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.