Analysis of leakage and corrosion of air preheater in coal-fired power plant

Abstract

A unit of a coal-fired power plant (300MW) in North China was selected to study. The flue gas parameters (NH3, O2 and flue gas temperature) at the outlet of denitration system, oxygen content at the inlet and outlet of air preheater, and composition of combustion coal were tested. Then, the air leakage and corrosion of air preheater were evaluated from the operation of denitration system, air preheater leakage detection, and acid dew point calculation of flue gas. The influence of ammonium hydrogen sulfate from denitration system on the downstream air preheater is limited due to the low ammonia escaping. The air leakage rates of the air preheater at the side A and B were 8.45% and 3.01%, which are higher than the normal value (< 3%). Due to the air leakage of air preheater on side B, the cold end temperature of air preheater is significantly lower than the acid dew point of flue gas, resulting in the condensation of sulfuric acid mist in flue gas on the air preheater and the sulfuric acid corrosion on the air preheater.