Erik Vlot details how mines can pump paste tailings sustainably
In the wake of several catastrophic tailing storage facility (TSF) failures, the mining industry is moving away from wet tailings and embracing safer, more sustainable alternatives. There is currently around 19 billion m3 of tailings produced annually and, with the growing demand for metals and minerals, as well as declining ore grades, this volume will continue to rise. Tailings management has, therefore, become one of the most important challenges facing the industry.
Issue Of Sustainability
Paste tailings allows miners to manage their waste more sustainably, increase their water efficiency and recover value from their waste. Over the past decade, water has become more of an economic and environmental concern for mine operators. Paste tailings reduce a mine’s environmental footprint by utilising considerably less water compared with liquid tailings. For example, at 60% weight solids concentration, paste requires six times less water to pump than tailings with 20% weight solids concentration. Paste tailings can then be used as mine backfill to help ensure the structural stability of the mine; this extends the life of mine (LOM), keeping it profitable for longer so that all the ore can be mined.
Sibanye-Stillwater mine in Montana, USA, is a platinum group metals mine. It’s a narrow vein operation and, therefore, it needs to backfill stopes once they’ve been mined. It uses the mill tailings as mine backfill, which are transported by custom-fit Geho pumps from Weir Minerals that pump 275 gallons a minute at 70% solids, 1,400ft. These pumps are critical to their operation from a production standpoint; reliability is paramount because if the operators can’t backfill a stope they have to halt the entire operation. But it’s also important from a sustainability point of view because it’s putting rock back underground where it originally came from, reducing the mine’s environmental footprint.
The paste that is used as backfill obviously doesn’t need to be stored on the surface. Despite these obvious advantages, there’s an on-going debate within the industry around whether filtered or paste tailings provide the more sustainable tailings solution.
It’s important that miners approach this question holistically, rather than focusing on individual aspects of tailings management. There is often a tendency, for instance, to see filtered tailings as the more sustainable solution because this offers a higher rate of water recovery. However, this comes at the expense of higher fuel and power consumption and, therefore, increases carbon emissions. Filtered tailings, after all, need to be transported to the TSF, spread and compacted.
Weir Minerals has taken this into account in the development of the Geho piston diaphragm pump – it has been designed to be the heart of the mine. When compared with other methods of transport, it provides up to a 20% energy saving, which equates to a 20% carbon footprint reduction. It also eliminates noise and dust pollution.
There is sometimes a perception that PD pumping technology is complex, but when operators see it in action, they understand that the control systems are what makes it so reliable. In recent years the Weir Minerals team has worked hard to improve the pump’s performance, increasing its flow and pressure capacity, while also optimising its reliability and availability.
All tailings management programmes need to be bespoke because no two mines are the same and no two sites are exposed to the same climatic and geological conditions. Weir Minerals works closely with its customers to help them devise the ideal solution based on their specific requirements.
Erik Vlot is with Weir Minerals