2010 Volume 51 Issue 5 Pages 838-843
The removal of magnesium from the molten aluminum scrap containing magnesium was examined by compound-separation method using Shirasu as an additive. When Sirasu is added to the molten aluminum scrap, which is followed by agitation, MgAl2O4 and MgO are formed by the reactions among SiO2 and Al2O3 in Shirasu and magnesium in the molten scrap. It is feasible to remove magnesium by separating these reaction products as dross. The effect of addition temperature of Shirasu on magnesium removal is smaller than that of the agitation time. In the case of the addition of flaky Shirasu with 63–150 μm of particle size, the amount of magnesium removed increases linearly with agitation time because the over-all reaction is mainly controlled by a surface-controlled reaction. In the case of the addition of granular Shirasu with 300–590 μm of particle size, the amount of magnesium removed increases parabolically with agitation time because the over-all reaction is mainly controlled by a diffusion-controlled reaction. The amount of magnesium removed can be controlled by changing the amount of Shirasu added.
