GB699934A - Improved process for producing aluminium by distillation from aluminium alloys or scrap - Google Patents

Abstract

699,934. Distilling aluminium. PECHINEY COMPAGNIE DE PRODUITS CHIMIQUES ET ELECTROMETALLURGIQUES. Aug. 17, 1951 [Aug. 21, 1950; June 28, 1951No. 19436/51. Class 82(i) [Also in Group XI] In a process for directly distilling aluminium from aluminium alloys or scrap at high temperature and under high vacuum, any parts of the apparatus which come, or are liable to come, into contact with aluminium in the liquid state are made of silicon carbide, aluminium carbide or aluminium nitride. Parts coming into contact with aluminium vapour may be made of compact graphite. The process may be applied to the treatment of aluminium-iron or aluminium-iron-silicon combinations under vacuum and at a temperature higher than 1400‹C. In the apparatus shown in Fig. 1 a sloping oblong crucible c made of aluminium nitride is mounted in tapered graphite casing a which serves as an electrical resistor. The alloy to be distilled is placed in vessel c1 at the more highly heated end of the crucible and aluminium collects in vessel c2 which may be cooled by an adjacent cooling body d. Inert gases are removed and vacuum maintained' in the crucible through orifice e. By a heat-protective cover b2 the temperature in the upper part of the crucible is reduced, the vapours condensing therein and flowing downwards over the slab c5 which acts as a reflux ramp giving fractionation of the ascending vapours. The run of the reflux ramp is increased by ribs c6 which constrain the flowing liquid to a tortuous path. In the apparatus shown in Fig. 3 a tapered chamber g of circular cross section is divided into three basins h, i and j at its lower part and is heated by resistors k in its upper part, a partition l protecting the resistors from any sprayed metal. The resistors and basins are displaced away from each other from right to left giving a controlled reduction of temperature in this direction. Raw aluminium alloy is fed to the basin h through inlet g<SP>1</SP> and purified aluminium collects in basin j, condensation being assisted by a circulating water system g<SP>3</SP>. Vacuum is maintained in the apparatus through orifice g<SP>4</SP> protected by baffle g<SP>5</SP>. The arrangement gives a fractional condensation of vapours from the basin h, aluminium tending to carry over to basin j and any impurities which are present in the vapour tending to concentrate in the middle chamber i.