Flue gas exit temperature from the
air preheater can range from 250 to
350°F depending on the acid dew
point temperature of the flue gas,
which is dependent on the
concentration of vapor phase sulfuric
acid and moisture. For power plants
equipped with wet FGD systems, the
flue gas is further cooled to
approximately 125°F as it is sprayed
with the FGD reagent slurry.
However, it may be possible to
recover some of this lost energy in
the flue gas to preheat boiler
feedwater via use of a condensing
heat exchanger.