Method of recovering fumed silica from spent potliner
AssigneeGoldendale Aluminum Company
InventorsRobert J. Barnett, Michael B. Mezner
Life of this patent
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Abstract
Spent potliner from an aluminum reduction cell is subject to an acid digest and the digest may be adjusted to produce a first gas component comprised of at least one material selected from the group consisting of silicon tetrafluoride, hydrogen fluoride, 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. The first gas component is removed from the digester and heated to a temperature sufficiently high to convert said silicon tetrafluoride to fumed silica and hydrogen fluoride. Thereafter, the fumed silica is separated from the hydrogen fluoride to recover fumed silica from spent potliner material.
Claims16
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.
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 sulfuric 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 fluoride, 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 in the presence of water vapor to a temperature in the range of 400° to 1000° C. 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.
In treating spent potliner material, 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 a digester in at least one acid selected from the group consisting of H2SO4, HNO3, HClO4, HF and H3(PO4) to produce:
- (i) a first gas comprised of silicon tetrafluoride and at least one gas selected from the group consisting of hydrogen fluoride, hydrogen cyanide and water vapor;
- (ii) 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) recovering said first gas component from said digester;
- (c) heating said first gas component from said digester in the presence of water vapor to a temperature range of 400° to 1000° C. to convert said silicon tetrafluoride to fumed silica and hydrogen fluoride;
- and
- (d) separating said fumed silica from said hydrogen fluoride to recover said fumed silica from spent potliner material.
In treating spent potliner material, 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 a sulfuric acid digester to produce:
- (i) a first gas comprised of silicon tetrafluoride and at least one gas selected from the group consisting of hydrogen fluoride, hydrogen cyanide and water vapor;
- (ii) 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) recovering said first gas component from said digester;
- (c) heating said first gas component from said digester in the presence of water vapor to a temperature range of 400° to 1000° C. to convert said silicon tetrafluoride to fumed silica and hydrogen fluoride;
- (d) cooling said fumed silica and hydrogen fluoride;
- and
- (e) separating said fumed silica from said hydrogen fluoride to recover said fumed silica from spent potliner material.
Dependencies are inferred from the claim text.