Computational modeling of flow field in boiler before and after urea injection under different conditions

Abstract

In order to achieve ultra-low NOx emissions, the effects of total excess air coefficient, air coefficient in main combustion zone, blended-coal combustion and ammonia nitrogen molar ratio on a 330 MW coal-fired boiler combustion were studied by numerical simulation. The results show that the velocity field and temperature field in the furnace have synergy, the better the synergy is, the faster the temperature rises, and the more NOx it generates. Compared before and after urea spraying, the NOx concentration decreased with the decrease of the total excess air coefficient, the optimum total excess air coefficient is about 1.15, and the denitrification rate is as high as 76.2%. The smaller the air coefficient in the main combustion zone is, the smaller the NOx concentration is. The optimum air coefficient in the main combustion zone is about 0.92, and the denitrification rate is 85%. After urea injection, the denitrification rate of high volatile coal combustion is higher than that of low volatile coal combustion, and the reasonable blending mode of coal can reduce NOx emissions. The larger the ammonia-nitrogen molar ratio is, the lower the NOx concentration is. When the ammonia-nitrogen molar ratio is greater than 2, the amount of ammonia escape at the flue outlet exceeds the standard. When the ammonia-nitrogen molar ratio is less than 1, the NOx concentration at the flue outlet is greater than that before urea injection. The optimal ammonia-nitrogen molar ratio is about 2.

Entransy-based optimization on the energy-saving potentials of thermal power generation

“…在大多数情况下, 百叶窗调节策略可以 . Yuan和Zeng [62] 通过对锅炉内部速 度场、温度梯度场的协同角度以及NOx浓度的分析发 现, 炉内温升随着协同数的增加而升高, NOx生成越 快, 如图18所示.…”