Analysis of NOx emission reduction and changes in exergy by flue gas re-circulation during natural gas combustion

With the development of the economy and society in the world, fuel consumption has increased, and thus the emission of pollutants into the environment. Since gaseous fuels represent the most environmentally friendly type of fossil fuel, the emission of NOx, as the main pollutant during their combustion, is causing more and more research interest. This paper deals with the impact of re-circulation of combustion products on the reduction of NOx emissions, and exergy destruction as its consequence. In the first part of the paper, mechanisms of NOx formation and the factors that affect it are reviewed. After that, a simplified analysis of the flue gases re-circulation was performed especially its influence on emission reduction and exergy losses in flue gases stream. The results are discussed in last part of the paper. Presented results can be very useful for quick emission calculations in process of designing natural gas boiler plants.