An environmental problem in need of a solution

The global primary aluminium production volume in 2009 was 36 million metric tons, and regardless of the recession these volumes continue to grow 5-6% per a year. The production of one metric ton of aluminium from ore (bauxite) requires about 17000 kWh of electricity while the same amount of recycled aluminium consumes approximately 750 kWh. Therefore, the recovery of aluminium from, aluminium dross requires only 5% of energy related to that which is needed to produce the aluminium from ore [1].

During aluminium melting the dross is generated, resulting typically 25 kg of dross per metric ton of molten aluminium (3 wt%) [2,3].  That means 0.9 Million tons of dross per year is generated. The generated dross contains 30-70% (in average 50%) metallic aluminium which equals 0.45 million tons.
Today the best technologies in dross processing make possible to get a recovery up-to 94%.

The existing dross processing technology suggests using salts (NaCl, KCl) in amount of
600kg per 1 MT of dross that have serious environmental threat. For economical reasons, it is desirable to recover in usable form as much as possible of the free metal that is carried from the furnace into the dross. However, separation of metal is difficult, because the metal is dispersed as fine particles that are surrounded by a matrix of non-metallic components of the dross. Further, the free metallic aluminium in the more or less porous dross is highly susceptible to oxidation, especially at elevated temperatures [4].

[1]     J. Mukhopadhyay, Y.V. Ramana, Upendra Singh. Extraction of Value Added Products  fom Aluminium Dross Material to Achieve Zero Waste. Light Metals 2004 Edited by A.T. Tabereaux. The Minerals, Metals & Materials Society, (2004)
[2]     Montagna D. Fluxless recovery of metallic aluminium from wastes. U.S. Pat. No. 3999980, (1975)
[3]     Kassabji F., Weber J. C. Aluminium dross processing in a rotary plasma furnace. (2003)
[4]     McLeod et al. Recovery of metal from dross. U.S. Patent 3676105 (1971)