Dissolution behavior of spent MgO–C refractory in the CaO–SiO2–FeO slag system as a steelmaking flux

A large amount of spent MgO–C refractory is generated in steel plant every year. Because of the similarities in chemical and mineralogical composition of slag formers and MgO–C refractory, it is possible to reuse the spent MgO–C refractory as a steelmaking flux. To achieve this goal, it should promote the dissolution of MgO–C refractory during slag forming. In this study, the effect of slag composition on the dissolution behavior of spent MgO–C refractory in the CaO–SiO2–FeO slag system and the dissolution kinetics were investigated. It showed that the dissolution rate of MgO–C refractory was controlled by surface chemical reaction. The dissolution of MgO–C refractory led to an increase in the MgO content in slag while the FeO content decreased because the graphite in refractory was oxidized by FeO. Increasing temperature significantly promoted the dissolution of MgO–C refractory. The MgO–C refractory was readily dissolved in the low-basicity slag. A higher FeO content in slag was beneficial for the oxidation of graphite in refractory, resulting in better dissolution. The dissolution thickness of MgO–C refractory could exceed 4.0 mm under these conditions and its dissolution supplied some MgO to slag.