Recycling of distributed aluminium turning scrap

The relationship between scrap type and its recoverable metal content can play a crucial role in industrial recycling processes. In this paper, the recyclability of different aluminium turnings has been experimentally studied. Various categories of scrap were melted at 800 °C to recover aluminium metal with the protective salt flux of NaCl–KCl–Na 3AlF 6 under nitrogen atmosphere. In order to understand the melting behaviour, thermo-gravimetric analysis was applied to investigate the weight loss during the melting process. It is shown that the difficulty of recycling the selected aluminium scrap depends on scrap type, scrap size distribution, contaminant, and the ratio of surface area to body volume. Lower distribution mean value, more non-metallic contaminates (oil, plastics), smaller size and higher ratio of surface area to body volume generally led to a lower metal yield. The effect of cryolite addition on the metal yield was also studied, especially for the scrap with higher ratio of surface area to body volume. It was shown that the accumulation of the metal beads was improved with higher amount of cryolite addition. A simple statistical approach is presented to correlate metal yield to scrap properties for inclusion in process optimisation and control models.