Up-concentration of chromium in stainless steel slag and ferrochromium slags by magnetic and gravity separation

Currently, about 75% of the chromium (Cr) is being imported in the EU. In the value chain of stainless steel production, significant amounts of Cr are lost in ferrochromium (FeCr) slags and stainless steel (SS) slags. In a slag, Cr is mostly present in entrapped metallic particles (Fe-Cr alloys) and/or in stable spinels. Cr concentrations in SS and FeCr slags are in the range of 1-2% and 2-8%, respectively. To unlock the potential of these low-grade resources, a new approach to metal recovery must be deployed. The available technologies for recovering Cr from Cr-containing raw materials (both primary and secondary) are mostly based on roasting at high temperatures (>1000°C), what incurs high processing costs. Due to the high energy consumption, using such technologies for the recovery of Cr from low grade materials would not be economically feasible. It is obvious that in order to valorize low grade materials such as SS slags and FeCr slags, Cr up-concentration by physical separation needs to be carried out. The European H2020 project CHROMIC (GA No 730471) aims to develop a process for recovering Cr from SS and FeCr slags based on the smart integration of physical separation and subsequent pyro- or hydrometallurgical treatment. Results of physical separation show significant Cr up-concentration by using magnetic separation and gravity separation techniques, where Cr content can be increased almost by a factor of 4.