The Chemical Looping Cyclic Reactivity Of Nanosized Solid Solution Oxygen Carrier Synthesized By Combustion Synthesis

In recent years,the problem of global warming caused by the large amount of carbon dioxide emitted from the combustion of fossil fuels has become increasingly severe.Therefore,it is necessary to seek a clean combustion method to achieve efficient CO₂emission reduction goals for the sustainable development of energy and the environment in China and even the world.It is of great significance.Compared with the traditional air combustion technology,the chemical looping combustion technology has the advantages of internal carbon dioxide separation and high energy utilization,and is considered as a promising carbon dioxide capture technology.In the process of chemical looping reaction,oxygen carriers play a vital role as carriers of oxygen and heat,and have always been the focus and difficulty of chemical looping technology research.Oxygen carrier materials of pure metal oxides will gradually sintering and become denser at high temperatures.Adding a certain proportion of inert carrier can relieve the phenomenon to a certain extent,but factors such as less inert components,active components react with inert components,uneven loading and phase separation have certain effects on the cyclic stability of the oxygen carrier.In response to the appeal,this paper starts with the directional design of oxygen-carrying materials,and integrates the active and inert components of the oxygen-carrying materials into a crystal structure,which is itself a carrier and is also an active component.Synthesis of oxygen carriers with spinel structure by artificial synthesis.The chemical looping reaction performance of these oxygen-carrying materials are comprehensively investigated through the combination of experimental exploration and characterization.The AB₂O₄ spinel structure oxygen-carrying materials were synthesized by combustion synthesis,and a series of characterizations of the materials were performed.The XRD results show that the grain size of the material is between 1 and 100 nm,and the increase of the annealing temperature is beneficial to the crystallization of the material.XPS results show that the surface oxygen absorbed in the CoFeAlO₄ accounted for 7.06%,while the lattice oxygen accounted for 92.94%.The surface adsorption in the NiFeAlO₄ material oxygen occupies 5.7%,while lattice oxygen accounts for 94.3%.Combined with raman spectroscopy and EDS analysis,this method can synthesize nanostructure oxygen-carrying materials with cubic inverted spinel structure successfully and uniform distribution of elements.CoFeAlO₄ itself has both active and inert components.In this paper,CoFeAlO₄ was used as an oxygen carrier to investigate its phase transition characteristics and cycling stability at different temperatures through characterization and experimental studies.The results show that the temperature increase is beneficial to the improvement of the ability of this type of oxygen carrier to convert the reducible gas CO,resulting in the reduction rate faster.But redox at high temperature?800??900??will cause CoFeAlO₄ oxygen carrier phase separation,it is difficult to maintain a stable self-supported spinel structure.The analysis of the crystal structure of the CoFeAlO₄ oxygen carrier before and after the cyclic reaction shows that the CoFe₂O₄ and CoAl₂O₄ detected after the redox cycle at high temperature is the main reason for the sintering of CoFeAlO₄ oxygen carrier and the decrease of its cyclic thermal stability.NiFeAlO₄ was used as the oxygen carrier to study its phase transition characteristics and cyclic stability under different reduction depths,and the changes of crystal structure and apparent morphology of oxygen-carrying materials were analyzed.The results show that the deepening of the reduction is not conducive to NiFeAlO₄ oxygen carrier to maintain a good cycle stability.After 20 cycles,the conversion rate of oxygen carriers decreased,with a decrease of 1.4%at a reduction depth of 25%,and a decrease of 12.4%when the reduction depth increased to 100%.The XRD results of the NiFeAlO₄ oxygen-carrying material after the cycle show that redox at deeper reduction will cause the phase separation of the material,and the NiFe₂O₄ and NiAl₂O₄ will cause the cycling stability of the NiFeAlO₄ oxygen carrier to decrease.