Polychlorinated dibenzodioxins and dibenzofurans in the aluminum recycling process

At a pilot-scale rotary furnace, aluminum scrap, to which organic material was attached, was molten together with salt at temperatures of ≈700-800 °C. Because these conditions are favorable for the production of polychlorinated dibenzodioxins and dibenzofurans (PCDD/F) the following measures were investigated to reduce PCDD/F emissions from the aluminum recycling process: (a) alternative duct configuration; (b) type of scrap feeding; and (c) postcombustion with subsequent quenching. Ad (a) In the typical setup of the rotary furnace, the burner is installed at one side and the exhaust gases leave the furnace at the opposite side. In the alternative duct configuration, exhaust gases were withdrawn at the burner-side. For both duct configurations, PCDD/F were in the same range. Ad (b) The aluminum scrap was shredded and continuously (rather than batch-wise) fed into the furnace. Continuous feeding reduced PCDD/F emissions as did (ad c) postcombustion with subsequent flue gas quenching.