Multilayer SiC Piping for 900C Supercritical CO2 Brayton Cycle

Small business proposals to develop components for energy conversion systems that support supercritical carbon dioxide (sCO2) Brayton power cycle systems were requested by the DOE.Specifically, DOE asked for proposals to develop piping systems that can accommodate the sCO2 at temperatures up to 900°C.Previous work sponsored by the DOE have focused on using high nickel alloy piping systems that can handle temperatures up to 750°C.However, these alloys have exhibited significant corrosion when exposed to sCO2 at these high temperatures, and a significant loss of their strength.Silicon Carbide (SiC) ceramic materials demonstrated better corrosion behavior in sCO2, and are known to retain high strength capability up to 1400°C.Ceramic Tubular Products proposes to develop an innovative multilayer SiC tube/pipe design that combines an inner monolithic SiC layer with an outer ceramic matrix composite layer that is not brittle, but fails in a graceful manner when excessive loads are applied.Smalldiameter multilayer SiC tubes are being developed for use as Accident Tolerant Fuel cladding for current light water reactor nuclear power plants.The proposed SBIR project seeks to scale this technology to larger diameter pipe systems and demonstrate their use with sCO2 at temperatures up to 900°C.All Phase I objectives were met.First, fabrication of 20-inch long multilayer SiC pipe sections was demonstrated using commercially available, 3-inch diameter SiC tubes and different low-cost materials and processing methods to produce the outer composite layer.Mechanical testing demonstrated high-strength and the ability to withstand internal pressures in excess of those expected for sCO2 Brayton cycles.Finally, chemical compatibility testing of the SiC material was performed in CO2 at 900°C; superior corrosion resistance of SiC was demonstrated in comparison to high nickel metal alloys.The proposed Phase II research project will be directed at the further development and testing of the multilayer SiC pipe system for use in sCO2 Brayton cycle power systems.This research will involve tasks focusing on: 1) design, finite element modeling and mechanical testing of pipe specimens fabricated using relatively low-cost fiber and matrix materials; 2) joining of SiC pipes to other materials; 3) chemical compatibility of the low-cost SiC specimens and joint specimens in CO2 at 900°C; 4) defining requirements for commercial sCO2 pipe systems; 5) evaluation of future multilayer SiC pipe scale-up and manufacturing cost.This work proposed, if successful, will enable the completion of one or more joint industry-DOE Brayton cycle demonstration projects, and subsequent commercial projects using the high-efficiency Brayton cycle to convert advanced nuclear energy, concentrating solar energy, and advanced fossil energy heat sources into low-cost electricity for US consumers.