Experimental Research On Urea/H₂O₂ Solution And Heterogeneous Fenton-like Wet Oxidation Denitrification

China's energy structure is dominated by coal,and the emissio n of coal-fired pollutants does great harm to human economic life.At present,the widely used combined desulfurization and denitrification technology has many problems,such as high investment,large land occupation,complex system and so on.The development of wet desulfurization and denitrification is one of the directions to solve this contradiction,and the key lies in the selection of appropriate oxidants to achieve wet denitrification.For this reason,the characteristics of urea/H₂O₂ and heterogeneous Fenton-like wet oxidation denitrification were explored on a self-made small bubble column experimental platform.The experimental results of wet denitrification with urea/H₂O₂ solution show that the oxidation of H₂O₂ can greatly promote the removal of NO from flue gas;the concentration of H₂O₂,solution temperature and solution acidity and alkalinity have great influence on the absorption of NO;when the concentration of H₂O₂ reaches 2 mol/L or high temperature and strong alkali environment?pH reaches 12.3?,the removal efficiency of NO can reach more than 90%,but it is not suitable for industrial application;H₂O₂ itself,the free radicals and O₂generated by decomposition constitute the process of oxidation and absorption of NO by H₂O₂;the thermodynamic analysis showed that H₂O₂ could effectively remove NO from flue gas,but higher temperature was disadvantageous to the absorption of NO by urea/H₂O₂solution.The reaction orders of NO and H₂O₂ were 1 and 0.28,respectively.The pre-exponential factor A₀ was 0.123 L^0.28/(mol^0.28·s)and the apparent activation energy Ea was 5.098 kJ/mol.In order to improve the oxidation ability of H₂O₂,supported catalysts were prepared by impregnation method,and heterogeneous Fenton-like system was constructed.The optimum carrier,precursor concentration,calcination temperature and calcination time for preparing heterogeneous Fenton-like catalysts were determined based on the evaluation criterion of NO removal efficiency.BET and XRD measurements showed that the specific surface area and pore volume of Fe₂O₃/zeolite catalyst were larger than those of zeolite carrier,and the average pore size is larger.The structure of the carrier remains unchanged before and after loading,and the active components are mainly highly dispersed on the surface of the carrier with low crystallinity and small particle size of Fe₂O₃.The study on wet removal of NO from flue gas by heterogeneous Fenton-like oxidation shows that heterogeneous Fenton-like oxidation can effectively remove NO from flue gas;the concentration of H₂O₂,initial pH of solution,amount of catalyst and reaction temperature have great influence on the removal efficiency of NO,and the optimal concentration of H₂O₂and the critical value of catalyst dosage are interrelated;the optimal reaction temperature is50?;the alkaline environment is not conducive to the removal of NO by heterogeneous Fenton-like oxidation.NO removal efficiency decreases slowly with the increase of catalyst recycling times.After five cycles of recycling,the removal efficiency of NO is still 48%.The catalyst is stable and reusable.The removal of NO from flue gas by heterogeneous Fenton-like wet process is mainly due to the oxidation of OH radicals generated by the catalytic decomposition of H₂O₂.