Study On Low Temperature Desulphurization And Denitrification After Modification Of Carbon Materials

Sintering process is the main source of SO₂ and NO_x.Reducing the emission of SO₂ and NO_x in the sintering flue gas is a great significance to environmental protection.This thesis employed the method of desulfurization with carbon material and SCR denitrification to treat sintering flue gas,and their low-temperature desulfurization and denitrification characteristics were systematically studied.Firstly,metallurgical coke,semi-coke,and self-made biomass char were modified.The results of characterization and activity tests showed that the microwave modification decomposed the acidic functional groups on the surface of the carbon material.This enhanced the basic characteristics,which enhanced the adsorption ability of SO₂?desulfurization rate increased from 20.3%to 33.5%for semi-coke at 150^oC?.The water vapor modification significantly increased the specific surface area of carbon materials,but it destroyed the acidic functional groups on the surface of carbon materials,which was not conducive to the adsorption of NH₃.Besides,its promotional effect on NO_x removal was not obvious.After the acid treatment,carboxylic acid and lactone acid functional groups were formed on the surface of carbon materials,which could enhanced the adsorption of NH₃.And thus exhibited relative higer denitrification activity?the denitrification rate of biomass coke increased from 8.3%to 29%at 150°C?.Furthermore,several transition metals?Mn,Ce,V and Fe?were loaded on nitric acid modified biomass char?BC?using an impregnation method.The catalytic activities for the as-prepared catalysts were investigated.Results showed the sequence of NO conversion within the temperature of 125-225°C was Mn/BC>Ce/BC>V/BC>Fe/BC>BC,and Mn/BC exhibited the highest NO conversion of 87.6%at 200?.BC supports provided higher surface area,which could contribute to the better dispersion of transition oxides.Additionally,the graphite crystallite structure of BC promoted the oxidation of NO to NO₂.Owing to the existence of“fast SCR”reaction process,the transition metal oxides supported on BC catalysts exhibited superior denitration efficiency at low temperature.Finally,the effect of Ce addition on the low temperature activity of the catalyst was studied.The results showed that the addition of Ce made the distribution of Mn more uniform on the carrier surface and enhanced the denitrification activity of the catalyst.As the active substance,MnO_x could promote denitration process by circulation redox itself.As the promoter,CeO₂ could speed up the catalytic reaction by oxidizing MnOx due to its high oxygen storage and adsorbed oxygen conversion capacity.After adding Ce,the denitrification activity of the catalyst was greatly improved.At 175°C,the denitration rate of Mn-Ce_?7:3?/catalyst was as high as 99.2%.