Mercury Emission from Co-Combustion of Sludge and Coal in a CFB Incinerator

Abstract

An experimental study on co-combustion of sludge and coal were conducted in a circulating fluidized bed incinerator with the dense bed cross section area of 0.23m×0.23m and the height of 7m. The mercury mass balance was measured and the distribution of mercury speciation in flue gas was discussed. Effects of major operational parameters such as Ca/S molar ratio, desulfurization sorbents, excess air coefficient, co-combustion temperature, and SO2 and NOx concentrations on the distribution of mercury speciation in flue gas, mercury in fly ash and slag were investigated during the co-combustion process. The results show that majority of mercury goesinto the fluegas in which the elemental mercury is the major speciation. Ca-based sorbent can remove Hg2+ in flue gas effectively, in which CaO has better mercury removal effect than CaCO3. The content of Hg2+ in flue gas increases with increasing of the concentration of SO2 and NOx in flue gas. It can also be concluded that the excessair coefficient exerts dominant influences on mercury speciation among the flue gas, fly ash and bottom ash.