1.1 Definition of Dross and General Scope of Related Aluminum Recycling
Aluminum Dross is a by-product of Aluminum production. Today much energy is consumed to recover the Al from the dross; energy could be saved if the dross was diverted and utilized as an engineering material. There are two forms of dross – white dross and black dross. White dross is formed during the primary Al refining process, while black dross is formed during the secondary refining process, which uses relatively large amounts of Chloride salt fluxes. Subsequently, the dross is processed in rotary kilns to recover the Al, and the resultant salt cake is sent to landfills. Although salt cakes are sealed to prevent from leaching, the potential for leaks exists and in fact does occur which harms the environment. There is much merit if the dross that is formed could be “recycled” as an engineering product for specific applications. Interestingly the main constituents of dross are Al and Al2O3, yet ironically, and MgO and MgAl2O4 as well, since there is much effort today to produce Al based composites containing a second phase constituents (such as Al2O3).