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Issue 52 | May 2009
Improving slurry viscosity can
increase flow to autoclaves
used in HPAL processes
CSIRO researchers are investigating slurry viscosity in an effort to help high pressure acid leaching (HPAL) operations increase production from low-grade nickel laterite ores.
The study is being conducted through the Minerals Down Under Flagship by researchers working through the Parker CRC for Integrated Hydrometallurgy Solutions.
Reducing the slurry viscosity allows operators to pump a higher density through the autoclaves at the centre of the HPAL process, says senior Research Scientist Goutam Das.
'This gives a higher nickel input into the autoclave and a higher nickel production', he says.
Goutam also stated that gaining even one per cent in production through such measures equates to a significant result on the bottom line.
The researchers are investigating the rheology of various nickel laterite ores and assessing how factors including mineralogy, particle size and the salinity of process water affect slurry viscosity.
Goutam says the nickel laterites commonly mined in Western Australia, where the research project is based, are smectite ores – a clay-like material. Slurries of this material have a particularly high viscosity and are difficult to pump into HPAL autoclaves at high concentration.
As the mineralogy and nature of laterite ores processed vary between sites, and even within an operation, the researchers have focused on measures to improve the viscosity of these smectite ores in particular.
'We are trying to understand the ore with the highest viscosity first, before understanding how other minerals are affected', Goutam says.
The team's studies showed a plant processing fine particle smectite ore could increase the pulp density and nickel feeding to its autoclave by seven to 10 per cent by weight, by using saline water for the ore slurry and blending it with coarser quartz or iron oxide minerals.
Goutam says every one per cent increase in slurry density would translate into nickel production gains of about two per cent.
