These can be removed via pre-treatment processes or in the melting furnaces.
Scrap such as used beverage cans (UBCs) and turnings sometimes require the removal of coatings or oils prior to melting, to improve metal recovery and to reduce potential emissions.
The choice of furnaces is to a large extent determined by the level and type of impurities. Scrap refining process can be generically described with the following steps:
Energy is consumed throughout the refining process. The transformation of scrap into recycled aluminium alloys requires approximately 5% of the energy input needed to produce primary ingot from bauxite. Depending on the impurities in the scrap, various air emissions may be generated, such as organic compounds and dust. Solid wastes such as dross, skimmings and salt slag can also be generated in the refining process. Dross and skimming are processed, often in the same plant, to recover the metal. Salt slags are recycled in specialised facilities to recover the metal and other products.
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