Experimental Study On Desulfurization And Denitration Of Iron Based Catalyst Supported By Biomass Based Support By Advanced Oxidation

NOx and SO₂ can cause photochemical smog,acid rain and other environmental problems,which seriously threaten the ecological environment and human health.The combined technology of selective catalytic reduction（SCR）and wet flue gas desulfurization（WFGD）is widely used in coal-fired power plants to deal with NOx and SO₂in flue gas.However,this combined method will aggravate the complexity of the purification system,resulting in higher investment and operating costs.Therefore,it is of great scientific significance and engineering value to develop a new process of simultaneous desulfurization and denitration with high efficient and low-cost.In this paper,the iron-based catalyst for biomass carrier was studied in the system of simultaneous removal of NOx and SO₂ by catalytic oxidation of H₂O₂/heterogeneous catalyst coupled with liquid phase absorption.And the red mud slurry was used as the absorption liquid,combined with liquid phase absorption in bubbling bed to conduct simultaneous desulfurization and denitration research.Firstly,silica supported iron-based catalyst（Fe₂O₃/Si O₂ catalyst）was prepared by co-impregnation method.Gas Fenton reaction system was used to investigate the effects of loading,catalytic temperature,H₂O₂ vaporization temperature,H₂O₂ flow rate and water vapor concentration on NO pre-oxidation,and commercial silica was used as carrier to prepare catalyst（Fe₂O₃/C-Si O₂catalyst）for the comparative experiment.The results show that the oxidation degree of NO can reach 73%under the optimal conditions,when the load is 50%,the catalytic temperature is 140℃,the vaporization temperature of H₂O₂ is 120℃,and the flow rate of H₂O₂ is 2.5m L/h.The comparative experimental results show that the NO oxidation degree of Fe₂O₃/C-Si O₂ catalyst is only 52%.The physical and chemical properties of the catalysts were characterized by H₂-TPR,XRD,BET,XPS and ESR.TPR results show that the catalyst carrier can reduce the reduction temperature and reduce the agglomeration of active components;the crystal structure of the catalyst is stable,mechanical strength and thermal stability are good;The BET results shows that the specific surface area and aperture of the catalyst is not the key factor affecting the performance of the catalyst;ESR and XPS results show that the catalytic performance of Fe₂O₃/Si O₂ catalyst is better than that of Fe₂O₃/C-Si O₂ catalyst.Secondly,biomass support iron-based catalysts with different biomass support and different iron sources were prepared by co-impregnation method and applied to NO pre-oxidation experiment.The effects of operating conditions such as support,iron source,calcination temperature,impregnation solution concentration and O₂ concentration on NO pre-oxidation were mainly studied.The optimal operating conditions are the combination of pine and Fe₂（SO4）₃,the calcination temperature is 650℃,the concentration of the impregnation solution is 0.1mol/L,the concentration of O₂ is 7%,and the oxidation degree of NO can reach 88%.The physical and chemical properties of the catalysts were characterized by XRD,FTIR,TG and XPS.XRD results show that all the catalysts can form stable crystal phase of Fe₂O₃.The results of FTIR show that the oxygen-containing functional groups on the surface of the catalyst can improve their catalytic performance.The TG results show that the transition temperature of Fe（NO₃）₃ is the lowest,and that of Fe₂（SO₄）₃ is the highest.The transition temperature of the same iron source is affected by the fixed carbon content of biomass.XPS results show that pine-Fe₂（SO₄）₃ catalyst has the best catalytic performance.Based on the above research,the simultaneous desulfurization and denitrification experiments of liquid phase absorption by red mud slurry without pre-oxidation were carried out in a bubbling bed reactor to investigate the effects of operating conditions such as the composition of red mud slurry,the solid-liquid ratio of red mud slurry and the volume of absorption liquid on the efficiency of desulfurization and denitrification.In the red mud slurry,OH^-,CO₃^2-and a small amount of HCO₃^-play a role in denitration,in which perovskite plays a catalytic role in the oxidation of NO.Alkali components and alkaline metal oxides play the role of desulfurization in red mud slurry.Under the optimal experimental conditions,the ratio of solid-liquid is 1:20,and the absorbed liquid volume is 600m L,the NO removal efficiency is 47.2%,and SO₂ removal efficiency is 100%.In addition,the pre-oxidation coupled liquid phase absorption experiments were carried out by using Fe₂O₃/Si O₂ catalyst and PW-SFe catalyst.The experimental results show that the simultaneous desulfurization and denitrification of red mud slurry coupled with pre-oxidation can significantly increase the removal efficiency of NO.The removal efficiency of SO₂ is 100%under all operating conditions.For Fe₂O₃/Si O₂ catalyst,the removal efficiency of NO increases with the increase of H₂O₂ flow rate,and tends to be stable gradually,and the removal efficiency of NO reaches about 96.5%.The low concentration of SO₂ can promote the removal of NO,while the high concentration of SO₂ has little restriction on the removal of NO.For PW-SFe catalyst,the influence law of H₂O₂ flow rate on NO removal is consistent with that of Fe₂O₃/Si O₂ catalyst,but PW-SFe catalyst has a higher denitration efficiency,up to 97.8%.