Recycling of Low-grade Aluminium Scrap

Aluminium scrap is often contaminated with a wide variety of materials, such as plastics, seals, oils, and woods, or it exists in a varnished form. These are organic compounds, which cause reactions in aluminium melting furnaces and lead to the loss of metallic Al. In the theoretical part of this work, an explanation of the customary industrial processes for recycling of Al scrap with a high organic content is given. Typically, it is processed in refiners where molten salts are used for the production of casting alloys, including deoxidation granules that are used in steel production. The melting process in a two-chamber furnace with pyrolysis in the scrap chamber offers a further possibility for producing these granules, whereby organic constituents can be removed partially before the actual melting of the scrap. In the experimental part, laboratory trials are carried out to determine the metal yields of mixed Al scrap with a high organic content. The basic metallurgical conditions are set in such a way that they can be compared with the industrial melting units. The best results were achieved by using molten salts for the recycling process. For the processing of contaminated scraps in a two-chamber furnace, a previous pyrolysis also leads to an increase in metal yields and to a reduction in the amount of formed dross. © 2021, The Author(s).