Simultaneous Desulfurization And Denitrification From Flue Gas By Catalytic Preoxidation Of NO With H₂O₂

The coal consumption in China is the highest among the world.The emissions of SO2 and NOx from the coal-combustion process result into serious environmental problems,such as asacid rain,photochemical smog and ozone depletion.These environmental problems have been seriously threatened human health.Conventional desulfurization and denitrification approaches have many disadvantages,such as high operation cost,large occupation area and complex systems.Therefore,it's important to develop a simple,reliable flue gas purification technology which can remove multiple pollutants in one system.In this paper,a new method is proposed where the catalytic decomposition of gas phase H2O2 over catalyst to produce OH radicals and the NO is oxidized by ·OH radicals into high-valent nitrogen oxides,and then use the ammonium-based solution to purify the flue gas.Under different experimental conditions,the performance of iron-based catalysts of two different carriers in denitrification,simultaneous desulfurization and denitrification experiments were studied in self-designed experimental bench.Fe2O3,Fe2O3/SiO2 and Fe2O3/Al2O3 catalysts with different Fe2O3 loading were prepared by sol-gel method.The microstructures of the as-prepared catalysts were characterized by FTIR,XRD,BET,H2-TPR and SEM.The characterization results show that compared with Fe2O3 oxide,SiO2 and Al2O3 as carrier can effectively improve the microstructure of the catalyst.With the increase of Fe2O3 loading,the particle agglomeration on the surface of catalysts becomes more and more serious,which causes the specific surface area of the catalyst decrease to a certain extent,but the number of active site in the catalyst is increasing.XRD analysis shows that Fe2O3/Al2O3 catalysts contain a certain amount of Fe3O4.The NO removal performance shows that the introduction of the catalysts can improve the removal efficiency of NO greatly.For all iron-based catalysts,with the catalytic temperature increasing,the removal efficiency of NO firstly increased and then decreased.The best reaction temperature is between 180 ? and 220 ?.With the increase of H2O2 concentration,the removal efficiency of NO is continuously increasing.Under the same experiment conditions,the removal efficiency of NO increased gradually with the increasing of Fe2O3 loading.In comparison,higher NO removal efficiency is obtained when Fe2O3/Al2O3 is used as catalyst than Fe2O3/SiO2 under the same Fe2O3 loading.The experimental results of simultaneous desulfurization and denitrification shows that SO2 can be 100%removed under various experimental conditions.The existence of SO2 does not affect the optimum reaction temperature of all catalysts.SO2 in flue gas will compete with NO for OH radicals to inhibit NO removal.The O2 and CO2 concentration have slightly effect on SO2 and NO removal efficiency.The change of catalysts before and after denitrification,simultaneous desulfurization and denitrification shows that the catalyst surface will produce nitrates and sulfates with the extension of reaction time.But the production of nitrates and sulfates does not affect the denitrification performance of the catalyst.Even the formation of sulfate can promote the NO removal.