OBJECTIVES

An important driver in the alumina industry is to increase the yield and rate of the gibbsite precipitation stage in order to boost the overall productivity of a refinery. The precipitation process is controlled by the interplay between crystal growth, agglomeration and nucleation. Recent work has significantly increased the fundamental understanding of some of these sub-processes. However, this understanding needs to be expanded and then utilised in advanced precipitation process modelling, design and optimisation.

The precipitation stage also plays a pivotal role in determining the quality of the resultant smelter grade alumina (SGA), which is characterised by parameters such as purity, particle size distribution and particle strength. More accurate relationships between SGA quality and chemical/morphological properties of the preceding gibbsite are required for further improvement of SGA product quality.

This project focuses on achieving the following objectives:

• improving fundamentally-based mathematical models for gibbsite crystal growth, agglomeration and secondary nucleation kinetics (rates)
  
• modelling the relationship between gibbsite quality and process conditions, and exploring ways to improve yield and quality
  
• identifying the effects of precipitation and calcination conditions on alumina properties such as strength
  
• improving the ability to model large-scale precipitators, which are commonly more complex to model due to their inhomogeneous nature
  
• implementing advanced developments to deliver to pre-competitive and 1:1 industry projects.

INDUSTRY BENEFITS

• better strategies for seeding alumina refinery precipitators with seed crystals of gibbsite to promote gibbsite crystal growth
  
• increased gibbsite yields from precipitation in the Bayer process
  
• improved design and operation of industrial gibbsite precipitators
  
• better quality smelter grade alumina product with improved properties, such as greater strength.

RESEARCH TEAM
Dr Iztok Livk (Project Leader)
A/Prof Parisa Arabzadeh-Bahri
Mr Peter Austin
Ms Dianne Bedell
Dr Andrey Bekker
Mr Neil Francis
Dr Alex Heath
Mr James Hockridge
Dr Tian Li
Ms Judy McShane
Mr Mark Schibeci
Ms Denise Vassallo

RESEARCH COLLABORATION
CSIRO Minerals
Murdoch University

PROJECT DURATION
2005-2008