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Migration and Emission Characteristics of Ammonia/Ammonium through Flue Gas Cleaning Devices in Coal-Fired Power Plants of China
journal contribution
posted on 2019-12-13, 18:10 authored by Wei Liu, Bobo Wu, Xiaoxuan Bai, Shuhan Liu, Xiangyang Liu, Yan Hao, Weizhao Liang, Shumin Lin, Huanjia Liu, Lining Luo, Shuang Zhao, Chuanyong Zhu, Jiming Hao, Hezhong TianTo investigate the up-to-date migration and emission
characteristics
of NH3/NH4+ in coal-fired power plants
(CFPPs) after implementing ultralow emission retrofitting, typical
air pollution control devices (APCDs) in CFPPs, including flue gas
denitrification, dust collectors, combined wet flue gas desulfurization
(WFGD), and wet precipitators are involved in field measurements.
The results show that most of the excessive injected and/or unreacted
ammonia from the flue gas denitrification system, whether selective
catalytic reduction (SCR) or selective noncatalytic reduction (SNCR),
is converted into particle-bound NH4+ (>91%),
and the rest (less than 9%) is carried by flue gas in the form of
gaseous NH3, with a concentration value of 0.15–0.54
mg/(N m3) at the denitrification outlet. When passing through
dust collectors, particle-bound NH4+ concentration
decreases substantially along with the removal of particle matter.
In WFGD, the dissolution and volatilization effects affect the gaseous
ammonia concentration, which decreases when using limestone slurry
and a 20% solution of ammonia as a desulfurization agent, while liquid
ammonia solution with a high concentration (99.8%) may cause the flue
gas NH3 concentration to increase considerably by 13 times.
Particle-bound NH4+ concentration is mainly
influenced by the relative strength of desulfurization slurry scouring
and flue gas carrying effects and increases 2.84–116 times
through ammonia-based WFGD. Furthermore, emission factors of NH3 for combinations of APCDs are discussed.