Abstract
The treatment of arsenical and other high impurity copper concentrates is an ongoing problem in the copper industry, with decreasing grades and increasing impurity levels in many deposits.
Pressure leaching of copper concentrates has been touted for decades as an alternative technology to smelting. Initially, this was based on the potential to reduce airborne emissions and/or the investment in gas handling systems in existing smelters, but recent developments have shifted the focus towards the use of pressure leaching as an alternative for processing high arsenic concentrates. However, while pressure leaching technologies have no airborne emissions, many technologies struggle to achieve high copper recoveries or highly stable residues when processing high arsenic feeds and/or struggle to integrate effectively with copper heap leaching operations. High silver recoveries from the leach residues may also come at the expense of the environmental stability of the residues produced.
Sherritt’s Dilute POX process overcomes the majority of these issues, with high copper recoveries and highly stable arsenic residues produced from copper concentrates with up to 7 wt% As, high gold and silver recoveries by direct cyanidation, and potential for integration with heap leaching operations. Copper can be recovered as cathode, or can be recovered as a high grade, arsenic free copper sulphide smelter feed.
A technology that can process high arsenic materials with lower copper grades has the potential to produce a paradigm shift in how copper mines process their ore or how new deposits are developed. If used in conjunction with differential flotation, copper miners would be able to maximize the flow of clean, higher grade concentrate as smelter feed and divert a much smaller flow of lower grade, high impurity concentrates to pressure leaching. This approach has the potential for improved returns on their products or recoveries from their deposits, while limiting capital investment. Similarly, this would reduce the impurity load on existing smelters and/or reduce potential investments in gas treatment or impurity handling.