Demand for tailings dewatering solutions is on the rise, led by growing recognition of the importance of responsible water usage, according to Metso Outotec, a leading technology and services provider to the mining, aggregates, recycling and metal refining industries.

About 70% of mines operated by major mining companies today are in locations where water scarcity is considered a significant risk, including Peru, Chile, South Africa, Australia, and the western half of the United States. These operators are looking for new solutions to improve water efficiency, filtered tailings and dry stacking of tailings is one option to solve their water problems, according to Geoff Foster, Director, Mining Filtration at Metso Outotec.

"An important challenge specifically in dewatering is community well-being and long-term environmental impacts with regards to water conservation, costs of tailings and reclamation for sustainable and economically viable plants. Issues such as safety, compliance, and sustainability should be addressed with the same sense of responsibility as quality, productivity, and cost-efficiency," Foster said.

According to Foster, dry filtered tailings can be a viable and long-term solution for tailings handling, as it not only helps in recycling significantly more water to the concentrator but also allows for a smaller freshwater footprint which and lowers the risk of dam failures and groundwater contamination.

"We believe dry stacking of tailings is a promising and sustainable way forward. Dry tailings can be more efficient from a capex and opex perspective when compared with wet tailings over the total life of the mine.  We strongly believe that within a few years, dry tailings will be the newly established standard in the mining industry."

Metso Outotec believes that in order to solve complex tailings-handling challenges, the industry requires innovative and smart solutions backed by proven technology and industry knowledge. It says these solutions should maximize ore and water recovery while optimizing operational costs. To this end, it has a Dewatering Technology Center in Lappeenranta, Finland where it conducts R&D and testing of its latest tailings solutions in cooperation with universities.

In each customer interaction, Metso Outotec proposes utilising the latest technology and finding the optimal solution according to the customer or site requirements. Its approach combines three practices: dewatering the tailings, handling them with dry stacking, and reprocessing new and existing tailings.

Foster said the decision phase was crucial because the way tailings are handled does have "a long-term impact" on the mine's economic efficiency and ecology.

New range of smart and sustainable filtration solutions

In April 2021, Metso Outotec launched a new range of smart and sustainable filtration solutions to meet the needs of the mining industry, including the most demanding concentrates and tailings dewatering applications. The selection includes 15 different filter types, from pressure filters of up to 100 bar pressure to vacuum filters and polishing filters.

"Metso Outotec's newest filter, the Larox FFP3716, is purely designed for Tailings dewatering in difficult environments. It is equipped with a new generation of filter plates designed for Tailings conditions to meet the highest throughput. Its enhanced slurry inlet design removes the need for feed shoe handling, increasing reliability and reducing operating costs," says Foster.

"For each case, Metso Outotec can also offer a customizable Life Cycle Services (LCS) for Filters package consisting of scheduled inspections, maintenance and reliability services, plate pack management programs and process optimization.  Programs can also include cost per ton -related commitments, which should be interesting for tailings," says Tomi Ravattinen, Director, Filtration Services at Metso Outotec.

Metso Outotec has also recently launched three filtration inspection packages aimed at improving filter availability and performance and extending the life of equipment. The packages are designed to quickly identify common wear and tear issues such as problems with the plate packs, leakages, and misalignments among others.

Metso Outotec also continues to offer its Inclined Plate Settler (IPS), a compact thickening and clarification solution. It says this solution substantially reduces the retention time, floor space requirements and installation costs compared to conventional thickening and clarifying  solutions. Avoiding water wastage is one of the key goals of the IPS. By using up to 50% less chemicals than alternative solutions, Metso Outotec says the IPS makes water recirculation and recovery easier.

In terms of handling, Metso Outotec provides a wide range of solutions - including conveying, pumping, stacking, and reclaiming - aimed at achieving efficient and cost-effective transportation and storage of dewatered tailings at large mining operations.

Looking forward, Foster said Metso Outotec was in the "early stages" of developing sustainable solutions focused on minimizing waste and re-utilizing the side streams. Its current focus is on developing a solution to re-use tailings as concrete.

"This may be beneficial in cases where tailings areas are not far away from cities," he said.

"The materials and water in tailings dams may be re-utilised, as there may be valuable elements still left - like metal, which can be captured with the new separation technologies. Then the tailings may be used as a component to produce cement concrete, which is still one of the most important construction materials in the world.  This process not only aids to reduce the storage volume of tailings but is also beneficial to the sustainable development of the cement and concrete industry or can be used to build infrastructure in the local community."