The formation of thermal NO and fuel type NO emission under the air staged combustion in a tower pulverized coal fired boiler that burners are arranged in the front and the rear wall are investigated in this paper. Effects of the distribution of oxygen in the main combustion zone on NOx are then analyze qualitatively. The results show that when the SOFA ratio is 34.98%, NOx yield is at the minimum; thermal NO is not only related to temperature, but also by the influence of oxygen distribution. When oxygen is more and the temperature is high, it is conducive to the formation of thermal NO. The formation of fuel NO and the amount of oxygen and CO have a positive correlation, and more oxygen is conducive to the formation of thermal NO. When CO is more, indicating that the reducibility is good, it will result in significant reduction of fuel NO. Based on the control of the mount of SOFA, the distribution of oxygen in the main combustion zone must be on the rational allocation; in the case of normal combustion, the input of air could not be too much through the first layer burners.

Influences of different SOFA ratios on NOx emission in a tower pulverized coal fired boiler that burners are arranged in the front and the rear wall are investigated in this paper. The front wall is arranged with three layers of burners, and the rear wall is arranged with two layers of burners. The upper layers are the SOFA nozzles. We adopt the method of adding SOFA to reduce NOx emission, and analyze the influence of SOFA on the internal combustion and NOx emissions for pulverized coal boiler. The results show that the addition of SOFA makes the pulverized coal fired boiler form a reduction zone in the main combustion zone, which can inhibit the NOx production increase, so as to achieve the goal of reducing NOx emissions. And the results show that, it is not true that the more SOFA ratio, the less NOx emissions. In fact, the percentage of SOFA has an optimal value, and below or above of this value, NOx yield will increase. Through comparison of different ratios of SOFA distribution modes with the furnace temperature, O2, CO and NOx, we analyze the influence of SOFA ratio on the internal combustion for pulverized coal boiler, and provide some guidance and bases for the optimization of other similar units.