Engineering company FLSmidth says its new FLSmidth Rapid Oxidative Leach technology can help copper mines increase their output by 3%.

“That would mean an extra $40-million a year in income for an average copper mine with primary sulphide ore,” says FLSmidth research and development group head Jens Almdal.

FLSmidth says the new technology, for which the patent is still pending, is expected to be implemented on a large scale in 2017.

The hydrometallurgy process of the FLSmidth Rapid Oxidative Leach technology can economically remove the passivation layer of primary suphfides, thereby allowing the extraction of copper.

The technology operates at atmospheric pressure and temperature which make it possible to leach directly at the mine and, hence, provide a seamless transition from oxide ore to sulphide concentrates.

Almdal says the FLSmidth Rapid Oxidative Leach process can leach more than 98% of copper from concentrates containing as low as 8% copper in less than six hours – which is a faster and much simpler process.

For a copper mine with remaining low-quality copper deposits producing around 200 000 t/y of copper, our 3% output increase would mean the extra $40-million a year at a copper price of around $6 600/t.”

He says this is a significant contribution to profitability in an industry that normally chases 0.1% to 0.2% increases in copper recovery by design modifications of flotation machinery.

For copper producers, the technology could mean a renewed business case for remaining deposits as several existing mines have lost the ability to make copper concentrates that are suitable for smelting, says Almdal.

He adds that the FLSmidth Rapid Oxidative Leach technology also makes it possible to develop mineral deposits that may be unsuitable for smelting.

The top ore layer of an openpit copper mine is easily processed using heap leach in tandem with solvent extraction and electrowinning to produce copper cathodes.

The copper mineral most predominant in mines is chalcopyrite, a refractory sulphide mineral that is found deeper in the mine.

Consequently, mining companies struggle to maintain copper production during the transition from oxide ore to sulphide ore, as openpit mines reach the later stages of development. Mining companies also struggle to recover copper from low-grade concentrates and from concentrates contaminated with arsenic.

Exploring Previously Unused Deposits
Meanwhile, FLSmidth minerals division president Manfred Schaffer notes that the FLSmidth Rapid Oxidative Leach technology also makes it possible to develop mineral deposits that contain arsenic for the recovery of copper, gold and silver, while complying with environmental air and land pollution regulations.

As the new technology operates at atmospheric pressure, a concentrate can be treated at the mine location, with complete control over the arsenic-bearing residues generated after leaching, making it possible to avoid the potential of arsenic contamination of sea, air and land while the minerals are being transported from the mine to the smelter.

“A lot of existing mines have piles of copper concentrate with more than 0.5% arsenic concentrations, which is too high for smelting. Our technology can be used to process these piles of high arsenic concentrate or even make it possible to develop new mineral deposits high in arsenic,” says Schaffer.