Dross Formation in Aluminum Melts During the Charging of Beverage Can Scrap Bales with Different Densities Using Various Thermal Pretreatments

Herein, dross formation (D) in used beverage can (UBC) scrap bales was investigated in laboratory-scale experiments to understand the reactions of solid can coating residues with aluminum melts. The experimental conditions were chosen according to a multi-chamber furnaces process, in which thermal pretreatment and submerged melting of the scrap bales are combined. The thermal pretreatment results show that the supply of oxygen should be continuously adjusted to meet the oxygen demand of UBC scrap bales for thermolysis. Moreover, it is necessary to maintain the UBC scrap bales at an effective material temperature of 550–570°C for at least 30 min. It is shown that adhering carbon-containing pyrolysis char and oxidized can sheet surfaces decrease the coalescence of molten scrap, resulting in dross with a high metal fraction. Further melting experiments with UBC scrap bales of different densities (ρ) show that by lowering the ρ, the dross formation reduces.