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Mount Isa Copper Smelter banks results thanks to silica

The Copper Smelter at Glencore’s Mount Isa Mines has started using a technique known as silica banking within the Pierce-Smith Converters. The technique will improve overall copper yield and reduce the amount of valuable copper lost to waste.

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.

Course silica is dried out completely before being added to the Pierce-Smith Converter.
The Pierce-Smith Converter.

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.

With the implementation of silica banking, the Copper Smelter is working towards improving the efficiency of separation between skim and the blister copper at the converter stage, thereby improving the operations overall copper metal yield.

Copper Smelter Plant Metallurgist, Michael Carkeet, explains 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.

Silica is added to the Pierce-Smith Convertor ‘mouth’.
Skim is transported to the slag dam by specialised vehicles known as Kress Haulers and cooled using water.

“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,” Michael says.

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’. This dam 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, emphasising the importance of knowledge sharing.

Copper Smelter Plant Metallurgist Michael Carkeet inspects cooled and hardened skim which is broken into small pieces so it can be re-processed through the Copper Smelter.
The idea to use Silica Banking at our Mount Isa Copper Smelter came from Glencore’s Altonorte Copper Smelter in Chile (pictured).

“It was something the Altonorte Copper Smelter 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,” says Michael.

“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.”

Copper Smelter Plant Metallurgist Michael Carkeet talks about the process of silica banking.

Smelting and Refining General Manager, Adrian Herbert, says the silica banking project is one of the many ways we are looking to improve the efficiency and longevity of our metallurgical assets within Queensland Metals.

“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,” says Adrian.

“Simply put, we can create more copper anode from the same volume of concentrate that we process through the smelter”.

“It’s great to see a team working together like this, challenging the status quo and coming up with innovative ideas that will help to ensure the sustainability of our metallurgical assets across Queensland Metals,” Adrian says.