Preparation Of Modified High-content Iron Ash Adsorbent And Study On Its Simultaneous Desulfurization And Denitrification Performance

A large amount of SO₂,NO_X,and dust produced by coal combustion seriously pollutes the environment.In order to prevent environmental pollution,the flue gas emissions of coal-fired power plants need to meet the ultra-low emission standards set by the government.Therefore,it is imperative to develop high-efficiency and low-cost pollution removal technology.In this thesis,fly ash,a solid waste from coal-fired power plant,was used as raw material to prepare sorbent.The iron oxides in fly ash was enriched by mechanical grinding and wet magnetic separation,and the high-content iron fly ash（DMA）was obtained.Mn-Ce/DMA adsorbents were prepared through the hydration impregnation method,and Mn and Ce components were loaded.The desulfurization and denitrification experiments were carried out on the fixed bed evaluation system.Combining the experimental results with the XRF,BET,SEM,XRD,and FTIR characterization results,the main conclusions were got as follows:The optimal conditions for preparing Mn-Ce/DMA adsorbents by hydration impregnation method are as follows:30g high-content iron ash,6g Ca O,0.1mol Mn（NO₃）₂,0.02mol Ce（NO₃）₃·6H₂O,hydration impregnation for 5h at 95℃then calcination for 2h at 500℃.The nitrate capacity and sulfur capacity of the optimal adsorbent Mn（4）Ce（2）/Ca-DMA500 are823μg/g and 32.4mg/g,respectively.The preparation conditions have great influence on the desulfurization and denitrification performance of Mn（4）Ce（2）/Ca-DMA500 adsorbent.Fe O_x in fly ash can be enriched by wet magnetic separation.Mechanical grinding and Ca O modification can destroy the vitreous body of fly ash and improve its pore structure.After loading Mn component,Mn Si O₃ and Ca₂Fe₂O₅active sites are formed on the surface of the carrier.The addition of Ce component improves the dispersion of Mn component on the surface of the adsorbent.When calcined at 500℃,the higher crystallinity of the active ingredient Ca Mn Si₂O₆can be obtained.The denitration product is mainly nitrate,and the desulfurization product is mainly sulfate.The simulated flue gas atmosphere has a significant effect on the desulfurization and denitrification performance of Mn（4）Ce（2）/Ca-DMA500 adsorbent.The optimal temperatures for desulfurization and denitration is 160℃and 220℃,respectively.The content of O₂ can affect the oxidation capacity of the adsorbent.The lattice oxygen O₂^-and other active oxygen species can be supplied in time by increasing O₂,and promote the catalytic oxidation of SO₂and NO.The initial concentration of SO₂ and NO in the simulated flue gas is inversely proportional to the desulfurization and denitrification performance.When SO₂ and NO simultaneously exsit,there is a competitive adsorption on the Mn（4）Ce（2）/Ca-DMA500 adsorbent.The nitroso group formed in the process of NO adsorption is the adsorption site of SO₂,so the adsorption effect of SO₂ weakly decreases.However,that metal sulfates formed from SO₂ can deactivate the adsorbent significantly reduces the adsorption capacity of NO.