Modern Mining March 2015

GOLD

new fine-grind process, which involves milling the slurry material with tiny beads using four vertical stirred mills (sourced from FLSmidth). At this stage the milled product, 80 % of which is smaller than 24 microns, has been liberated from the sulphides, making recovery of the pre- viously encapsulated gold easier as it comes into contact with cyanide during the CIP pro- cess that follows. The dissolved gold is adsorbed onto acti- vated carbon and the ‘loaded carbon’ in each circuit enters the carbon treatment section where the gold is eluted from the carbon. The carbon then returns to the CIL circuit via a regeneration kiln. Once the gold has been eluted, it undergoes electro-winning where the gold is precipitated, calcined and smelted in the existing smelthouse. What comes next after the FFG? Pretorius told the media group that DRDGOLD would now focus on optimising its high grade opera- tion further and that it was also planning lifting production by up to 300 000 tonnes a month by bringing the 21 Mt Van Dyk tailings dam resource into the feedstock mix, a low capex (R23 million) project which would involve

refurbishing five tanks within the CIL section at Brakpan. Finishing his presentation to the media, he said DRDGOLD had an operational profile far closer to that of a processing facil- ity than a conventional mine and that it would continue to pursue innovative technologies to enable it to efficiently and profitably treat the huge – but increasingly lower grade – resources to which it had access and which total some 750 Mt of material. Photos by DRDGOLD unless otherwise acknowledged

The flotation section produces two streams. One stream, the flotation concentrate, contains the sulphides which are enriched with gold while the second stream, the flotation tails, is made up of lower-grade material which is treated in a conventional CIL process (photo: Arthur Tassell).

March 2015  MODERN MINING  23