HIGH-GRADE NI-CU-PT-PD-ZN-CR-AU-V-TI DISCOVERIES IN THE "RING OF FIRE"
NI 43-101 Update (September 2012): 11.1 Mt @ 1.68% Ni, 0.87% Cu, 0.89 gpt Pt and 3.09 gpt Pd and 0.18 gpt Au (Proven & Probable Reserves) / 8.9 Mt @ 1.10% Ni, 1.14% Cu, 1.16 gpt Pt and 3.49 gpt Pd and 0.30 gpt Au (Inferred Resource)
Message: Nitric Acid leaching for Nickel projects
If this process is successful for laterite HPAL projects it could impact future nickel supply / demand projections in coming years.
“A new environmentally friendly processing method that uses and recycles nitric acid could unlock 70 per cent of the world’s nickel.
RECYCLING is good for the environment, everyone knows that, but what if it is the answer to one of the mining world’s trickiest problems?
Extracting nickel from low grade ore at a commercially attractive cost is the problem at hand. In the quest for a solution, these ores have been subjected to multiple attacks using sulphuric acid in a high-temperature, high-pressure process over the past 20 years.
Unfortunately, many of the high pressure acid leach (HPAL) projects have encountered severe problems, fooling some of the best brains in the mining sector.
Even the world’s biggest mining company, BHP Billiton, found HPAL a process too difficult to tame, selling its multi-billion dollar Ravensthorpe mine in Western Australia to the Canadian company, First Quantum.
Now nitric acid is in the mix and while it’s even more aggressive than sulphuric in digesting nickel- bearing ores, it can do the job at significantly lower pressure and lower temperature, eliminating the need for expensive titanium-lined equipment.
However, the potential ‘big win’ from using nitric acid is not in the digestion of the ore, but in the way the acid can be captured and recycled, eliminating one of the major costs that has bugged the sulphuric acid HPAL plants – neutralisation of waste acid.
‘The key to this new process is the recycling of the nitric acid,’ says Dr Dave Robinson, leader of mineral processing research at CSIRO.
‘The process has its origins in patented technology developed for the treatment of wood. Large amounts of nitric acid are used in certain wood processes and that led to a search for a way to recycle the acid. ‘Someone then did a bit of thinking outside the box and asked – why don’t we look at using it in metallurgy?’
This was just the beginning. The application of nitric acid in the nickel processing industry has a few more hurdles to clear. While small-scale tests have yielded positive results, the next challenge is to successfully operate a one tonne a day pilot plant at CSIRO’s facility in Perth.
‘The pilot plant is a major development in better understanding the process,’ Dr Robinson said.
‘It will provide the engineering data that will validate our technical and economic predictions.’ Much of the credit for that early work goes to a US-based company, Drinkard Metalox, and the management team behind an Australian company attempting to commercialise the process, Direct Nickel.
Over the past few years Direct Nickel has marshalled a number of interested parties to provide support for studies into the nitric acid based process, including the big Canadian miner, Teck Resources, Australia’s OZ Minerals, and London-based Regency Mines. All have invested in Direct Nickel and Regency made available its Mambare nickel laterite deposit in Papua New Guinea as the site for the first commercial use of the process.
CSIRO’s involvement, which started with small leaching trials, has grown to an investment of $3.5 million under the Australian Growth Partnerships (AGP) program.For Direct Nickel, the next few months are an important stage in its evolution. If the nitric acid process works as promised and 95 per cent of the nitric acid is captured and recycled, it can be applied to a wide range of nickel-bearing ores including laterites currently used in HPAL projects and other low grade ores such as limonite and saprolite.
Direct Nickel has published an estimated processing cost of US$1.84 per pound of nickel recovered – a low figure compared with HPAL plants and competitive with nickel sulphide ores, which are more easily mined and processed.
Specialist technical consulting firm Aker Solutions calculated the likely capital and operating cost of a nitric acid plant processing three million tonnes of ore a year and producing 34 000 tonnes of nickel. The result is a capital cost of US$12 per tonne of annual capacity.
If those costs can be achieved, the Direct Nickel process will be highly competitive not only with HPAL projects, but also with traditional high grade nickel (sulphide) mines such as those near the centre of the WA nickel industry, Kambalda.
For CSIRO, the pilot plant will be an opportunity to examine in detail a process that has the potential to make a major contribution to the world’s nickel industry as sulphide ore bodies are depleted and the spotlight shifts to laterite and saprolite ores, which contain an estimated 70 per cent of the world’s nickel.
‘This pilot plant is very different to a test tube,’ Dr Robinson said.
‘What we’ll be looking at is the performance of the process and the ability to recycle the nitric acid, which has both economic and environmental benefits.
‘In the HPAL process, a large amount of sulphuric acid is consumed, requiring expensive waste treatment systems and disposal. ‘The Direct Nickel process still uses a lot of acid in the upfront leaching, but what nitric acid does, because it’s a little bit more aggressive, is enable us to work at atmospheric pressure and at about 95–100 degrees Celsius. This saves a lot of energy.’
The pilot plant trials are expected to be underway this month.
"Nitric Nickel” by Tim Treadgold
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