Recycling and utilization of spent potlining by different high temperature treatments

Abstract

Spent potlining (SPL) is generated at the end of the service life of aluminum reduction cells and is a hazardous solid waste that negatively impacts the environment and ecology. Based on the differences in the hazardous and valuable components of SPL, a classified recycling and utilization path is proposed in this work. Three different high-temperature processes of oxygen-controlled treatment, vacuum treatment, and co-processing in a cement kiln were adopted for spent cathode carbon block (SCCB), spent silicon carbide block (SSCB) and spent barrier and insulating refractory materials (SBIM), respectively. After the classified treatments, all the cyanides in SCCB were decomposed, almost all the Si3N4 was decomposed and Na2SiO3 was removed from SSCB, and over 99% of the fluorides was separated from SCCB and SSCB to obtain high graphitization carbon and silicon carbide. The fluorides in SBIM were converted into a mineralizer that lowered the burning temperature of the cement clinker. The performances of prepared cement met the requirements of Portland slag, Portland pozzolana and Portland flash ash cements.