title: Impacts of halogen additions on mercury oxidation, in a slipstream selective catalyst reduction (SCR), reactor when burning sub-bituminous coal.
abstract: This paper presents a comparison of impacts of halogen species on the elemental mercury (Hg(0)) oxidation in a real coal-derived flue gas atmosphere. It is reported there is a higher percentage of Hg(0) in the flue gas when burning sub-bituminous coal (herein Powder River Basin (PRB) coal) and lignite, even with the use of selective catalytic reduction (SCR). The higher Hg(0)concentration in the flue gas makes it difficult to use the wet-FGD process for the mercury emission control in coal-fired utility boilers. Investigation of enhanced Hg(0) oxidation by addition of hydrogen halogens (HF, HCl, HBr, and HI) was conducted in a slipstream reactor with and without SCR catalysts when burning PRB coal. Two commercial SCR catalysts were evaluated. SCR catalyst no. 1 showed higher efficiencies of both NO reduction and Hg(0) oxidation than those of SCR catalyst no. 2. NH3 addition seemed to inhibit the Hg(0) oxidation, which indicated competitive processes between NH3 reduction and Hg(0) oxidation on the surface of SCR catalysts. The hydrogen halogens, in the order of impact on Hg(0) oxidation, were HBr, HI, and HCl or HF. Addition of HBr at approximately 3 ppm could achieve 80% Hg(0) oxidation. Addition of HI at approximately 5 ppm could achieve 40% Hg(0) oxidation. In comparison to the empty reactor, 40% Hg(0) oxidation could be achieved when HCl addition was up to 300 ppm. The enhanced Hg(0) oxidation by addition of HBr and HI seemed not to be correlated to the catalytic effects by both evaluated SCR catalysts. The effectiveness of conversion of hydrogen halogens to halogen molecules or interhalogens seemed to be attributed to their impacts on Hg(0) oxidation.
authors: Institute for Combustion Science and Environmental Technology, Western Kentucky University, Bowling Green, Kentucky 42101, USA. yan.cao@wku.edu
authors: Yan
authors: Y
authors: Cao
authors: Zhengyang
authors: Z
authors: Gao
authors: Jiashun
authors: J
authors: Zhu
authors: Quanhai
authors: Q
authors: Wang
authors: Yaji
authors: Y
authors: Huang
authors: Chengchung
authors: C
authors: Chiu
authors: Bruce
authors: B
authors: Parker
authors: Paul
authors: P
authors: Chu
authors: Wei-Ping
authors: WP
authors: Pant
mesh_terms: D000148:Acids, Noncarboxylic / Q000737:chemistry*; D000393:Air Pollutants / Q000032:analysis / Q000737:chemistry*; D000641:Ammonia / Q000737:chemistry; D002244:Carbon / Q000032:analysis; D002384:Catalysis; D003031:Coal / Q000032:analysis; D060729:Coal Ash; D006219:Halogens / Q000032:analysis / Q000737:chemistry*; D008628:Mercury / Q000032:analysis / Q000737:chemistry*; D009569:Nitric Oxide / Q000032:analysis; D010084:Oxidation-Reduction; D052638:Particulate Matter / Q000032:analysis; D011210:Power Plants
chemical_list: D000148:Acids, Noncarboxylic; D000393:Air Pollutants; D003031:Coal; D060729:Coal Ash; D006219:Halogens; D052638:Particulate Matter; D009569:Nitric Oxide; D002244:Carbon; D000641:Ammonia; D008628:Mercury