Effect of Industrial Waste Fluxes (Red Mud and White Mud) on Dephosphorization and Refractory Corrosion: Applications to Electric Arc Furnace Process Using Direct Reduced Iron

Abstract

The effect of industrial waste flux addition on dephosphorization of molten steel and refractory corrosion(-protection) by electric arc furnace (EAF) slag using direct reduced iron (DRI) at 1823 K (1550 degrees C) was investigated. The activity of CaO and FeO is the thermodynamic driving force for dephosphorization, but it decreased with the use of DRI due to increased SiO2 content in the slag. Industrial waste fluxes were added to the slag to minimize refractory corrosion and improve dephosphorization efficiency. Red mud (RM) and white mud (WM), which are generated in the process of manufacturing aluminum hydroxide from bauxite using the Bayer process, were used as fluxing materials. The RM and WM mainly consist of Fe2O3 and CaO, respectively, and these positively affect the dephosphorization. Dephosphorization efficiency increased as industrial waste fluxes addition increased (3 to 7 mass pct). At the same time, the effect of industrial waste fluxes on the refractory corrosion-protection behavior was confirmed by considering the change in thickness of the magnesiowustite (MW) layer that formed at the interface between the 'FeO-rich' EAF slag and the magnesia refractory. Experimental results confirmed that 3 to 4 mass pct WM addition in the slag can compensate for the dephosphorization efficiency while minimizing the refractory corrosion in the EAF process using 20 pct DRI as an alternative iron source.