Imperial’s Dave Rennard foresees a time, not too long from now, when tailings ponds reclamation efforts will see us looking onto restored landscapes of boreal forests where tailings ponds currently sit.
“I’m very excited and confident that the technologies commercialized in the last few years will lead to solutions,” says Dave Rennard, the tailings technology area lead in Heavy Oil Mining Research and chair of COSIA’s Tailings Research Working Group.
It’s the result of unprecedented national and international collaboration in reclamation research between Imperial, the University of Alberta’s Institute for Oil Sands Innovation (IOSI) and COSIA, leading to real progress and results. And Dave sees it all firsthand.
“I’m very excited and confident that the technologies commercialized in the last few years will lead to solutions” – Dave Rennard
The crux of the issue: How to separate water from the mostly fine clay referred to as fluid fine tailings (FFT) that remain in the middle of the tailings pond following the mining and bitumen extraction process, dry the resultant mud, and reclaim the area to soil suitable to a thriving and sustainable ecosystem.
Left on its own, FFT could take centuries to solidify.
One of the priorities of IOSI’s program is tailings research, so every year IOSI invites proposals from government, academia and private companies, who are pushing the boundaries. COSIA’s Tailings Working Group helps assess the proposals and identify which ones offer the most promise, and should be co-funded by COSIA. Dave’s group has helped review close to 250 research funding suggestions since 2013.
“From that, we have about 15 active projects on the go, and currently have 30 of them at various stages of development,” he says.
Adding to that mix is the learnings and techniques being shared by COSIA-member organizations across the oil sands.
“The collaboration that happens at COSIA is world-leading as far as consortium interface is concerned,” says Dave, a native Nebraskan on assignment at Imperial from ExxonMobil in Texas.
“Everybody is working in the same challenge space and we’re bringing different skillsets to bear. The exciting thing from my perspective is that in working together, COSIA-member companies are commercializing and optimizing the best of tailings treatment strategies.”
John Brogly, COSIA Director, Water and Tailings, agrees. “The continuous improvement of tailings management is an integral component of successful oil sands mining operations,” John says.
“Reducing the size and need for tailings ponds, and increasing the speed at which they can be reclaimed are ongoing challenges being addressed by the industry.”
With FFT comprised of about 70 per cent water and 30 per cent solids, mostly fine clay, a variety of new commercialized technologies will enable tailings to be de-watered, dried and turned into materials solid enough to produce reclaimable land.
One common treatment approach is the use of flocculants an additive that sticks to the clay particles in the FFT and causes them to bundle together, allowing the clay to be separated from the water with the liquid being recycled.
Once enough water is removed, the tailings are then capped, usually through hydraulic placement of sand or fine petroleum coke. The cap helps provide separation between the tailings and the soil and plants that overlay the cap and also provides additional de-watering of the tailings, with the pressure driving more water out while consolidating the tailings ponds contents.
In the end, the resulting mix will be geo-technically stable enough to reclaim and allow for machinery to re-seed the soil in a later stage of reclamation.
Among other projects is one at the University of Alberta exploring under-saturated soil and how factors such as wind flow and rainfall impact the speed of dewatering.
Another at Carleton University is researching FFT flow rates, placing the material into depositional cells to leverage nature to enhance the dewatering process.
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Read more on how COSIA is focused on improving the management of oil sands tailings.