Abstract: The mercury removal situations in wet, semidry and dry desulphurization systems of coalfired power plants were introduced. The conversion processes of the mercury in different desulphurization systems and the factors influencing on the conversion were analyzed. The results show that due to the differences of the mercury removing mechanism, the activated coke dry desulphurization system has highest mercury removal efficiency; the semidry desulphurization system is in second place, and the mercury removal efficiency of the wet desulphurization system is lowest. In addition, the mercury secondary pollution caused by the mercury removal function of desulphurization equipments was discussed.

Key words: coal-fired power plant, desulphurization system, mercury emission, elemental mercury Hg 0, oxidation state mercury Hg 2+