Separation Technologies for the Industries of the Future (1998) / Chapter Skim
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5 Aluminum Industry
5 Aluminum Industry
Pages 51-58
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From page 51... ...
SEPARATION NEEDS Various sectors of the aluminum industry, from primary smelters to producers of finished products, have diverse separation needs. In terms of basic processes, the industry needs improvements in separation processes that increase metal purity.
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From page 53... ...
Dry scrubbers, which are designed to put the gases in contact with alumina in dispersed phase or fluidized bed reactors, are the preferred technology because unreacted alumina is used to capture hydrogen fluoride and electrolyte compounds that can be returned to the cell. Elemental impurities (e.g., fluorine, vanadium, lithium, iron, phosphorus, and nickel)
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From page 54... ...
The magnesium is present in the melt because a mixture of scrap, including both cast and wrought alloys, is used for the melt, and the wrought alloys contain magnesium levels that exceed the cast alloy target specification. The industry would benefit from alternatives to removing impurities via chlorine fluxing, which is expensive and creates environmental problems.
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From page 55... ...
The global scrap aluminum balance is maintained today because of the healthy growth of the secondary foundry alloy business, particularly for automotive casting applications. Indeed, this industry consumes not only all of the old scrap castings and automobile scrap, which are a good mix of cast and wrought alloys, but also mixed wrought and cast alloy white goods, such as refrigerators and other household appliances.
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From page 56... ...
Solid Residues Dross is the oxide-rich by-product of aluminum melting operations. White dross from smelting or clean remelt operations may be rich in metal, with the balance aluminum oxide, whereas so-called black dross or salt cake contains salt flux, which is used to facilitate the wetting of aluminum scrap, as well as oxide and reduced amounts of metal.
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From page 57... ...
High-speed noncontact techniques have been identified that would be capable of differentiating all alloys of interest. The successful separation of different types of aluminum alloys will require continued work on the fundamental mechanics of high-speed conveying, the positioning scrap pieces in sequential arrays before they enter analysis, and methods of physically sorting analyzed pieces by alloy type.
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From page 58... ...
SUMMARY The aluminum industry has a broad array of separation needs that affect all production processes, from primary smelting to the manufacture of finished products. Specific areas for improvement include: · the separation of impurities from alumina feedstock · the separation of impurities from dry scrubber alumina · alternatives to chlorine fluxing for the removal of light metals and magnesium molten metal filtration · methods for sensing inclusions · decreasing or eliminating CO2 emissions by the development of nonconsumable electrodes methods of reducing and recycling spent potliner methods for segregating/sorting scrap by alloy separation/uses for nonmetallic by-products salt/water separation for efficient recycling of salt cake treatment of dilute gas streams lower cost oxygen for oxyfuel burners efficient removal of excess water in the Bayer process
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