Patent ID: 8591849

Claim:
A method for reducing NOx emissions from a lean burn combustion source, comprising the steps of: providing an injection grid in a primary exhaust duct of a lean burn combustion source upstream of a NOx reduction catalyst; providing a continuous duct between an air intake and the injection grid, the continuous duct having a hot portion and a reaction portion, the reaction portion connected to the injection grid; passing air from the air intake through the continuous duct, at least a portion of the hot portion of the continuous duct positioned in a convective zone of the lean burn combustion source, the hot portion of the duct having a first average cross-sectional area perpendicular to the passing air, the hot portion of the duct supplying heated air to the reaction portion, the reaction portion having a second average cross-sectional area perpendicular to the passing air; positioning at least one injector in the reaction portion; supplying an aqueous solution of urea from a storage chamber to the at least one injector; injecting the urea solution into the heated air in the reaction portion for evaporation and decomposition into ammonia gas; supplying the ammonia gas to the injection grid; injecting the ammonia gas into the exhaust duct; and wherein the second average cross-sectional area of the reaction portion of the duct is the same or greater than the first average cross-sectional area of the hot portion of the duct.