As the Global Tailings Review prepares to issue a new industry standard in 2020, Weir Minerals has chosen now to examine the subject of dewatering tailings.

The company, already offering solutions to help dewater tailings, says it is developing an “innovative tailings dewatering solution” to allow operators to pump slurry containing an extremely high percentage of solids. It says it plans to launch the new technology in 2020.

Mike Swintak, Regional Senior Product Manager for Weir Minerals, said dewatering tailings can be a difficult process, yet, when undertaken successfully, “it can deliver significant benefits to mine operators”.

The foremost benefit of dewatering tailings is the reduction of water that needs to be transported from a process plant to a tailings storage facility (TSF).

Reduced water content means tailings slurry volume is decreased, allowing for smaller pipelines and pumping equipment to be used. This can also minimise power requirements.

Thickened tailings and paste can improve the stability of TSFs and diminish their footprint. In some instances where existing TSF capacities are limited by regulatory or other environmental considerations, thickened tailings can help to extend the life of the mine, Weir says.

“Proper containment of tailings reduces the risk to people and the environment, and when decommissioning a mine, thickened tailings facilities are easier to rehabilitate,” the company added.

To a growing extent, thickened tailings are also used for underground mine backfill. This can increase productivity and reduce mine cycle times as well as surface TSF disposal volumes. Underground mining conditions can also be improved due to decreased water and slimes handling.

Important considerations and challenges

“When tailings are not properly managed, the results can be lethal. It is vital that mine operators have a clear understanding of key risks and considerations related to this process, in particular, tailings dewatering,” Swintak said.

Every mine site is different and subject to varying environmental, regulatory, capital and operating cost constraints.

Cost is a key consideration for many operators and can adversely affect the viability of a mine site, according to Weir. Therefore, it is necessary to implement a tailings management strategy that provides both reliability and value for money.

“Environmental limitations are also a major factor when establishing a TSF,” Weir says. “In parts of the world where there is challenging topography, such as mountainous regions or other environmentally sensitive landscapes, TSFs may need to be built further away from the process plant. This can result in slurry being transported across longer distances or higher elevations. Dewatering of tailings is a viable option in these scenarios as less slurry needs to be moved, in turn reducing operational costs.”

Some operations produce highly diluted tailings that require extensive dewatering to reach the desired level of thickness. Other slurries may contain extremely fine particle solids that are also difficult to manage. Large mine sites, or those with complex orebodies, can produce many types of tailings waste slurries, which may require varying methods of treatment.

“Across this multitude of situations, the operator must determine all associated costs and assess the level of dewatering required to confirm the most suitable solution for their site,” Weir says.

“While some mines are in a position to increase the size of their TSFs, many are not, and must implement a viable dewatering process, which can involve significant capital expenditure.”

If dewatering tailings to the highest possible degree, operators also need to develop a suitable strategy for transporting the waste material. Tailings that are too thick to be pumped may need to be transported by either a conveyor system or truck.

Finally, when a mine site reaches the end of its life and moves into the decommissioning phase, TSFs must be dealt with in accordance with regulatory and legislative requirements. As many mine sites need to be rehabilitated and restored to a natural state, a key benefit of producing thickened tailings is its ability to be covered with overburden and re-planted with suitable vegetation.

Weir Minerals offering

“Weir Minerals realises dewatering tailings can be a daunting process for many operators,” it says. “In order to provide the highest level of support and service, the company has invested heavily in its tailings management capabilities. More than just a supplier, every mine site is assessed on a case by case basis to provide a complete tailings dewatering system customised to the customer’s applications and constraints.”

Swintak added: “From developing flow sheets and process requirements to supplying equipment including dewatering systems incorporating our Isodry thickeners and filters, Multiflo floating and mobile pump systems for use on tailings ponds, or GEHO positive displacement pumps capable of transporting high density slurries up to 200 km, we provide customers with peace of mind through our tailings solutions.”

A key point of difference, according to Weir, is the intensive pilot plant testing Weir Minerals can perform at the Weir Technical Centre in Australia. This facility is designed to test tailings samples from around the world to help ascertain the best way to process them in line with the customer’s requirements. Testing is conducted using thickeners/clarifiers, hydrocyclones, filters and centrifuges, as well as a comprehensive pipe loop facility for determining high density slurry pipeline design.

Weir Minerals can also conduct testing at customer mine sites to assess the viability of various tailings management strategies.

As the mining industry gains a better understanding of tailings, it is vital new and improved methods of containment and storage are developed.

“Weir Minerals believes that the dewatering of tailings has a fundamental role to play in this, and continues to push the boundaries of possibility,” it said.