King River Resources produces its first 4N high purity alumina from Speewah project

King River Resources (ASX: KRR) has produced the first 4N high purity alumina (HPA) from its wholly-owned Speewah specialty metals project in the east Kimberley region of Western Australia.

For the past year, the company has been examining a process route to produce vanadium pentoxide, titanium dioxide pigment and iron oxide products via a re-scaled operation.

It has also identified the potential value of extracting other high-value specialty commodities from the project such as HPA, magnesium oxide and vanadyl sulphate.

Recent hydrometallurgical refining testwork by TSW Analytical in Perth has focused on producing a greater than 99.99% HPA (4N) product and increasing the final purification efficiencies.

In November, TSW made a breakthrough in extracting aluminium directly from the sulphuric acid leach solution as the first precipitation product from which 99.98% HPA was produced.

The precipitation process has since been repeated on several leach solutions resulting in precipitation efficiencies up to 95% and a better understanding of how to reduce the amount of reagent used.

The final high purity alumina assayed 99.99% aluminium oxide, calculated on an oxide basis where impurities are converted to oxides then subtracted from 100%.

Two-stage process

The precipitate was purified by a two-stage process to reduce contaminant metals to very low levels in a precursor product suitable for production of 4N HPA.

Stage one involved recrystallisation to recover 95% aluminium oxide, while a stage two ion exchange recovered approximately 76%, with a targeted 80% for pre-feasibility study purposes.

The main contaminant metal oxides in the 4N HPA product are calcium and magnesium, with lesser amounts of sodium, potassium, manganese, silicon and iron.

Further HPA testwork and analysis has been planned to improve the stage two purification efficiency, increase the calcination temperature and testing to ensure all the HPA phase is alpha-alumina and report the HPA purification to three decimal places.

Step forward

King River chairman Anthony Barton said the new sulphuric acid leach process was a step forward in Speewah’s development.

“The production of 4N HPA by [this] process is a very significant step forward for and it has justified delaying the pre-feasibility study to achieve this level of control and produce high specification material,” he said.

“Refocusing the PFS on a smaller project which produces only high value HPA product has simplified our process flowsheet and may deliver valuable improvements to project economics.”

Speewah’s pre-feasibility study is currently being costed as a smaller scale beneficiation-agitated tank sulphuric acid leaching precipitation process operation to produce high purity alumina.

Mr Barton said the potential to add vanadium pentoxide, titanium dioxide and iron oxide into the product mix would be investigated at a later stage.

At mid-morning, shares in King River were up 50% to $0.051.