Influence of flue gas recirculation of NOx and CO formation

NOx emissions have been limited in many countries because of their adverse impact on the environment. Different strategies to reduce the amount of NOx realized into the environment from combustion devices have been developed but the main technique to prevent NOx formation in accordance with the limit level of the regulation at a lower cost is flue gas recirculation (FGR). This paper presents the result of a series of laboratory tests to determine the emissions of nitrogen oxides and carbon monoxide from a standard natural gas fired burner applied very often in metallurgical practice. There was a marked effect on the NOx and CO emissions by varying the excess air and the quantity of recirculating flue gases in the combustion air. Significant reductions in the NOx and CO emissions of approximately 80 % and 70 %, respectively, were achieved by external flue gas recirculation.