Patent ID: 6217836
Filing Date: 2001-04-17
Classification: C01B,C01C,C01F,C03C,C04B,C22B,Y02P,Y02W

Abstract:
A method of recovering alumina, carbon and silica from spent potliner, material from aluminum reduction cells, which spent potliner material selected includes a material selected from the group consisting of fluoride compositions, cyanide compositions, iron compositions, calcium compositions, magnesium compositions, alumina, carbon, silica and sodium sulfate, the method comprising the steps of:(a) contacting the spent potliner with sulfuric acid in an acid digester to produce a gas component containing at least one gas selected from the group consisting of HF and HCN and a slurry component comprised of a solids and a liquid solution, the solid comprised of carbon, silica, alumina and calcium sulfate;(b) maintaining said digester at less than atmospheric pressure to remove said gases from said digester;(c) separating said liquid solution from said solids;(d) rinsing said solids at least once to remove residual acid from said solids;(e) reacting said calcium sulfate with ammonium chloride to form ammonium sulfate and calcium chloride; and(f) separating said ammonium sulfate and calcium chloride to recover a mix of solids comprised of carbon, silica and alumina.