Sustainable Mining and Metallurgy

Carbon slag is a kind of dangerous solid waste produced in the process of electrolytic aluminum production, which contains high content of electrolyte. A company treated carbon residue by high temperature roasting and recovered the electrolyte. In this paper, the process conditions of industrial high temperature roasting treatment of electrolytic aluminum carbon slag were studied, and the phase composition of the main products in the process of high temperature roasting treatment of electrolytic aluminum carbon slag was studied by X-ray diffraction analysis. The results show that when the overall temperature in the furnace reaches more than 1200℃, the electrolyte in the carbon slag is completely melted and has good fluidity and no curing state, the electrolyte and carbonaceous components in the carbon slag were effectively separated. After high temperature roasting, a new phase will be formed. The electrolyte is mainly composed of Na₃AlF₆, CaF₂, Al₂O₃, K₂NaAlF₆, LiNa₂AlF₆, Li₃N, LiF, Mg₃Al₂ (SiO₄)₃ and NaAl₁₁O₁₇. Tailings are mainly composed of Na₃AlF₆, CaF₂, Al₂O₃, K₂NaAlF₆, LiNa₂AlF₆, Li₃N and C; the dust is mainly composed of Na₅Al₃F₁₄, Na₃AlF₆, LiNa₂AlF₆, AlF₃, NaAlF₄ and KAl₁₁O₁₇. The calcium salts in the carbon residue in aluminum electrolysis always exit in the form of dissociative CaF₂, part of which is included in the recovered electrolyte, and the other part exits in the tail residue.