Against the frequent NO_xemission overrunning and increasingly air preheater ammonium bisulfate(ABS)blocking in the ultra low emission situation

reason analysis was carried out and the reasons are considered as the followings

the improved requirement of the NH3/NO_xmixing uniformity

the increased SO_2 to SO_3oxidation rate

the higher requirement of denitration control system

the improved minimum ammonia injection temperature and more difficulty with management catalyst life

and so on.To solve these problems

several countermeasures were put forward

such as adjusting the ammonia injection grid to improve the distribution uniformity of NH3/NO_x

reducing the amount of catalyst and vanadium proportion to control the SO_2/SO_3 oxidation rate

decreasing the ammonia injection quantity

SO_3 concentration or by equipment modifications to broaden the scope of low load operation

performing ammonia injection control system optimization to reduce the NO_xemission overrunning and the risk of excessive spraying ammonia

prolonging the service life of the catalyst and reducing the amount of spent catalyst through effective catalyst management.All of these can provide guidance for realizing safety

economic and efficient operation of the SCR equipment in coal-fired power plants.