China Nonferrous Metallurgy

Anode carbon slag is a hazardous waste generated during the aluminum electrolysis process, mainly composed of cryolite, subglotite, and carbon. Currently, it is mainly stored in a temporary manner through stacking, which not only pollutes the environment but also causes resource waste. This article uses anode carbon slag provided by an electrolytic aluminum plant in Gansu as raw material, and conducts characterization analysis on it. Based on thermodynamic analysis and TG-DSC analysis within the calcination temperature range, a single factor calcination test is conducted, and the following main conclusions are obtained. In areas with low electrolyte content in anode carbon slag, electrolytes adhere to the surface and gaps of particles, while higher areas wrap around carbonaceous materials; The Gibbs free energy analysis of chemical reactions indicates that the roasting method is feasible for recovering electrolytes from anode carbon slag; The optimal roasting process obtained from the single factor experiment is a temperature of 800℃, a heating rate of 5℃/min, and a holding time of 1.5 hours. Under these conditions, the weight loss rate of anode carbon slag is 23.73%, the removal rate of electrolyte carbon is 96.17%, and the recovery rate is 91.32%; K₂NaAlF₆ and LiF new phases appeared in the recovered electrolyte, with a uniform distribution and increased content of Na, Al, F, Mg, Ca, and K elements. The initial crystallization temperature of the electrolyte was 921.5℃, which can meet the industrial application requirements of aluminum electrolysis.