Introduction
Australia is the world's largest producer of alumina (aluminium oxide). In 2002/03, over 16 million tonnes, valued at more than A$5 billion, were produced from Australia's six refineries via the Bayer process. This involves the dissolution of aluminium minerals in bauxite using hot concentrated caustic solutions. The loaded liquor is separated from the waste solids and then the aluminium is recovered as gibbsite (alumina hydrate) by cooling of the liquor and seeded precipitation. Finally, the gibbsite is calcinated to alumina by heating.

A schematic of the Bayer process is shown below. Being a mature industry, there is an on-going need for process improvements and new technologies to keep the Australian alumina industry competitive.

Specific Areas of Research
Following discussions with the Parker Centre’s Alumina Industry Technical Panel (which involves the R&D managers from all five Australian alumina companies), the Alumina Program’s research effort for 2002-2005 is focusing on five key areas, namely:

• Precipitation Chemistry
• Precipitation Technology
• Solid-Liquid Separation
• Impurity Control
• Bayer Environmental Issues

Research projects involving CRC funds are directed towards pre-competitive discovery activities which enhance the fundamental understanding of the Bayer process. Collaborative projects involving industry funds focus on the solution of specific processing problems, although some multi-sponsored collaborative industry projects (generally through AMIRA International) also address fundamental research issues.

Some current research areas include:

Expertise/Capabilities
The Alumina Program draws upon research skills from across a range of disciplines and includes chemists, engineers, fluid dynamicists and process modellers. These researchers are supported by an extensive array of Bayer-specific research equipment, including many unique instruments developed within the Parker Centre. Laboratory and pilot plant equipment as well as equipment for site-based work are available.

Specific expertise and capabilities includes:

• Molecular modelling of chemical processes
• Identification and quantification of solution species
• Understanding the factors which control crystallisation processes
• Modelling unit operations using computational fluid dynamics
• Small scale physical simulations of fluid flow patterns
• Flocculation, rheology and thickener design
• In situ particle characterisation
• Digestion and associated autoclave processes
• Adsorption mechanisms under high ionic strength conditions
• Characterisation and separation of organics in Bayer liquor
• Inorganic impurity reactions and control strategies
• Quantitative identification of bauxites and complex inorganic phases
• Environmental issues including residue treatment

Program Manager: Dr John Farrow