燃煤锅炉空气分级燃烧降低NO_x排放的数值模拟

Numerical simulation of low-NO_x emission in a coal-fired utility boiler with staged-air combustion

为了降低燃煤电站锅炉的NOx排放量,在阐述空气分级配风方法降低NOx生成机理的基础上,应用CFD计算软件FLUENT6.0,对一台330MW电站锅炉采用空气分级配风方式,对其炉内燃烧过程进行了冷态、热态的数值模拟。分析比较了NOx排放的测试数据与模拟数据。结果表明,旋流燃烧器对冲布置的锅炉炉内空气呈对称分布,炉内温度沿炉膛高度先升高,然后又略有降低。炉内燃烧区温度最高,O2体积分数最低,NOx密度最高,随着炉膛高度的增加,温度和NOx密度逐渐降低。对现有锅炉在不进行结构改造和不增加设备投资情况下,通过对某些燃烧器功能的适当调整,运用空气分级技术达到了降低NOx的目的。

Based on the mechanism of reducing NO_x emission with staged-air combustion technology, the numerical simulation using CFD (FLUEBT6.0) software on the combustion process in the cold and hot states with staged-air technology for a 330MW coal-fired power plant and the comparison of simulated NO_x emission values with the tested NO_x emission data were conducted. The results indicate that aerodynamic distribution is symmetrical in a utility boiler with opposed-installation whirl burners. The temperature first rises along with furnace height and then slightly decreases. In the combustion zone, the temperature and NO_x concentration are the highest, while the oxygen concentration is the lowest. Without reconstruction and additional equipment cost, the staged-air technology can reach a low NO_x emission by regulating some burners for the existing boilers.