• Impact Minerals flags new HPA production process which could reduce capital and operating costs for its Lake Hope project
  • The new LTL Process has no need for sulphuric acid roasting, reducing the number of steps from five to four
  • Process now undergoing further optimisation to increase recoveries and lower contaminants


Special Report: Impact Minerals has identified a new proprietary metallurgical process that could make it cheaper to produce high purity alumina (HPA) from its Lake Hope project in Western Australia.

The proprietary and patented Playa One Sulphate Process, which underpinned Impact Minerals’ (ASX:IPT) recent scoping study and has been the focus of test work to date, successfully produced better than 99.99% (4N) HPA using raw lake clay sourced from Lake Hope.

Lake Hope is unique deposit of clay which contains a resource of 3.5Mt @ 25.1% Al2O3 for a contained 880,000t of alumina.

The deposit also boasts a zero strip ratio and hosts high-grade mineralisation at surface, meaning no on-site beneficiation is required and the kinetics of the metallurgical process are expected to deliver cost-effective mining and processing.

Using the Sulphate Process, IPT’s scoping study flagged production of 10,000tpa 4N HPA over an initial 25-year mine life for an initial capex of $253 million, delivering post-tax NPV of $1.334 billion, IRR of 55% and annual cashflow of $174 million.


New process could lower costs

As impressive as the Sulphate Process might be, IPT has now identified a new proprietary metallurgical process that could further reduce the capex and operating costs associated with producing HPA.

The simpler low-temperature leach (LTL) and acid digestion process – the LTL Process – has successfully produced 4N HPA following months of laboratory test work.

This is understood to be one of the fastest known times to produce HPA from raw materials reported by an ASX-listed company.

This process is a direct low-temperature leach 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.

As such, it could offer further reductions in operating costs and capital costs to produce HPA.

Adding interest, the LTL Process is yet to be optimised and improved recoveries (currently 84.7% of the raw alumina) and further reductions in contaminants are likely as test work is progressed.

Like the Sulphate Process, the LTL Process also produces a fertiliser by-product that could be a key factor in offsetting operating costs.

“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,” IPT managing director Dr Mike Jones said.

“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.”


Upcoming work

IPT’s Lake Hope PFS is progressing on schedule and is due for completion in late 2024.

Metallurgical test work is the critical component of the upcoming PFS and will be the focus of the forward work program, which will now include batch production from both the Sulphate Process and LTL Process.

Results from this work, which includes final optimisation of the LTL Process and preliminary economic studies along with results from a third possible process route, are due in the next quarter.

This will allow a final choice to be made of the process route required for commercial production of HPA.

IPT will also carry out an assessment of the mineral potential of the wider Lake Hope playa system due to the potential to produce valuable chemical and fertiliser by-products.

This has involved some preliminary shallow auger and push tube drilling, and a detailed review and interpretation of the results is in progress.



This article was developed in collaboration with Impact Minerals, a Stockhead advertiser at the time of publishing.


This article does not constitute financial product advice. You should consider obtaining independent advice before making any financial decisions.