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New online slurry analyser cuts complexity

CSIRO has developed a completely new, ‘online’ slurry analyser that combines XRF and XRD technologies, writes Karen Wrigglesworth.

It was during the late stages of design work to create two very different x-ray based slurry analysers that CSIRO researchers had a ‘light bulb’ moment, prompting them to change tack. Although they had been designing two systems — an x-ray fluorescence (XRF) slurry analyser for sensitive chemical composition analysis and an x-ray diffraction (XRD) slurry analyser for more general use — they began to realise there could be value in combining them into the one analyser.

The minerals industry has traditionally relied on these two x-ray-based technologies to determine a material’s characteristics: XRD for mineralogy and XRF for chemical composition. But as work progressed, researchers found a growing commonality in their designs.

CSIRO ’s Dr James Tickner, who heads the team developing the analysers, says the amalgamation of the XRD and XRF methods came fairly late and was “a big leap for us”.

“Originally, we set out to build separate systems tackling very different problems,” he says. “Our XRF analyser is designed to be extremely sensitive for key elements. The XRD analyser is a more general tool, capable of measuring a wide range of minerals in both slurries and dry powders.”

Essentially, the work has combined the best aspects of XRD and XRF analysis technologies to create a new prototype. It is capable of measuring both mineralogy and ultra-low elemental composition directly on a process-stream without the need for labour-intensive, time-consuming and potentially error-prone sampling.

The spin-off has been a near halving in the tool’s cost and complexity, meaning the new unit is a more compact and cost-effective product. “This is a bonus for us. Our initial focus was to achieve simultaneous mineralogical and elemental analysis in one package,” said Tickner.

The technology, dubbed XRDF for its dual origins, has been designed to operate directly on-stream for plant control and monitoring applications. It measures a material’s characteristics as it passes through the analyser in the form of a slurry. By using a ‘launder tank’ geometry, a wide range of flow rates — up to 100 litres per minute — can be accommodated. The analyser reports updated composition parameters every minute, allowing rapid responses for plant control.

The first industrial prototype, being developed now, will undergo an industrial trial in early 2010. “We need to ensure that the instrument is fairly bulletproof for industry applications and that it can survive any rough handling it might receive,” said Tickner.

The XRDF prototype can be readily adapted to measure different elements and minerals, making it well-suited for a wide range of applications and industries. “In our testing, we deliberately targeted a cross section of materials, including important minerals from the alumina, iron ore and titanium industries,” Tickner said.

For elemental analysis, the research team also believes the prototype is 10 times more sensitive than other commercial slurry analysers. “We can detect down to a level of about 100 parts-per-billion, allowing us to measure valuable metals such as gold, silver, uranium and the platinum group elements, which may only be present at levels of a few grams per tonne or less,” said Tickner.

“We are not aware of any other system capable of doing accurate, on-stream mineralogy, and we have already received considerable interest from industry representatives about our prototype. And the ability to detect elements at parts-per-billion levels in an on-stream system is unique.”

[This article originally appeared in the October 2009 issue of CSIRO’s Process magazine. Karen Wrigglesworth is a freelance writer for CSIRO.]

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