Process for cleaning and purifying molten aluminum

A process for treating molten metal with a particulate treating agent which comprises the steps of:

• (a) providing a melt of a metal in a treatment vessel,
• (b) providing a mixing impeller within the treatment vessel beneath the surface of the molten metal, the impeller being selected from the group consisting of a plate with a series of spaced blades extending upwards from a surface of said plate and a flat plate with a series of spaced blades extending downwards from the surface of said flat plate, said impeller being adapted to provide high shear mixing with minimum vortex, and
• (c) while rotating the impeller on a substantially vertical axis, feeding particulate treating agent together with a small flow of inert gas downwardly through an injection tube below the surface of the molten metal adjacent the upper or lower surface of the impeller in a region between the axis and the periphery of the impeller, whereby the treating agent in the form of molten or partially molten droplets is subjected to a high shearing action causing the treating agent to be quickly formed into finely divided droplets within the molten metal.