Patent ID: 6193944
Filing Date: 2001-02-27
Classification: C01B,C01C,C01F,C03C,C04B,C22B,Y02P,Y02W

Abstract:
A method of recovering fumed silica from aluminum reduction cell spent potliner material which is comprised of fluoride compositions and silica and at least one material selected from the group consisting of cyanide compositions, iron compositions, calcium compositions, magnesium compositions, alumina, carbon, and sodium sulfate, the method comprising:(a) digesting the spent potliner material in an acid digester to produce a first gas component comprised of silicon tetrafluoride and hydrogen fluoride, and at least one material selected from the group consisting of hydrogen cyanide gas and water vapor, and a slurry component comprised of at least one material selected from the group consisting of carbon, silica, alumina, and sodium, iron, calcium and magnesium compounds;(b) removing said first gas component from said digester;(c) heating said first gas component recovered from said digester to a temperature sufficiently high to convert said silicon tetrafluoride to fumed silica and hydrogen fluoride; and(d) separating said fumed silica from said hydrogen fluoride to recover fumed silica from spent potliner material.