Tailings management is an environmental area that receives a lot of attention from the oil sands mining industry. The tailings – a mixture of clay, silt, sand, water and small amounts of leftover bitumen – is produced during the water-based extraction process as part of mining operations, and stored in dedicated areas called tailings ponds.
While most of the materials readily settle to the pond bottom, a significant portion of the silt particles and clays remain suspended in the mix. This mixture is known as mature fine tailings (MFT) and it can take decades for the water to separate from these materials naturally. It’s the reason that Imperial and other COSIA member companies are working aggressively on innovative solutions to speed up the water separation process. Success in this area will accelerate tailings pond reclamation and allow tailings ponds to be returned to natural habitat faster.
At Imperial’s Kearl mine, a key focus of tailings management is a thickener process that dewater fine tailings into a thicker stream, which can be dried and stored for future reclamation needs. The paste is achieved by mixing tailings with a polymer compound that helps them bond together more easily.
At the same time, the company is researching complementary avenues. “We’re also testing a supplementary technology that could help us treat and remediate more fine tailings,” says Atoosa Zahabi, tailings technology area lead at Imperial’s Calgary Research Centre.
The investigation got its start in 2012, when researchers at Imperial’s laboratory at the Centre were testing the response of MFT samples to various treatments. They were trying different combinations and dosages of chemical compounds to see what effects each treatment had on the behaviour of MFT – an approach that is regularly used in tailings treatment.
In 2018, Imperials’ lab team improved the breakthrough research work using three chemical compounds: silica (used in the paint and wine industries), polymer and coagulant (both used in water treatment) to treat and remove the water from MFT. “We found we were getting better results by treating the tailings with the new combined treatment instead of just using the single polymer,” Zahabi explains.
The next step was to prove this result in the field and Imperial began a pilot project at Kearl in September 2019. During the pilot run, a three-kilometer pipeline has been carrying MFT from the tailings pond to specially constructed disposal areas. While the MFT is in the pipe, it is injected with the three chemical compounds to treat the tailings before it arrives at the disposal site.
Meanwhile, the research team is working through innovative solutions to optimize the new treatment to achieve the best results. “Our end goal is to create an MFT that is drier and more easily used in reclamation activities,” Zahabi says. “So far, the treatment is performing well and helping MFT to dewater sooner.”
Over the next year, the team will monitor the deposit to understand the advantages of this new tailings treatment. If all goes well, Imperial could apply the new process commercially within the next few years.
Innovators, you may be interested in:
• Tailings Research Report
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