GB1428146A - Purification of aluminium - Google Patents

Abstract

1428146 Refining aluminium ALUMINUM CO OF AMERICA 13 Sept 1973 [18 Sept 1972] 43125/73 Heading C7D Molten aluminium and aluminium alloys (e.g. Al-Si alloys and scrap aluminium) are refined by introducing chlorine containing gas at least 10" below the surface of the molten aluminium contained in a chloridization chamber while maintaining agitation conditions at the chlorine introduction site such as to produce a substantially uniform distribution of small gas bubbles throughout the melt and to avoid any shearing of the molten metal into streams of droplets and thereby to prevent emulsification of molten aluminium and chloride salts of metal impurities (e.g. Mg, Sr, Li + K) and to degas the melt. The chlorine may be introduced through conduit 56, Fig.1, in shaft 52 so that it enters chloridization chambers 12 and 16 through turbine impellers 54. The so formed chloride salts form a layer 20 above the molten metal which passes through settling chamber 24 and into outlet chamber 26, the average residence time in the reaction zone being 2-6 minutes. The chloridization and settling chambers may be heated and several different configurations of chloridization chamber, settling chamber and baffles are described. The process may be carried out under a dry non- reactive atmosphere (e.g. N 2 , Ar, CO 2 or inert gas) and the chlorine containing may be provided in an amount which is at least the stoichiometric amount required for reading with the metallic impurities and may additionally comprise a non- reactive gas (e.g. inert gas, N 2 or CO 2 ) to provide sufficient gas for the required agitation conditions which are governed by the shape and dimensions of the chloridization chamber and turbine impeller (examples are disclosed) and by the depth of the salt layer which may be controlled by skimming.