Process For the Electrolysis of Aluminiumsulfide

Abstract

Process for the electrolysis of Al 2 S 3 , using a bath of molten salt, preferably a bath of molten chloride salt, in which Al 2 S 3 is dissolved characterized in that measures are taken to improve the electrical conductivity of the bath, so as to enable an increase in the current density in the bath.

1 . Process for the production of primary aluminium by the electrolysis of Al 2 S 3 , using a bath of molten chloride salt in which Al 2 S 3  is dissolved, wherein the bath is substantially free from MgCl 2 , and wherein an additive comprising a fluoride compound is added to the bath to improve the electrical conductivity of the bath to enable an increase in the current density in the bath. 
     
     
         2 . Process according to  claim 1 , wherein the additive consists essentially of the fluoride compound. 
     
     
         3 . Process according to  claim 1 , wherein the additive mainly consists of the fluoride compound. 
     
     
         4 . Process according to  claim 1 , wherein the fluoride compound is cryolite. 
     
     
         5 . Process according to  claim 4 , wherein the concentration of the cryolite is in the range of 5 to 30 wt %. 
     
     
         6 . Process according to  claim 1 , wherein the effective area of an anode extending into the bath is enhanced by reducing the amount and/or size of gas bubbles covering the anode. 
     
     
         7 . Process according to  claim 1 , wherein the bath of molten chloride salt mainly comprises alkali metal chlorides. 
     
     
         8 . Process according to  claim 1 , wherein the bath of molten metal is substantially free of earth alkaline chlorides. 
     
     
         9 . Process according to  claim 1 , wherein the electrolysis is carried out at a bath temperature of between 600° C. and 850° C. 
     
     
         10 . Process according to  claim 1 , wherein the electrolysis is carried out in a multi-polar electrolysis cell. 
     
     
         11 . Process according to  claim 4 , wherein the concentration of the cryolite is in the range 7 to 15 wt %. 
     
     
         12 . Process according to  claim 4 , wherein the concentration of the cryolite is about 10 wt %. 
     
     
         13 . Process according to  claim 1 , wherein the bath of molten chloride salt mainly comprises KCl and NaCl. 
     
     
         14 . Process according to  claim 1 , wherein the electrolysis is carried out at a bath temperature of between 700° C. and 800° C.