Cryogenic carbon capture (CCC) is another of the technologies which received a USDOE development grant as part of the recent ARPA-E program. Making it cheaper and easier to capture carbon from industrial exhaust flues is an important technology, but that's not the whole story with CCC technology.
An abstract for the American Institute of Chemical Engineers explains the outlines of Cryogenic CO2 Capture for Improved Efficiency at Reduced Cost. The work is still developmental, and the DOE grant should help with the further verification and validation of the system. So far, the simulations and initial testing indicate that this is a technology that will be 2 to 4 times as energy efficient as current absorbtion technology. Furthermore, it can be retrofitted onto existing installations fairly easily, which is not true for absorbtion systems.
Contaminant removal is also improved (sometimes greatly improved) with the cryogenic carbon capture method. Mercury emissions would be reduced from 1 part per million to less than 1 part per billion (a thousandfold improvement in one of the worst problems from current coal plant flues). Sulfur oxides are already well contained by absorbtion methods, and are similarly low with the CCC technology, but nitrogen oxide emissions would be also be negligible, which the absorbtion method cannot do.
The CO2 captured with the CCC process is pure, and should be usable for commercial applications. As stated in teh abstract, "The final products of the process are a liquid CO2 stream at about 150 bar pressure and a gaseous nitrogen stream at atmospheric pressure, both near room temperature. The CCC process exhibits low energy and total costs compared with the current state of the art with high capture efficiency and CO2 purity."
While phasing out the use of coal is certainly an important long range goal, the fact is that coal is going to remain a fuel that will be in use for decades to come. Finding ways to make this a cleaner technology can help improve the environment as other technologies continue to be developed and deployed.
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