HEAP LEACHING & SX
a metre high to 10 metres high – and a range of diameters – from tens of centimetres to 5-metre diameter cribs . Some of those range from tens of kilograms to 300 tonnes – large scale with a lot of instrumentation .”
Combining this body of work with a 70,000 t leaching trial the company carried out at Kennecott from 2012 to 2014 , Nuton has been able to calibrate its computational fluid dynamic models to accurately predict a range of inputs and outputs for leaching suitability .
“ We are left in a position today where we have a high degree of confidence in being able to evaluate the suitability of different ore types and Nuton ’ s leach response fairly quickly ,” Burley said .
This has led to the company going out to market , partnering with companies that own deposits that pass the Nuton thresholds .
The company has signed deals with Lion Copper and Gold Corp , and Arizona Sonoran Copper Company to test out the technology on Lion ’ s copper assets in Mason Valley , Nevada , and Arizona Sonoran ’ s Cactus Mine and Parks / Salyer projects , in Arizona .
It has also more recently agreed a pact with McEwen Copper on the Los Azules project in Argentina .
These assets , agreements and potential leaching applications are all different – covering former operating mines and greenfield assets ; earn-ins , exclusivity periods and equity stakes ; and oxides and sulphides .
“ We recognise that due to the high variability of copper deposits and mine waste that one size doesn ’ t fit all ,” Burley said . “ A single technology solution is unlikely to perform well at every site .
“ Our approach is to work with our partners to understand site-specific characteristics , such as the mineralogy of the available ore and waste , designing a tailored approach by selecting the most applicable technology configuration from within the Nuton portfolio .”
And , according to Burley , these current and
The Kennecott Nuton test site being prepared and lined ready for the rock to be leached ( left ) and the heap pad , stacked and under leach ( right )
future agreements could see Nuton operate the equipment and plant associated with the Nuton process .
“ In many cases , we envisage supporting our partners with an end-to-end process , including engineering , build out and operating the gear ,” he said .
While the sulphide copper recovery numbers are likely to take the headlines , Burley was able to point out several key differentiators from other leaching solutions targeting minerals such as chalcopyrite .
“ Those recovery numbers are a step change , as opposed to an incremental improvement ,” he said . “ That gives us a lot more optionality in terms of the cutoff grade of the material we can process economically .”
And , with that higher resource utilisation , comes less waste and an overall higher process efficiency , meaning , under certain conditions , Nuton can compete with a pre-existing processing route such as a concentrator , Burley says .
“ In some cases in a greenfield setting , we could see a better economic and environmental outcome than a concentrator , particularly given no tailings or smelting is required , and you could have a finished product produced in country .” He continued : “ Our focus on ESG and our ability to process waste due to that low cutoff grade is one of the key differentiators that opens a whole set of use cases in the legacy mine domain too . Being able to restore and reclaim mine sites by reprocessing waste is very attractive .”
The eventual aim , according to Burley , is to deliver carbon-neutral copper from the Nuton process , yet Rio estimates it can already deliver 0.4 tonnes of CO 2 equivalent for Scope 1 and 2 emissions per tonne of Nuton copper produced ,
compared with a global average of 5.2 tonnes of CO 2 equivalent as per standard , conventional primary copper production .
Away from the technical elements , the “ partnership ” business model Nuton uses also stands out .
“ The approach is to work with our partners and assess the value case at specific sites , agreeing a commercial framework that works for everyone ,” Burley said . “ We are quite open minded as to what that might look like – it could be ownership and equity participation to royalty and licensing type arrangements .”
While this open approach is beneficial to Nuton ’ s partners , a lot of the current progress made with these technologies is tied to the development of Rio ’ s own project , La Granja .
“ In that case , part of the resource contains high arsenic and arsenic-related mineralogy ,” Burley said of La Granja . “ That was the trigger really for a concerted effort to look at an alternative to a concentrate and processing route . We made a number of Nuton breakthroughs in our study of that deposit .”
La Granja has been in Rio ’ s portfolio since winning the right to develop it in 2005 but is not currently in the development pipeline .
Asked if other assets within the company ’ s portfolio were potential Nuton candidates , Burley answered : “ We are currently evaluating a number of internal deployment options across our assets and joint ventures , but we also recognise the full value potential of Nuton – environmental and social , as well as financial – lies outside of the Rio Tinto portfolio .
“ To capture the full size of prize that Nuton offers , we need to go out to market , which is what we have been doing pretty aggressively throughout the year and will continue to do going forward .”
Chloride for copper
Rio is not the only miner arming itself with a proprietary leaching process of its own to leach
72 International Mining | NOVEMBER / DECEMBER 2022