Removal Of Elemental Mercury From Simulated Flue Gas Over Activated Coke Loaded With MnO_x-NiO

In our country,coal resource is one of the important energy sources,which could promote the rapid development of the national economy,while causing great pollution to the atmospheric environment.Coal combustion produces a variety of pollutants,including dust,NOx,SOx and mercury.Among them,mercury has attracted considerable concern because of its high toxicity,long-range mobility in the atmosphere,persistence and bioaccumulation and neurotoxic influence on human health.Three main forms of mercury existed in coal combustion flue gas:particle-bound mercury(Hgp),elemental mercury(Hg0),and oxidized mercury(Hg2+).Hgo is difficult to remove due to its higher volatility and lower water solubility.Therefore,development of a method for efficiently removing Hgo is crucial for controlling mercury emissions from coal-fired flue gas.In this study,a series of MnxNiy/AC(AC,activated coke)synthesized by the impregnation method and their activity for Hgo removal were studied.The effects of the MnOx-NiO loading value and molar ratio on the removal efficiency of Hgo was researched,as well as the effect of reaction temperature(90-240℃)and gas constituents(O2,NO,SO2 and H2O).The methods such as BET,ICP-OES,SEM,XRD,H2-TPR,XPS,FT-IR and TGA were carried out to investigate the characterization of different samples.Furthermore,the mechanisms concerned with Hg0 removal were discussed based on the results and characterization of experiment.The experimental results showed that compared with virgin AC,the samples modified by MnOx-NiO had better removal performance for Hg0.And the loading value and molar ratio of MnOx-NiO could affect the removal performance of Hg0.Mn6Ni0.75/AC exhibited the optimal removal efficiency of 96.6%in the condition of 6%O2 and balanced in N2 at 150℃The results of flue gas experimental exhibited that both O2 and NO facilitated the Hgo removal,while SO2 and H2O could inhibit the Hg0 removal.In addition,Mn6Ni0.75/AC possessed excellent stability and regen er ability.The characterization of the samples indicated that Mn6Ni0.75/AC possessed larger specific surface area,higher dispersion of metal oxides and stronger redox ability.Meantime,the results of XPS and FT-IR demonstrated that the lattice oxygen and chemisorbed oxygen made contributions to the Hgo removal and the consumed oxygen could be compensated by the redox cycle of metal oxides and gas-phase O2.