Experimental study of NO and NO2 formation in a PF oxy-fuel firing system

► Oxy-fuel energy based NO emissions lower compared to air combustion values. ► Wet flue gas recycle achieves better NO reduction efficiency at lower inlet O2 concentrations. ► El Cerrejon coal achieves higher reduction efficiency for recycled NO than Lausitz coal. ► NO2/NOX ratio increase with increasing inlet O2 but substantially during wet flue gas recycle. ► NO2 formation peaks at the near flame region.