Glencore's Mount Isa copper smelter has started using a technique called silica banking in the Pierce-Smith Converters to improve its overall copper yield and reduce the amount of valuable copper lost to waste.
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Within the Copper Smelter, the Peirce-Smith Converters take copper matte, an intermediary product from the primary smelting stage, to produce two products, skim and blister copper (almost pure copper).
Skim is an iron and copper oxide slag (waste by-product) created during smelting through reactions from the copper in the Pierce-Smith Converters (stage 2) and Anode Furnaces (stage 3).
Despite being a waste by-product, skim is rich in copper, often containing between 50 to 60 per cent of the valuable metal.
Skim can re-enter the smelting process at the converter stage to extract the copper, however, the smelter's production of skim often outweighs its capacity to re-process it, resulting in an imbalance and accumulation of skim in stockpiles.
Silica banking is helping the smelter work towards improving the efficiency of separation between skim and the blister copper at the converter stage, improving the operations overall copper metal yield.
Copper Smelter Plant Metallurgist Michael Carkeet said that without this step the skim travels with the blister copper to the next stage of the process where it contributes to further skim and slag production.
"If we can contain skim within the Peirce-Smith Converter, with the aid of silica banking, we can convert it into copper and freely separate the iron slag," Mr Carkeet said.
Using a specially fabricated 'charging boat', the converter aisle crane pours two to three tonnes of course silica behind the lip of the converter vessel to create a physical dam or 'bank' which retains the skim in the converter vessel and allows the copper metal to pour underneath into the anode furnace pot.
The idea to trial silica banking at the Mount Isa Copper Smelter came from one of Glencore's overseas smelting operations.
"It was something the Altonorte Copper Smelter (Chile) was already doing and with great success, so we were able to reach out to their Metallurgical team and develop a plan for our smelter," Mr Carkeet said.
"The initial silica banking trials have far exceeded our expectations, and while we've only been employing the process for a short time, it's proving to be a valuable part of our metallurgical production process."
Smelting and Refining General Manager Adrian Herbert said the silica banking project is improving the efficiency and longevity of metallurgical assets.
"The Copper Smelter team started silica banking in August last year and we are already reaping the benefits with a noticeable improvement in our copper recovery," Mr Herbert said.
"We can create more copper anode from the same volume of concentrate that we process through the smelter".
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