Postmortem analysis of MgO–C bricks used in smelting furnace for fabricating TiC-bearing slag

Abstract

The process of “high temperature carbonization and low temperature chlorination”, considered as one of the most promising technologies, can extract over 60% titanium from blast furnace slag containing TiO2 at a concentration of 20%–25%. The primary equipment for high temperature carbonization is an electric furnace lined with MgO–C bricks. In this study, post-mortem analysis was conducted to investigate the corrosion and failure mechanisms of MgO–C refractory bricks taken from different areas of a circular electric furnace after 1200 cycles of service. Through XRD, SEM-EDS, and thermodynamic calculation analysis, the reaction and corrosion mechanism between MgO–C bricks and the slag were analyzed. The results demonstrated that the gradual corrosion of the brick was primarily attributed to the alternating effects of carbon oxidation and MgO dissolution. Moreover, an increase in temperature led to a higher corrosion rate of the refractories. At temperatures exceeding 1560 °C, the pre-formed barrier layer composed of MgAl2O4 and MgTi2O4 melted into the slag. And as TiO2 content decreased and TiC content increased, there was a gradual decline in the erosive impact of the slag. Furthermore, the failure mechanisms of refractory bricks in different areas varied due to the distinctive structure of the electric furnace. The bricks at the slag line area were mainly destroyed by slag corrosion, oxidation and thermal shock spalling, which had the shortest service life.