选择性催化还原烟气脱硝系统速度场及组分分布对脱硝效率的影响

Influence of inlet velocity field and component concentration distribution on de-NO_x efficiency of SCR denitration systems

为了获得较高的选择性催化还原(SCR)反应器内脱硝效率,通过Fluent软件耦合SCR详细反应机理的方法建立了脱硝反应三维数值模型,研究了脱硝反应入口烟气速度及氨氮摩尔比分布不均对脱硝效率和氨逃逸量的影响。结果表明:首层催化剂入口烟气速度分布不均对脱硝反应影响不大;氨氮摩尔比分布不均对脱硝反应影响较大,当氨氮摩尔比为0.85∶1时,其相对偏差系数从0增大到30%,2层催化剂的脱硝效率从84.6%降低到77.8%,出口氨逃逸量从2.02×10-6增大到36.00×10-6。所以在设计SCR脱硝反应器时,应尽可能地提高喷氨格栅及混合器对NH3和NO的混合效果,使进入前层催化剂的氨氮摩尔比相对偏差控制在5%以内。

To obtain a high de-NOxefficiency in selective catalytic reduction（SCR）reactor,a three-dimensional numerical model was established by using Fluent software coupled with detailed SCR reaction mechanism.On this basis,the effects of non-uniform distribution of both flue gas inlet velocity and mole ratio of NH3 to NO（n（NH3）∶n（NO））on the system de-NOxefficiency was investigated.The results show that,for the first catalyst layer,the uniform degree of flue gas inlet velocity has little influence on the system deNOxefficiency,while that of the mole ratio of NH3 to NO has a great influence.When the feed mole ratio of NH3 to NO equals 0.85∶1,the relative deviation coefficient of n（NH3）∶n（NO）increases from 0to 30%,the de-NOxefficiency of the second catalyst layer reduced from 84.6% to 77.8%.At the same time,the volume fraction of ammonia slip increased from 2.02×10^-6 to 36.00×10^-6.Therefore,during the SCR deNOxreactor design,it is necessary to improve the mixing of NO and NH3 with ammonia injection grid and mixer.