CSIRO research will unlock bauxite deposits currently thought to be uneconomic to process.

Processing lower-grade bauxites

Light Metals Flagship researchers are developing new technology to process lower quality, high silica bauxite.

• 20 April 2006 | Updated 14 October 2011

• Current activities
• Outcomes
• Partners

The world is fast using up its reserves of high-grade bauxites. Low-grade bauxites might be lower in extractable alumina, but more importantly they are high in ‘reactive silica’.

As the name implies, silica in the bauxite reacts with the caustic soda in the refining process to produce ‘DSP’ (desilication product), which is removed from the process along with the bauxite residue.

The higher the reactive silica in the bauxite, the more caustic is consumed.  At a certain level of reactive silica, bauxites are just not economical to process. In addition uncontrolled desilication leads to a number of other processing problems such as enhanced scale formation.

Current activities

Flagship researchers are working with industry to develop ways of processing lower-grade (high silica) bauxites. The strategies are to:

• reduce the silica that enters the process
• modify the extraction process to alter the nature of the DSP formed
• recover soda from the DSP in residue.

A number of processes are currently being investigated, including:

• beneficiation of ores (rejecting the silica before it enters the process)
• bauxite pre-treatment to change the relative reactivity of minerals
• substitution of lime for soda in high temperature DSP
• hydrothermal caustic recovery from DSP 
• new variations of acid routes for extraction of alumina from high silica bauxites.

Outcomes

The development of new technology to treat high reactive silica ores would enable currently uneconomic bauxite resources to be processed, and would be applicable to reserves such as the Aurukun deposit in northern Queensland. Economic benefits from the development of the Aurukun resource alone would exceed A$2 billion.

New technology could also significantly extend the life of the nearby Weipa bauxite mining operation.

Two new processes are currently being developed in CSIRO to reduce caustic consumption in the processing of high silica bauxites:

• the first is a pre-treatment process that has could reduce caustic losses by approximately 40 per cent
• the second is a refining process variation with similar potential to save caustic, but applicable only to a specific type of high silica bauxite.

The next phase of the project is to move both processes from the lab scale to the proof of concept stage. 

Partners

This project is based at CSIRO Minerals’ Waterford site, and is being carried out with the Parker Centre for Hydrometallurgy.

Learn more about CSIRO's work in Minerals Processing & Metal Production.