GB802959A - Improvements relating to the electrolysis of fused salt - Google Patents

Abstract

802,959. Electric furnace electrodes. MONTECATINI SOC. GENERALE PER L'INDUSTRIA MINERARIA E CHIMICA and VARDA, G. DE. Dec. 6, 1955 [Dec. 31, 1954], No. 34922/55. Class 39(3) [Also in Group XXXVI] In fused salt electroylsis, e.g. of aluminium compounds, in which a consumable anode 9 is employed, the anode is periodically restored by locating a replaceable layer 14, e.g. of electrodic carbon, against the surface of the anode 9 to be restored to leave an interstice between the anode 9 and the layer 14, an electrically conductive durably liquid layer, e.g. of fused electrolyte, being formed in the interstice. A carbonaceous substance, e.g. carbon dust, may be suspended in the liquid, which is introduced into the interstice. The liquid is poured into the interstice while the layer 14 is held about 2 mm. away from the electrode 9, the layer 14 being slowly advanced towards the electrode to take up its final position as the interstice is filled. In one embodiment. Fig. 4, in which statioary inclined anodes 9 are employed, the layer 14, which may be 3 to 10 cms. thick, is preheated and its rear face may be corrugated or undulating to correspond with similar shapes on the face of the anode, its lower edge 17 resting on an inert ledge 18. A plurality of juxtaposed strips may form the layer 14. A stop, e.g. of magnesite, alumina or aluminium nitride prevents the layer 14 rising in the bath. In the interstice, pitch, a molten metal, e.g. aluminium, (where the .cell is producing aluminium) fior ne carbon dust e.g. in fused bath, may be dispersed to increase the conductivity. In another embodiment, Fig. 7 in which vertically adjustable anodes 21 are employed, the anodes 21 are withdrawn from the bath and the replaceable layer, which is a plate 22 having a peripheral flange 22<SP>1</SP>, its floated on the bath 2. On the inner face of the plate 22, which may be corrugated, a thin layer 23 of fine carbon dust, aluminium chips, a mixture of bath and carbon dust or molten aluminium, e.g. of 1 per cent to 5 per cent by weight of the plate 22, may be spread. The anode 21 is then lowered to contact the plate 22. A protective layer 24. e.g. fused or sintered alumina or magnesia, or aluminium nitride may cover all but the lower face of the anodes 21. The method described with reference to Fig. 7 is equally applicable to self-bakd Soderberg anodes, and the restorable layer may comprise a plurality of mating strips flanged at least at one end. Specification 800,092 is referred to.