CaO表面CO对NO还原作用的实验与模型研究

循环流化床炉内石灰石脱硫对NOx排放产生影响,包括对挥发分氮氧化的催化作用以及对CO-NO还原的催化作用。利用固定床反应器对不同条件下CaO颗粒表面NO+CO的催化反应特性进行了探究。实验表明,无氧条件下,CaO能够显著催化CO还原NO,NO转化率与反应温度和CO浓度正相关,与NO浓度负相关.基于Langmuir-Hinshelwood机理建立了CaO催化NO+CO反应动力学模型,模型考虑了颗粒内、外扩散的影响.该模型适用于氧气浓度很低、CO浓度较高条件下。而在有氧气氛中,该反应受到明显抑制,且O2浓度越高,抑制作用越明显;当CaO周围氧气浓度远大于CO时,可忽略CaO对NO的催化还原作用。

Experimental and Kinetic Studies on the NO Reduction by CO Over CaO Particle Surfaces

The limestone desulphurization has significant influence on NOx emission for circulating fluidized bed boilers,partly due to the catalytic oxidation of volatile nitrogen and catalytic reduction of NO over calcined limestone.The effect of CaO particles on NO reduction by CO was investigated using a fixed bed reactor under different conditions.Experimental results showed that CaO can obviously catalyzed NO reduction in the absence of oxygen.The NO conversion showed positive correlation with temperature and CO concentration,while showed inverse correlation with NO concentration.A kinetic model about NO+CO catalytic reaction system was established based on the Langmuir-Hinshelwood mechanism.The modeling results showed that the external and intraparticle diffusion cannot be ignored.This model is suitable for the conditions of low oxygen content and high CO concentration.However,the experimental results also showed that the NO+CO catalytic reaction over CaO particles was significantly inhibited under oxidizing atmosphere,and the higher oxygen concentration,the weaker the reactivity.Furthermore,when the oxygen concentration is much higher than the value of CO,the reduction of NO by CO on CaO particles is negligible.