The coal-fired power units in Guizhou Province generally use high-sulfur

high-ash and high-contamination coal

which causes serious ash accumulation in the selective catalytic reduction(SCR) flue gas denitration system

like in the ammonia spray grid

horizontal flue

deflector

rectifier grid

catalyst and other places. Moreover

the ammonia escape is obviously exceeding the standard value

resulting in high differential pressure of air preheater. For this reason

this paper proposes an SCR anti-blocking ash flow field optimization technology and applies it to the SCR flue gas denitration system of a 660 MW unit W-type boiler. The main transformation plan is to replace the original ammonia-spraying grid with petal-type ammonia-spraying grid which has strong anti-ashing ability

optimize the baffle arrangement

and increase the flow velocity at the deflector and flue bottom to reduce the ash accumulation and optimize the angle of the incident rectifying grid. After 5 months operation since the transformation

the boiler shutdown inspection shows that the abnormal ash blocking of the ammonia spray grid

flue and deflector was solved fundamentally. It provides favorable conditions to achieve good performance of the SCR denitration system and to reduce ammonia escape concentration.