy Route Revealed at the Lake Hope Project, WA

A new proprietary metallurgical process has been identified for producing high-value High Purity Alumina (HPA) from the lake clays at Impact Minerals Limited’s (ASX:IPT) Lake Hope project, located 500 km east of Perth in Western Australia (Figure 1). Impact can earn an 80% interest in Playa One Pty Limited, which owns the Lake Hope project, by completing a Pre-Feasibility Study (PFS) on the project which is in progress (ASX Release March 21st 2023 and November 9th 2023).

• 99.99% (4N) Al₂O₃ produced from a new low-temperature leach (LTL) and acid digestion process called the “LTL Process”:
• The LTL Process is a simpler process that may lower the Capital and Operating Costs to produce HPA compared to the Sulphate Process, which has been the focus of test work to date.
• The Sulphate Process underpinned the recent Scoping Study, which indicated an operating cost of
• The LTL Process will now be included in the ongoing Pre-Feasibility Study in parallel with the Sulphate Process at marginal extra cost to determine the best processing route to HPA.
• The PFS is due to be completed on schedule in late 2024.

Impact Minerals’ Managing Director, Dr Mike Jones, said,“Today we reveal a further exciting breakthrough for producing HPA from the unique mix of minerals that are present at Lake Hope, minerals which have allowed our new LTL Process to produce the benchmark 99.99% pure HPA very quickly after starting the test work.

The LTL Process is simpler than the Sulphate Process that underpinned our recent Scoping Study and showed that at less than US$4,000 per tonne, Lake Hope may produce HPA at up to 50% cheaper than our peers.

We think that further work on the LTL Process could result in even lower operating and capital costs, and this would only further enhance the already impressive economics of the project, which has an NPV8 of well over A$1 billion.

We have now started further optimization studies for the LTL Process and will push forward with our Pre- Feasibility Study using both process routes for the time being to determine the best strategic choice for processing at the project. Given we can run all these tests in parallel for little extra cost, we are still on course to finish the PFS later this year and continue to look forward towards producing HPA from Lake Hope”.

Figure 1. Location of the Lake Hope Project.

The new process, called the LTL Process, has produced High Purity Alumina (HPA) at 99.99% purity from the raw lake clay in only a few months of laboratory test work (with its attendant delays for holidays and other customer work) (Table 1). This is one of the fastest times to produce HPA from raw materials reported by ASX-listed companies and attests to the relatively straightforward nature of the process. It involves different reagents to those used in the Playa One Sulphate Process, which has also recently successfully produced 4N HPA (ASX Release 19th February 2024).

Table 1. Assays results for Lake Hope HPA via the LTL Process. Repeat samples derived from sample LHMET001 (see Table below for sample location). Assays units are parts per million (ppm).Note that the LTL Process has not been optimized and further reductions in contaminants are anticipated.

The LTL Process is a direct low-temperature leach (<90o C) that removes the requirement for sulphuric acid roasting, which was a key part of the Sulphate Process and reduces the number of steps to produce HPA from five stages to four (Figure 2). Accordingly, the new process could offer further reductions in operating costs and capital costs to produce HPA compared to the Playa One Sulphate Process.

The recently released Scoping Study on Lake Hope, which was based on the Sulphate Process, showed that at an operating cost of less than US$4,000 per tonne, Lake Hope could be the lowest-cost producer of HPA globally by a significant margin of up to 50% over Impact’s peers (ASX Release November 9th 2023). Therefore, this margin could be increased should test work on the new process support these initial results and further demonstrate the potential world-class economics of the Lake Hope project.

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