Process Chemistry of Br Addition to Utility Flue Gas for Hg Emissions Control

作者：Niksa Stephen^*; Padak Bihter; Krishnakumar Balaji; Naik Chitral V

来源：Energy & Fuels, 2010, 24(2): 1020-1029.

DOI：10.1021/ef901106t

This paper describes a detailed reaction mechanism tor Br/Hg/Cl chemistry in coal-derived flue gas and interprets the Hg oxidation performance across a broad range of Br addition rates in recent field tests at plants Miller, Milton R. Young, and Monticello that burn low-rank coals. The dominant channels of the homogeneous Hg chemistry with Br are analogous to those for Cl, whereby a Br atom partially oxidizes Hg(0) into HgBr, which is then oxidized into HgBr(2) by Br(2). Mercury also oxidizes heterogeneously on unburned carbon (UBC) with Br species. This mechanism is analogous to the surface mechanism for Cl species, except that (i) elemental mercury (Hg(0)) adsorption is faster on brominated sites and (ii) the higher Br atom concentrations in flue gas promote recombination reactions that maintain very low surface coverages of Hg/Br species. Therefore, the accelerated Hg(0) adsorption rate on brominated UBC promotes Hg(0) oxidation at the hottest gas cleaning temperatures but does not enhance the production of particulate Hg (HgP). The amount of HgP was predicted to increase for progressively greater loss-on-ignition (LOI) levels, although the removals of this form of Hg by eletrostatic precipitators (ESPs) are always low for low-rank coals.

• 出版日期2010-2