OBJECTIVES

The majority of alumina refineries around the world, and all of those in Australia, have two major problems with impurities. Firstly, crystalline scale deposits form on almost every piece of processing equipment, which reduces the useful operating capacity of pipes and vessels and severely affects heat exchange properties. Secondly, soluble impurities, both organic and inorganic, limit the productivity of the Bayer liquor. Sodium oxalate, a by-product of the breakdown of organic impurities, adversely affects liquor productivity and product quality. In addition, a number of organic compounds in Bayer liquors are very volatile and could pose environmental problems.

The consequences of impurities in Bayer liquors are reduced productivity and increased processing and capital costs, which amount to well over A$1 billion per year in Australia alone. To address the problems caused by impurities, this project aims to:

• discover better methods for decreasing the impact of scale in the Bayer process
  
• understand nucleation of scale on metal surfaces in order to develop strategies to prevent or delay scale formation
  
• investigate reactions and deportment (location) of organic impurities, and technologies for removing organics from Bayer liquor or directly from bauxite
  
• study factors affecting sodium oxalate precipitation and develop techniques to control this precipitation
  
• increase understanding of the deportment, types of chemical species and reactions of certain inorganic impurities (especially fluoride), and how their concentrations might be decreased.

INDUSTRY BENEFITS

• processes for removing inorganic and organic impurities from Bayer liquors, leading to improved efficiency of Australian alumina refineries
  
• improved technologies for reducing the rate of scale formation on refinery processing equipment.

RESEARCH TEAM
Dr Chris Vernon (Project Leader)
Ms Greta Brodie
Dr Allan Costine
A/Prof Glenn Hefter
Dr Franca Jones (leds the Scale component)
Dr Erich Koenigsberger
Ms Melissa Loan
Dr Joanne Loh
Prof Peter May (leds the Fluoride Speciation component)
Mr Jonathon Morton
Dr Mike Thornber
Prof Bill van Bronswijk
Felicia Lee (PhD student)

RESEARCH COLLABORATION
CSIRO Minerals
Curtin University
Murdoch University
RMIT University

PROJECT DURATION
2005-2008