Taking the SCR denitrification system of a 660 MW coal-fired unit as the object

to solve such problems as large amount of ammonia escape and air-preheater blockage within short operation time

a three dimensional model for this denitration system was established

combining with the results of velocity field cold test in physical model and local NO_xconcentration distribution test.Moreover

numerical simulation of flow field and components field with different disc deflector installation angles and variant ammonia injection schemes was performed by using Fluent fluid calculation software.The results show that

increasing the disc deflector angle properly and adjusting the parameters of each ammonia injection entrance distinguishingly and rationally can improve the distribution situation of NH_3 concentration and the molar ratio of NH_3 to NO_xat the catalyst layer inlet

the standard relative deviation of molar ratio of NH_3 to NO_xcan be controlled within 4%

which satisfies the design and operation requirements well.The optimal solutions can provide a theoretical reference to optimization of SCR denitrification system and operation of large-scale coal-fired units.