Thermodynamic analysis of zinc ferrite (ZnFe₂O₄) formation inside the HIsarna off-gas system

HIsarna reactor is characterized by a high raw materials versatility and is therefore attractive for processing secondary iron sources. Among the materials that can be recycled through HIsarna, zinc-bearing material has drawn a special attention. Based on the plant data, once dust-containing Zinc was injected into the main reactor, a final collected dust with a zinc content of 16% was achieved which opened up possibilities of higher enrichment for direct reuse in Zn smelting as a secondary source and an alternative for Zn ore (the primary source). However Zn vapor can react with iron oxide to form zinc ferrite (ZnFe₂O₄), which is an undesired product. Hence, the main focus of this study is to minimize the formation of ZnFe₂O using thermodynamic (FactSage) and computational fluid dynamic tools. After detecting regions with high potential of ZnFe₂O₄ formation, proper geometrical and operational modifications of the off-gas system is proposed to minimize the formation of zinc ferrite.