FLSMIDTH

Water reduction and footprints of tailing facilities can be achieved with FLSmidth’s Ecotails tailings solution – a game changing opportunity for the mining sector.

“The large footprint of conventional tailings dams is a key issue for many mines, as dilute tailings usually take up a large surface area of a mine’s property,” says Leonard Neluvhola, regional product line manager (dewatering) at FLSmidth.

This article first appeared in Mining Review Africa Issue 6, 2019
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“Most mining companies are also looking closely at the environmental impact, including water consumption. This technology brings a quantum leap in the volume of water that can be removed from tailings and returned to the plant for reuse.”

The beauty of the Ecotails solutions, says Neluvhola, is that the combination of drier tailings with waste rock forms a GeoWaste, which is much more stable than conventional tailings.

This geo-stability allows higher stacking, and hence a smaller footprint. At the same time, it does away with the separate need for waste rock dumps, which also takes up significant space.

The stable GeoWaste has another important environmental benefit. The product can be used in concurrent environmental rehabilitation.

This is an approach that is increasingly favoured by forward-thinking mining firms, as it can mitigate the costs and risks of mine closure. Mining operations with both short and long lives will have a particular interest in this technology.

“In their combined form as GeoWaste, the tailings and waste rock are much more conducive to vegetation growth than either product on their own,” he says.

“This makes it more effective for rehabilitation than relying solely on topsoil cleared before mining.”

Instead of being pumped to a tailings facility as a highly diluted slurry, the Ecotails system dewaters and filters tailings to result in a moisture content of just 10% to 25%.

Up to 90% of the water in tailings can therefore be reused in the plant, rather than being lost to evaporation from a traditional tailings dam.

“Our years of experience in the dewatering space has made us market leaders in large thickeners and in fast-filtering equipment, both technologies being vital to the success of the Ecotails concept,” Neluvhola adds.

The company’s range of high-rate and high-density thickeners employed in the Ecotails solution deliver a product with about 65% solids.

This reports for fast-filtering, further reducing the moisture content so the material can be transported by conveyor.

The waste rock is prepared for the GeoWaste by being sized to a conveyable size fraction. The filtered tailings and sized waste rock are then mixed using specially designed transfer chutes.

The GeoWaste can then be placed by a stacking system and can contribute immediately to the rehabilitation of the environment.

“With our Ecotails experience and complete system offering, FLSmidth can provide a complete materials handling solution,” he continues.

This includes crushers, sizers and screen, Krebs pumps, thickeners and filters, conveyor and stacking systems, conducting tests and studies, system engineering and automation systems.

To develop the Ecotails solution, FLSmidth has worked closely over recent years with a leading Canada-based gold mining company.

Given the success of trials to date, the company says it plans to lead the trend of eliminating wet tailings facilities in the mining sector.

Apart from the water saving benefit, it says the Ecotails technology will allow it to combine two of the main “footprint consumers” on its mines - the conventional tailings dam and the waste rock dump.

It expects the solution to have very broad application across its global mining portfolio, as well as in the wider mining industry.

“As FLSmidth in South Africa, we can work with customers from the ground up to ensure the application of Ecotails on mines is fit-for-purpose,” Neluvhola explains.

This first involves testing at laboratory scale for filtering and crushing aspects. From there, the testing advances to pilot stage when a mini-plant can be operated on-site.

“This allows us to extensively test the technology using the customer’s own mined material in the thickening, filtering, conveying and blending phases,” says Neluvhola.

“The data gathered from these tests guides our design of chutes and other equipment.”

Prefeasibility and feasibility studies are conducted to generate the required confidence for the financial commitment that leads to a full project roll-out.

He highlights that the South African office is geared up with the necessary expertise and equipment to conduct laboratory tests and on-site tests and has the pilot plant available.