The chemistry of mercury in combustion systems and air pollution control devices: A review

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Constance Senior, senior@reaction-eng.com, Reaction Engineering International, 77 West 200 South, Suite 210, Salt Lake City, UT 84101
Compliance with these new regulations for mercury emissions from coal-fired boilers necessitates a solid understanding fundamental understanding of mercury chemistry. Removal of Hg from the combustion flue gas can be achieved by two general means: (1) adsorption of gaseous Hg (either Hg0 or Hg2+) on solids such as fly ash or sorbents, with subsequent removal of those solid particles, or (2) absorption of Hg2+ in an aqueous medium, as in a desulphurization scrubber. Exploitation of either of these pathways for Hg control depends on getting Hg into the correct chemical form at a specific point in the flue gas path. Theoretical, laboratory, and pilot-scale research efforts in the last fifteen years have enhanced understanding in several key areas. In this review, the state of knowledge of Hg behavior in coal-fired power plants is reviewed, highlighting the role of chemistry research in bringing greater clarity to a complicated chemically reacting system.