Abstract As part of a test of a solid-fueled heater system, a simple recuperated sCO2 test system was designed, built and installed at the Utah San Rafael Energy Laboratory for extended test operations. The system design parameters included a maximum pressure of 20 MPa, and a maximum primary heater discharge temperature of 600 °C, and a design CO2 flow rate of 5 kg/s. The design point thermal input from the fired heater to the CO2 working fluid was 1.2 MW. Residual heat rejection to the environment was via evaporative water cooling using a conventional cooling tower, and the CO2 to water heat exchanger was of the diffusion-bonded heat exchanger type. The recuperator was of similar design, while the primary heat exchanger was similar to a tangent-tube fired boiler design, while the heat source was alternately coal, biomass and natural gas. The primary purpose of the test campaign was the demonstration of the fired heater - thus a work-extraction turbine was not included in the system for simplicity. A variable area throttle valve was used to control the system flow and pressure, allowing for more flexible operation than possible with a fixed geometry turbine. A robust closed-loop control system was designed for the test system permitting unattended fully automated operations. During the test campaign, extended-duration fired testing in excess of 200 hours of continuous operation were successfully achieved including several switches between gas and solid fuels, and variation in firing rate.
Held et al. (2025) studied this question.