Material flow analysis of aluminum dross and environmental assessment for its recycling process

Approximately 400,000 tons per year of aluminum dross (Al dross) are generated during a melting process of aluminum metal in Japan. The Al dross and the residue, which have high concentration of metallic Al, are mostly used as an Al resource for Al production or as a deoxidizer in the steel industry. On the other hand, the residue with the Al content is less than 20%, is difficult to be recycled and is therefore land filled. This paper deals with (1) a material flow analysis (MFA) of the domestic Al dross in order to achieve clear targets for recycling of Al dross and residue, and (2) an environmental assessment of newly developed technologies for its recycling, such as the process of hydrogen production from residue. The result of material flow analysis on the domestic Al dross in 2003 shows that 2.344 × 10⁵ t of aluminum is recovered and 2.150 x 1051 of residue is generated from the dross. The residue is mostly used in the steelmaking process, whereas 5.0 × 10⁴ t of residue is landfilled in the final disposal site. As the result of the environmental assessment through the material flow, there is a possibility of reduction of CO₂ emission and waste emissions by using residue (Al content: 10%) as a hydrogen resource, which is presently landfilled.