Migration, transformation and removal characteristics of escapted ammonia before wet desulfurization in coal-fired power plants

The ammonia composition and emission concentration in the flue gas at denitration outlet, air preheater outlet and dust remover outlet of three ultra-low emission coal-fired units were collected and analyzed by flue gas sampling method of stationary source, indophenol blue spectrophotometry and ion chromatography. Considering the characteristics of units operating conditions and flue gas treatment system, the migration, transtration and removal characteristics of escaped ammonia in air preheater and dust collector were studied. The results showed that the escaped ammonia at denitration outlet of all units was gaseous ammonia under high and low load operating conditions, and the distribution was uneven, with the ammonia emission concentration at typical locations higher than 2.5mg/m3. Gaseous ammonia begined to transform into filtrable ammonia when it flowed through the air preheater along with the flue gas. The filtrable ammonia emitted at the outlet of the air preheater could account for 47.21%∼68.85% of the total ammonia. The temperature drop and flow velocity of flue gas in air preheater affected the generation of filtrable ammonia. The dust collector could remove most of the escaped ammonia, and the removal effect mainly came from the removal of filtrable ammonia. The removal performance of filtrable ammonia varied with dust collector systems. The escaped ammonia in the flue gas of dust remover outlet was mainly in the form of gaseous ammonia, and the concentration was between 0.15 and 0.60mg/m3 © 2024 Chinese Society for Environmental Sciences. All rights reserved.