Capturing the power of a tornado in a tank, CSIRO’s Swirl Flow may offer a better performing agitation and mixing system for gold processing. Its benefits start right at the top for Fosterville Gold Mine where it’s being applied to improve safety. DAVID SIMPSON reports

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Solutions to improve the effectiveness of critical parts and equipment used in mineral processing plants are needed. And it's not just about productivity improvements; most importantly, better performing parts can provide a safer environment for employees.

Working with Fosterville Gold Mine

This was the case for Fosterville Gold Mine who sought out an innovative solution to improve the safety for workers maintaining their slurry mixing tanks at their operation in Fosterville, Victoria. 

Slurry mixing is an integral part of their operation. Due to their configuration, conventional agitators tend to create dead zones in which there is little movement in the mixture, resulting in the precipitation and build-up of unwanted scale.

Fosterville Gold Mine was managing scale build-up through frequent tank wall cleaning and "dropping" (i.e. draining) tanks.

However, the possibility of pieces of scale breaking off and falling when the tank is drained, or when the agitator is removed for maintenance, creates a health and safety risk for employees cleaning and maintaining the tanks.

Swirl flow solution

A meeting between technical teams from CSIRO and Fosterville Gold Mine identified a CSIRO-developed solution – Swirl Flow – that could reduce the amount of maintenance required.

Swirl Flow offered Fosterville Gold Mine superior mixing and suspension, while minimising problems associated with dead zones and sedimentation, and has since been installed at their operation.

With an innovative, yet simple, impeller design, Swirl Flow creates a vortex or tornado-like motion in the tank, which prevents stagnant flow, while creating higher wall velocities to help cleanse the walls to reduce scale and build up in the tank.

"For us, the driving benefit of Swirl Flow was the health and safety aspect," Fosterville Gold Mine’s technical process superintendent, Susan Mills, says.

"The safety of our people is paramount and the benefit of reducing the hazards of falling scale during maintenance made the decision simple."

Ms Mills says there are other benefits too.

"The actual conversion process is very straightforward and not costly to retrofit from a maintenance perspective, plus the reduction in scale build-up is anticipated to reduce operational costs incurred for cleaning."

Cost-effective greenfield installation

A comparison suggests that for a greenfields installation in the gold industry, Swirl Flow has the potential to be more cost effective than traditional systems.

It is cheaper due to its simple, light engineering design, and because steel baffle structures are not required. This lightweight design also means that retrofit costs are low to replace failed conventional agitators.

"Currently, companies tend to buy a complete processing system and not look at the individual components within that system to see if there are better alternatives," CSIRO lead scientist, Jie Wu, says.

Prior to the installation at Fosterville Gold Mine, CSIRO had mainly supplied the technology to the alumina industry.

"Processes and mixing applications vary from industry to industry, so we design a Swirl Flow system for the process or requirements of a producer's particular processing, mixing or tank requirements," Dr Wu says.

"We look at the process, we model it and then we work with the manufacturer and the client company to optimise the performance of the Swirl Flow installation."

Looking for development partners

CSIRO is looking to expand the applications of Swirl Flow and is interested in working with both producers and mining equipment technology and services supplier companies to help resolve operational mixing problems. 

"We started in the alumina industry and are now making inroads with applications and plant trials in gold processing, uranium leaching and other minerals sectors.
We hope that Swirl Flow will become a mainstream alternative mixing technology for a number of applications in the minerals sector."

CSIRO has a deep knowledge in the underlying fluid dynamics which cause problems in mineral processing unit operations. They combine this expertise with world class laboratory, pilot scale and modelling facilities and capabilities in mixing to come up with processing solutions for industry.

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