Mercury emissions in utility-scale coal combustion have been the
subject of regulations by the US Environmental Protection Agency
(EPA). After more than a decade of examination of emissions data, the
issuance of regulations in 2005, and the vacating of those regulations
by theDistrict of Columbia US Circuit Court in February 2008, EPA issued
the Mercury and Air Toxics Standards (MATS) (EPA, 2012) and the
Cross-State Air Pollution Rule (CSAPR) (EPA, 2013). The MATS rules
(Office of the Federal Register, 17 February 2015) limit Hg emissions
to 50 × 10−6 lbs. Hg/MMBtu (21.5 × 10−6 kg Hg/MJ) for existing coalfired
generating units in the eastern U.S. The latter rule specifically addressed
the reduction of SO2 and NOx emissions for power plants in
the eastern United States; the lowered SO2 emissions limits required
most existing coal-fired eastern US power plants to install newor to improve
existing flue-gas desulfurization (FGD) equipment. For divalent
forms of mercury (Hg2+), absorption in wet FGD processes is a highly
effective removal mechanism; promoting Hg oxidation upstream of
wet FGD processes has been shown to be an effective means of reducing
total Hg emissions from coal combustion