Stabilization of aluminum dross by using hydrothermal reaction

Residues of aluminum dross, an unavoidable by-product of aluminum production, have been discharged over than 200,000 tons per year in Japan. Aluminum dross is composed of aluminum, aluminum nitride, Al2O 3, chlorine and other oxides. The main purpose of this study is to investigate the feasibility of nitrogen removal from residues of aluminum dross by hydrothermal reactions. Aluminum nitride and aluminum dross were treated at temperature ranging from 100 to 400°C and corresponding saturated vapor pressure. The reaction time was varied from 0 to 120 min. For aluminum nitride, 91% of nitrogen was converted into ammonia under the reaction conditions of 200°C and 10 min. In the case of aluminum dross, it was obtained a reduction ratio of 53% in the nitrogen contents at 250°C for 10 min. A bench plant of aluminum dross treatment system was developed in terms of above results. The treatment capacity was 60 kg of aluminum dross per unit in the bench plant. These results demonstrated that hydrothermal reactions could be successfully used as a treatment strategy of aluminum dross.