BHP Billiton is engaging in further development of the heap leach process in order to improve the odds of success for its Olympic Dam expansion.
BHP Billiton CEO Andrew Mackenzie has announced that work on the heap leach process for uranium and copper extraction has achieved significant progress after the federal government gave the mining giant permission to conduct trials on site.
The miner hopes the low-cost extraction process will help it to exploit uranium deposits at the Olympic Dam site in South Australia with greater efficiency and economy, salvaging ambitious expansion plans for the ore body. Those plans were shelved just over two years ago.
The heap leaching process involves crushing ore and placing it in a surface pile or “heap” before gradually dripping a weak acid solution over it in order to leach out the uranium and copper content.
The resulting “pregnant” solution is then collected from the bottom of the pile and further processed to recover the leached off minerals.
Advantages of the technique include significant reductions in processing costs, particularly for low grade ores in large amounts, as well as lower energy consumption, thus diminishing the overall environmental impact of mineral extraction.
BHP is currently testing the method at the Unit 2 mineral testing laboratory in South Australia, using an array of huge steel tanks each containing as much as 25 tons of sample ore. The tests will run for 300 days, with the goal of collecting nearly all of the uranium during the heap-leach phase.
The heap-leach technique is already employed by BHP at its Spence copper project in northern Chile, while chief rival Rio Tinto hopes to commercialise the technology in Namibia and Australia and French nuclear utility Areva is exploring its usage at mining operations in Africa.
BHP’s exploration of the technology is part of the $650 million that the company reportedly agreed to spend on the research phase of the project in order to obtain a four-year extension for the Olympic Dam expansion from the South Australian government in November 2012.
The mining giant scuppered its US$20 billion expansion plans for Olympic Dam in August 2012 as a result of tepid commodities prices and high operating costs. At the time of the cancellation, BHP said it would examine “new technologies” for reducing the cost of the project.
Mackenzie is hopeful that the heap-leaching method can resuscitate hopes for the Olympic Dam uranium site, which the BHP CEO calls a “phenomenal resource.”
He points out that the site’s combination of one per cent plus copper with associated uranium makes Olympic Dam a rare find in terms of global minerals deposits, and that at an estimated 200 years it has the longest mine life of all of BHP’s assets.
In addition to copper and uranium the Olympic Dam ore body also contains gold and silver, with its total mineral load valued at around $1 trillion.