HEAP LEACHING
Mining marginal gains
GlyCat can reduce cyanide consumption by 75 % in a lot of cases , according to Draslovka
Miners are finding a market opportunity to leverage their own leaching innovations , Dan Gleeson reports
The heap leaching sector is one that works on fine margins , with reductions in recoveries , increases in reagent costs , additional heap stabilisation methods and the like having big impacts on an operation ’ s bottom line .
The sustainability agenda has also added another layer to this variability , with many stakeholders looking for alternatives to traditional cyanidation processes .
This backdrop makes for a market dynamic that encourages innovations , many of which are covered in this article .
Real world performance
Draslovka says it offers a range of sustainable solutions to the global mining industry , and its glycine leaching technology ( branded as its GlyLeach™ and GlyCat™ processes ) represents the best environmentally-friendly alternative to traditional acid and cyanide leaching .
Due to its selectivity over gangue minerals and the recyclability of glycine , glycine leaching use enables the recovery of both base and precious metals from lower-grade resources like tailings , leading to a more sustainable production process and improved economics .
Jackson Briggs , Senior Product Manager , Leaching Technologies , says the heap leaching sector represents one of the biggest market opportunities for the company , spelling out two particular applications in particular for its GlyCat product , meant for gold specifically .
“ The first is heap leaching operations that have high or rising cyanide consumption ,” he told IM . “ These would be operations that , having exhausted the oxide ores , are moving into transitional or sulphide ores that come with higher processing complexity , higher cyanide consumption and , related to that , higher operating costs .”
GlyCat ’ s ability to reduce cyanide consumption – by up to 75 % in many cases , according to Briggs – can lead to reduced reagent costs as much of the glycine is recycled and the original cyanide doses needed for an effective leaching process are rationalised .
“ Cyanide can represent 40-50 % of operating cost for heap leaching in some instances ,” he said . “ The ability to reduce that consumption by 75 % in a lot of cases and replace it with a recyclable reagent makes a significant impact on the operation .”
The other potential area where Briggs sees a major opportunity is with older heap leaching operations that are close to end of life .
In this transitory period , operators would typically rinse the heaps with water to leach the cyanide out . This process can , Briggs says , sometimes take five to 15 years as part of a
BHP expects to produce circa-410,000 t in copper cathodes at Escondida over a 10-year period once Full SaL is implemented through improved recoveries and shorter leach cycle times closure and reclamation process . “ By using a sustainable reagent like GlyCat instead , you can reduce this leaching time , while , at the same time , boosting the amount of gold recovered thanks to GlyCat ’ s catalytic properties ,” he said .
“ In fact , if you start using GlyCat prior to that end of life process , you are decreasing the amount of cyanide in the heap to begin with meaning your closure and reclamation period will be shorter than it would have been otherwise .”
An emerging use case in the heap leaching space is the ability to add “ uneconomic ” heap leach pads to leaching complexes through the application of GlyCat .
Briggs expanded on this : “ Heap leach operations typically involve multiple deposits and multiple heaps that are being stacked on pads . Sometimes you will have a deposit that is not the best fit for heap leaching on a larger property where the majority are . GlyCat ’ s properties enable operators to take that deposit and , by reducing the operating cost , turn it into one that is economically ‘ heap leachable ’.”
The sustainability side is key here too , with regulators in many mining hubs insisting on certain weak acid dissociable ( WAD ) cyanide levels that , with increasingly complex deposits coming to the fore , may not be met via traditional cyanidation .
“ With GlyCat , we ’ re able to significantly reduce the amount of WAD cyanide generated , which is a major win upfront ,” Briggs explained . “ Then over the life of the heap , if you are using GlyCat with cyanidation , you are reducing the amount of cyanide that goes in , which means you are reducing the amount of cyanide staying in the pad . You have less cyanide in general getting to the mine , as well as a lower threshold in the pad to get to that reclamation point .
“ Lower concentrations naturally lead to lower environmental risks associated with cyanidation .”
In pilot and industrial scale trials , Draslovka
48 International Mining | NOVEMBER / DECEMBER 2024