预热燃烧模式下热态焦炭NO排放和燃尽特性实验研究

Experimental study on NO emission and burnout characteristics of thermal char in preheating combustion mode

随着煤粉预热燃烧技术的不断发展,焦炭氮在最终氮氧化物生成的贡献中占据主导地位。为研究预热燃烧模式下入炉热态焦炭(区别于常规冷态焦炭)的NO排放和燃烧特性,自行搭建了两段沉降炉系统,着重考察了煤粉热解温度、燃烧温度及过量空气系数对高温焦炭燃烧生成NO及燃尽率的影响规律。结果表明:区别于冷态焦炭实验结果,提高煤粉热解温度有利于热态焦炭燃烧降低NO排放,过量空气系数(α)为1.0时,最大降氮效率为21.1%;燃烧温度对热态焦炭NO排放的影响主要依赖于燃烧区域α,当炉内呈现较强还原性气氛时,随燃烧温度升高,NO排放量降低,当炉内呈现氧化性气氛时规律则相反;提高煤粉预热温度及燃烧区域温度均有利于降低飞灰含碳量,α为1.0时,飞灰含碳量最大降幅28.6%。

With the continuous development of pulverized coal preheating combustion technology,char-N occupies a dominant position in the formation of nitrogen oxides.In order to study the NO emission and combustion characteristics of thermal char(different from room-temperature char)in the preheating combustion mode,a twostage drop-tube furnace was built,and the effects of pyrolysis temperature,combustion temperature and excess air ratio on NO emission and combustion characteristics of the boiler were experimentally investigated.The results show that,increasing the pyrolysis temperature of pulverized coal is beneficial to reduce NO emissions for thermal char which is different from the experimental results of room-temperature char.When the excess air ratioα=1.0,the maximum NO emission reduction efficiency is 21.1%.The influence of combustion temperature on NO emissions strongly depends on the excess air ratio in the combustion zone.The NO emission decreases with the increasing combustion temperature on NO emission when strong reducing atmosphere appears in the furnace,and the law is reversed when the oxidation atmosphere appears in the furnace.Increasing the preheating temperature and the combustion temperature are beneficial to reduce the carbon content in fly ash.Whenα=1.0,the maximum decrease of carbon content in fly ash is 28.6%.