Karara's dry stack tailings solution cuts water use, costs and environmental footprint

With these factors in mind, Karara looked at implementing a dry-stacked/filtered tailings system which would allow for significant water recovery and reuse. As well as reducing costs, dry stack would reduce the tailings footprint to around four square-kilometres.

Bis worked with Karara and FL Smidth to develop a solution to build, own, operate and maintain a unique mobile stacking conveyor. This fixed infrastructure solution was developed by Bis, Karara and FLSmidth to integrate a walking conveyor and stacking technology normally utilised in large scale copper mining operations.

Arriving at the right tailings solution

Leaving aside the significant reduction of the physical footprint to a fraction of the wet tailings alternative, Karara were looking for cost efficiencies in other areas. For instance, the planning of a wet tailings storage facility needs to factor in an ongoing maintenance strategy, this comes with a perpetual cost that can only be guessed at while the decades pass. With dry-stack tailings, the total cost of ownership over the mine’s lifetime is easier to estimate and Karara were confident the dry stack solution would be cost competitive.

Water usage was another key consideration for Karara. With environment and cost factors in mind, Karara wanted to look at ways to have greater control over water assets on site. The ability to reuse and recycle water in the mining process would lead to substantial cost efficiencies by minimising the amount of makeup water needed for the mining operation. 

Choosing experienced partners

It was important for Karara to work with partners who had industry experience and had successfully engineered and previously installed similar systems around the world. The technology implemented into Karara’s Tailings Storage Facility was also an important factor as Karara sought the flexibility to continually update the equipment with the view of running it more efficiently as new technology became available. Innovative resources logistics company Karara engaged Bis to operate the Tailings Storage Facility machinery based on their deep industry experience with materials handling and bulk logistics.

When it came to choose a partner, FLSmidth was identified by Karara as being able to meet the project’s requirements and mine-specific needs.

A primary demand was the ability to supply a cost-effective dry stacking technology ideal for dry climate mining operations that reduced water requirements. With FLSmidth’s advanced stacking capability (machinery working off stacked pile) and ability to stack tailings at 15% moisture content, this meant tangible water savings for Karara. At Karara, the dry tailings will be stacked in 4 Lifts to the maximum height approved by the WA government. The solution proposed by FLSmidth also created a smaller tailings storage footprint, which also meant improved site rehabilitation potential.

Karara worked closely with Bis and FLSmidth to get the project off the ground and make Karara the first mine in Australia to take full advantage of this dry-stack technology.

Overcoming challenges

The expansion stages posed the biggest challenges when it came to estimate the ongoing costs incurred through running the machine. However, Karara, Bis and FLSmidth worked together to come up with estimates for each expansions stage.

Results

Karara’s dry stack Tailings Storage Facility will continue to be expanded with sweep changes throughout its lift at the mine. The Tailings Storage Facility is fast approaching the completion of Lift1, and together with Karara, Bis and FLSmidth are already in the planning stage to lift the equipment to the second level. The next few years will be exciting times for Bis, Karara and FLSmidth.