Emission and Behavior of Mercury from a Coal-fired Power Plant

摘要

Characterization of mercury emission and behavior from a coal-fired power plant were carried out in the 500 MW, bituminous coal consuming electric utility boiler. This facility is equipped with a cold-side ESP (electrostatic precipitator) and a wet FGD (flue gas desulphurization) in series as APCDs (air pollution control devices). Mercury sampling points were selected at up and down streams of ESP and outlet of FGD, which is at stack. Two different types of sampling method were employed, one is Ontario Hydro Method and the other is US 101 A. Various samples were collected from the coal-fired power plant such as fuel coals, fly ash in hoper, lime/lime stone, gypsum, and effluent water from FGD. These samples were analyzed by EPA 7470A and 7471 A to understand the behavior and mass balance of mercury in the process of coal-fired power plant. Mercury emission and speciation depend on the Hg concentration in the fuel coal, type of APCDs, and flue gas temperature and composition. There are no significant differences with two sampling methods, but Ontario Hydro Method seems to have more advantage for Hg sampling from a coal-fired power plant because mercury speciation is quite important factor to estimate the mercury emission and control efficiency from combustion flue gas. Approximate Hg mass balance could be obtained from various samples in the study; however a series of long term and comprehensive study is required to evaluate the reliable Hg emission and behavior from a coal-fired power plant.