A NOVEL CRUCIBLE METAL TREATMENT PROCESS FOR IMPURITY REMOVAL IN SECONDARY ALUMINIUM

摘要

Treatment of aluminium in crucibles is well established in the aluminium smelting industry as a very efficient technology to remove alkali elements such as lithium and sodium. The utilization of crucibles is a common tool in remelt and recycling plants to transport metal recovered from dross recycling and scrap melting operations. In these cases, the metal is often contaminated with alkali elements, mainly calcium, and undesired oxides and inclusions. This paper presents the development work of a new crucible-based metal treatment process adapted to remelt and recycling operations. This method, which involves utilization of flux to improve metal cleanliness and alkali elements removal, is specially designed to promote efficient dispersion of the reactant in the melt to achieve optimal performance. Laboratory work covering a new impeller design and salt dispersion methods to meet specific requirements for alkali, oxides and inclusion removal is explained. Results from an industrial demonstration are detailed, including the metal cleanliness measured by PoDFA and the alkali removal efficiency. The positive impact of this process to maximize utilization of internal and external scraps in plants is outlined.