Tailings are a by-product of Syncrude’s process to extract bitumen from oil sand. They are composed of water, sand, clay and other substances naturally found in oil sands deposits, and are stored in mined-out areas and large above-ground containment structures called settling basins or tailings ponds. Tailings ponds play an important role in oil sands mining operations by recycling process water, which minimizes consumption of fresh water. The primary tailings management challenge is the long period of time – several decades – that it can take for the fine clay and solids to settle.
In 2010, Syncrude became the first operating mine to receive approval for a tailings management plan designed to meet the long-term intent of stringent new regulations for drastically accelerating reclamation of tailings ponds called Directive 074. Syncrude’s plans to incorporate a multi-pronged approach that employs the following three technologies:
- Composite tails or “CT”: CT mixes mature fine tails with sand and gypsum to accelerate the separation of water from the clay. The CT is then capped with sand and soil, enabling the creation of landscapes that support grass, trees and wetlands.
- Water capping: A layer of fresh water is placed over MFT to form a lake. This technology is supported by over 20 years of research and pilot projects, the largest of which was 4 hectares.
- Centrifuging: Separating the water and clay through centrifuge. Syncrude has successfully piloted the use of centrifuges to remove the water in the fine tailings. This technology produces a soft, clay-rich soil that can be used as a landform foundation in oil sands reclamation areas. We plan to implement this technology in three stages: a commercial-scale demonstration, followed by the development of a commercial plant and finally, a further increase in fine tailings conversion capacity.
Other methods, such as accelerated dewatering, are also being explored.
Syncrude also participates in an industry consortium formed in December 2010 to share best practices and advance innovative tailings management technologies.
More information about Directive 074 is available at www.ercb.ca.
Dried tails after centrifuging processing.