Moltech Invent S.a.

Moltech Invent S.a. Luxembourg

Vittorio Bello

Jean-Jacques R Duruz

Fausto Manganiello

The invention relates to a method of producing aluminum in an electrolytic cell, particularly in a drained cell, such cell comprising a cathode ( ) and facing anodes ( ), each anode ( ) being spaced apart in its operative position from the cathode ( ) by an anode-cathode reduced distance defining an anode-cathode gap containing the bath being electrolyzed. The method comprises: feeding alumina into the electrolyte where it is dissolved; electrolyzing an alumina-rich bath in the anode-cathode gap; and periodically moving at least one anode ( ) in order to intake rich-alumina electrolyte into the anode-cathode gap thereby distributing alumina-rich electrolyte under the entire anode surface.

Distribution of alumina-rich electrolyte in aluminum electrowinning cells

A prebaked carbon-based anode of an electrolytic cell for the production of aluminium, in particular by the electrolysis of alumina in a molten fluoride electrolyte, is treated over its sides and top to improve the resistance thereof to erosion during operation of the cell by oxidising gases released at the anode, by immersing the anode in a boron-containing solution containing 5-60 weight % of H.sub.3 BO.sub.3 or B.sub.2 O.sub.3 in methanol, ethylene glycol, glycerin or water with a surface-active agent, e.g. at 80.degree. to 120.degree. C. After 2-60 minutes immersion, the boron-containing solution is impregnated to a depth of 1-10 cm, usually about 2-4 cm over the top and side surfaces of the anode to be protected, producing a concentration of boron in the impregnated surface from 200 ppm to 0.35%. The same treatment can be applied to cell sidewalls.

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Rome, Italy

Vittorio Bello