Metal-solvated carbothermal production of aluminium

Commercial aluminium production by electrolysis of alumina dissolved in cryolite is carried out in Hall-Héroult cells. Several attempts have been made by other investigators to develop alternate routes that are more intense and reduce pollutants [1-4]. At CSIRO Process Science and Engineering, a program investigated the carbothermal reduction of alumina. An experimental study was conducted at the kilogram-scale in a reactor designed to operate up to 2000°C and down to about 10 kPa. Experiments employed a bed of C-Al2O3 pellets contacting a bath containing tin or copper as a solvent metal. The experiments confirmed the feasibility of smelting alumina with high recoveries of aluminium metal to an alloy at temperatures as low as 1750°C and furnace pressures up to about 45 kPa. A key finding was that the method of contacting the charge with the solvent had a significant influence on the extent of undesirable side reactions and loss of aluminium to the gas. The reaction rate was increased with higher temperature, lower reactor pressure and lower concentration of aluminium in the alloy. The amount of aluminium lost to the fume decreased at lower temperatures and higher pressures. Losses were lower with copper than with tin as the solvent.