[Characteristics of Mercury Emissions from Modern Dry Processing Cement Plants in Chongqing]

Three typical modern dry processing cement plants in Chongqing were chosen to investigate mercury emission characteristics and its source and fate through a mercury mass balance method by analyzing mercury contents in all input and output materials. The results showed that limestone was the main source of mercury in three cement plants followed by coal, and their mercury concentrations were (0.025±0.001)-(0.032±0.002) mg·kg^-1and (0.080±0.002)-(0.110±0.012) mg·kg^-1, respectively. The highest mercury level in all required input materials was (0.447±0.007)-(0.525±0.009) mg·kg^-1 for gypsum, while the mercury content of other raw materials were very low. Most of the mercury released from these cement plants entered into flue gas, and the mercury of gypsum entered into cement. The mercury emission fluxes were calculated to be (73.42±8.10)-(215.18±10.75) g·d^-1 in these three selected plants. The mercury emission factors for clinke and cement (EF_clinker and EF_cement) were (0.016±0.001)-(0.049±0.001) g·t^-1 and (0.011±0.000)-(0.036±0.001) g·t^-1, respectively, which were significantly lower than that employed in cement industry according to the foreign mercury emission factors in the past.