CRYSTALLISATION METHOD FOR THE PURIFICATION OF A MOLTEN METAL, IN PARTICULAR RECYCLED ALUMINIUM

摘要

Method for the purification of a molten metal, the molten metal having a specific density and comprising one or more foreign elements which are to be removed, the method comprises the steps of : (a) a cooling step wherein the molten metal is cooled to a eutectic temperature to simultaneously form purified metal crystals and crystals comprising at least one foreign element, and (b) a separation step wherein at least some of the purified metal crystals are separated from the crystals comprising at least one foreign element by adjusting the specific density of the molten metal within a range delimited by a lower value being the specific density of the purified metal crystals and by an upper limit being the specific density of the crystals comprising the at least one foreign element, and wherein the specific density of the molten metal is adjusted to this range by the addition of a metal to alter the specific density of the molten metal and maintained within this range during separation. The proposed method is advantageously applicable for the purification of aluminium melts from recycle aluminium and aluminium scraps.