Modeling of nitrogen oxides formation and destruction in combustion systems

The formation of nitrogen oxides (NOX) in combustion systems is a significant pollutant source in the environment, and the control of NOX emissions is a world-wide concern as the utilization of fossil fuels continues to increase. In addition, the use of alternative fuels, which are typically of lower quality, tends to worsen the problem. Advances in the science of NOX reactions, mathematical modeling, and increased performance of computer systems have made comprehensive modeling of NOX formation and destruction a valuable tool to provide insights and understanding of the NOX reaction processes in combustion systems. This technology has the potential to enhance the application of various combustion techniques used to reduce NOX emissions from practical combustion systems. This paper presents a review of modeling of NOX reactions in combustion systems, with an emphasis on coal-fired systems, including current NOX control technologies, NOX reaction processes, and techniques to calculate chemical kinetics in turbulent flames. Models of NOX formation in combustion systems are reviewed. Comparisons of measured and predicted values of NOX concentrations are shown for several full-scale and laboratory-scale systems. Applications of NOX models for developing technologies, in order to reduce NOX emissions from combustion systems are also reported, including the use of over-fire air, swirling combustion air streams, fuel type, burner tilt angle, use of reburning fuels, and other methods. (C) 2000 Elsevier Science Ltd. All rights reserved.