A game changer for copper processing

FLSmidth's operations at Salt Lake City in the United States

FLSmidth’s Rapid Oxidative Leaching (ROL) technology is facilitating and maximising clean copper production from hard-to-process and arsenic-heavy concentrates.

Designed to operate at 80 degrees and normal atmospheric pressure – two characteristics that enhance safety compared with traditional smelting – FLSmidth’s Rapid Oxidative Leaching (ROL) process is both faster and simpler.

It can leach more than 98 per cent of the copper from chalcopyrite concentrates in less than six hours. Existing atmospheric leach processes leach a maximum of 95 per cent copper in 20-60 hours.

According to FLSmidth, ROL technology is a more efficient and profitable alternative to selling concentrate to smelters for removal of the arsenic and extraction of the copper.

The 2016 winner of the prestigious global R&D 100 Award, the ROL technology is being developed by FLSmidth’s research and development division. A pilot plant at the facility includes four scaled reactors, which enable batch and continuous operation of the ROL process.

Currently 10-litre and 100-litre continuous stirred tank reactors in series with stirred media reactors (SMRt) are being used to test the process in batch leaches and have delivered positive results.

SMRt reactors are used to mitigate passivation of the chalcopyrite copper concentrates. Included with each apparatus is equipment used in measurement and control of temperature, the potential of hydrogen (pH), REDOX potential and oxygen addition, as well as a sample tracking system.

The ROL process uses a Mechano-chemical leach to overcome passivation and the company aims to deliver a pregnant liquor solution that will match with the new generation reagents being developed by chemical companies to maximise the potential yield from hard-to-process and arsenic-laden concentrates.

According to the company, the ROL process can be used to economically produce copper at a range of throughputs.  Small to mid-tier miners can develop smaller deposits or supplement ageing heap leach operations and produce 5000 to 150,000 tpa cathode copper at the mine rather than selling their concentrate to a smelter.

FLSmidth’s ROL technology offers benefits across several ore types.

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

This ROL technology makes it possible to recover more copper from low- to mid-grade concentrates. Also, there are known mineral deposits, yet to be developed, that are unsuitable for smelting, but would be suitable for leaching with the new technology.

ROL also makes it possible to develop mineral deposits containing arsenic for recovery of copper, gold and silver, while complying with stringent environmental air and land pollution regulations.

As the technology operates at atmospheric pressure a concentrate can be treated at the mine site with complete control over the arsenic-bearing residues generated after leaching.

This makes it possible to avoid the potential for arsenic contamination of sea, air and land during transport to a smelter, or as a consequence of the smelting process.

ROL could be considered revolutionary technology but it is a technology that, according to Manfred Schaffer, group executive vice president of FLSmidth’s minerals division, will deliver economic and productivity benefits to the copper sector internationally.

“Many existing mines are holding tonnes of copper concentrate with more than 0.5 per cent arsenic concentrations, which is too high for smelting. Our technology can be used to process those tonnes of high-arsenic concentrate into saleable product or even make it possible to develop new deposits that are high in arsenic,” Schaffer explained.

This article also appears in the April edition of Australian Mining.

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