Speciation of Mercury in Combustion Gases of Solid Fuels

摘要

Three forms of mercury are found in the combustion flue gases of solid fuels: elemental mercury, oxidized mercury, and particulate mercury. Based on thermochemical equilibrium calculations at the temperatures typically produced when fuel is combusted in a furnace, mercury in the fuel may be generated in an elemental form as gaseous mercury. As the flue gas cools and interacts with other gases and fly ash, some of this elemental mercury is converted into oxidized forms. In addition, elemental mercury can be oxidized in a selective catalytic reduction system designed to control nitrogen oxides in the flue gas. Because oxidized forms of mercury are highly water soluble and readily captured by alkali and alkaline earth metal compounds, significant amounts of oxidized mercury are reported to be captured in flue gas desulfurization systems designed to control sulfur oxides.