Continuous Emission Monitoring, 3rd Edition

CHAPTER 12MONITORING FOR MERCURY

Monitoring mercury emissions from coal‐fired power plants, cement plants, and other industrial sources presents challenges that go far beyond those associated with measuring criteria gases such as SO₂ and NO_x. In flue gas emissions, mercury can be found as atomic mercury in the form of a vapor (Hg^o), as a compound in an oxidized form (Hg⁺²) such as HgO or HgCl₂, or in a particle, bound to fly ash or other particulate matter. Without applying proper techniques, both atomic and oxidized forms are difficult to transport through monitoring systems. Although the analysis of atomic mercury in the vapor form is relatively easy, calibration techniques can be problematical, requiring solutions that go beyond utilizing the traditional calibration gas cylinder. Despite of these challenges, accurate and reliable continuous mercury monitoring (CMM) systems capable of measuring at levels of a few tenths of a microgram per cubic meter (μg/m³ or parts per trillion) were developed within a relatively short period of 2000–2010.

MERCURY ISSUES

The United Nations Environment Program (UNEP) provides periodic assessments of global emissions (UNEP 2008, 2013). Mercury is emitted into the atmosphere from human (anthropogenic) activities and geological sources such as volcanoes and mineral surface exposures; anthropogenic activities accounting for approximately 2000 tonnes/year, and natural sources and remission both contributing emissions of several thousand tons ...