To ensure a high de-nitration efficiency of selective catalytic reduction(SCR) system and keep NOxemission below regulation requirements

excessive reductants are used frequently in the SCR denitration system of a large number of coal-fired units

which will result in excessive ammonia escape

increase the operation cost

and bring a series of hidden troubles to the equipments downstream

such as air pre-heater and dust collector. Therefore

from the aspect of ammonia-air mixing and combining with the computational fluid dynamics simulation

the effects of installing ammonia-air mixer

optimizing pipe header size and adopting partition mixing on ammonia consumption of the SCR denitration system is discussed. The application of this technology on retrofitting of a 300 MW unit shows that

the ammonia consumption reduced by about 37.8% and the purchase cost of liquid ammonia can be saved by 68 790 000 yuan per year

indicating this technology has a significant economic effects.