Recycling of Aluminium from Mixed Household Waste

Abstract

Aluminium is used in packaging due to its density, strength and preservative capabilities. This paper outlines a methodology to evaluate the recyclability of aluminium waste, where parameters of scrap type, pre-treatment and remelting conditions are alternated in a factorial design, with measurements of yield and analysis of metal quality. In preliminary experiments three aluminium waste materials were evaluated for recyclability. The methodology was tested on one of the waste materials from mixed household waste, named Cans, and will be described in detail. Cans was decoated at 300 and 550 °C. The decoated material was then remelted, 4 separate additions of ~2 kg per experiment, by submerging the sample material in molten aluminium. Porosity, oxide inclusion content and alloy composition were analysed to determine metal quality. The experimental results show that the yield of remelting, dross formation relative to melted sample material and the alloy composition of the remelted metal is dependent on decoating temperature. In conclusion: Cans are recyclable, with good quality and yield, when decoated before melting. Decoating at 550 °C improves metal yield and oxide inclusion content compared to decoating at 300 °C, however it also reduces magnesium content in the resulting alloy. Hopefully the methodology is useful for assessing the recyclability of an aluminium-rich waste and for evaluating the effects of various process parameters during recycling on metal yield and quality.