神华煤燃烧再燃中NO_x生成与还原试验研究

Experimental study on NOx formation and reduction by Shenhua coal during combustion and reburning

为了了解神华煤再燃过程中NOx的还原机理，研究了不同氧气体积分数下燃烧和再燃过程中NOx的动态释放和还原特性．试验采用在线式烟气分析仪，在电炉加热的固定床反应器上进行．结果表明，燃烧过程中NOx的生成挥发份析出峰和焦炭析出峰的双峰释放特性．在氧气体积分数为0％～18％范围内，随氧气体积分数的增大，NOx生成量呈近似线性增长．氧气体积分数从0增至15％，NOx生成量增加约11倍．再燃过程中NOx曲线具有挥发份均相和焦炭非均相还原的双谷分布趋势．相比于焦炭非均相还原过程，挥发份均相还原过程对NOx的还原贡献最大，挥发份随气氛变化更加敏感．当氧气体积分数大于7％以后，煤粉再燃过程不再具有脱硝效果．

To understand the NOx reduction mechanism of Shenhua coal during reburning process, the dynamic releasing and reduction Characteristics of NOx by combustion and reburning at different oxygen volume fraction were investigated. The experiments were conducted on an electrically heated fix bed reactor equipped with online flue gas analyzer. Results show that the formation of NOx has bimodal distribution of volatile NO, and char NOx during combustion. The amounts of NO, keep near-linearly increasing with the increasing oxygen volume fraction at 0%-18%. The NOx amount formed at oxygen volume fraction of 15% is nearly 11 times than that of 0%. The NOx profile during reburning process has two valleys including volatile＇s homogeneous reduction process and char＇s heterogeneous reduction process. The homogeneous reduction process of volatile has greater effect than the heterogeneous process of char on the NOx reduction, and the homogeneous process is sensitive to the atmosphere change. When oxygen volume fraction is larger than 7%, the coal reburning process is ineffective for NO, reduction.