mercury removal

Prior to 1990, little reliable data was available on mercury concentrations in coal plants' stack gas or anywhere within the plant gas stream. The ERA attempted to change that by developing an emissions inventory known as the 1999 Information Collection Request (ICR). The ICR collected basic information on all 1,140 coal-fired utility boilers in the U.S., and more detailed information as well. The detailed data included analyses of coal's calorific value and its mercury, chlorine, sulfur, moisture, and ash content. Also included were analyses of total and speciated (elemental and oxidized) mercury in the inlet and outlet flue gases of 81 units representing a cross-section of the various types of boilers and fuels used in the U.S.

No single technology will work for every coal-fired power plant. The mercury control options under investigation can be classified into six broad categories:

• Sorbent injection involves injecting a material, usually in powdered form, that adsorbs mercury upstream of a particulate collector such as a baghouse or electrostatic precipitator (ESP). Activated carbon injection currently represents one of the most promising controls on the horizon. It is the only technology that is close to being commercialized.