Migration behavior of fluorides in spent potlining during vacuum distillation method

Abstract

Recently, the application of SPL in metallurgical industry has gained significant attention since SPL was proved to have an indelible potential to be applied in pyrometallurgy as a low-cost fuel. However, the volatile fluorides in SPL, especially, NaF and Na3AlF6, limit this application due to environmental concerns, and practical/engineering issues. In this manuscript, the new vacuum distillation method (VDM) was recommended to pretreat SPL first cut below 1000 °C to separate volatile fluorides and graphite. The products, leachable fluorides and carbon enriched residue, are expected to be reused in metallurgical industries for cost-saving. To confirm the feasibility of this idea, pure fluorides, artificial fluorides-graphite mixtures (NaF, Na3AlF6, CaF2, C) as well as SPL were submitted to the VDM process. The migration behavior of the components during VDM treatment has been studied, and soluble fluoride content in the VDM treated residues was examined to draw a VDM map for fluorides treatment. The overall goal is to develop an environmentally friendly technique to extract the economic value of SPL in an efficient manner.