高温低氧气氛煤粉燃烧NO排放实验研究

Experimental study on NO emission during coal combustion at high temperature and low oxygen atmosphere

利用自制等温热重实验台,模拟炉膛烟气气氛,对高温低氧气氛下煤粉燃烧同步NO生成特性进行了研究。结果表明:烟气气氛下提高温度燃烧速率增大,燃尽时间缩短,NO瞬时生成峰值前移、升高,NO释放集中于燃烧前期;燃烧初期挥发分释放主要受温度的影响,导致燃烧初期提高氧气浓度而燃烧速率却提高较少;氧气浓度越高,NO的释放越集中于前期,即挥发分型NO比例越大;煤阶高,NO的异相还原作用较弱,NO累积排放量大;随水蒸气浓度的增加,燃烧速率增加,但对燃烧初期影响较小,主要影响后期焦炭燃烧速率;高温1 300℃下,CO2浓度增加到15%时不利于提高燃烧反应速率,但气氛中含有一定量的水蒸气和CO2可以减少NO排放量。

On the basis of a customized isothermal thermo-gravimetric test rig, the NO formation characteristics during pulverized coal combustion at high temperature and low oxygen atmosphere were investigated,by simulating the furnace flue gas atmosphere. The results show that,in flue gas atmosphere, with an increase in temperature, the combustion rate and peak increased, the burn-out time shortened, the NO instantaneous formation peak went forward and the NO emissions mainly concentrated in early reaction stage. The release of volatile was affected mainly by temperature, which makes the combustion rate increase slightly in the initial stage of combustion. High oxygen volume fraction resulted in more release of NO in early reaction, which means the proportion of volatile NO would increase. The higher the coal rank, the weaker the heterogeneous reduction function of NO and the larger the cumulative NO emissions. With an increase in water vapor concentration, the combustion rate increased and this influence was little in the ini- tial combustion stage but dramatic in the late stage. At 1 300 ℃ ,it will go against the combustion rate if CO2 concentration was increased to 15 %, but the presence of water vapor and CO2 with a certain concentration range can reduce NO emissions.