LOOKING FOR A BETTER WAY
Emerging technology in oil sands mining takes on tailings
By David Coglon
When Sola Adeyinka talks about the potential impact of one of Imperial Oil's emerging technologies – non-aqueous extraction – on the oil sands mining industry, he uses words like "step-change." The excitement is audible in his voice.
"It has the potential to change the whole landscape of the industry," says Adeyinka, a research engineer who is part of a team helping to develop the technology at Imperial's Calgary Research Centre.
It's a bold claim, but one backed by years of work by researchers at the centre that point to non-aqueous extraction (NAE) being a game changer.
Currently, oil sands mining operators rely on a hot water separation process to extract the bitumen ore from the sand and clay. This process also results in leftover material – a mixture of water, clay, silt and sand – that must be stored in large tailings ponds over long periods of time in order to let it settle.
NAE would eliminate the need for wet tailings storage altogether, dramatically accelerating the pace of reclamation.
The process involves mixing the ore with a solvent and a small amount of water. This slurry is then transported in a segment of pipe. As the contents mix in the pipe, the solids – sand, silt and clay – bind together to form agglomerates about the size of a grain of sand. The bitumen and solvent pass through a filter, while the solids are left behind, ready to be washed, dried and placed back into the mine.
The bitumen is produced and the solvent is collected for reuse.
"It's an elegant solution," says Adeyinka. "The fine particles are naturally attracted to the water. The solvent dissolves the bitumen but doesn't like to mix with the solids and water, so everything comes together."
While water-based extraction methods primarily rely on thermal and mechanical energy to recover bitumen from oil sands ore, solvent-based extraction also uses chemical energy to dissolve the bitumen. By using mostly solvent, NAE could reduce water use by more than 90 percent and eliminate the need for wet tailings ponds. The dry tailings generated by the NAE process enable rapid reclamation, which, in turn, means the mine footprint is much smaller than typical oil sands mining operations. And because the solvent does a better job than water at dissolving bitumen, bitumen recovery for NAE is expected to exceed water-based extraction across a wide range of ores.
Keith Abel, an Imperial Oil research scientist at the centre, says the technology provides improved environmental performance and a smaller mine footprint. "And it's not sacrificing anything on the recovery side – in fact, it actually offers better recovery performance, so it's a win-win," he says.
While NAE's merits are apparent, it's taken time for the process to emerge as a technological contender. Its history goes back to a concept originally conceived at Canada's National Research Council (NRC) in the 1970s and later abandoned for economic reasons.
"Solvent extraction is an idea that's been around for a long time, but the industry also recognized that it's a difficult and costly technology to develop," says Abel.
Seven years ago something happened to spark renewed interest. With Imperial building its oil sands mining business, the company's research team was tasked with intensifying its search for breakthrough oil sands solutions. The group soon identified the NRC concept as a key opportunity.
"The original NRC process had some significant issues at the time, so we did our own studies and began extensive experimentation, drawing on experts across Imperial and ExxonMobil," Adeyinka says of the effort that's involved lab-scale tests and larger stand-alone unit tests at research facilities in Calgary, as well as facilities in the United States in Houston, Texas, and Clinton, New Jersey. "The result is we were able to make a number of innovative changes which we've patented and evolved into a viable technology we now call NAE."
Since then, the technology has proved so successful in the laboratory that Imperial is readying for the next step – testing NAE in the field. A team of researchers and process engineers is now designing a pilot plant that could begin operation in Alberta within the next five years.
"It's exciting to see how the technology is evolving," says Adeyinka. "Future oil sands development could be significantly different from what is practised today."