Recovery of Valuable Materials with the RecoDust Process

The RecoDust process is a pyrometallurgical process for treating steel mill dusts that cannot be recycled internally due to their zinc content, providing numerous benefits compared to conventional processes. State-of-the-art processes often face the problem of recycling only zinc, but not iron, which is frequently landfilled and withdrawn from a closed loop. Furthermore, these processes are also often limited to a specific zinc content in the feedstock. Within the described RecoDust smelting campaigns, basic oxygen converter dust with about 15 wt.% zinc was taken as feedstock. After high-temperature treatment of the input material, the RecoDust slag (RDS) has a zinc content of 0.4 wt.% and the crude zinc oxide (CZO) has a ZnO content of up to 80 wt.%. The RDS is suitable for use in the sinter plant as a secondary raw material. To investigate the influence of adding RDS to a common sintering mixture, sintering pot tests followed by RDI (reduction disintegration indices) tests were carried out. The influence of the admixture of RDS on the RDI values is not detectable. The CZO was fed into a soda extraction system for halogen removal. The halogen removal of this two-stage leaching was highly efficient with over 90% for chlorine.