HEAP LEACHING has progressively been showcasing the benefits of GlyCat to the wider mining community , with Briggs highlighting an example in Mongolia of how it has overcome any doubts about its potential in sub-freezing conditions .

“ The Bayan Airag operation in Mongolia is a great example here ,” he said .

This case study – which led to the first instance of commercial implementation of GlyCat in a heap leach operation anywhere in the world – saw a 1,000-t trial heap leach take place that showcased 78 % overall gold recovery , with a 65 % reduction in cyanide and high recyclability of the glycine . Overall , due to high cyanide unit costs the operation has experienced , the total reagent costs at Bayan Airag are projected to drop by over 70 %.

Tests in high altitude locations – some that also experience sub-freezing temperatures – have also been carried out in regions such as Latin America , with GlyCat ’ s leaching ability , again , proven out .

“ Quite often with heap leaching , there are question marks about how GlyCat is going to perform in real world environments – heavy rainfall , high altitude , extreme temperatures , etc – and we ’ ve shown that it works just as well in any number of conditions ,” Briggs concluded .

Full SaL , Nuton and Cuprochlor-T

Speaking of high altitude operations , BHP will

soon start producing copper from its Full SaL heap leaching project at Escondida , located more than 3,000 m above sea level in the Atacama Desert .

The BHP-operated and 57.5 % -owned mine in Chile ( Rio Tinto owns 30 % and JECO Corp owns 12.5 %) has become the second candidate for Full SaL , a BHP-designed leaching technology , after having been successfully deployed at its Spence mine .

In the company ’ s financial year 2024 results released in August , BHP said it was on track for first production during its 2025 financial year , which runs through to June 30 , 2025 .

“ We expect capital expenditure to implement Full SaL to be circa- $ 300 million and for it to produce circa-410,000 t in copper cathodes at Escondida over a 10-year period once implemented through improved recoveries and shorter leach cycle times ,” the company said .

Full SaL ( Simple Approach to Leaching ) technology has the potential to simplify operations into one leach process instead of having to use chemical leaching for oxide ores and bioleaching for sulphides via the addition of salt ( sodium chloride ), bringing increased metal recoveries and faster leach kinetics , BHP says .

On top of Full SaL , BHP has four other leaching technologies under study or execution , with trials aiming to unlock both resource and latent capacity .

These include its own BioLeach technology that uses acid and bacterial leaching and which is already in use at Escondida ; the so-called BHP Leach with alternative reagents and increased process temperatures ; and two third-party technologies – Jetti Resources ’ catalytic leaching , in which BHP is an investor via BHP Ventures , and the Rio Tinto-owned Nuton™ venture .

The Nuton technologies are an extensive portfolio of advanced copper heap leaching technologies targeted at primary sulphide minerals ( including lower-grade mineral deposits , copper-bearing waste and tailings ), which could not otherwise be processed using traditional leaching or sulphide processing technologies . The suite of technologies is also expected to achieve higher copper recoveries on oxide and transitional material , allowing for a significantly increased copper production outcome , according to Rio Tinto .

At the core of Nuton ’ s portfolio is an elevated temperature biological leach process driven by naturally occurring microorganisms , which have been carefully cultivated and adapted to work on specific ores . Under favourable conditions , the microorganisms accelerate the copper leaching process and enable copper recoveries from primary sulphides of up to 85 %, surpassing the industry norm , Rio Tinto says .

These nature-based technologies can be deployed in greenfield , brownfield and legacy

IM November/December 2024 November/December 2024 | Page 51

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