GB893345A - Improvements in or relating to processes and apparatus for the production of aluminium and of mixtures of aluminium and aluminium carbide - Google Patents

Abstract

<PICT:0893345/III/1> In a continuous process as in Specification 865,861 for the production of a mixture of aluminium and aluminium carbide by the reduction of alumina with carbon at a temperature of 2300 DEG -2600 DEG C. in an electric arc furnace, the molten mixture is intermittently tapped from the furnace. Thus in the furnace shown in Fig. 1, the molten aluminium-aluminium carbide mixture is periodically tapped from the furnace hearth 1 by piercing the crucible wall with an auxiliary electrode 9 and is allowed to run into a subcrucible 2 arranged within the heat insulating material surrounding the furnace. The mixture is allowed to cool slowly and solidify in the subcrucible and is removed through a door 10. The weight ratio of carbon to alumina in the charge supplied to the furnace is 0,43\sB10%. The carbon of the charge may be in the form of charcoal, crude or baked petroleum coke, purified powdered coal or coke, sawdust or carbohydrate. The alumina may be prepared by a carbothermal reduction of aluminium ore with excess carbon at 2100 DEG C., the pure alumina then being tapped, communicated by an air stream and solidified into hollow spherical particles. Aluminium may be separated from the product mixture by distillation or preferably by treatment of the mixture with a flux, e.g. at least one halide of an alkali metal or alkaline earth metal or aluminium. The slag is removed from the aluminium and washed with water to recover the aluminium carbide which may be added to fresh charge for the furnace. Boron may be added to the furnace charge as borax, boric acid, boron carbide or boracite to prevent titanium contamination of the pruduct aluminium.