Fixing Coal's Carbon-Capture Problem
(NOTE: This item is the second in a three-part series on clean-coal technology. For links to other parts of the series, see the end of this item.)
Changing U.S. environmental policy has upped the ante on what constitutes "clean coal." Although the power industry has made great strides in cleaning up emissions of mercury, sulfur, nitrogen and other air toxins, the trick now is to also reduce coal-related emissions of carbon dioxide, considered the main culprit in climate change.
Since roughly a third of U.S. CO2 emissions come from power plants, carbon capture and storage technology implemented at power plants would seem to be the magic bullet industry is looking for. That's why the Department of Energy spent years on the $1.8 billion FutureGen project, an ambitious effort to build prototype zero-emission, coal-fired power plants.
In 2008, however, DOE scrapped FutureGen over its soaring costs, turning the effort into a scramble for cost-shared R&D funding among many players pursuing their own, less ambitious projects. Among those companies in the hunt for carbon capture and storage solutions are GE, Praxair, Air Products & Chemicals, Alstom, and Foster Wheeler.
The toughest nut to crack is the challenge of capturing CO2 at power plants. Three approaches are under consideration in DOE's carbon capture R&D program: pre-combustion, post-combustion, and oxy-combustion.
Pre-combustion captures CO2 after the coal is converted to synthetic gas in a coal gasification process, but before the syngas is burned to generate power. The other two options entail add-on technologies at existing coal-fired plants that would capture the CO2 after the coal is burned.
A new Pratt & Whitney Rocketdyne gasifier design shows promise in working more efficiently and producing cheaper electricity than gasifiers from GE and Shell that are already widely available commercially.
A Trimeric Corp. post-combustion R&D project demonstrated that using advanced solvents to "scrub" CO2 from the waste gas of an existing coal-fired power plant can cut the cost of carbon capture by as much as 18 percent versus conventional scrubbers.
On the oxy-combustion front, a Foster Wheeler Development Corp. project led to a process that burns the coal in oxygen instead of air, making it easier to capture the resulting CO2. In terms of electricity and CO2 capture costs, Foster Wheeler contends its process is competitive with the most advanced commercial gasification process today.
Making headway on CO2 capture costs is good news for the coal and utility industries, but the next big question is: What to do with all that captured CO2?
Next: Storing CO2 for the Long Term
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