Dissolution Kinetics of Synthetic FeCr₂O₄ in CaO–MgO–Al₂O₃–SiO₂ Slag

Abstract

Cleaner production of alloys is of great significance to the protection of the ecological environment. At present, it has received widespread attention all over the world. Chromite smelting reduction direct alloying is an important production process in the production of stainless steel, which can make full use of chromite resources, thereby reducing production costs and preventing environmental damage caused by traditional processes. In order to reveal the dissolution mechanism of chromite ore, pure phase of synthetic FeCr₂O₄, the main component of chromite ore, was used to replace the real chromite with a complex composition and the dissolution process of it was investigated. The effects of basicity (w(CaO) + w(MgO)/w(SiO₂) + w(Al₂O₃)), Al₂O₃ content and temperature on the dissolution of FeCr₂O₄ in CaO–MgO–Al₂O₃–SiO₂ refining slag were studied under high purity argon atmosphere. The composition range of the slag sample is 35%–55%SiO₂, 15–35%CaO, 10–20%Al₂O₃ and 10%MgO. The results show that the solubility of FeCr₂O₄ increases with the decrease of basicity of slag from 1 to 0.54 and then the solubility of FeCr₂O₄ decreases with the decrease of slag basicity from 0.54 to 0.33. In the low basicity slag (B = 0.54), the solubility of FeCr₂O₄ will decrease with the increase of w(SiO₂)/w(Al₂O₃) from 2.25 to 5.50. The slag system with the best dissolution is 45% SiO₂, 25% CaO, 20% Al₂O₃ and 10% MgO. The solubility of FeCr₂O₄ increases with increasing temperature from 1500 to 1600°C. Meanwhile, distribution of elements in interface of FeCr₂O₄ and slag was analyzed by EDS. During the dissolution process, Fe, Mg and Al elements form a concentration gradient on the surface of the FeCr₂O₄. The width of the gradient interval is inversely proportional to the reaction time and solubility. The dissolution kinetic of FeCr₂O₄ was also investigated. The dissolution reaction on the surface of FeCr₂O₄ was the controlled step in the dissolution process. The activation energy of the dissolution reaction of FeCr₂O₄ in this slag is 266.05 kJ·mol⁻¹.