Numerical Research Of Combustion And NO_X Emission Characteristic Of 100MW Hexangular Fired Boiler

China is now the largest coal producer and consumer in the world. During coal combustion, many kinds of pollutants are released. Among them, nitrogen oxide (NOX) has received much more concern due to its adverse effects on the environment. A large number of control technologies have already been available up to now. However, the formation mechanisms of NOX are still not clear due to their complicated nature, which are influenced by many factors, such as temperature profile, concentrations of components, fuel characteristics, etc. CFD (Computational Fluid Dynamics) has been shown to be capable of providing insights into coal combustion and pollutant (such as NOX) formation processes. The present thesis focuses on simulating NOX formation and coal combustion processes in a real furnace by CFD method.A numerical approach is used to investigate the performance of a 100MW hexangular pulverized-coal-fired boiler of a thermal plant, with the emphases on simulating flow field, temperature profile, components concentrations, particle tracks and NOX emissions. The simulation data are re-examined to elucidate the distributing law of physical parameters. The NOX formation mechanisms and their influencing factors have been discussed in detail. Three different approaches for retrofit of boiler configuration have been suggested to reduce NOX emissions using air-staged combustion techniques. The upper secondary air jets are promoted along the furnace height as to be over fired air jets to supply air, the temperature is reduced because of the fuel - rich environment of combustor region, and the NOX emissions fall because of the low temperature of the furnace. The distance between OFA jet and original upper secondary air jet of different retrofit methods are 1m, 2m, 3m. The air-staged combustion techniques not only reduce the emissions of NOX, but also reduce the burn-off rate of coal, to considerate comprehensively, the second method maybe the best retrofit method to the boiler.The research results gained in this paper could provide reference and guidance to engineering applications.