GB962599A - Electrolytic furnace for aluminium production - Google Patents

Abstract

<PICT:0962599/C6-C7/1> An electrolytic fused bath furnace for producing aluminium is equipped with stationary vertical or sub-vertical bipolar and monopolar electrodes 4 and 4b supported or suspended through insulating members by means, e.g. from supporting bars 7 fastened to beams 17 by bolts 19 (Fig. 2) or collars 19b (Fig. 6) through insulators 20, located either entirely outside the furnace or connected to the furnace only at parts not in contact with the bath, e.g. through insulators 18 (Fig. 2), and the faces of both the bipolar and monopolar terminal electrodes 4 and 4b which are not intended to be electrolytically active and the inside of the vat 1, preferably of amorphous carbon, are coated with a refractory electrically insulating material, such as by framing the electrodes with side, base and top coatings 6, 22 and 43 as well as transverse coatings 21 (Fig. 2) for the terminal electrodes 4b. The coatings are separated from each other to allow electrolyte circulation and may be fixed by means of dovetailed joints (Fig. 2) and/or binder. The electrodes at least in cathodic portions may be of graphite. The coatings are preferably of material based on silicon-nitride-bonded SiC or, at least in anodic portions, on boron nitride. The terminal electrodes 4b may be provided with current-supply bars 28 supported from beams 17 (Fig. 6). Each electrode may have a renewable anodic layer such as a consumable anode portion 5 fed from the top through a stack (not shown). The furnace may be multicelled e.g. of the necklace type described in Specification 814,754, with alumina being fed continuously through a device 8 (Fig. 2) to flow into the electrolysis spaces 16 between adjacent electrodes. The bottom of the vat may be inclined and include a groove 25 below each electrolysis space 16 for collecting the <PICT:0962599/C6-C7/2> <PICT:0962599/C6-C7/3> aluminium metal produced and allowing it to flow off through a conduit 29 and an overflow 33 into a collection receptacle 31 common to each series of cells. The furnace vat 1 may be protected on the outside by a thermally insulating jacket 3. In a modification (Fig. 5), a bipolar electrode 35 may be suspended instead by a pipe 36 through which methane may be introduced through bores 37 into the vicinity of the active anode surface where it decomposes to form spongy consumable carbon black 40. Specifications 800,092, 802,959, 815,076, 846,305, 846,331, 847,970, 852,899, 871,114, 881,452, 881,453 and U.S.A. Specification 2,900,319 also are referred to.