GB583831A - New or improved apparatus for the refining or recovery of aluminium - Google Patents

Abstract

583,831. Electrolytic recovery of aluminium; fused electrolyte apparatus. AERLEC (ALUMINIUM), Ltd., and PARRY, E. A. Nov. 25, 1944, No. 23526. [Class 41] A cell for the recovery of pure aluminium from alloy scrap containing, for example, not less than 80 per cent. of aluminium with relatively small amounts of copper or other metals by the three layer process comprises an electrolysing chamber 10 communicating by a submerged passage 13 with a reservoir chamber 11 for molten crude metal which may be fed from a pouring trough 29. Electric heating elements 14, 15 are arranged in vertically spaced zones round both chambers ; these may be tungsten steel wires enclosed in hard glass or silica tubes' and embedded in the walls. Surrounding both chambers and the heaters is a jacket 17 consisting of a double-walled shell of steel plate the interior of which is connected to a vacuum pump or is alternatively exhausted initially and sealed. The shell is set in a housing of insulating brickwork enclosed in an outer steel casing 19. The bottom of both chambers consists of a graphite plate 22 cemented by creosote pitch .and coke dust to a carbon block 23 to which the anode connection is made by a copper bus-bar 24 having lateral extensions. Connection to the cathode layer is made by a vertically movable graphite plate 26 of the same length as the electrolyzing chamber and one-eighth its width. Pure aluminium is removed from the cathode layer by ladling or by syphoning through silica tubing. The several zones of the heating elements are controlled by independent switches so that one or more may be connected selectively and successively to induce connection currents. The sides of the electrolyzing chamber are concave as shown, to promote movement of the electrolyte and prevent formation of a crust. The walls of the chambers may be of magnesia tiles or magnesia cement plaster. An adjustable auxiliary cathode 27 may be provided in the reservoir chamber to assist in melting the electrolyte when starting up. The cell is separated from its base 20 by a layer 21 of asbestos. To form the cathode layer a high purity aluminium tray with long handles at each end is lowered on to the surface of the molten electrolyte and pure molten aluminium poured into it whereupon the tray melts. The scrap metal to be fed to the. reservoir 11 may be melted in a tiltable crucible housed in the heat-insulating brickwork of the cell; alternatively, in a plant comprising a number of cells, the scrap metal may be fed to them by an overhead conveyer system. The cells may be connected in series. The anode layer should contain not less than 30 per cent., preferably 33 per cent., of copper at starting ; when the aluminium content of the layer is reduced to about 11 per cent., the alloy is run off by a tap not shown or is removed by ladling and renewed. A cover, not shown, is provided which may consist of a hollow steel member packed with indurated asbestos fibre.