Study On The Spatiotemporal Evolution Characteristics Of Active Components In The Reduction Process Of Oxygen Carrier In Chemical Looping

The carbon peaking and carbon neutrality goals is an important guarantee China to achieve green development,and CCUS（Carbon Capture,Utilization and Storage）is an important part of achieving the carbon peaking and carbon neutrality goals.In CCUS technology,chemical looping combustion technology has received extensive attention due to its intrinsic carbon dioxide separation properties.The oxygen carrier with excellent performance is an important part of the CLC,and the reactivity is an important index of the oxygen carrier performance,which has an important influence on the combustion efficiency and system economy.At present,the method of improving the chemical composition and molecular structure of oxygen carriers is basically used to improve their reactivity,and certain results have been achieved,but the modification process is blind.The key is the lack of understanding of the active ion migration and microscopic reduction process of the oxygen carrier phase.In view of the above problems,the study of the lattice oxygen migration in the reaction process and the evolution characteristics of the active components with time and space will provide theoretical support for the regulation,structural design and modification of the oxygen carrier components,which is of great significance to improve the reactivity of the oxygen carrier.The characterization results showed that the oxidation degree of the oxidized oxygen carrier was good;as the reduction reaction proceeds,the proportion of lattice oxygen in the bulk phase of oxygen carrier decreases continuously.The active metal components Cu and Fe contain two valence states,and the proportion of Cu⁰ and Fe²⁺increases gradually.The closer to the edge point,the more lattice oxygen consumed,and the higher the proportion of Cu⁰ and Fe²⁺.Fe⁰ was not detected in the reduced oxygen carrier,and the lattice oxygen of the bulk phase gradually changed from uneven distribution to balanced distribution of the final content after the reduction reaction.The results of density functional theory show that the deeper the lattice oxygen of the two substances is,the more difficult it is to realize the migration process,and the larger the energy barrier that needs to be overcome is,resulting in the gradual increase of the difference in the oxygen distribution of the oxygen carrier bulk phase.With the gradual outward migration of deep lattice oxygen,the migration barrier will decrease,and the increase of bulk oxygen vacancies and defects will also promote the migration of lattice oxygen.The oxygen release ability of Cu O is less than that of Cu Fe₂O₄ in the early stage,and the oxygen release ability of Cu O is greater than that of Cu Fe₂O₄ in the later stage.The lattice structure change of Cu Fe₂O₄ during lattice oxygen migration was smaller than that of Cu O.The reaction kinetics results show that the reduction reaction mechanism of Cu-Fe composite oxygen carrier is a three-order chemical reaction control mechanism,and the rate-limiting step in the gas-solid reaction process of oxygen carrier is chemical reaction.The activation energy of the reaction process calculated by the single scanning method is 61.11 KJ/mol,and the pre-exponential factor is 1.35 min^-1,The multiple scanning method calculates that the activation energy is constantly changing during the reaction,the activation energy ranges from 41.02～95.94 KJ/mol,and the pre-exponential factor ranges from 2.71×10⁵～1.88×10⁸ min^-1.The kinetic activation energy of the macroscopic reaction and the energy barrier of the microscopic simulation lattice oxygen migration process have the same trend:the activation energy of the oxygen release process of the oxygen carrier first increases and then decreases.