The Sudy Of Element Mercury Adsorption In Coal-Fired Flue Gas By Selenium Modified Adsorbent

Mercury is a kind of toxic heavy metal,which widely exists in coal combustion flue gas in the form of mercury vapor,and it had resulted humungous damage to human’s health owing to the chemical activity(highly toxic,high stability,bioaccumulation,persistance,and longdistance mirgration)and toxic Hg-based derivative.Coal combustion is the main anthropogenic mercury emission source,and the key to control mercury pollution is the efficient and stable removal of elemental mercury(Hg~0)from coal combustion flue gas.In this paper,the application of selenium and metal selenides in the removal of Hg~0 is investigated.Seleniumloaded activated carbon(Sex/AC),manganses selenium(α-MnSe),copper selenium(CuSe)and nickel diselenide(NiSe2)are prepared by different methods,and the Hg~0 removal performance o different adsorbents was investigated by Hg~0 adsoprtion experiments.The effect of temperature,O2,SO2 and NO on the efficiency of adsorbents of mercury removal are explored,and the mercury removal mechanism of adsorbents is investigated by adsorption kinetic analysis and characterization of BET,XRD,SEM,XPS,FTIR,Hg-TPD.It was found that the Hg~0 adsorption activities of different adsorbents are different.Among them,the Sex/AC has the best activity.It can maintain more than 90%of Hg~0 adsorption efficiency within 154 h under optimal conditions(Se0.5/AC,160℃ and N2),and the maximun adsorption capacity reach 17.89 mg/g which exhibited 120 times versus the conventional activated carbon.The Hg~0 adsorption efficiency of metal selenides are lower than that of Sex/AC,but it still reaches above 80%.In the flue gas components,O2 inhibit the Hg~0 removal efficiency of the adsorption because selenium has strong antioxidant properties,and it leads to competitive adsorption between O2 and Hg~0.SO2 also inhibited the adsorption of Hg~0 because it would react with metal components,but NO had little effect and the adsorption efficiency of Hg~0 would still be maintained at a high level.According to the kinetic fitting results and sample characterization analysis,it can be concluded that the specific surface area,structural integrity and chemisorption active sites of adsorbents have the effect on the Hg~0 adsorption performance,and chemisorption determines the Hg~0 adsorption efficiency of selenium and metal selenium.As the active component,selenium greatly improves the adsorption efficiency of Hg~0,and formed HgSe on the surface of the adsorbents.HgSe is an extremely chemically stable mercury compound that prevents secondary mercury pollution.The research in this thesis can demonstrate that the adsorbents modified by selenium have excellent performance in controlling Hg~0 pollution in flue gas,which provides certain hele for the development of this field.