Influence of Slag Chemistry on the Dissolution of FeCr₂O₄ in CaO–SiO₂–Al₂O₃–MgO Slag with Graphite Crucible

Abstract

The effect of Al₂O₃ and SiO₂ content and basicity (w(CaO) + w(MgO)/w(SiO₂) + w(Al₂O₃)) on the chromite ore dissolution in CaO–SiO₂–Al₂O₃–MgO slag system was studied under the condition of 1550°C. The results show that the increase of basicity (R = 0.54, 0.67, 0.82) results in the reduction of the dissolved amount and dissolution rate of chromite ore in the slag. The dissolved amount of Cr in lower basicity slag (R = 0.54) is about 1.5 to 2 times higher than that in higher basicity slag (R = 0.67, R = 0.82). The dissolved amount of Cr tends to increase when the Al₂O₃ mass content decreases from 20% to 15%. While as the Al₂O₃ mass fraction continues to decrease from 15% to 10%, the dissolved amount begins to decrease. This may be related to the viscosity of the slag. The spinel phase tends to form on the surface of the unreacted FeCr₂O₄, thus hindering the further dissolution of FeCr₂O₄. After starting to dissolve, the FeCr₂O₄ decomposes into FeO and Cr₂O₃ dissolving in the slag. The FeO in the slag is preferentially reduced to metal iron attached to the surface of the FeCr₂O₄. The main forms of Cr element in the slag are CrO and Cr₂O₃, and the proportion of these two depends on the composition of the slag and the experimental environment. The proportion of CrO in the slag with lower basicity is larger. In the experiment, the maximum solubility of FeCr₂O₄ in 60 min was obtained in the slag system with 45% SiO₂, 15% CaO, 20% Al₂O₃ and 20% MgO.