Kinetic Behavior of Dissolution of Sintered Alumina into CaO-SiO2-Al2O3 Slags

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The effects of revolution speed, temperature and slag composition on the dissolution rate of sintered alumina into molten CaO-SiO2-Al2O3 slags were examined by the rotating cylinder method. The slags used had 10% Al2O3 and CaO/SiO2 ratios of 0.64 to 1.25.The dissolution rate of alumina into CaO-SiO2-Al2O3 slags increased with increasing revolution speed and rising temperture. It was concluded from these results that the dissolution rate was controlled by mass transport in the slag boundary layer. The dissolution rate of alumina also increased with increasing CaO/SiO2 and an abrupt increase was observed in the vicinity of CaO/SiO2=1.The addition of 15% NaF or CaF2 to slags with CaO/SiO2 ratio of 0.80 to 1.25 increased the dissolution rate by a factor of 2 to 6 compared with those of CaO-SiO2-Al2O3 slags. Such an increase of the dissolution rate is estimated to be caused mainly by the increase of mass transport coefficient.The penetration of slag components, CaO and SiO2, into an alumina cylinder was observed in all experiments. Besides, CaO·6Al2O3 compound was formed in the slag penetration layer for CaO-SiO2-Al2O3 slags with CaO/SiO2≥1.