Kirkland Lake Gold’s Fosterville gold mine, in Victoria, Australia, has employed one of CSIRO’s innovative gold processing solutions to improve safety for workers maintaining the slurry mixing tanks at the operation.
CSIRO’s Swirl Flow offered Fosterville workers superior mixing and suspension, while minimising problems associated with dead zones and sedimentation, according to Australia’s national science agency.
Slurry mixing is an integral part of the Fosterville operation, CSIRO said. “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’ (ie draining) tanks,” CSIRO said.
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.
A meeting between technical teams from CSIRO and Fosterville identified Swirl Flow as a possible option to reduce the amount of maintenance required, according to CSIRO.
“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,” CSIRO said.
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,” CSIRO said.
Fosterville Gold Mine’s Technical Process Superintendent, Susan Mills, said: “For us, the driving benefit of Swirl Flow was the health and safety aspect. The safety of our people is paramount and the benefit of reducing the hazards of falling scale during maintenance made the decision simple.”
Mills said there other benefits.
“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,” she said.
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, according to CSIRO. “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,” the agency said.
CSIRO Lead Scientist, Jie Wu, said: “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.
“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.
“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.”
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,” Dr Wu said.
“We hope that Swirl Flow will become a mainstream alternative mixing technology for a number of applications in the minerals sector.”
Swirl Flow technology was developed with CSIRO partners at Queensland Alumina. The technology enhances the agitation process by mixing liquids and suspended solids to create a tornado-like vortex in a tank. It uses a motor, gearbox and a specially-designed radial impeller with a short shaft near the top of the tank. The system improves agitator reliability, resulting in reduced maintenance and shutdowns. Due to higher and more uniform wall veolcities, the scale formation rate is also reduced, according to CSIRO.