Abstract
The sintered MgO (porosity 29.9% and 13.0%) was immersed into molten FetO-CaO-SiO2 slags at temperatures from 1 350 to 1 425°C and the dissolution rate of MgO was determined with the rotating cylinder method by measuring the decrease of the cylinder radius. Also, the section of the MgO cylinder after immersion was examined by EPMA to know the penetration of slag and the dissolution mechanism.
The results obtained are as follows :
(1) The dissolution rate of MgO was increased with the rotating speed of cylinder and with temperature, and was found to be controlled by mass transport in the boundary layer of molten slag.
(2) The change of mass transfer coefficient at 1 400°C with slag composition was correlated well to the change of kinematic viscosity of slag. Utilizing the nondimensional correlation found in literature, the values of diffusion coefficient of MgO into molten slags were estimated to be 1.0×10-53.0×10-5cm2/s at 1 400°C.
(3) The dissolution of MgO proceeded through the formation of (Fe, Mg)O solid solution layer at the interface and its dissolution. The penetration of slag was retarded by this dense (Fe, Mg)O layer and the depth of penetration after 560 min was only 13 mm in high porosity MgO and <1 mm in low porosity MgO.
