Carbon Dioxide Capture from Flue Gas Using Dry Regenerable Sorbents
Regenerable sorbents based on sodium carbonate (Na{sub 2}CO{sub 3}) can be used to separate carbon dioxide (CO{sub 2}) from coal-fired power plant flue gas. Upon thermal regeneration and condensation of water vapor, CO{sub 2} is released in a concentrated form that is suitable for reuse or sequestration. During the research project described in this report, the technical feasibility and economic viability of a thermal-swing CO{sub 2} separation process based on dry, regenerable, carbonate sorbents was confirmed. This process was designated as RTI's Dry Carbonate Process. RTI tested the Dry Carbonate Process through various research phases including thermogravimetric analysis (TGA); bench-scale fixed-bed, bench-scale fluidized-bed, bench-scale co-current downflow reactor testing; pilot-scale entrained-bed testing; and bench-scale demonstration testing with actual coal-fired flue gas. All phases of testing showed the feasibility of the process to capture greater than 90% of the CO{sub 2} present in coal-fired flue gas. Attrition-resistant sorbents were developed, and these sorbents were found to retain their CO{sub 2} removal activity through multiple cycles of adsorption and regeneration. The sodium carbonate-based sorbents developed by RTI react with CO{sub 2} and water vapor at temperatures below 80 C to form sodium bicarbonate (NaHCO3) and/or Wegscheider's salt. This reaction is reversed at temperatures greater than 120 C to release an equimolar mixture of CO{sub 2} and water vapor. After condensation of the water, a pure CO{sub 2} stream can be obtained. TGA testing showed that the Na{sub 2}CO3 sorbents react irreversibly with sulfur dioxide (SO{sub 2}) and hydrogen chloride (HCl) (at the operating conditions for this process). Trace levels of these contaminants are expected to be present in desulfurized flue gas. The sorbents did not collect detectable quantities of mercury (Hg). A process was designed for the Na{sub 2}CO{sub 3}-based sorbent that includes a co-current downflow reactor system for adsorption of CO{sub 2} and a steam-heated, hollow-screw conveyor system for regeneration of the sorbent and release of a concentrated CO{sub 2} gas stream. An economic analysis of this process (based on the U.S. Department of Energy's National Energy Technology Laboratory's [DOE/NETL's] 'Carbon Capture and Sequestration Systems Analysis Guidelines') was carried out. RTI's economic analyses indicate that installation of the Dry Carbonate Process in a 500 MW{sub e} (nominal) power plant could achieve 90% CO{sub 2} removal with an incremental capital cost of about $69 million and an increase in the cost of electricity (COE) of about 1.95 cents per kWh. This represents an increase of roughly 35.4% in the estimated COE - which compares very favorable versus MEA's COE increase of 58%. Both the incremental capital cost and the incremental COE were projected to be less than the comparable costs for an equally efficient CO{sub 2} removal system based on monoethanolamine (MEA).
- Research Organization:
- RTI International, Research Triangle Park, NC (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- FC26-00NT40923
- OSTI ID:
- 964644
- Country of Publication:
- United States
- Language:
- English
Similar Records
Development of Novel Carbon Sorbents for CO{sub 2} Capture
Evaluation of Solid Sorbents As A Retrofit Technology for CO{sub 2} Capture from Coal-Fired Power Plants