Australian Company Develops Online Moisture Analyser for Rotary Disk

Australian Company Callidan Instruments, developers of the MoistScan(tm) online microwave moisture analysis technology; recently completed commercialization of an inline analyser for measuring moisture in mineral concentrates dewatered and filtered using rotary disk filters.

Canadian-owned nickel producer, INCO, has installed a MoistScan(tm) online microwave moisture analyser in their Sudbury smelting facility. The unit is mounted on one of a battery of rotary disc filters used to dewater nickel concentrate to produce a filter cake of 9-10% moisture.

A rotary disc filter is a segmented wheel, each segment comprising a skeletal plastic support frame with filter cloth on either side. The lower half of the wheel, which is submerged in concentrate slurry, has a vacuum applied to the inside of the segments to pull the solids onto the cloth. As the wheel rotates, bringing the segment out of the slurry, vacuum is further applied to draw residual moisture through the cloth thus drying the solids. Before the segment rotates around to return to the slurry, the vacuum is reversed and the solid filtrate is blown from the cloth into a collecting chute.

The Moistscan(r) unit is mounted just prior to the blow-off point, enabling the unit to measure the moisture content of the filter cake. This is critical as it determines the output particle size, and ultimately the efficiency of the baller and the quality of the enriched nickel matte; the end-product of the smelting process.

If moisture content is too high or too low, ball formation becomes problematic costing valuable time and energy . The MoistScan(tm) is proving invaluable. The analyser is being used to adjust the rotational speed of the filters. We’ve integrated the output from the analyser with our DCS. Control room operators observe the moisture content of the filter cake in real time. When it strays outside of our set tolerance range an operator immediately adjusts the rotational speed of the filters to bring the moisture content back in line. At the moment adjustments to the rotary disc filters are done manually, however we are moving to automate adjustment of the rotational speed and possibly also the vacuum levels based on the moisture readout from the MoistScan(tm).

Managing Director, Garry France believes that Callidan Instruments is the first company to successfully develop a real-time moisture analyser for rotary disc filters. I’ve heard that others have considered developing such an analyser but deemed the application “too hard”. It’s what we do best says Mr. France; develop customized solutions to solve a problem or capitalize on an opportunity. Other innovative online microwave moisture meters recently developed by Callidan include analysers for use on screwfeeders and augers; and batch fluid bed dryers.

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