With the major recycling objective being to recover the metallic aluminum content of scraps and residues with the highest possible yield combined with the lowest effort, the tilting rotary process gives some good advantages over the fixed axis single route.
Key in the application of recovery of aluminum, zinc, lead and platinum the advantages of the tilt rotary process includes greater safety, efficiency, and loading capacities.
Raw materials dedicated to the recycling of aluminum have to contain it in non-oxidized but metallic form. The transformation of such oxides into metal is technically and economically infeasible. The major recycling target is to recover the metallic aluminum content of scraps and residues with the highest possible yield combined with the lowest effort. Some countries, particularly those rich in electricity resources have explored the plasma torch route or electric arc type furnace; both working on a similar principal of melting in an ‘oxygen free’ environment under pressure to avoid parasite air ingress and both of these techniques offer efficient recoveries but are not economically viable unless the electrical power source is very cheap.
Also these techniques are limited to small production units (a few tonnes of dross at most). More recently other manufacturers have opted for TRF (Tilt Rotary Furnace) units fitted with oxy/fuel combustion systems - they have their advantages, the main one being the reduction of off-gas volumes but they remain complex and costly.
Tilt Rotary Furnaces have significant advantages compared to fixed axis rotary furnaces. In Figures 1 and 2 is schematically presented both processes.
A high salt-to-oxide ratio is required to ensure the slag is liquid to run through the small tap hole.