Lean Premixed Combustion of Raw Biogas Interchangeability in a Porous Radiant Burner Operated in the Submerged Mode

Abstract

Raw biogas has the potential to be a valuable solution to the world’s insatiable energy demand as well as reduce waste and greenhouse gas emissions. This study investigates the raw biogas interchangeability potential of a circular porous radiant burner (PRB) made of Silicon Carbide (SiC) foam and ceramic. The experiment was carried out on PRB for three different raw biogas mixtures at the firing rate of 200–400 kW/m2 and stable combustion was observed for the equivalence ratio range of 0.75–0.96. The raw biogas mixtures of higher CO2 percentage reduce the surface temperature, radiation efficiency, NOx emission but increase the CO emission. The surface temperature, CO, and NOx emission increased due to the increase in firing rate and equivalence ratio, but the radiation efficiency increased due to the increase in equivalence ratio only. The PRB operates steadily with the radiation efficiency of 15.87–38.92%, NOx emission of 0.7–2.9 ppm, and CO emission of 30–93 ppm for all studied raw biogas mixtures within the range of firing rates of 200–400 kW/m2 and equivalence ratio of 0.75–0.96. A correlation for radiation efficiency in terms of percentage of CO2 in the raw biogas mixtures, firing rate, and equivalence ratio was developed and found that the predicted radiation efficiency agrees well with the experimental results. Overall, the newly developed PRB offers better radiation efficiency than that of other designs operated in the submerged mode for raw biogas.