Aluminium Mass Balance in Waste Incineration and Recovery Potential From the Bottom Ash: A Case Study

The recovery of aluminium scraps from waste incineration bottom ash is becoming a common practice for both its environment and economic advantages. However, only a fraction of the aluminium scraps in the residual waste can be actually recovered from bottom ash and subsequently recycled, due to their fragmentation in the furnace and their partially oxidation. The paper is then aimed at the investigation of the behaviour of the aluminium scraps in the furnace of waste-to-energy plants. The partitioning of the aluminium among the residues of the incineration process, its oxidation level and its recovery potential from the bottom ash were evaluated in two incineration plants located in northern Italy. About 21-23 % of the Al fed to the furnace with the residual waste is recovered and potentially recycled from the bottom ash. Out of this amount, 76-87 % is found in the bottom ash fraction above 5 mm and thus can be recovered with standard eddy current separators. The remaining amount of the Al fed to the furnace concentrates in the bottom ash fine fraction or in the fly ash, from which it cannot be recovered with current technologies. On average, about 54-63 % of the aluminium is oxidized during the combustion process. This Al represents a loss from the material recovery point of view; however, it contributes to about 1 % of the energy released in the combustion chamber.