In tailings, sand, silt and clay particles, and small amounts of residual bitumen remain suspended in water. If left to settle on their own, they can take decades to settle to a state where reclamation is possible. This mixture, called fluid fine tailings (FFT), also contains large quantities of water and ultimately limits the amount of tailings water available for recycling. This, in turn increases the amount of land needed to store tailings in ponds.
Most of the tailings reduction technologies currently used by oil sands operators to dewater FFT require dredging the material from the tailings pond and, after treatment, depositing it in a dedicated disposal area to further consolidate. This movement and external treatment of FFT increases the footprint of tailings operations.
Shell (now Canadian Natural) Albian Sands has been working with Alberta Innovates and ElectroKinetic Solutions (EKS) to conduct laboratory and pilot tests of a new tailings reduction technology that has the potential to accelerate FFT consolidation within a tailings pond. It’s called In-place Electro-Kinetic Remediation (EKR).
“Simply put, the EKR process involves inserting electrodes into an existing FFT deposit and applying an electric current that causes the release of water and consolidation of the fine particles,” says Gavin Freeman, Technology Development at Canadian Natural. “The solids, particularly the charged clay particles collect and consolidate based on the expected behavior of charged particles in an electric field. As a result, water is released, which is then suitable for reuse within the plant, and the fine solids are concentrated into a much higher density deposit which accelerates ultimate land reclamation.”
The use of electrokinetics in environmental remediation is not new and has been used in different ways, most commonly it is used to stabilize soil for reclamation by forcing any liquids out of the soil. According to Jim Micak, CEO at EKS, many of the previous attempts to use electrokinetics have resulted in very high power requirements and costs with electrodes burning out frequently and difficult to replace.
“EKS has found a way to apply electrokinetics cost effectively and preventing electrodes from burning out, making EKR a unique technology for treating FFT in place, at a cost that is likely to be on par or potentially lower than other treatment technologies,” says Jim.
EKS began developing the technology at a lab scale in 2013. They reached out to industry members for input on how the technology could be applied to tailings.
“Shell supported us and followed our work very closely,” says Jim. “In September of 2014 they worked with us to develop a series of scale-up tests at the Centre for Frontier Engineering Research’s (C-FER) facilities in Edmonton using FFT from one of Albian’s ponds.”
The first test is being conducted in a 25 cubic metre tank using only horizontal electrodes. The material in the tank which started at just over 35 per cent solids has now consolidated to just over 60 per cent.
Tailings is treated in a 135 cubic metre tank with horizontal electrodes
The second pilot is being conducted in a much larger 135 cubic meter tank with horizontally and vertically placed electrodes. The combination has caused the material in the larger tank to consolidate at almost the same rate as the material in the smaller one.
Tailings was also treated in a swimming pool sized tank using horizontally and vertically placed electrodes
“The objective of the program was to prove we could treat the FFT to 60 per cent solids at a competitive price,” says Jim. Adding that percentage is what other tailings reduction technologies are seeking to achieve. “We are sitting at 60 per cent solids and we hope to hit 70 before the end of the year. At every level we have applied the technology it has worked and worked well.”
Jim’s team plans to continue to run the pilot until the materials hit 70 per cent solids.
EKR in action
If EKR continues to work successfully as it is scaled up, the technology could increase the amount of water available for reuse in the extraction process, while reducing the volume of tailings ponds and accelerating reclamation at the end of the mine’s life.
“Implementation of the technology could be simpler compared to other FFT treatment approaches,” says Gavin, “as it would not require substantial process equipment or FFT transport.”
“Albian is working with EKS and Alberta Innovates on the development of this technology,” says Tailings and Water EPA Director Jonathan Matthews. “Other Tailings EPA members are interested in understanding the potential and will be keen to learn from Albian’s pilot study findings.” Additional industry partners are considering forming a Joint Industry Project (JIP) through COSIA for the next stage of the project which will be a commercial scale pilot in an operator’s tailings pond.
“Shell has been a tremendous partner in the development of this technology,” says Jim. “They’ve taken the time to educate us on the special needs and particulars of operating in the oil sands, which has helped us to successfully advance this technology.”