Dross Reduction in the Aluminum Casthouse: General Considerations and Practices
Peter D. Waite, Alcan International Limited, Jonquière, Canada
Track: BILLET PROCESS and EQUIPMENT - Furnaces
ABSTRACT --- Many casthouse operations involving the melting of aluminum
scrap, or the processing of molten aluminum, result in the generation of dross.
Composed essentially of metallic aluminum and metal oxides, dross is undesirable
due to the direct costs related to post-treatment, the associated loss of metal units,
and because of potentially negative environmental impact. Although dross
reduction is a priority for many casthouse managers, the identification of specific
practices or operations that contribute to increased dross formation is not always
straightforward, and can require considerable effort. This undertaking is further
complicated by the fact that several practices and/or casthouse operating parameters
can act collectively to increase dross generation, but while considered individually,
no causes and effects are apparent. The various aluminum batch preparation
practices that can contribute to dross generation will be reviewed primarily from the
perspective of a smelter casthouse, but with application to secondary remelt
operations as well. With the aim of recognizing specific areas of the casthouse
where dross reduction efforts should be focused, a strategy of dross weight
measurement and statistical data analysis has proven to be very effective, and will be
illustrated by way of example.
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