Alcan International Limited

David R Chinloy

George D Fulford

Kwat I The

Jean Doucet

Pierre G Cousineau

Stephen Ostap

Michael A McKenzie

In a process for biodegrading under highly alkaline conditions organics in a waste stream derived from a Bayer processing system for producing aluminum oxides,

Processes for the alkaline biodegradation of organic impurities

A method of transferring heat between process liquor streams such as streams of caustic liquor in the Bayer process for producing alumina from bauxite, utilizing a heat pipe arrangement for heat exchange. The process streams respectively pass in contact with one surface of a first heat-exchange wall and one surface of a second heat-exchange wall while being isolated from the second surfaces of the two walls; these second walls are exposed to a closed volume (also isolated from both process streams) containing a heat transfer fluid that vaporizes below the temperature of the hotter process stream and condenses above the temperature of the cooler process stream. The heat transfer fluid vaporizes at the exposed surface of the wall contacted by the hotter stream, and condenses at the exposed surface of the wall contacted by the cooler stream, thereby transferring heat (as heat of vaporization) from the former stream to the latter.

Method for transferring heat between process liquor streams

A process for producing alumina from bauxite by the Bayer process. Bauxite slurry is pressure digested in caustic soda solution to dissolve aluminum hydroxides in the bauxite as sodium aluminate while leaving most of the remaining constituents of the bauxite in solid form as red mud. The red mud is separated from the digested slurry to obtain a caustic-aluminate pregnant liquor, alumina hydrate is precipitated from the pregnant liquor and the alumina hydrate is calcined to obtain the alumina. The separation of the red mud from the digested slurry is carried out at a temperature above the boiling atmospheric temperature of the liquor phase of the slurry.

Growing community of inventors

St. Catherine, Jamaica

David R Chinloy