Analysis on ammonia escape is one of the test projects for denitrification systems in thermal power plants. After flowing through the SCR flue gas denitration system

the fly ash in the flue gas would adsorb a certain amount of escaped ammonia

causing change in physical properties of the ash surface

thus resulting in corrosion and blockage of the heating surface in the boiler tail

which affects safe and stable operation of the thermal power units. To solve this problem

the authors sampled the fly ash at four sites in front of and behind the SCR flue gas denitration system of a 300 MW coal-fired unit

and detected the ammonia and acid gas absorbed by the fly ash. The results show that

as the temperature of the flue gas decreased along the gas flow direction

the mass fraction of the ammonia in the fly ash increased

and there was a certain low temperature residence time in dust collector

the ammonia absorbed by the fly ash increased obviously. The content of sulfur trioxide adsorbed by the fly ash was relatively large

and its change was closely related to the content of sulfur trioxide in the flue gas. Behind the SCR flue gas denitration system

along the flue gas flowing direction

the content of hydrogen chloride adsorbed by the fly ash gradually decreased. The ash surface had an adsorption effect on the escaped ammonia and acid gas

and the two promoted each other

and the adsorption concentration increased with the decrease of temperature

which caused corrosion and clogging of the heating surfaces.