Experimental and numerical study of pollutant emissions from a domestic condensing boiler fed with natural gas enriched with H[formula omitted]

Hydrogen is recognized as a promising resource for decarbonizing not only the industrial sector, but also the domestic heating systems. Through the partial substitution of natural gas with hydrogen, domestic combustion-based conversion systems can potentially offer improved efficiency, reduced carbon emissions, and cleaner combustion, i.e., lower levels of particulate matter. However, hydrogen exhibits properties that are significantly different from natural gas: (i) because of its higher laminar flame speed, hydrogen is more susceptible to flashback, which may pose significant concerns from the safety point of view; (ii) because of its higher adiabatic temperature, NOx emissions are expected to increase. Thus, experimental and numerical investigations are needed to better understand how the addition of hydrogen to the fuel mixture modifies the combustion process and how to mitigate/control the higher propensity to flashback and NOx formation within domestic devices.