NaOH作添加剂对NO_xOUT工艺的试验影响

对NaOH作添加剂对尿素作还原剂的选择性非催化还原(NOxOUT)脱硝工艺的影响进行了试验研究。无添加剂时,在780℃～1 000℃范围内随温度升高,NO的浓度先降低后升高,N2O浓度先升高后降低,转折点为900℃。随着氨氮比增大,NO去除率增大,N2O浓度也随之升高,总的NOx去除率由于N2O的影响提高不明显。有NaOH作添加剂时,随着NaOH的添加量的增大,N2O的浓度逐渐减小,NO的浓度在较低温度时,先减小后增大,较高温度时,一直增大,但变化幅度要比N2O小。在氨氮比为1.5且有NaOH作添加剂时,900℃条件下可得到73.48%的总NOx去除率。NaOH对工艺的影响是产生活性基元和去除尿素分解生成的HNCO联合作用,后者作用较大。因尾气中钠盐主要以NaNCO形式存在,由此引起的烟气碱性增大的程度并不严重。

The Experimental Study of the Influence of NaOH as Additive to NO_xOUT Process

The experimental study of SNCR process with urea as reducing agent and NaOH as additive had been carried out.In the temperature range of 780 ℃~1 000 ℃,the components of NO decreases at first and then increases,while the component of N2O increase at first and then decreases with the increasing of temperature with no additive.With increasing of 0.5CO(NH2)2/NOx,NO removal efficiency increases and the components of N2O also increases,the total NOx removal efficiency has not been improved significantly.With NaOH as additive,the component of N2O decreases with NaOH addition increasing at all temperatures,while the component of NO decreases at first and then increase at lower temperature and increases at higher temperature with NaOH addition increasing,but the extent was much smaller than N2O.The removal efficiency of total NOx achieved at 900℃with 0.5CO(NH2)2/NOx=1.5 was 73.48% and addition of NaOH.The influence of NaOH as additive to the process is the combined effect of the production of active species and the removal of HNCO produced by the decomposition of urea,of which the latter play a major role.The addition of sodium acetate causes the flue gas became alkaline gas,but it is not serious for sodium salt existed as NaNCO.