Influence of FeO/SiO2 ratio of ZnO-rich fayalite slags on the degradation of magnesia-chromite refractories under reducing atmosphere

The objective of this work is to investigate the influence of the FeO/SiO2 ratio of ZnO-rich fayalite slags on the corrosion behavior of magnesia-chromite refractories under reducing atmosphere. Rotating finger tests were performed with a direct-bonded magnesia-chromite refractory submerged in ZnO-rich (20 wt.%) secondary smelting copper slags (ZnO-FeO-SiO2-Al2O3-CaO) in a vertical tube furnace under reducing atmosphere at 1200°C for 4 h. The degradation behavior of the magnesia-chromite refractory is determined through microstructural and chemical characterization of the corroded fingers with Scanning Electron Microscopy (SEM) and Electron Probe Micro Analysis (EPMA). Both periclase and chromite grains are more severely attacked by the slag with lower FeO/SiO2 ratio, as concluded from the higher amount of dissolution of the MgO grains and from the more severe reactions between slag and primary chromite grains and the consequent delamination of the formed ZnO-containing spinel. The results show that from a furnace lining protection viewpoint, the use of ZnO-containing fayalite slag with a higher FeO/SiO2 ratio would be beneficial in secondary copper smelting.status: publishe