Patent ID: 7481987

Claim:
A method for reducing fouling during the removal of SO 3 from a flue gas stream comprising SO 3 and fly ash, the method comprising: providing a reagent, comprising sodium sesquicarbonate, wherein the mean particle size of the reagent is less than about 40 microns; injecting the reagent into the flue gas stream in a flue gas duct, wherein the temperature of the flue gas is between about 500° F. and about 850° F.; maintaining the reagent in contact with the flue gas for a time sufficient and at a sufficient temperature to react a portion of the reagent with a portion of the SO 3 to reduce the concentration of the SO 3 in the flue gas stream and to substantially avoid formation of a liquid phase NaHSO 4 reaction product that combines with the fly ash so as to not form a sticky ash residue that adheres to the flue gas duct, wherein the reaction product of the reagent and the SO 3 is selected from the group consisting of Na 2 SO 4 , Na 2 S 2 O 7 , and mixtures thereof.