Abstract: In order to control the corrosion on the cold section of the air preheater caused by NH4HSO4 in the flue gas, reduce the risk of ash accretion in the air preheater and lower the consumption of denitration catalyst, the specifications on ammonia slip are quite strict for the denitration equipments. The tests on ammonia slip indicate that the ammonia contents in fly ash have great impacts on ammonia slip; the NH3 and NH4+ absorption by fly ash is the main reason for the low ammonia slip but the large pressure drop of the denitration equipments. Therefore, it is suggested that power plants detect ammonia slip and the ammonia contents in fly ash at the same time to determine whether the air preheater is blocked up.

Key words: flue gas denitrification, ammonia slip, ammonia contained in fly ash, air preheater