There is current interest in the use of supercritical CO2 (sCO2) as the working fluid for fossil, nuclear and concentrated solar power applications, particularly above 700°C where very little experimental data are available. To address this knowledge gap for compatibility, a broad range of experimental data are needed to populate a predictive model for candidate structural alloys. Initial 500h exposures at 700°-750°C and 1-300bar have shown little effect of pressure and no significant compatibility issues for precipitation strengthened Ni-base alloys, however, longer-term exposures will provide more confidence in designs for 25,000 to beyond 100,000h operation. An “open” sCO2 cycle represents additional challenges due to the incorporation of combustion products in the sCO2, but may be a revolutionary path for CO2 capture from fossil fuel combustion. Simulating open cycle conditions in the laboratory also is a challenge.
Research supported by the U.S. Department of Energy, Office of Fossil Energy.