Advancing mineral processing through automation

mineral processing

Newcrest Mining’s Lihir operation in Papua New Guinea.

A first-of-its-kind solution, the OnLine Rheometer has the potential to redefine mineral processing in Australia and beyond.

Rheology Solutions has been servicing the mining and mineral processing industry for the past 25 years with specialist engineering supply and expertise, primarily in the measurement and characterisation of slurry properties.

Rheology Solutions developed the first OnLine Rheometer (OLR) – an instrument that can be fitted in a pipeline and can provide feedback on the flow properties of the materials that pass through it in real-time, without the need for manual sampling and laboratory testing.

Recently, the company has pioneered a more specialised version of the instrument, the OLR M2000, focused on the needs of the mining industry.

The ruggedised instrument can be fitted in a pipeline or thickener underflow and relays the measurement data to the process operator. The operator can input specific flow property data to establish optimal production specification parameters.

The OLR can then monitor proceedings and display the slurry conformance throughout the mining and production process.

The OLR M2000 is differentiated from all other instruments available in the market by its ability to index the yield stress. The yield stress is the minimum stress needed to make a concentrated slurry flow. It is often felt when rakes, mixers and pumps commence operation, and the machine requires more energy than normal to begin rotation.

A 3D render of Rheology Solutions’ OLR M2000 unit.

The OLR provides a wealth of data and insight and the mining industry has shown particular interest in the product due to a specific valuable metric – the yield stress index (YSI).

The instrument not only accurately displays the YSI, but does so in an automated manner. This aids understanding of the presence of clays, for example, and accelerates rapid, informed process control by warning of adverse process conditions.

The OLR is evolved automation, because customers need to understand what the sensor is telling them and then act accordingly, whether it is through software-enabled process control or with operator control.

Rheology Solutions partnered with Rheological Consulting Services (RCS) to trial the OLR using slurry from Newcrest Mining’s Lihir gold operation in Papua New Guinea. Lihir had reported periodic “high viscosity events” in the pressure oxidation (POX) circuit with little warning, which reduced throughput, gold recovery rates and increased operating costs.

Following a thorough laboratory investigation, RCS found the yield stress of the slurries changed dramatically during these “high viscosity events”. 

“If this number is really high then the material would become excessively thick and lumpy, flow will be affected, blockages may occur and the reactions and separations are not going to happen efficiently. All this means gold recovery decreases,” Rheology Solutions director of research Pradipto Bhattacharjee said.

“In some cases, you just dilute it. But you got to know ahead of time that this material coming in has got a yield stress of that level.

“If this figure is not good, then it may need to be diluted. Importantly, the level of dilution required can be determined and can be automated to reduce the downstream production effects caused by over dilution.”

The challenge was to find a way to constantly monitor the yield stress of the slurry such that a warning could be obtained for an imminent “high viscosity event”.

Manual sampling and laboratory testing could be done a finite amount of time during the day and was not an option.

This is where the OLR technology became relevant. Prior to the OLR, there was no suitable method for monitoring the yield stress of the slurry, in-line, continuously and in an automated manner.

Through the YSI, which correlates linearly with the yield stress, using the OLR to provide forewarning of a future “high viscosity event” became a viable option. First-of-its-kind laboratory and pilot work ensued and demonstrated that through the YSI metric the OLR detected small changes in material flow behaviour in response to very small changes in solids concentration.

These results showed for the first time that the yield stress of a concentrated particulate slurry could be measured in-line and in a flowing material, and were presented and published at a peer reviewed conference.

Rheology Solutions owner and managing director Patrick Griffin said while the OLR was a valuable mineral processing solution, it has the versatility to be used across various other applications.

“There are many places in a mining operation where rheological information is needed,” Griffin said. “It is not just production but also waste management, other storage, and other operational needs.”

And when it comes to automation, the OLR has the potential to be a universal solution, uniting different applications under a single control.

“At Lihir, for example, the possibility is that OLR units could be placed at many various sites in the mining process,” Griffin said. “Then working again with RCS, OLR units could be the heart of automatic control and the data could be used to control the process automatically.” 

This feature appeared in the April issue of Australian Mining.

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