A Denitrification-Phase Transition and Protection Rings (DPP) Process for Recycling Electrolytic Aluminum Dross

The continuous growth of the aluminum electrolysis industry has produced large amounts of electrolytic aluminum dross (EAD) as a waste product, which lacks proper recycling methods and poses serious environmental pollution risks. A short and clean process for recycling EAD is proposed involving the preparation of anode protection rings, which can effectively reduce the corrosion of anode steel stubs, improve the quality of molten aluminum, and return to aluminum reduction cells for recycling alumina and fluoride after being broken. The phase transition path of Al(OH)3 in denitrified EAD by thermal decomposition was bayerite → boehmite → γ-Al2O3 → α-Al2O3. The calcination temperature should be controlled at 600–800 °C for 2 h to obtain a higher content of activated γ-Al2O3. The average dissolution rate of denitrified EAD in the aluminum electrolyte was 7.33 times higher than that before denitrification treatment. After using EAD anode protection rings, the corrosion rate of anode steel stubs decreased by 67.7% on average. Furthermore, the iron and silicon contents in the molten aluminum were reduced by 18.57% and 6.25%, respectively. The alumina consumption for producing primary aluminum was reduced by 8.14 kg·t–1. The experimental results suggest that the proposed process is economical and promising for EAD recycling.