BEHAVIOR OF MERCURY IN COAL COMBUSTION SYSTEMS

Mercury is one of a number of pollutants (like dioxins) that persist in the environment and bioaccumulate in the food chain. Because of its toxicity and the potential for bioaccumulation, mercury emissions to the environment are the subject of environmental regulation. U.S. EPA estimates that 87% of the man-made emissions of mercury come from point sources of combustion. There are currently emission limits on mercury from certain categories of combustion sources, including coal-fired utility and industrial boilers, cement kilns and incinerators burning hazardous waste. The behavior of mercury in coal combustion systems is complex. Under some circumstances, substantial fractions of mercury entering the boiler system are removed in the existing air pollution control devices. Removal of mercury within the combustion system depends both on the conditions in the combustion system and on the composition of the coal. Understanding the removal of mercury within coal-fired combustion systems leads to cost-effective solutions to compliance with emissions regulations. In this paper, the behavior of mercury in coal combustion systems and in air pollution control devices will be explored, with emphasis on the relationship between coal quality and mercury emissions from combustion systems.