Mercury removal by wet, semi-dry and furnace desulphurization technology in circulating fluidized bed

By applying the ontario hydro method (OHM) and the US EPA standard methods, the flue gas mercury sampling was carried out before and after wet flue gas desulphurization and novel integrated desulphurization semi-desulphurization, respectively, in two coal-fired power plants. Various mercury speciations, such as Hg0, Hg2+ and HgP in flue gas, were analyzed. The flue gas mercury sampling before and after electrostatic precipitator of circulating fluidized bed combustion was also done and analyzed. The solid samples, such as coal, bottom ash, electrostatic precipitator (ESP) ash and desulphurization product, were analyzed by DMA80. According to mercury balance, mercury speciation and its distribution at different locations downstream the flue gas were obtained. The research results show that mercury mainly exist in the form of gaseous state in a pulverized coal-fired power plant, while it mainly exists in the form of particle-bound mercury in a circulating fluidized bed coal-fired power plant. Generally, mercury in the bottom ash is dissipative, while it is rich in dust collector (DC) ash, ESP ash, mixed ash and desulphurization product. The circulating fluidized bed combustion furnace desulphurization system shows the highest mercury removal efficiency, while the wet flue gas desulphurization system the lowest.