330 MW机组煤粉炉还原区喷入水煤浆热解气还原NO_(x)数值模拟

Numerical simulation of NO_(x) reduction by injecting coal-water slurry pyrolysis gas into reduction zone of a 330 MW pulverized coal boiler

以330 MW机组煤粉锅炉为研究对象,采用数值模拟方法研究了水煤浆热解气的脱硝作用,重点讨论了主燃区过量空气系数α1和热解气比例β对炉内燃烧特性和NO_(x)排放的影响规律。结果表明:当β保持不变时,随着α1减小,主燃区温度降低,燃尽区及炉膛出口温度升高;同时,α1的减小增强了主燃区的还原性气氛,有利于提高热解气的脱硝速率,从而降低炉膛出口的NO_(x)质量浓度,但α1的减小会影响煤粉的燃烧性能并使得炉膛出口CO增多;随着β的增加,炉膛火焰中心上移,热解气对NO_(x)的还原速率升高;当β从5%增至20%时,炉膛整体的NO_(x)质量浓度呈现先减小后增大的趋势,β=15%时NO_(x)质量浓度最低,热解气的NO_(x)还原效率为44.35%。

The denitrification effect of coal-water slurry pyrolysis gas is investigated by numerical simulation in a 330 MW power station pulverized coal boiler,focusing on the influence law of excess air coefficientα1 in the primary combustion zone(PCZ)and pyrolysis gas ratio β on the combustion characteristics and NO_(x) emission in the furnace.The results show that,when β is kept constant,the temperature of the PCZ decreases and the temperature of over-fire air(OFA)zone and furnace outlet increases as α1 decreases.Meanwhile,the decrease of α1 enhances the reducing atmosphere in the PCZ,which is beneficial to improve the denitrification rate of pyrolysis gas and thus to reduce the NO_(x) mass concentration at the furnace outlet.But the decrease ofα1 will affect the combustion performance of the pulverized coal and increase the CO concentration at the furnace outlet.With the increase of β,the center of the furnace flame moves up and the reduction rate of NO_(x) by pyrolysis gas increases.When β increases from 5% to 20%,the overall mass concentration of NO_(x) in the furnace shows a trend of first decreasing and then increasing,and when β=15%,the NO_(x) mass concentration reaches the lowest and the NO_(x) reduction efficiency of the pyrolysis gas reaches 44.35%.