超超临界锅炉燃烧配风优化的三维数值模拟

Three-dimensional numerical simulation on optimization air distribution for combustion of ultra-supercritical boiler

建立了带二次风道的660 MW超超临界墙式切圆锅炉的三维数理模型,采用Realizable k-ε双方程湍流模型模拟气相湍流流动,采用P-1辐射模型来描述炉内辐射换热,采用混合分数/概率密度函数模型模拟气相湍流燃烧.研究了锅炉二次风风门挡板的阻力特性,并探究了附加燃尽风门挡板开度对660 MW墙式切圆锅炉燃烧与污染物排放特性的影响.结果表明:附加燃尽风风量与其风门开度阻力系数有关,当风门开度小于50%时,附加燃尽风风门阻力系数曲线斜率大幅增加,风量随开度变化的幅度增大;随着附加燃尽风门挡板开度增加,NOx浓度降低,但在炉膛上部煤粉发生二次燃烧,引起屏底烟气温度升高.

The three-dimensional numerical simulation was carried out to study the pulverized-coal combustion process in the 660 MW tangentially fired ultra-supercritical boiler with secondary air duct.The realizable k-e model was used to simulate gas coupled with discrete phase model for coal particles;P-1 radiation model was used to describe radiation and the mixture fraction/Probability density function(PDF)model was used to simulate the gas phase turbulence combustion.The resistance characteristics of the boiler damper are analyzed,and the influences on the combustion characteristics and pollution emission of unit wall type tangentially fired boiler are studied for four damper opening of additional air.The results show that the volume of additional air is related to its damper opening resistance coefficient,when the damper opening is less than 50%.The slope of the additional air damper resistance coefficient curve increases significantly,and the air volume changes with the opening degree.With the increase in the opening of the additional air damper,the NO x concentration decreases,the carbon content of the fly ash increases,but the secondary combustion of the pulverized coal in the upper part of the furnace caused the temperature at the bottom of the screen to increase.