Dissolution of MgO based refractories in CaO-Al2O3-MgO-SiO2 slag

Dissolution of different types of MgO based refractories into molten CaO-Al2O3-MgO-SiO2 slag was studied. Formation of micro spinel particles by addition of either colloidal alumina or micro alumina powder in the MgO matrix efficiently reduced the dissolution. The dissolution of MgO was found to be controlled by the slag penetration into the MgO matrix. In the case of stagnant slag, the slag-penetration would lead to the final dissociation of the decarbonized commercial MgO-carbon cube in less than 6 min. The major dissolution took place between the MgO grains and the liquid in this penetrated layer. The increase of the thickness slowed down the dissolution. In the case of stagnant slag and slag stirred at low speed, the internal mass transfer in the slag-penetrated layer is the controlling step. At higher stirring speeds, the slag-penetrated layer was removed. The removal of the penetrated layer would enhance the dissolution process.