refining the art of treating third party material
Our Townsville Copper Refinery has again recently started receiving and treating copper material from 'third party' sources allowing the refinery to produce additional cathode and utilise the vacancy in our processing capacity.
This third party material comes from a number of different sources and can often have different physical and chemical characteristics. Some may be anodes weighing around 400 kilograms while others can be in a copper block weighing one tonne, or more.
The chemical characteristics of the third party material is dependent upon the chemical composition of the concentrate used to produce the anodes and these can be significantly different to the material that is used from our own sources in North Queensland.
Kellie Whitby, Superintendent Metallurgical Process says when assessing the rate at which the refinery can treat various third party sources of copper it's necessary to take into account both the physical and chemical properties, including the chemical impurities associated with the product.
"High amounts of some copper material impurities are beneficial to the refining process while others can cause difficulties. Arsenic is a beneficial impurity for the refinery as it prevents the formation of 'floating slimes' within the process," says Kellie.
Slimes are insoluble anode impurities that settle at the bottom of electrolytic cells during the refining process. They are a valuable by-product of the refining process as they contain precious metals such as gold and silver.
'Floating slimes' are low density slimes that do not settle well and 'float' in the electrolyte solution used in the refining process. They can become stuck to the newly refined copper cathode and then trapped as more cathode is deposited. This can result in contaminated cathode containing elements such as lead, nickel and iron.
While arsenic is beneficial to the process, Kellie says other impurities such as selenium and tellurium can be troublesome as these can cause floating slimes when processed in high amounts.
Some third party anodes received have to first be remelted through the anode furnace and this allows us to blend some of the impurities with our own 'cleaner' material making it easier to process through the Tankhouse.
"When assessing the treatment of new copper material that requires remelting we create a 'blend ratio'," says Kellie.
"This is the ratio of third party material to anode scrap that will be melted in our furnace."
"The blend ratio calculates a final impurity level based on both the third party and anode scrap chemical compositions."
"We can use the ratio to produce anodes with our target impurity levels. Through test work, we are also continually re-assessing our target levels as the greater the impurity levels we can treat, the more product that is available to us on the market," Kellie says.
Recently, the Townsville Copper Refinery successfully treated different anodes from three different third party sources outside of Australia.
This is expected to continue throughout 2020 with a view to further testing and expanding the Refinery's capabilities to treat more complex materials.