Feed processing for improved alumina process performance
AssigneeComalco Aluminium Limited
InventorsMichael Hollitt, Stephen Grocott, Gerard Roe
Life of this patent
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Abstract
A process is disclosed for the treatment of an alumina process feedstock prior to transferring the treated feedstock to an alumina process for extracting refined alumina from the treated feedstock. The treatment process includes the following steps: (a) heating the alumina process feedstock to a temperature of 400C. to 650C. by direct contact with combustion gases, and (b) cooling the heated feedstock to a temperature at which it can be handled and fed to the alumina process. The treatment process is characterised by controlling the contact time of the solid alumina process feedstock at temperatures in the above range in step (a) to less than 5 minutes.
Claims32
A process for the treatment of a Bayer process feedstock prior to transferring the treated feedstock to a Bayer process for extracting refined alumina from the treated feedstock, which treatment process includes the following steps:
- (a) heating the Bayer process feedstock to a temperature of 400° C. to 650° C. by direct contact with combustion gases, and
- b) cooling the heated feedstock to a temperature at which said heated feedstock is suitable for being handled and fed to the Bayer process,
- and which treatment process comprises controlling the contact time of the feedstock at temperatures in the range set forth in step (a) above to ensure decomposition of alumina trihydrate and alumina monohydrate present, by dehydration, while not:
- (i) forming alumina monohydrate from alumina trihydrate, or
- (ii) reducing residual bound water such that extraction is adversely affected, or
- (iii) allowing sufficient time for contact with water vapour that a slower, water vapour-dependent loss of extractability is experienced.
A Bayer process for extracting refined alumina from a Bayer process feedstock, which Bayer process includes a treatment process for treating the feedstock prior to extracting refined alumina from treated feedstock, which treatment process includes the following steps:
- (a) heating the Bayer process feedstock to a temperature of 400° C. to 650° C. by direct contact with combustion gases, and
- (b) cooling the heated feedstock to a temperature at which said heated feedstock is suitable for being handled and fed to the Bayer process, and which treatment process comprises controlling the contact time of the feedstock at temperatures in the range set forth in step (a) above to ensure decomposition of alumina trihydrate and alumina monohydrate present, by dehydration, while not:
- (i) forming alumina monohydrate from alumina trihydrate, or
- (ii) reducing residual bound water such that extraction is adversely affected, or
- (iii) allowing sufficient time for contact with water vapour that a slower, water vapour-dependent loss of extractability is experienced.
Dependencies are inferred from the claim text.