The need for new carbon-sequestration technologies has increased due to concerns about global warming and potential regulations requiring the sequestration of CO₂ emissions from fossil-fuel-fired power-generating stations. Specifically, technologies are needed that will 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.

Southern Research has completed a retrofit of the 1 MWth pilot-scale Combustion Research Facility (CRF) to allow firing with oxygen or air, including firing with flue-gas recycle. The most promising current technology for retrofitting an existing coal-fired power plant to produce a relatively pure stream of CO₂ is one that allows firing with pure oxygen instead of air. Coupled with flue-gas recycle, this technology eliminates the nitrogen addition accompanying air firing and provides recycled flue gas (mainly CO₂) to replace the missing nitrogen; as a result, this process maintains flame temperatures, heat transfer, and flow rates similar to those that existed while firing with air. This innovative new technology is termed oxy-firing with flue-gas recycle or oxy-firing with CO₂ recycle, emphasizing that the flue gas is primarily CO₂.

Technology Advantages

• Coupled with flue-gas recycle, this technology eliminates the nitrogen addition accompanying air firing and provides recycled flue gas (mainly CO₂) to replace the missing nitrogen; as a result, the technology maintains flame temperatures, heat transfer, and flow rates similar to those that existed while firing with air.
• In developing this technology, Southern Research mapped out the response to the adjustable parameters available for retrofitting this technology to a full-scale power plant. In creating such a response map of operating conditions, Southern Research and its partners in the project have identified the most efficient method of modifying a power plant with this new technology as well as the optimum method of operating the retrofit plant to maximize efficiency and minimize cost and pollutant emissions.
• Future testing in the Oxy-Fired Combustion Research Facility (OCRF) will continue to be used in conjunction with CO₂ sequestration technology development efforts. Specifically, a stream of relatively pure CO₂ flue gas produced in the facility will be used for development of novel carbon sequestration technologies.