Abstract: In order to better understand the mechanism of mercury emission from coal-fired power plants and the effects of existing pollution control equipment on synergistic mercury removal, the test study on the mercury emission from four thermal power units in Jiangxi Province is carried out by using Ontario Hydro Method, thus the current mercury emission characteristics of power plants are obtained. The results show that the mercury removal efficiency of the units without mercury oxidant is between 69.01% and 75.63%, while that with mercury oxidant can reach as high as 89.69%. The SCR denitration does not seem to take significant impact on total mercury reduction. However it can promote the oxidation of Hg⁰ to Hg²⁺ and Hg_p. The oxidation ratio of Hg⁰ to Hg²⁺ can be increased drastically with the mercury oxidants being put into use. The electro-static precipitator(ESP) can remove almost all Hg_p, and its average total synergistic mercury removal efficiency is 24.37%. The removal efficiency of Hg²⁺ by wet flue gas desulphurization (WFGD) is 88.39%. After processed through SCR, ESP and WFGD, the mass concentration of mercury in the exhaust gas is limited within the range between 3.91 and 8.89 μg/m³, which is far below what is specified in the national emission standard.

Key words: coal-fired power plant, mercury emission, SCR denitration, dust removal, WFGD, mercury oxidant