On 11 February 2015, OZ Minerals announced it was undertaking a number of initiatives to improve the medium to long-term value of its Carrapateena copper assets. A key initiative included the progression of a Hydromet demonstration plant following successful testing of the process in 2014, to verify scalability to full production.
OZ Minerals has now announced the first trial results from the Hydromet demonstration plant indicate that the process is scalable and is already returning copper-in-concentrate levels of more than 55%. Impurity elements are well below penalisable levels.

This compares favourably to globally produced concentrates with copper-in-concentrate grades that typically average less than 30%. “This is a great set of first results for OZ Minerals and the copper industry in South Australia,” said Andrew Cole, CEO and Managing Director. “The successful completion of this demonstration trial will allow us to produce some of the best and cleanest copper concentrate in the world with virtually no impurities.”

This builds on encouraging results from the laboratory scale test work and pilot plant last year, where a final product exceeding 55% copper-in-concentrate was produced from a starting concentrate grade of 30-35%. The company has now increased the trial capacity of the Hydromet demonstration plant by a factor of fifty.

The very low copper and precious metals recovery loss during the process was comparable to traditional existing processing techniques. The aim of this trial work is to prove that the process can be economically scaled up to a fully operational plant. “On the back of these promising results, we will continue to feed samples of concentrate through the plant over the next few months to build on our technical understanding and confidence in the process,” Cole said.
The results of the Hydromet demonstration plant trial will contribute to the ongoing studies in optimising the value proposition for Carrapateena.

Hydromet combines new chemistry with existing technology in order to significantly increase copper-in-concentrate grades and reduce impurities to very low levels. “When the process is applied commercially, it has the potential to significantly reduce concentrate transport costs and produce a copper concentrate quality that is highly sought after in all concentrate smelting markets.” The Hydromet process involves processing copper concentrate containing chalcopyrite and bornite. It converts these two minerals into chalcocite, by leaching out the iron and other impurities.

The South Australian Government recognises the economic potential for the innovative use of processing techniques, such as Hydromet, to realise and enhance the copper resources in the Gawler Craton. In support of their South Australian Copper Strategy, the State Government has pledged A$10 million to fund a joint study of the Hyrdromet process between OZ Minerals and Orway Mineral Consultants, with research conducted by Adelaide University. OZ Minerals will contribute A$8 million to this work. South Australian copper concentrates are already successfully produced and sold to the global concentrate market. They are typically sought due to their quality and accessibility to the markets themselves. The Prominent Hill mine produces one of the highest copper concentrates on the global market at around 50%. “This is crucial research that could help maximise the value of South Australia’s copper resources for generations to come. When considered in the context of the South Australian Copper Strategy, it is a very exciting time for the industry,” Cole said.