NO2 Emissions in Oxy-Fuel Combustion

Other conference contribution, 2011

Few studies are available about the chemistry of NO2 in oxy-fuel combustion, despite the thought that the formation of NO2 in oxy-fuel plants is higher than in air combustion. A kinetic modeling study of the NO2 formation and reduction process in oxy-fuel combustion is performed. Calculations are based on experiments carried out in a 100 kW test unit fired with pulverized coal. The modeling approach is performed in order to assimilate the process as a gas-phase flow reactor system. NO2 is mainly formed through the HO2 mechanism. In the high temperature region, all NO2 is reduced, but the low temperatures favor the formation of NO2 in the final section of the boiler. SO2 has an important effect on the in-furnace NO2 formation, while the influence of O2 is minor. According to the model, a much higher formation of NO2 is attained in oxy-fuel compared to air combustion, while similar NOx reduction efficiencies are found with recycled-NO2 than with recycled-NO.