Characterization of mercury emissions from a coal-fired power plant

An emissions study for mercury was conducted at a 300 MW coal-fired plant equipped with an electrostatic precipitator (ESP). The input and output streams such as coal, slag, ESP ash, and flue gas were collected. Gaseous mercury was sampled using the Ontario Hydro method. The experimental data indicate that the majority of mercury goes into flue gas. The mercury quantity in flue gas to total combustion products is about 83%. The distribution of mercury in slag and fly ash is about 1 and 13%, respectively. The result also shows that, among the stack emissions after ESP, the gaseous mercury concentration in the flue gas is about 13-21 mu g N-1 m(-3). The proportion in particulate form was extremely low; the content of Hg2+ in flue gas is about 55-69%; and the content of Hg-0 is about 31-45%. In addition, the absorption mechanism of mercury in fly ash was studied. It was found that the mercury concentration in fly ash is independent of the particle size and has a positive correlation with the loss of ignition of fly ash.