The challenge – water scarcity
Today’s mines are under more scrutiny than ever before to be in compliance with ever increasing environmental regulations. Water scarcity is a large factor and becomes especially challenging when a critical part of the conventional mining process relies on water as an indispensable element used in the extraction of precious minerals from mined ore. To compound the problem, many ores are being mined in remote locations or in arid climates where water becomes an even more precious commodity.
These challenges are not new to our process and equipment experts. Our experience spans over a century of research, development and practical application to continually improve on process technologies to not only meet today’s demanding standards but to also prepare for future requirements and legislation.
The need for sustainable tailings management
One effective way to increase water recovery is to look at a more sustainable solution for a plant’s tailings management requirements. The processes used in mineral extraction produce enormous volumes of waste, known as wet tailings. The tailings slurry mixture often contains close to 75% water saturation and, in many conventional plants, is pumped directly into massive tailings ponds to allow any excess water to evaporate or dissipate back into the soil. A traditional tailings pond takes up a large area of land and requires a great deal of maintenance and monitoring. Such ponds carry a heightened risk for affected water to seep into the groundwater or for dams to break, despite precautions taken to protect the local environment. The large surface area of the pond also means that it will claim a higher percentage of precipitation.
Recover more water and improve dry stacking ability
FLSmidth’s Deep Cone® paste thickener equipment minimizes the above mentioned problems by increasing the underflow solids concentration, and reducing the amount of water sent to tailings. The additionally captured water from FLSmidth’s paste-thickening procedures can be re-circulated in the plant.
For even more effective tailings management, FLSmidth pressure filters are installed after the tailings thickeners, increasing the efficiency of squeezing moisture from the remaining tailings to create a filter cake that typically contains less than 15 percent moisture. The drier tailings can then be stacked and compacted by FLSmidth conveying and spreading equipment in multiple lifts per pad, taking up less than half of the area of a tailings pond.
FLSmidth’s AFPIV™ minerals pressure filters are installed at the end of the mineral processing line to assist in the recovery of water for re-use in the process. FLSmidth’s newly designed Colossal™ filter press has been engineered to be twice as wide as previous filter presses to efficiently capture even more water for recirculation at the plant.
Increase water conservation and minimize environmental impact
FLSmidth tailings management solutions help conserve precious water for reuse within the plant while lowering overall water consumption. Pressure filters are the most effective way of squeezing moisture from tailings to create a filter cake with a moisture content of only 15 percent. The filtered dry tailings concept means a mine site is able to operate with much less external water compared with similar concentrator plants.
When combined with our dry stack tailings technologies, the solution makes for a far more environmentally friendly mining site. Mining companies can stack and compact the tailings and start the re-vegetation process much earlier. The dry stacked tailings have the benefit of being highly reusable, and can be contoured to allow the stacks to blend in with the local landscape. The area can then be replanted with a native seed mixture as operations continue. This supports and speeds up the environmental reclamation process and expedites the re-vegetation of the surrounding landscape. Upon completion, the dry tailings storage pile eventually blends in with the local terrain and surroundings.
Dry stacking has proven to be the safer and more sustainable option, not only for the mine site, but for neighboring communities, too. Local community acceptance is a highly important business factor for mining customers, who often find it difficult to secure water rights for their operations.
Reduce the need for tailings ponds
Wet tailings disposal is commonly identified as the single most important source of impact on long-term economic costs and environmental concerns for many mining operations. What has long been regarded as standard operating procedure will need to be replaced by more responsible and maintainable mining practices.
FLSmidth’s dry tails stacking technology bridges these evolving mining paradigms and effectively eliminates the critical liabilities associated with wet tailings disposal.
When used for reclamation efforts, customers quickly realize the added benefits of utilizing FLSmidth’s paste, filtration, conveying and dry stacking technologies to maximize the recovery of water for re-use in the process. You can effectively reduce the need for tailings ponds and promote ongoing reclamation and revegetation of the surrounding landscape, thus creating more favorable circumstances for obtaining and renewing operating permits.
Flexible and cost-effective
A typical mining operation using a concentrator with a 100,000 tonnes per day capacity requires greater than 200,000 tonnes of water per day. When utilizing legacy thickener technology and pond evaporation, approximately 50% of that water is lost.
Compare that with optimizing a plant with FLSmidth’s new large capacity filter press technologies; approximately 50,000 tonnes per day of water can be saved! At a cost of US$2.50 per tonne, this amounts to a savings of US$45 million per annum in this example.
Adding the proven AFP high speed filter press technology to the tailings equation allows for a reduction of the number of filters required for any given tonnage. Fewer filters mean fewer controls, instruments, pumps and piping, resulting in lower installed costs.
FLSmidth tailings management offerings include extensive experience in designing in-plant, overland, fixed and movable stacking conveyors (RAHCO® and Conveyor Engineering®) that offer flexibility, are cost-effective and maintenance friendly. Combine all of this with proven Dorr-Oliver® and EIMCO® Hi-Rate tailings thickeners and Krebs® pumping technology to obtain the highest degree of technological advantages for your plant.