Study On Oxygen Release Performance And Microscopic Mechanism Of Iron-Based Oxygen Carrier

Global warming is jeopardizing the living environment of human beings.In order to cope with global climate change,the development of carbon capture technology to control greenhouse gas emissions has become a key issue,and capture integration has always been an important factor which restricting the development of carbon capture technology.The chemical looping combustion technology uses the lattice oxygen provided by the oxygen carrier to react with the fuel,avoiding the dilution of CO₂ in the flue gas by other gases such as N₂ in the air,and has the advantage of internal CO₂ separation,achieving low energy consumption of CO₂ from the source and even zero energy capture.Highly active oxygen carriers are the key to chemical looping combustion technology.Improving the reactivity of oxygen carriers is an important task for the development of this technology.Iron-based oxygen carriers have great potential for application at low cost and environmental friendliness,but the reduction rate is slow for reaction performance.Improving the reduction reaction rate is an important way to increase fuel conversion rate and increase system economy.This paper focuses on the changes in the reduction process of iron-based oxygen carriers,and studies the reduction and deoxidation process of regular-shaped iron-based oxygen carrier particles,the kinetic model of reduction,and the changes of bulk lattice oxygen.First,two types of iron-based oxygen carrier particles,pure Fe₂O₃ and Fe₂O₃?50?/Al₂O₃,required for the experiment were extruded through a mechanical mixing.The differences between the pure Fe₂O₃ oxygen carriers were studied on a thermogravimetric test bench.The effect of the heating rate on the particle reduction process was obtained.The low heating rate is helpful for the heat and mass transfer inside and outside the oxygen carrier particles,and it is helpful for the transfer of lattice oxygen to deepen the reduction of the oxygen carrier particles.The effects of different reaction temperatures on the deoxidation process of the two types of oxygen carriers were analyzed.The research found that the higher the reaction temperature of the two types of oxygen carriers in the early stage of the reaction,the more helpful the consumption of lattice oxygen and the faster the weight loss rate.Compared with pure Fe₂O₃,Fe₂O₃?50?/Al₂O₃ oxygen carrier has a higher solid phase conversion rate.Secondly,the dynamic processes of the two types of oxygen carrier particles were analyzed,and the"kinetic triplets"E,A and f?X?of the two types of oxygen carriers were obtained.The activation energy and preexponential factorof pure Fe₂O₃oxygen carrier particles and Fe₂O₃?50?/Al₂O₃ oxygen carrier particles are52.46KJ/mol,74.42KJ/mol,and 0.70×10⁶min^-1,0.525×10⁶ min^-1,And the reaction process of pure Fe₂O₃ and Fe₂O₃?50?/Al₂O₃ during the reduction by CO to FeO can be expressed by the chemical reaction mechanism model G?X?=C1=?1-X?^?-1/2?,And the reaction order is n=3/2.Finally,the X-ray photoelectron spectroscopy analysis technique was used to analyze the lattice oxygen change process of the two types of oxygen carriers from the microscopic level.The lattice of the circular cross section of the pure Fe₂O₃ particles was close to the four points of the lattice near the outer surface of the particles.Oxygen and iron valence state analysis found that the lattice oxygen in the reduction process of pure Fe₂O₃ oxygen carrier particles continuously migrated to the reaction interface and reacted with the reducing gas,so that the ratio of lattice oxygen on the surface and interior of the particles after reduction was similar,and combined with the iron price In the state change analysis,the migration of the reaction interface relative to the lattice oxygen is fixed.The same method was used to analyze the Fe₂O₃?50?/Al₂O₃ oxygen carrier.The addition of an inert carrier caused a significant increase in the proportion of lattice oxygen in the oxidized Fe₂O₃?50?/Al₂O₃ oxygen carrier,and caused the lattice oxygen consumption to change.After reduction,the proportion of lattice oxygen near the particle surface is greater than the proportion of internal lattice oxygen.The paper has 32 pictures,18 tables,and 114 references.