CH4对于尿素选择性非催化还原脱硝的影响研究

摘要

The effects of CH4addition on urea selective non-catalytic reduction(SNCR)denitration in simulated flue gas were investigated in a heated quartz tube reactor.The results showed that adding CH4not only made the denitration curve move to low temperature,but also improved the denitration efficiency at low temperature and the width of denitration temperature window,while the best denitration efficiency dropped slightly;when CH4additive proportion increased from 0 to 6.0,the best denitration efficiency of urea SNCR decreased by 14 percent points,the corresponding temperature reduced by 200 ℃;when CH4additive proportion was 2.0,the width of denitration temperature window reached the peak value of 296 ℃.Adding CH4could relieve the escape of NH3,HNCO in urea SNCR system;the near-zero emission temperature of NH3and HNCO were both dropped about 150 ℃,when CH4was sprayed into the flue gas;the temperature was better not lower than 850 ℃ to prevent CH4escape.Adding CH4would improve the concentration of N2O at low temperature,so the emission of N2O at low temperature should be paid enough attention.Improving ammonia nitrogen ratio enhanced the promoting effect of CH 4on the denitration efficiency when the temperature was below 1 000 ℃,but it could inhibit the promoting effect when the temperature above 1 000 ℃.%在加热的石英反应器中研究CH4对于模拟烟气尿素选择性非催化还原(SNCR)脱硝过程的影响.结果表明:添加CH4可使脱硝曲线向低温方向移动,提高低温下的脱硝效率及脱硝温度窗口宽度,但最佳脱硝效率略有降低,当 CH4添加比由0增大到6.0时,尿素SNCR最佳脱硝效率减少了近14百分点,最佳脱硝温度降低了200 ℃,当CH4添加比为2.0时脱硝温度窗口宽度最大,为296 ℃;添加CH4可以缓解尿素SNCR体系的 NH3、HNCO逃逸,NH3、HNCO的近零排放温度均下降约150 ℃,为控制 CH4逃逸,喷入CH4时应尽量保证喷入处温度不低于850 ℃;添加CH4会提高低温下尿素SNCR的N2O生成浓度,因此低温下N2O的排放问题要引起足够重视;温度低于1000 ℃时,提高氨氮比可以增强C H4对脱硝效率的促进作用,但高于1000 ℃时则起抑制作用.