Dissolution Rate of Al₂O₃ into Molten CaO-SiO₂-Al₂O₃ Slags

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The dissolution rate of Al₂O₃ into the CaO-SiO₂-Al₂O₃ slag system was investigated at 1 873 K by employing a novel experimental method which involved continual measurement of the torque variation on a rotating alumina rod dipped into a molten slag. Measured torque variation was successfully related to the dissolution rate of the rod. The dissolution rate of alumina was found affected by a number of factors: the rate increased with increasing temperature, the rotating speed of the rod, the CaO content in the slag, and the Al₂O₃ content in the slag for a fixed CaO content. It was found that the dissolution rate was highly dependent on the viscosity and the diffusivity of slags. The activation energy obtained from an Arrhenius type analysis was in the range of 84 kJ mol^-1 . It was concluded that the dissolution of Al₂O₃ into the CaO-SiO₂-Al₂O₃ slag system was controlled by the mass transfer in the slag phase. An iso-dissolution rate diagram was constructed for the dissolution of Al₂O₃ into the CaO-SiO₂-Al₂O₃ slag system at 1 873 K.