Multi-mode ultra-low-NOX burner for hydrogen-enriched natural gas combustion: Novel in-flame temperature diagnostics and NOX performance

For the decarbonization of hard-to-abate industries, the use of hydrogen (H 2 ) instead of natural gas (NG) is considered a viable and technically feasible option. However, due to potentially higher temperatures within the main reaction zone, hydrogen combustion is often linked to increased nitrogen oxides (NO X ) emissions compared to state-of-the-art natural gas combustion. In this paper, a novel industrial prototype burner was investigated in a standard air-fuel combustion mode and a low-NO X staged air-fuel combustion mode. The burner power varied from 270 to 337 kW , and the oxidizer flow rate was adjusted to maintain a residual oxygen concentration of 1 Vol.-% w.b. To examine the effects of the operating modes as well as the differences between NG and H 2 combustion in detail, an innovative approach for recording in-flame temperatures within the main reaction zone was developed. These temperature measurements revealed fuel-specific temperature profiles perpendicular to the burner axis. The experiments showed only minor differences in NO X emissions, measured in mg/kWh , between NG and H 2 combustion under the investigated operating conditions. The low-NO X mode reduced the emissions to approximately one-third of those in the standard mode. The results support the possibility of decarbonizing hard-to-abate industries using hydrogen instead of natural gas. Low-NO X combustion modes of modern industrial burners will help to comply with strict emission regulations in the future. Furthermore, the innovative temperature measurements presented in this paper proved to be a useful tool for in-depth investigations of the main reaction zone.