The Experimental Study On Simultaneous Removal Of NO And Mercury Over Ferromanganese Ore At Low Temperature

China is the world's largest consumer of coal,and coal accounts for a large proportion of China's primary energy consumption.This situation will not change in the long term.Therefore,the problem of environmental pollution caused by coal combustion cannot be underestimated,especially the release of nitrogen oxides?NO_x?and mercury.With the popularization of SCR denitrification devices in coal-fired power plants,the simultaneous removal of NO_x and Hg⁰ is an economical and practical method.In recent years,the research on the removal of NO_x and Hg⁰ from coal-fired flue gas by using transition metal oxides as SCR catalysts has received widespread attention.In view of this,this paper adopted natural ferromanganese ore,which contains a large number of transition metals such as manganese and iron,to conduct a series of experiments of denitrification and demercuration on a laboratory-scale apparatus.The influencing factors and the reaction mechanism of denitrification and demercuration were investigated.Firstly,the sample characterization of virgin and calcined ferromanganese ore were performed by various techniques,including X-ray fluorescence?XRF?analysis,surface structure analysis?BET?,X-ray diffraction?XRD?,and X-Ray photoelectron spectroscopy?XPS?.The results showed that the low-temperature calcination makes the pore structure of samples more developed.In addition,XPS tests showed that calcination treatment had no obvious effect on the iron valence,but decreased the content of lattice oxygen and Mn⁴⁺.Then,this paper explored the feasibility of denitrification over ferromanganese ore on a laboratory-scale apparatus.The suitable gas hourly space velocity?GHSV?was adopted to carry out subsequent experiments.Finally,the effects of calcination temperature?350-550^oC?,reaction temperature?100-400 ^oC?,and flue gas composition?SO₂,O₂,etc.?on denitrification efficiency were studied.The results showed under the condition of GHSV ranged from 7500 h^-1-50000 h^-1,the denitrification efficiency evaluated at 200 ^oC maintained above 90%.The study also found that calcination treatment would weaken the low-temperature denitrification performance of ferromanganese ore,mainly because MnO₂ was decomposed to Mn₂O₃ during the calcination process.Due to the better denitrification performance of ferromanganese ore at low temperature,this paper continued to explore the feasibility of mercury removal over ferromanganese ore on a laboratory-scale apparatus.The effects of calcination temperature?350-550 ^oC?,reaction temperature?100-400 ^oC?,flue gas components?SO₂,NO,etc.?on mercury removal performance were investigated.Then the reaction mechanism of mercury removal was revealed by identifying the behavior of mercury adsorption/oxidation,XPS and TPD testing.This will lay a theoretical foundation for the practical application.The experiment results showed that the mercury removal efficiency of virgin sample was better than that of being calcined.And the optimal reaction temperature range for mercury removal over ferromanganese ore was 150 ^oC-200 ^oC,which partially coincided with the optimal denitrification temperature range?200 ^oC,250 ^oC,300 ^oC?.In summary,the utilization of natural ferromanganese ore can effectively achieve the technical goal of simultaneous removal of NO_x and Hg⁰ at low temperature.