Colloquia

Samenvatting

Currently, 61% of the global electricity generation is produced by power plants relying on fossil fuels. To mitigate emissions, advanced systems like the Allam cycle have been developed. This cycle operates as a dry transcritical cycle utilizing supercritical carbon dioxide (sCO2) and captures produced emissions. However, it still relies on the combustion of natural gas. To achieve a zero-emission system, it is necessary to replace fossil fuels with renewable energy sources like hydrogen (H2). The HERMES project proposes a solution by replacing the working fluid, i.e., supercritical carbon dioxide (sCO2), with supercritical argon (sAr), because of the higher specific heat ratio and higher thermodynamic efficiency. These properties also allow Argon Power Cycles (APC) to achieve higher efficiency than the Allam cycle, while eliminating carbon and NOx emissions entirely. 

This work investigates how the variations in operational parameters affect the thermal behavior and exhaust gas composition during the oxy-combustion of hydrogen in an argon environment. For that, the combustion process was experimentally studied in a tailor-made setup under various operating conditions. The investigated operational parameters included: fuel power input, pressure inside the combustor, the fuel-to-oxidizer ratio, and the flow rate of argon cooling.  The experiments involved an initial combustion test with methane (CH4) followed by H2 combustion experiments ranging from 3 to 8 [kW] and pressures from 1 to 20 [bara].  Furthermore, gas analyses were performed to verify the combustion products and quantify unburnt H2.

In conclusion, power input was identified as the primary cause of increased temperature inside the combustor. Furthermore, active argon cooling significantly reduced the temperature of the combustor walls. Although increasing pressure from 1 to 20 [bara] showed negligible effects on internal combustion temperature, it significantly improved combustion stability, especially during the start-up process. Gas analysis results confirmed that the studied combustor design has achieved stable and complete combustion with 0 [ppm] of unburnt H2 during operation. The experiments were conducted in atmospheric and subcritical regimes, providing experimental data that yield deeper insights into the overall behavior of oxy-combustion of hydrogen in pressurized argon.