Patent ID: 7846240

Claim:
A method of reducing an amount of ammonia in a CO2 lean flue gas stream resulting from an ammonia-based CO2 capture system, the method comprising: contacting a flue gas stream with an ammoniated slurry or solution within an absorption tower, wherein the ammoniated slurry or solution removes carbon dioxide (CO 2 ) from the cooled flue gas stream thereby forming an ammonia-containing flue gas stream; and introducing at least a portion of the ammonia-containing flue gas stream from the absorption tower to a wash vessel, the wash vessel having first and second absorption stages to absorb ammonia from the ammonia-containing flue gas stream thereby reducing an amount of ammonia in a flue gas stream exiting the wash vessel, each of the first and second absorption stages including a mass transfer device and a liquid delivery path; introducing a first liquid to the liquid delivery path of the first absorption stage such that the first liquid flows in a direction countercurrent to the ammonia-containing flue gas stream to contact the ammonia-containing flue gas stream and the mass transfer devices of the first and second absorption stages; introducing a second liquid having a different ammonia content than the first liquid to the liquid delivery path of the second absorption stage such that the second liquid flows in a direction countercurrent to the ammonia-containing flue gas stream to contact the ammonia-containing flue gas stream and the mass transfer device of the second absorption stage, whereby the first and second liquids absorb ammonia from the ammonia-containing flue gas stream.