Investivation On The Simultaneous Removal Mechanism Of SO₂ And NO From Sintering Flue Gas Under A Microwave Field

In this work,the porous high-activity adsorbent was prepared by microwave modification with using the industrial waste?fly ash : carbide slag=1:1,RM?as raw materials as well as the active coke acting as additives,and the effects of single-component gas and multi-component gas on the desulfurization and denitrification of adsorbents were investigated in detail.The quasi-second-order kinetic model and the internal diffusion model were used to explore the rate-limiting links of desulfurization and denitrification under different gas phase components,and the synergistic removal mechanisms of SO₂ and NO under different gas components were studied.After RM is treated under the conditions of microwave power of 1000 W,modification time of 10 min,and 15% active coke added,the specific surface area,micropore volume and total pore volume of the adsorbent are increased from 10.550 m²/g,0.011 cm³/g,0.061 cm³/g to 53.702 m²/g,0.052 cm³/g,0.105 cm³/g respectively,and the average pore size is decreased from 18.138 nm to 7.792 nm.The content of C=C increase and the content of-OH decrease in the adsorbent after the microwave modification,while the phase structure of C and CaO₂ are unchanged during the microwave modification.For a single component atmosphere,10%O₂ and 4%H₂O have the optimal promotion with respect to the single desulfurization,while CO and CO₂ have the inhibition effect on the desulfurization alone.On the other hand,under the condition of 15%O₂,4%H₂O and 6%CO,the denitrification rate is optomal,and CO₂ has little effect on denitrification.For a multi-component atmosphere,there is a competitive adsorption between SO₂ and NO.With the addition of O₂ and H₂ O,the efficiency of synergistic desulfurization and denitrification are continuously improved.CO inhibits desulfurization process,but it can improve denitrification efficiency effectively.CO₂ takes up the desulfurization active site,exacerbating the competitive adsorption between SO₂ and NO,and the efficiency of desulfurization and denitrification is reduced.After the desulfurization and denitrification process,all of the specific surface area,micropore volume and total pore volume of the adsorbent decreases,and the average pore diameter increases.In the gas phase components of SO₂/NO+O₂ and SO₂/NO+O₂+H₂O,the denitrification has a stronger dependence on the C=C functional group,and the reduction for C=C is the largest.According to the results of XPS,the main products of desulfurization and denitrification are sulfate and nitrate.Under the single-component SO₂ or NO atmosphere,the fitting degree of the quasi-second-order kinetic model is higher than that of the internal diffusion model,and chemical adsorption is the main rate-limiting link.For the synergistic desulfurization and denitrification,chemical adsorption is the rate-limiting link of the cooperative desulfurization and denitrification under the SO₂/NO gas phase component.The fitting degree of the quasi-second-order kinetic model is decreased,and that of the internal diffusion model is increased under the SO₂/NO+O₂ and SO₂/NO+O₂+H₂O gas phase components,and the restriction effect of the internal diffusion on desulfurization and denitrification is enhanced.For SO₂/NO+O₂+H₂O +CO gas phase components,the quasi-second-order kinetic model has a higher fitting degree for the desulfurization process,and the chemical adsorption is the rate-limiting link of desulfurization.For the denitrification process,the internal diffusion is the rate-limiting link.Under the SO₂/NO+O₂+H₂O+CO+CO₂ gas phase components,as CO₂ occupies the SO₂ adsorption active site,the competitive adsorption between SO₂ and NO is intensified,and chemical adsorption is the rate-limiting link.Under the conditions of 1000 W microwave power and 10 min modification time,the specific surface area of the activated coke increases from 185.867 to 351.727 m²/g and the average pore diameter of the activated coke decreases from 1.9319 to 1.2318 nm after the microwave modification.The peak intensity of the C=C and-OH functional group are increased.At the reaction temperature of 140 °C and the O₂ content of 10%,the desulfurization and denitrification breakthrough time are 70 and 75 min,respectively,while the affinity of activated coke to SO₂ is better than that of NO,and the overall desulfurization effect is better than denitrification.After the desulfurization and denitrification process,the characteristic peak intensity of C=C and-OH in the active coke are weakened,and the characteristic peak intensity of C-O functional group is increased.The desulfurization and denitrification products are CaSO₄,CaS and Fe?NO₃?₃.