Concerns over Global Warming and potential regulations requiring the sequestration of CO2 emissions from fossil-fuel-fired power-generating stations has led to a need for a technology that would allow the carbon dioxide in flue gas to be separated from the nitrogen and other gas species in preparation for its compression, condensation, and permanent sequestration deep beneath the earth's surface. Currently, about a quarter of the flue gas in conventional power plants is composed of inert nitrogen that cannot be compressed with the CO2. The most promising technology to date for retrofitting an existing coal-fired power plant to produce a relatively pure stream of CO2 is a retrofit that allows firing with pure oxygen instead of air. Coupled with flue-gas recycle, this eliminates the nitrogen addition accompanying air firing, and provides recycled flue gas (mainly CO2) to replace the missing nitrogen, thus maintaining flame temperatures, heat transfer, and flow rates similar to those that existed while firing with air. This new technology is termed "Oxy-Fired Flue-Gas Recycle" or "Oxy-Fired CO2 Recycle", emphasizing that the flue gas is primarily CO2.
MAXON Corporation staged oxygen-burner flame
with flue-gas recycle - Southern Research
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Engineers at Southern Research are in the process of retrofitting the 1 MWth pilot-scale Combustion Research Facility (CRF) to allow firing with oxygen or air, including firing in oxy-fired CO2 recycle mode. The initial work to be done with oxy-firing and flue gas recycle in this new facility will be mapping out the response to the adjustable parameters available when retrofitting this technology to a full-scale power plant. By creating such a response map of operating conditions, Southern Research and its partners on this project will be able to identify the optimum way to modify a power plant with this new technology and the optimum method of operating the retrofit plant to minimize cost, maximize efficiency, and minimize pollutant emissions.
Once this initial pilot-scale investigation has mapped the response surface described above, and provide supported data for scaled-up demonstrations at full-scale power plants, the facility will continue to be used in conjunction with CO2 sequestration technology development efforts, by (among other things) providing a stream of relatively pure CO2 flue gas for use in developing the second stage of this important effort, carbon sequestration.
For more information on oxy-fired flue-gas recycle technology development efforts conducted at Southern Research, contact Thomas K. Gale at gale@southernresearch.org.