US Patent 7846240 Chilled ammonia based CO

A method and system for reducing an amount of ammonia in a flue gas stream. The system 100 includes: a wash vessel 180 for receiving an ammonia-containing flue gas stream 170, the wash vessel 180 including a first absorption stage 181a and a second absorption stage 181b, each of the first absorption stage 181a and the second absorption stage 181b having a mass transfer device 184; and a liquid 187 introduced to the wash vessel 180, the liquid 187 for absorbing ammonia from the ammonia-containing flue gas stream 170 thereby forming an ammonia-rich liquid 192 and a reduced ammonia containing flue gas stream 190 exiting the wash vessel 180.