Thursday, September 27, 2012

British Announce New Carbon Capture Technology

A new Senate bill introduced last week aims to provide incentives for carbon capture though improved access to tax credits, but it may be a bit premature. The process has not yet been proven on a commercial scale, and some scientists think the ammonia-based materials currently used in typical carbon capture technology actually may contribute to toxic emissions during the process of trying to reduce them.

Current capture processes also require large amounts of heat to separate the carbon so that it can be transported and stored. Power plant officials complain that the capture process is "parasitic"--that is, it significantly reduces the efficiency of the plant by diverting heat to the carbon separation process.

Recent innovations, however, may improve the efficiency and reduce the cost of carbon capture. For example, the Department of Energy last month announced preliminary results of its tests with a new carbon sorbent called BrightBlack, which demonstrated efficiency rates as high as 95% and yielded carbon with purity rates between 95 and 100 percent.

In the BrightBlack process, CO2 is absorbed in a bed of proprietary sorbent pellets and desorbed in a separate reactor that regenerates the sorbent and cycles it back to the absorber at  low thermal temperatures. Through 7,000 absorption-regeneration cycles, and a total of 130 hours of operation, the sorbent showed little-to-no mechanical or chemical degradation. The DOE plans to use the data from the initial pilot project to run scaled-up trials of the process, with the eventual goal of testing it in a pulverized coal boiler.

Meanwhile, British scientists this week announced a new low-cost sorbent called NOTT-300 (from Nottingham University where some of the research occurred) made from aluminium nitrate salt, cheap organic materials and water. In additon to being non-toxic, the material enables captured CO2 to be released using virtually no heat.

The NOTT-300 technology uses two filters. When one filter becomes saturated with carbon, it is removed and the carbon is released through a pressure reduction process while the exhaust gases are diverted to the second filter. The regenerated filter is then reconnected to be used when the second filter becomes saturated, a process the Nottingham scientists say can occur repeatedly and at normal temperatures.

The capture rate during the trial was nearly 100%  The researchers say the rate could be lower in an actual power plant application but should still approach 90%. They also think NOTT-300 could be used in gas separation processes since other gases such as hydrogen, methane, oxygen and nitrogen cannot interact with the material in the same way and therefore cannot be adsorbed.

It is important to point out that these new technologies, while showing great promise, are still only laboratory experiments. It's unknown whether they will work in commercial power plant applications, which are likely many months from being tested.


• The U.S. Department of Energy, "Novel Sorbent Achieves 90 Percent Carbon Capture in DOE-Sponsored Test", August 21, 2012
• Financial Post, "Boost for carbon capture from new non-toxic absorber", September 24, 2012
•TCE Today, "New NOTT-300 MOF offers CCS Potential", September 25, 2012

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