Experimental Study of the Influence of Oxygen Enrichment in Hydrogen-enriched Natural Gas Combustion at a Semi-industrial Scale

This study investigates the effect of Oxygen-Enriched Combustion on hydrogen-enriched natural gas (H2 -NG) fuel mixtures at a semi-industrial scale (up to 60 kW). The analysis focuses on flame structure, temperature distribu tion in the furnace, NOx emissions, and potential fuel savings. A multi-fuel, multi-oxidizer jet burner was used to compare two oxygen enrichment configurations: premixed with air (PM) and air-pure O2 (AO) independent feed. The O2 -enriched flames remained stable across the entire fuel range. OH* chemiluminescence imaging for the H2 -NG fuel mixture delivering 50 concentration kW revealed that higher O2 increases the OH* intensity, narrows and elongates the flame, transitions from buoyancy- to momentum-driven shape, and relocates the reaction zone. At 50 % oxygen enrichment level (OEL), flame shape, OH* intensity, and temperature profiles resembled pure O combustion. Up to 29 % OEL, furnace temperature profiles were similar to those 2 of air-fuel combustion. The power required to maintain 1300 ± 25 ◦C at the reference position decreases with O2 enrichment. Higher OELs resulted in a sharp increase in NOx emissions. The effect of hydrogen enrichment on NOx levels was significantly less pronounced than that of oxygen enrichment. The rise in NOx emissions correlates with increased OH* in tensities. For a 50 % H2 2 blend, increasing the O concentration in the oxidizer from 21 % to 50 % resulted in a 27 % reduction in flue gas heat losses. Utilizing O2 co-produced with H2 could be strategic for reducing fuel consumption, facilitating the adoption of hydrogen-based energy systems.