Bitumen is extracted from mined oil sands ore by mixing it with warm water. Once the bitumen has been removed, a mixture of water, sand, clay and silt is left over. This mixture is referred to as tailings. The water is recycled back through the bitumen extraction process, reducing the amount of water needed from the Athabasca River. The solid material can be used during the reclamation process.
Tailings materials are stored in large ponds where the solids settle to the bottom, leaving the water available to be recycled. A portion of the tailings materials – mostly the smaller clay and silt particles – are too light to settle to the bottom and remain suspended in the water. On their own, they can take years to settle to a state where reclamation is possible. This mixture, called mature fine tailings (MFT), traps the water and thereby reduces the amount of water available for recycling and increases the amount of land needed to store tailings at mine sites.
The members of COSIA’s Tailings Environmental Priority Area (EPA) have been working to develop a suite of tailings reduction technologies to deal specifically with MFT. Syncrude Canada Ltd. has been working with Newalta Corporation, an industry service provider and COSIA Associate Member, to integrate centrifuge technology into their operations to reduce MFT. Syncrude contributed both the technology and their pilot study findings to the Tailings EPA.
In 2010, Shell Albian Sands mine began developing its own centrifuge technology, but in 2012, decided to pick up Syncrude’s technology and the lessons learned from the Syncrude pilot project to fine-tune the technology to fit its operational needs. Albian, now under Canadian Natural, is now operating four centrifuges as part of its Jackpine Mine operations.
Centrifuges use centrifugal force to separate water out of MFT. By spinning the mixture in a large cylindrical vessel at high speeds (between 1,200 and 1,800 rotations per minute (rpm)), the water is forced from the tailings mixture in much the same way a salad spinner removes excess water from lettuce.
Dewatering MFT using centrifuges is a three-step process. First, MFT is harvested from the tailings pond using a dredge. It is subsequently treated with flocculent and/or coagulant, which helps the solid particles to bind together, making it easier for the water to separate from the silt and clay.
The MFT and flocculent/coagulant mixture is then pumped into the centrifuge. The process of spinning the mixture, aided by the coagulating agent, removes the water and causes the solids to bind together. Once the desired solids density is reached, the released water is returned to the tailings pond and ultimately recycled through the extraction process. The solids are transported to a dedicated disposal area (DDA) where they are stored for future reclamation. By removing the water from the MFT before depositing it in the DDA, the footprint for storing tailings is significantly reduced. Compared to other tailings reduction technologies, tailings centrifuges have the potential to reduce the amount of space needed for drying and storing MFT by as much as 50 per cent.
Centrifugation technology is now considered commercially ready. Syncrude Canada’s full-scale centrifuge plant has been operational since 2015. The full-scale plant will has 18 centrifuges that are winterized to run year-round.
Learn more about Syncrude’s centrifuge technology
In 2010, Syncrude worked to scale up its centrifuge facilities, and fine-tuned flocculent mixing, byproduct transport and deposits. In 2011, Syncrude implemented a commercial prototype to understand throughput and commercial readiness. From 2012 through to 2014, Syncrude worked with Newalta to operate a commercial MFT centrifugation demonstration plant.
The findings from all of this work have been shared with the members of the Tailings EPA, to allow other operators to take Syncrude’s work and build on it.
Syncrude’s commercial demonstration MFT centrifugation plant units were developed using modular centrifuge equipment. The units are constructed in pieces, or modules, off-site and are then transported to site where the modules can be quickly assembled. Syncrude utilized the modular concept in the construction of their full-scale plant, in order to manage production costs by reducing field construction time. Modules for the Syncrude facility were fabricated in Edmonton, Alberta, and then transported to site where over 110 pieces were set together like puzzle pieces in just 10 months.
Using a similar approach, Shell constructed their plant 2.5 times faster than they would have been able to if they had constructed the facility in place. By using Newalta’s modular equipment, they are able to scale out their centrifuge plant as their operations grow and potentially take it apart and move it when their current DDA is full.
“Working with both Syncrude and Shell on the development of their centrifuge technologies has been very much about collaboration and the sharing of knowledge,” says Bryne Gramlich, Vice President, Heavy Oil for Newalta. “We used our knowledge of centrifuges in other industries with other customers to assist Syncrude in the development of their commercial-scale demonstration plant and then take that knowledge further to help Shell develop theirs.”
By dewatering the MFT before it reaches the DDA, Syncrude’s centrifuge technology reduces the land footprint associated with tailings storage. It also increases the amount of water available for recycling and the dewatered MFT can be used as part of the reclamation process.
Albian’s addition of hydraulic pumps to transport a slightly wetter dewatered material to the DDA has reduced GHG emissions associated with centrifuging by removing trucks from the transportation process and allowing nature to assist in drying out the MFT material.
Syncrude contributed its tailings centrifuge technology to the members of COSIA’s Tailings EPA. In 2012, Shell Albian Sands picked up the technology and used Syncrude’s findings to further develop the technology for use in its own operations. Since acquiring Albian in June 2017, Canadian Natural will continue to contribute its findings back to the Tailings EPA in order to allow other members to continue to develop the technology.
A number of other companies and organizations were involved in supporting Syncrude’s efforts to develop the technology, including Natural Resources Canada’s CanmetENERGY.
Newalta has been closely involved in both Syncrude’s and Albian’s commercial-scale demonstration plants.
“The collaboration and sharing of knowledge that has led to the success of both implementations of this technology is what COSIA is all about,” says John Brogly, Director of COSIA’s Tailings and Water EPAs. “I look forward to watching this technology continue to evolve as other operators look to make use of Syncrude’s, Albian’s and Newalta’s shared knowledge and experience to develop centrifuge technologies for their own operations.”