Aluminum Recycling

This line of research started in 1990. Since then, several projects have been carried out. Recently they studied processes for separating aluminum and copper from electrical wires and cables and aluminum flotation of white lees (white drosses). Other aspects of the recycling process were studied in the 90s, such as the oxidation of aluminum alloys in cans, removal of liquid aluminum Mg, removal of liquid aluminum Fe, optimization of decomposition of saline fluxes. The following summary shows the thesis work of Professor. Dr. Jorge Alberto Soares Tenório.

This work aims to study the fundamental and technological aspects involved in the aluminum can recycling process. For that, the following items were researched: oxidation and removal of the organic coatings of the alloys that make up the cans, remelting of cans by varying the temperature, type of flow and presence of organic materials on the surface of the cans, salt / drosse interaction and effect of the addition of NaF in the viscosity of the saline flow. The tests were performed on a laboratory scale, using a thermogravimetric scale, well ovens, optical and scanning microscopy, X-ray diffraction and a device for measuring viscosity using the falling body method.

The results showed that the increase in temperature causes an increase in the oxidation speed of the materials of the lid and the body of the cans. Temperatures of 800ºC should be avoided, as there is a high increase in the oxidation rate of the body’s alloy. The oxidation of the body and cap alloy promotes the formation of MgO, Al2O3 and MgO, respectively. The increase in the melting temperature causes a decrease in the process yield. Agitation, the presence of chlorides in the charge and fluorides in the flow increase the yield. The drosses produced are basically composed of Al,
MgO, MgO.Al2O3 and Al (OH) 3, consisting of branched chains of oxides that retain aluminum. The salt acts to attack the grain contours of the oxides, promoting the release and coalescence of aluminum. The addition of NaF to the flow causes a 30% decrease in flow viscosity. Thus, the effects of fluoride additions are to increase the attack speed of the oxides and to decrease the flow viscosity.