Image: Mount Owen: Using flotation to improve coal recovery

Minerals & Metals3 min read

Mount Owen: Using flotation to improve coal recovery

Hunter Valley, Australia

Ausenco and long-term client, Glencore, collaborated to add a flotation module to the Mount Owen coal processing plant in New South Wales, Australia. A lump sum engineering services contract included the world’s first successful use of a jet pump in the coal flotation process, reducing the risk of frothing out and improving overall efficiency.

The Challenge

Historically in thermal coal processing in the Hunter Valley, particles smaller than 100 microns were discarded as tailings. About a decade ago, to address issues of efficiency and sustainability, Glencore process engineers began sampling waste streams and putting a dollar value on this lost coal, leading to greater emphasis on its long-discussed potential for recovery.

In 2019, Glencore approached Ausenco to add a new flotation plant to their Mount Owen operation. Having worked closely with Glencore to develop similar plants at Bulga Coal in 2015 and at Ravensworth in 2018, our team was well-positioned to continue to improve this technology at Mount Owen.

The Better Way

Across the three projects, Ausenco and Glencore teams worked seamlessly to incorporate standard flotation tank cells – themselves a reliable and long-established technology – into the existing operation. Since its first use at Bulga, this process has led to significant improvements in efficiency, and an increased plant yield of approximately three percent. In addition, our team has re-engineered the transfer of feed – from the plant to the flotation cell to the centrifuge and onto the conveyor – using gravity alone, saving considerable energy on additional pumps.

A significant issue in coal flotation is the risk of frothing out the existing plant. Froth forms as chemicals are added to aid in coal flotation, occasionally reaching volumes that can overwhelm and even shut down the entire facility. To avoid this, operators are often prevented from using the volume of chemicals needed for efficient flotation, which reduces recovery.

At Mount Owen, our team implemented the first successful use of a jet pump in coal flotation. These pumps remove air from the stream as they operate, eliminating the frothing risk and allowing greater volumes to be pumped – at ideal chemical levels – reducing this bottleneck in the process.

Our proven history of working successfully together with Glencore enabled us to provide a lump-sum Engineering Services contract, progressing from concept to operation in under two years.

The Outcome

The three percent increase in plant yield has had several knock-on benefits, beyond just the additional coal recovered. Removing this volume of coal from the waste stream reduces total tailings by approximately 20%-30%. That in turn reduces the amount of water needed to pump tailings, lowers water loss through normal tailings losses, and extends the life of tailings facilities.

More efficient coal recovery reduces energy consumption across the operation, recovering more product from every truckload, reducing diesel use. Gravity feed in the floatation circuit eliminates the need for pumping, saving as much as seven gigawatt hours per year alone.

Most significantly, lessons learned from Mount Owen are now being applied back to Bulga and Ravensworth, bringing the same jet pump technology online at those operations. Our collaborative client relationship with Glencore has allowed us to quickly implement these improvements, bringing the same benefits to the rest of their operations.