Comalco Aluminium Limited

Comalco Aluminum Limited

Stephen Grocott

Michael John Hollitt

Colin John Beeby

Gerard Roe

John Peter Kisler

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.

Feed processing for improved alumina process performance

A process is provided 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: (a) heating the alumina process feedstock to a temperature of 400&deg; C. to 650&deg; C. by direct contact with combustion gas, and (b) cooling the heated feedstock to a temperature at which it can be handled and fed to the alumina process. The treatment process also includes controlling the contact time of the alumina process feedstock at temperatures in step (a) to ensure decomposition of alumina trihydrate and alumina monohydrate. The process also includes: (i) limiting the maximum temperature of incoming gas to a stage of the process in which the alumina process feedstock reaches the above temperature range of 400&deg; C. to 650&deg; C. (which is to be considered to be the highest temperature stage, and/or (ii) limiting the heat input into the highest temperature stage by ensuring that the main thermal load associated with thermal dehydration of the alumina process feedstock is taken up in earlier stage or stages into which combustion gas, at a temperature above that of the inlet gases of the highest temperature stage, is added.

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Sunnybank Hills, Australia

Stephen Grocott