DRDGOLD Limited (NYSE:DRD) (JSE:DRD) (FRA:DUBA) reports that the new copper elution circuit at its Far West Gold Recoveries (FWGR) surface retreatment operation southwest of Johannesburg, is expected to deliver an additional 1.2 kilograms (kg) to 1.8kg of gold per month.
The company said the additional gold would otherwise have been lost to refining charges.
DRDGOLD said FWGR is currently retreating material reclaimed from the Driefontein No. 5 dam. The material reclaimed contains high levels of copper, which competes with gold and co-adsorbs onto activated carbon. Copper and gold are removed from the carbon and subsequently recovered together in the electro-winning process.
A consequence, the company said, has been that gold purity in the bullion has been low due to high levels of copper. Copper in bullion incurs penalty charges of between 1 and 5% at refinery level; FWGR has been allocated on average 98% of its gold production in the past, with 2% lost to refining charges.
To remedy this situation, FWGR conducted test work to determine how to reduce the copper levels in its bullion. This test work indicated that up to 74% copper could be desorbed from carbon without significantly desorbing gold.
Further, it showed that, if FWGR were to achieve bullion purities above 60%, the refinery’s gold allocation would shift upward from 98% to 99.5%.
DRDGOLD said this led to the construction and commissioning of the copper elution circuit to improve FWGR’s payable gold content. Construction began in January 2021, commissioned in May and a steady-state operation was achieved in June.
The initial plant results show that, on average, 69% of the copper is stripped from the loaded carbon. The first smelt contained mostly copper-eluted carbon and yielded a gold purity of 48.76% compared to the previous five smelts, which averaged 33.64%.
The second smelt went to 50% purity and was able to get 99% payable content, and the third smelt achieved 53.6%, again achieving 99% payable content.
DRDGOLD said the goal is to move to 60%, at which point FWGR will receive 99.5% payable content.
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