The Effect Of Metal Oxides On Low Temperature Oxidation Of Char During The Process Of Flue Gas Denitrification

Coal is the primary energy source in China.The serious problems of air pollution caused by the emissions of NOX from coal utilization have affected the environment and human life.In order to alleviate the severity of the atmospheric pollution,the governments around the world have legislated to control the emissions of NOX.Activated char catalysts for NOx removal have the characteristics of high adsorption efficiency and low cost.Therefore,this study was carried out to understanding the reduction reactions between activated char and NO during the process of denitrification.The presence of about 5% oxygen in flue gas can improve the denitrification efficiency of activated char catalysts.However,the residual oxygen can react with the carbon in the activated catalyst,which causes the consumption of the activated carbon support and catalyst deactivation.This phenomenon prevents the effective removal of NO in flue gas.Therefore,investigating the characteristics of low temperature catalytic oxidation of activated char can assist the control of carbon loss in practical applications.In view of the mechanism of low temperature catalytic oxidation reaction of activated char,the ultrasonic immersion method was used in this study to impregnate metal oxide into lignite activated char.Under the simulated atmosphere,catalytic oxidation experiments were systematically carried out using a fixed-bed reactor in isothermal conditions to investigate the effects of oxidation temperature,metal content,metal varieties,and other atmosphere on the characteristics of low temperature catalytic oxidation of activated char.The changes of physical and chemical properties before and after oxidation of activated char were analyzed by Fourier transform infrared（FTIR）,X-ray diffraction（XRD）,and Scanning electron microscope（SEM）.The low temperature oxidation mechanism and metal oxide catalytic mechanism have been discussed.The experimental results showed that the increase of oxidation temperature can promote the reaction between oxygen and char,and the catalytic reactivity of metal oxide.The metal content,and the amount of metal impregnated into the char affected the NOx removal ability of the catalyst.It was found that iron oxide can catalyze the oxidation reaction to generate CO,while the copper oxide can catalyze the oxidation reaction to generate CO₂.The presence of CO₂ in the flue gas has an inhibitory effect on char reaction and oxidation to generate CO.It was found that the presence of NO in the flue gas promotes the char reaction and oxidation to generate CO.CO can participate in denitrification reactions with NO to generate CO₂ and N₂.