Study On The Formation Of Pahs And Soot In Coke Chemical Looping Combustion Of Iron-based Oxygen Carrier With CO₂ Hypoxia Dilutio

Chemical looping combustion?CLC?can achieve efficient CO₂ capture and control CO₂ emissions,but carbon deposition?especially soot?on the surface of oxygen carriers during CLC process will affect its reaction performance.In order to control the formation of polycyclic aromatic hydrocarbons?PAHs?and soot in coke CLC and improve the reactivity of oxygen carriers,Fe₂O₃/Al₂O₃ and Fe₂O₃/SiO₂ oxygen carriers were prepared by mechanical mixing method.The chemical looping combustion of 4 kinds of coke?coke 1?2?3?4?was simulated without CO₂ and CO₂.The effects of different factors on the formation of PAHs in flue gas and soot on the surface of oxygen carriers were studied.Quantitative analysis of PAHs by gas chromatography and soot by elemental analyzer.The main conclusions are as follows:?1?Fresh oxygen carriers have abundant pore structure,active components and inert carriers did not react in solid state.In the case of CO₂,the oxygen carriers were less likely to agglomerate.The pore structure of Fe₂O₃/SiO₂ oxygen carriers was reduced after reaction.In both cases,the products were Fe.Passing CO₂ can slow down the reaction rate of oxygen carriers and coke.?2?In the absence of CO₂,the carbon content of 82.92%,n?H?/n?C?=0.032,which produced the least PAHs.When the carbon content was 85.23%,n?H?/n?C?=0.09,the PAHs were the most;in the case of CO₂,the carbon content of 84.12%,n?H?/n?C?=0.049,which produced the most PAHs.When the carbon content was85.23%,n?H?/n?C?=0.09,the PAHs were the least.?3?When coke 1 reacted with Fe₂O₃/Al₂O₃ oxygen carrier,PAHs were produced the most at 750°C.PAHs were produced the least at 850°C when CO₂ was not used,and produced the least at 1050°C when CO₂ was passed.The effect of CO₂ on the formation of pentacyclic aromatic hydrocarbons was greater.Fe₂O₃/Al₂O₃ oxygen carrier and coke 1 were burned at different ratios.In both cases,when the ratio is 3.6,the production of PAHs is less.The Fe₂O₃/Al₂O₃ oxygen carrier with different ratios was burned with coke 1.When the ratio of oxygen carrier was 7:3,the amount of PAHs was the least.Fe₂O₃ was supported on different inert supports?Al₂O₃,SiO₂?and burned with coke 1.When CO₂ was not available,Fe₂O₃/SiO₂ produced less PAHs than Fe₂O₃/Al₂O₃.When CO₂ was passed,the PAHs produced by Fe₂O₃/SiO₂were more than those without CO₂.?4?In the absence of CO₂,the carbon content of 77.07%,n?H?/n?C?=0.05,which produced the most soot.When the carbon content was 84.12%,n?H?/n?C?=0.049,the soot was the least.in the case of CO₂,the carbon content of 77.07%,n?H?/n?C?=0.05,which produced the most soot.When the carbon content was82.92%,n?H?/n?C?=0.032,the soot was the least.?5?At different temperatures,the soot produced most at 950°C and produced least at 850°C.With the increase of the ratio of Fe₂O₃/Al₂O₃ oxygen carrier to coke 1,the production of soot increased first and then decreased when CO₂ was not available,and the production of soot first decreased significantly and then increased slightly when CO₂ was passed.The most suitable ratio was 3.6.The optimum ratio of Fe₂O₃/Al₂O₃ is 7:3.In the absence of CO₂,Fe₂O₃/Al₂O₃ produced more soot than Fe₂O₃/SiO₂.In the case of CO₂,the soot phase produced by the two was similar.In conclusion,under the condition of CO₂ hypoxic dilution,the reaction rate can be slowed down,PAHs can be reduced under specific conditions,and soot can be effectively inhibited.