Experimental evaluation of a 20 kW oxygen enhanced self-regenerative burner operated in flameless combustion mode

Results are presented on the effects of oxygen enrichment on the performance of a flameless combustion furnace equipped with a regenerative burner. Natural gas was used as fuel (∼97% CH4) and the oxygen concentration in the combustion air was varied from 21% to 35% (volumetric percent). The influence of oxygen enrichment on temperature and species profiles, pollutant emissions, thermal efficiency and regenerators effectiveness was quantified; measures were registered under steady state conditions for average wall temperatures of 880 °C. The results showed that for all oxygen enrichment rates it was possible to obtain the flameless combustion phenomena with its typical features, like no luminous effect, wide reaction zone and uniform temperature profile. A temperature peak of 1034 °C was measured for the operation with oxygen enriched air (35% O2) compared to 975 °C when normal air (21% O2) was used. NOx emissions were below 5 ppm and the global efficiency increased almost 5% for an oxygen enriched level of 30%. Some comparisons to the burner operating without oxygen enrichment in conventional and flameless mode are presented to highlight the advantages of oxygen enhanced flameless combustion (OEFC) using self-regenerative burners.