Therefore, emissions of toxic heavy metals and chlorinated organics are expected from smelters. A large part of these emissions were formed from the PVC plastics used in electrical cables and equi other ment. Because of the great savings in energy and resources, a high percentage of scrap aluminum is currently being recycled. Due to the increasing use of this light metal in automotive production, any potential toxic emissions from processing scrap aluminum is of great concern for smelters. Pre-cleaning involves roasting at elevated temperatures to vaporize organic impurities and sweating at temperatures above the melting point of the metal.
Chlorine gas is used to reduce the magnesium content during smelting.
The dioxin emissions from four secondary aluminum smelters have been analyzed in 1994, three of which were performed in conjunction with representatives of the U.S. Environmental Protection Agency and the Aluminum Association. In 1995, the secondary aluminum industry smelted 1.3 million metric of aluminum scrap. U.S. and European studies of aluminum smelters point out very significant differences in the dioxin emissions from this industry. Differences in these emission levels were largely due to the levels of impurities of the scrap, the pre-cleaning and smelting technologies employed, and the control technologies applied. The fact that all smelters of aluminum scrap are basically performing the same task but with drastically different emission levels, suggests that toxic emissions from this industry can be largely avoided.