Fuel interchangeability for lean premixed combustion in cylindrical radiant burner operated in the internal combustion mode

The trend towards a transition from fossil to renewable energy makes urgent the development of fuel-flexible burners that provides interchangeability between natural gas and a wide range of renewable gases. This study examines the fuel interchangeability potential of a novel annular cylindrical burner made of a Ni-Al intermetallic with advanced high-temperature properties. The burner is designed to operate in the internal combustion mode when the reactions are aerodynamically stabilized in the volume of the cylindrical cavity. The stability limits, radiation efficiency, and CO/NO_X emissions of the burner were studied within the firing rate range of 160–420 kW/m² and the equivalence ratio range of 0.5–1.0. Experiments were carried out for the natural gas and its blends with CO₂, H₂ and H₂-CO, whose flame speeds differ by a factor of three. The addition of H₂ and CO to natural gas was found to reduce emissions and expands the radiant operation mode to a lean region without loss in radiation efficiency. The addition of CO₂ to natural gas also reduces NO_X, but CO emission increases, radiation efficiency decreases and the infrared range is narrowed. For all studied fuels, within the ranges of firing rates of 260–420 kW/m² and equivalence ratios of 0.70–0.95, the burner operates in stable radiant mode with a radiation efficiency up to 30–45%, NO_X emission of 10–50 ppm, and CO emission of 0–40 ppm. In general, the results confirm the fuel flexibility of the new radiant burner to be much the same as for other radiant burners; however, the radiation efficiency is substantially higher than that for cylindrical radiant burners of other designs.