Removal properties and migration patterns of mercury in coal-fired power plant

In order to study the characteristics of mercury distribution and migration,EPA OHM method was used to determine the Hg concentrations in flue gases emitted from two typical pulverized coal-fired boilers.Then the effect of major flue gas purification systems on Hg emission was clarified.Experimental results indicate that Hg~0 will be catalytic oxidation into Hg~(2+)in SCR system that promotes the mercury be absorbed by fly ash and desulfurization slurry in WFGD system.ESP system and WFGD system plays the leading role foe mercury removal which the total removal efficiency reach more than 60% and WESP system has only limited removal effect.Ash content of coal particles can affect the ratio of granular mercury between the gaseous mercury. The absorption of Hg~(2+)will be inhibition by SO_2,caused Hg~0 emissions again,which affects mercury removal efficiency of WFGD system. In addition,most of the Hg is transferred into desulfurization gypsum and fly ash,and smaller particle size of fly ash has the stronger adsorption ability to mercury,while the enrichment ability of bottom slag is limited.