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CASE STUDY—ALUMINUM RECYCLING 421

32.7 Case Study—Aluminum

Recycling

The recycling of aluminum scrap has significant economic, energy, environmental,
and resource-savings implications. Compared with the primary aluminum produc-
tion, aluminum recycling has a great advantage due to lower production cost
(Campbell, 1996; Henstock, 1996). In order to efficiently recycle metals the industry
is faced by various issues which include scrap sampling, scrap purchasing, metal
recovery (based on recoverable metal in scrap) and yield (based on total mass of
scrap), production cost and hence profit margins, product quality, environmental
issues, and regulation. The chemical composition of the molten aluminum product
is controlled not only by the process operation, but also to a large extent by proper
selection of charged aluminum scrap.
As the real metal content of the scrap remains unknown, metal yield becomes a
crucial factor for the recycling of aluminum scrap. Unfortunately, due to aluminum’s
high reactivity, metal yield of aluminum is a function of numerous parameters such
as surface area–to-volume ratio (due to oxidized surface), shape of the scrap, type of
alloy, scrap history, contaminants (e.g., oxides, water, oil, and paint), and amount
of required flux additives in the melting process. For example, any increased level
of contamination on scrap reduces metal recovery due to reaction with aluminum,
and further lowers the metal yield. Figure 32.1 shows a metal scrap pile commonly
found in the United States.

Figure 32.1 Metal scrap.