Separation and Recycling of Spent Carbon Cathode Blocks in the Aluminum Industry by the Vacuum Distillation Process

• DOI: 10.1007/s11837-018-2858-4
• Publication Date: 2018-04-19T14:08:13Z
• Authors: Wang Yaowu; Peng Jianping; Di Yuezhong
• Keywords: Carbon fibers; Refining (metallurgy)

Aluminum is the second most produced metal after iron. China is the top producer of primary aluminum with a production capacity of 41,000 kt and an output in 2016 of 32,000 kt. A large amount of spent carbon cathode block (SCCB) is produced after electrolytic pot failure. SCCB consists of carbon, fluorides, alkali metals, carbides, nitrides, cyanides, and oxides, and is considered to be a hazardous material because it contains significant concentrations of toxic and soluble cyanides and fluorides. There is no economical and efficient process for the treatment of SCCB and is most commonly disposed in landfill. In this study, the vacuum distillation process (VDP) has been used to separate and recycle SCCB. The results show that Na3AlF6, NaF, and sodium metal can be effectively separated from SCCB by VDP, and the distillation ratio is above 80% at a distillation temperature of 1200°C. The carbon content in the distilled SCCB is above 91% and the impurities are mainly CaF2 and Al2O3.