GB208711A - Improvements in or relating to electrolytic refining of metals - Google Patents

Abstract

208,711. Aluminum Co. of America, (Assignees of Hoopes, W.). Dec. 21, 1922, [Convention date]. Aluminium, obtaining. - A cell for refining metals is provided with an electric insulating lining 41, by fusing therein material, such as a mixture of fluorides, which solidifies at a suitable temperature and cooling the bides of the cell to cause a crust to be formed thereon, while maintaining electrically neutral a portion of the cell surface above an electricallyseparated lower portion. The cell comprises a metal shell divided horizontally into two sections 10, 13, insulated from one another, the former section being connected to a source of current. Water-jackets 14, 12a connected in series, are arranged as shown, the flow and return pipes and the connecting pipe between the jackets consisting of rubber hose pipe. The section 10 is provided with a heat-insulating layer 28 of bauxite, alumina, magnesia or refractory bricks and a bowl-shaped lining 29 of carbon. The latter is made by tamping into the shell a mixture of tar, pitch and granular or powdered cake when in a plastic condition and then baking in an'oven at 600‹ C. Conductor plates 33 are bolted to metal pads 32 on the section 13, and metal plates 31 welded to the shell ensure good contact with the carbon mass. The upper electrodes consist of a number of carbon cylinders 34 adjustably secured to conductors 37 carried by a framework 38, by means of metal rods 35 provided with clamps 36. When the cell is to be used for refining aluminium, a mixture containing aluminium, sodium and barium chlorides, or a mixture of cryolite and fluor-spar in equal proportions, is placed in the cell and fused to form a crust over the joint between the sections. Molten alloy of the kind to .be used as the anode is then poured into the cell, the fluorides being lighter rising to the top and forming a layer thereon, with the subsequent formation of a crust on the sides of the upper section 13. Part of the fluoride bath is then dipped out and a layer of pure aluminium is poured on the top of the remaining bath mixture to form the cathode. Tap-holes are arranged at the top and bottom of the cell for removing the refined aluminium and the impoverished anode alloy. Fresh alloy may be added by inserting a heated carbon funnel into the cell and pouring the alloy therethrough after the refined metal therein has been removed. In some cases, air may be used as the cooling medium in the jackets instead of water.