METHOD OF PREPARING CRYOLITE Russian patent published in 1999 - IPC

FIELD: metallurgy of aluminium, more particularly processing of dusts from electric filters and slurries resulting from gas purification of electrolytic aluminium production. SUBSTANCE: electrolytic aluminium production waste comprising fluorides and carbon is treated with 23-35% solution of fluorochloric acid, weight ratio thereof to waste being 0.2-0.25:1. The resulting product is isolated and dried. The resulting solution is neutralized with soda-containing reagent to pH of 2-6. The resulting carbon-containing foam is separated. EFFECT: method makes it possible to reduced CO₂ outbursts into atmosphere and to simplify the process. 1 ex, 1 tbl