Numerical Simulation Of Low-NOx Reformation Of A600MW Boiler

The problem of NOx emissions do not allow to ignore for atmospheric pollutants such as NOx influencing people’s life in recent years. Aiming at the problem that the NOx emitted from a600MW tangentially fired boiler at full load bad a high concentration of about400mg/Nm3, which can’t meet the NOx emissions requirements of country for the Power plant boiler, use air-staged combustion method conducted by adding OFA nozzles. Combustion situation and NOx emission of this boiler in different conditions,were numerically simulated using FLUENT software. By weighing the advantages and disadvantages, key parameters were determined and transformation scheme was improved.We used the realizable k-epsilon model with the numerical simulation software FLUENT in the numerical simulation of the NOx emissions and pulverized coal combustion process of the original burner structure, getting the flue gas temperature field, the flue gas velocity field, and the concentration distribution of CO, O2, NOx. The results can show the rationality, and we can think the calculation model used above was reasonable and reliable for the prediction of transformation condition.By using the same simulation analysis method for the numerical simulation study on the different modification conditions and contrasting between the original condition and modification conditions, we can see the burning rate and burnout wind nozzle height have influence on the combustion and NOx emissions. On the basis of the comparison between the temperature and the concentration distribution, we discuss the change of the concentration of NOx and its chemical reaction speed distribution and analysed the influence of air-staged combustion on the NOx generating character.The results show that the increase of the over-fire air ratio and the height of OFA nozzles will make NOx emission decrease. However, these increase had an negative impact on the burning-out and the temperature in the upper furnace. It was analysed when the over-fire air ratio was25%, the height of H1was3.6m and H2was6.1m, the decrease of NOx emission reached the maximum value and the adverse effects was controlled within the acceptable range. The numerical simulation results can predict NOx generation and emission, which provide some theoretical basis for the burner design and operation.