Finding the Most Efficient Way to Remove Residual Copper from Steel Scrap

Katrin E. Daehn André Cabrera Serrenho Julian Allwood

The supply of end-of-life steel scrap is growing, but residual copper reduces its value. Once copper attaches during hammer shredding, no commercial process beyond hand-picking exists to extract it, yet high-value flat products require less than 0.1 wt pct copper to avoid metallurgical problems. Various techniques for copper separation have been explored in laboratory trials, but as yet no attempt has been made to provide an integrated assessment of all options. Therefore, for the first time, a framework is proposed to define the full range of separation routes and evaluate their potential to remove copper, while estimating their energy and material input requirements. The thermodynamic, kinetic, and technological constraints of the various techniques are analyzed to show that copper could be removed to below 0.1 wt pct with relatively low energy and material consumption. Higher-density shredding allows for greater physical separation, but requires proper incentivization. Vacuum distillation could be viable with a reactor that minimizes radiation heat losses. High-temperature solid scrap pre-treatments would be less energy intensive than melt treatments, but their efficacy with typical shredded scrap is yet unconfirmed. The framework developed here can be applied to other impurity-base metal systems to coordinate process innovation as the scrap supply expands.