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| CSIRO | SOLVE | Issue 6 Feb 06 | |
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ARTICLE
MINERALS PROCESSING:
Scanning for Solutions By Tony Kaye
Mining is no longer just about big mechanical shovels as miners embrace CT scanning. Miners are digging deeper and deeper in their quest for the earth’s resources, but increasingly this delving for riches is not just with a big mechanical shovel but with tools that analyse the microscopic heart of ore bodies. Using computerised tomography (CT) X-ray scanning systems – smaller versions of those used in hospitals for medical diagnostics – Australian scientists have developed a tool that helps miners ‘dig’ on a microscopic scale.
Scientists from the CSIRO Minerals’ Perth site, operating as a partner in the Parker CRC for Integrated Hydrometallurgy Solutions, are researching a wide array of minerals processing issues to help mining companies tackle some of the problems they face. Those issues relate to widely varying problems such as the flocculation and consolidation of solids in tailings treatment at large-scale mining operations, to the mechanisms of dust creation on bauxite residue disposal areas.One of the new tools at their disposal is state-of-the-art micro-CT scanning equipment developed by Belgian company SkyScan. Samples measuring up to 68 millimetres in diameter are placed inside the micro-CT scanner and rotated about a vertical axis as sequential X-ray images – typically about 500 – are taken. The images are converted into a series of slices through the sample, showing the components with differing X-ray absorption, which are used to build up a false-colour three-dimensional model to understand the structure of the systems being studied. The SkyScan equipment has a detail detectability down to 1 micron, about a thousand times more detailed than medical CT scanners. “The main reason the micro-CT gets such good resolution down to the micron level is that it’s on an entirely smaller scale,” says CSIRO scientist Dr Craig Klauber, who is leading one of several team research efforts into various minerals processing areas, using the micro-CT. “If you imagine shrinking down a medical scanner by a factor of 10 to 20 or so, you could start to approach that resolution, but you then get limited by sample size. In the systems of interest to mineral processing that is not a problem.” Dr Klauber and his co-workers are using CT scans to help with a variety of problems, such as using the three-dimensional imaging to analyse the formation of residue dust on red mud lakes created as a by-product of refining bauxite into alumina. This can be an environmental issue. “We want to use the micro-CT system to look at the dust-creation process as it occurs so we can potentially determine if other solutions to dealing with this issue can be achieved,” Dr Klauber says. “We may even try and make a time-based three-dimensional movie of the dust-creation process using the CT images acquired over a 30- to 60-day period.” The detailed information gleaned from the micro-CT will also benefit other projects being undertaken. For example, CSIRO Minerals researchers have a successful track record in research into thickeners, the large circular tanks that are iconic images of virtually all mineral-processing sites and are key to recycling process water. Their research has combined computational fluid dynamics and aggregate characterisation to optimise flocculation in thickeners. The micro-CT will be employed to examine the micro-structure of flocculated structures after consolidation, allowing them to extend the understanding of behaviour in thickener beds. “There really is no limit to the number of areas that could benefit from this imaging technology. Even within the narrow confines of hydrometallurgy, we will be looking at all sorts of dissolution and crystallisation problems; potentially even micro-prospecting for the platinum group elements. Problem solving is not limited by imagination, just the handling of large data sets,” Dr Klauber says. APPLICATION An X-ray source is used on one side of a sample, and a 10-megapixel X-ray camera on the other, to create 3D images For further information contact: |
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The CT system uses an X-ray source on one side of the sample of interest and a 10-megapixel X-ray camera on the other, that takes three-dimensional images through the sample as it rotates.
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