SPL Recycling and Re-processing

Aluminum smelters generate a considerable amount of spent potlining (SPL), which results from the chemical and mechanical degradation of carbon, refractory and insulating materials used to isolate them from a high-temperature and chemically aggressive process of electrolysis. The specific amount of generated SPL is 18–40 kg/t Al, and it depends on the life of the cell, which varies from 5 to 7+ years. Besides considerable expenses for cell relining, SPL has a negative impact on the environment due to fluorine compounds and cyanides, and for this reason it is classified as a hazardous waste. There are two most evident ways of minimizing the above negative impact from SPL: a decrease in the amount of SPL, and SPL re-processing, including SPL neutralization and the production of sub-products such as fluorine, carbon and aluminosilicates. These materials can either be used in-house or sold to third parties. This paper covers RUSAL’s efforts aimed at developing and implementing a technology to recycle and re-process SPL.