Research On Mercury Control With Semi-dry Adsorption Process During Coal Combustion

At present, the research of mercury emission and control in coal-fired power plant was in the beginning process, especially in China. The mercury transformation mechanism in coal-fired power plant and mecury control in flue gas were studied in this paper, based on experimental and theoretical analyse.The studies of the influence of control equipment to general pollution to mercury emission and mercury transformation mechanism in circulating fluidized bed were conducted at a 6 MW stone-coal-fired plant. The experimental data showed that the speciation of mercury occurring under the systems was similar to the present in references; the dusters have the ability to decrease the mercury emission.A bench-scale experimental is conducted to study effect of flue gas composition on the speciation distribution of mercury in simulated flue gas streams, such as HC1, SO2 and NO.The mechanisms and rate of elemental mercury (Hg0) capture by activated carbons and some other modified chemically sorbents have been studied using a bench-scale fixed-bed apparatus. We have screened out some efficient sorbents such as activated carbons were impregnated with MnO2, FeCl3 and sulfur at 600, zeolite were impregnated with MnO2, roseite were impregnated with MnO2, FeCl3, and bentonite were impregnated with MnO2. The effects of flue gas composition, inlet mercury concentration, adsorption temperature and ratio of C/Hg were investigated to determine the abilities to remove mercury in simulated flue gas streams.Semi-dry mercury control method that injected sorbents and water or some oxidizers in flue gas for Hg control in coal-fired power plant was developed in bench-scale and pilot-scale.A Theoretical model was developed to predict mercury removal in duct based on activated carbon injection for Hg control as determined in pilot-scale experiments at different conditions. The simulation results indicated that the model is capable of describing the test data. Base on the model predictions, lower operating temperature, higher C/Hg ratio and mercury inlet concentration, and smaller sorbents particle size should be utilized to achieve higher Hg removal in this system.