Silica step enhances copper smelter yield
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 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,” copper smelter plant metallurgist Michael 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.”
Within the copper smelter, the Pierce-Smith Converters take copper matte – an intermediary product from the primary smelting stage – to produce two products: skim and blister copper (almost pure copper).
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 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 to improve the operation’s overall copper metal yield.
Mr Carkeet said that without this step the skim travelled with the blister copper to the next stage of the process where it contributed to further skim and slag production.
“If we can contain skim within the Pierce-Smith Converter, with the aid of silica banking, we can convert it into copper and freely separate the iron slag,” he 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’.
This dam retains the skim in the converter vessel and allows the copper metal to pour underneath into the anode furnace pot.
Smelting and refining general manager Adrian Herbert said the silica banking project was one of the many ways Glencore’s Queensland Metals was looking to improve the efficiency and longevity of its 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,” he said.
Below: The Pierce-Smith Converter at the Mount Isa copper smelter.