Comparison of salt-free aluminum dross treatment processes

Dross is an unavoidable by-product of the aluminum production. It forms at the surface of the molten metal as the latter reacts with the furnace atmosphere. Depending on the process, it contains, on average, about 50% free aluminum metal dispersed in an oxide layer. Since the aluminum production is highly energy-intensive, dross recycling is very attractive from both the energy and the economic standpoints. The conventional recycling process using salt rotary furnaces is thermally inefficient and environmentally non-acceptable because of the production of salt slags. Several salt-free dross treatment processes have been proposed in the last few years, their operation, energy consumption and metal yield will be described in detail and compared in the present paper.