选择性非催化还原烟气脱硝反应影响因素实验分析

摘要

In order to meet the ultra-low emission standards,a supercritical660 MW unit with circulating fluidized bed boiler installs a set of selective non-catalytic reduction (SNCR) denitration device in the cyclone separator.The effects of temperature,ammonia nitrogen molar ratio,oxygen content and circulating ash components on the SNCR flue gas denitration were experimentally investigated.The results show that,as the temperature increased from 800 ℃ to 950 ℃,the denitrification efficiency increased continuously and reached the peak value at 950 ℃.At higher temperatures,the denitration efficiency dropped due to the NH3.At temperatures lower than 850 ℃,temperature became the controlling factor of the reaction and rising the mole ratio of ammonia to nitrogen had little influence on the denitration efficiency enhancement.While at temperatures higher than 850 ℃,rising the mole ratio of ammonia to nitrogen would significantly improve the denitrification efficiency,but when the mole ratio of ammonia to nitrogen is larger than 1.50,the denitrification efficiency rise slowed down.When the oxygen content was 0,the number of OH and other active roots was very small,which resulted in a decline in the SNCR reaction,and the increasing oxygen content improved the NH3 oxidation and decreased the denitrification efficiency.The circulating ash containing Fe2O3 and CaO could enhance the NH3 oxidation thus to reduce the denitrification efficiency.%为达到超低排放标准,某电厂筹建超临界660 MW循环流化床(CFB)锅炉机组时在旋风分离器处安装了选择性非催化还原(SNCR)脱硝设备.本文通过实验研究了反应温度、氨氮摩尔比、含氧量和循环灰组分对SNCR脱硝反应的影响.结果表明:随着反应温度从800℃升至950℃,脱硝效率不断提高,在950℃达到峰值,继续升温后由于NH3的氧化作用脱硝效率下降;当反应温度低于850℃时,温度是脱硝反应的控制因素,此时提升氨氮摩尔比对脱硝效率影响不大,当反应温度超过850℃时,提升氨氮摩尔比会明显提高脱硝效率,但氨氮摩尔比大于1.50后,脱硝效率增速放缓;含氧量为0时,OH等活性根很少,会导致SNCR反应进行缓慢,而含氧量增加会加强NH3氧化,减小脱硝效率;循环灰含有Fe2O3、CaO金属氧化物可以促进NH3的氧化反应,从而降低脱硝效率.