Removal of iron for aluminum recovery from scrap aluminum alloy by supergravity separation with manganese addition

Abstract

In this study, a novel method using supergravity separation with manganese addition to remove iron for aluminum recovery from scrap aluminum alloy was explored. The effects of separating temperature (T), Mn/Fe mass ratio, and gravity coefficient (G) on iron separation efficiency were evaluated. Increasing the separating temperature improved the Al yield but decreased Fe removal. The higher Mn/Fe mass ratio resulted in a rise in Fe removal but a drop in Al yield, since Mn addition transformed the needle-like β-AlFeSi to compact α-AlSiFeMn phase in aluminum alloy. The gravity coefficient showed no effect on the Fe removal but greatly influenced Al yield. At the optimal conditions of T = 670 °C, Mn/Fe=1.0, and G = 500, the Fe removal and Al yield were well balanced at 60.4% and 82.5%, respectively, and the purity of recovered Al was 94.6 wt%. In addition, the Scheil-Gulliver solidification model of the Thermo-Calc software was used to calculate the solidification diagram and solidified phase fraction of scrap Al alloy, and it was found that the addition of Mn altered the solidification path, increased alloy solidification temperature, and promoted the formation of α-AlSiFeMn phase in the melt, which was able to reduce the balanced content of iron in the liquid phase.