Effects of transition metals on the kinetics of slag-refractory reactions

The dissolution kinetics of dense alumina discs in calcium aluminosilicate based melts was determined with a rotating disc technique at 1560 degreesC to 1590 degreesC, under a controlled atmosphere of Ar-CO-CO2. The effects of rotation speed and the concentration of iron and manganese oxides on the dissolution rate of alumina into slags were measured by monitoring the concentration of species in the slag. Analysis of the results obtained indicated that at low concentrations of these transition metal oxides in 53 pct CaO-5 pet MgO-12 pet SiO2-30 pet Al2O3 slags, the dissolution rate is most likely controlled by mass transfer in the slag phase. The rate data obtained also showed that the addition of iron oxide or manganese oxide results in considerable increase in the mass transfer by increasing the apparent diffusivities of species in the slag. Comparison of these results with published data on the diffusivities of species in similar slags are made and practical implications of the findings are briefly discussed.