Process for production of aluminum by carbothermic production of

Abstract

An improved process is disclosed for carbothermically producing an alkaline earth metal aluminide from an aluminum-bearing material which, in one aspect comprises forming a mixture of a carbonaceous reducing agent and a slag comprising the aluminum-bearing material, the alkaline earth metal compound; forming, at a first temperature, an alloy containing impurities in the slag; removing the alloy containing the impurities from the slag; and then heating the slag to a higher temperature to form the alkaline earth metal aluminide. The alkaline earth metal compound used in the process may comprise calcium carbide. Alternatively, both the alkaline earth metal compound and the aluminum-bearing material may be obtained using a calcium aluminate slag such as a byproduct from the steel industry. The calcium aluminate slag is purified in a preliminary step to remove silicon by alloying it with iron and then removing a ferrosilicon alloy formed in this step. Byproducts formed during the reactions may be recycled back if desired. Either metallic aluminum, the alkaline earth metal, or both may be recovered from the aluminide material using, respectively a halide, a sulfurous, or a nitrogen stripping agent, or by reducing both metals in an electrolytic reduction cell. The alkaline earth metal aluminide may also be used as a reducing agent to recover other metals such as magnesium oxide by reduction from their respective compounds.