Low-Cost Composite Fe/Cu Oxygen Carrier Particles Prepared By The Extrusion-Spheronization Method For Chemical Looping Combustion

Chemical looping combustion（CLC）is widely regarded as one of the most potential carbon capture technologies with low cost and low energy consumption,which can achieve the enrichment and internal separation of CO₂ during the combustion of fossil fuels.After more than 30 years of research,chemical looping combustion technology has developed from laboratory scale to pilot scale,and has the foundation for industrial application.However,the large-scale preparation of low-cost and high-reactivity oxygen carriers is still the prerequisite for the industrial application of chemical combustion technology.In this work,the low-cost and high-reactivity ore type composite oxygen carriers were prepared by extrusion-spheronization method and their chemical looping combustion performance was studied.Firstly,the process flow of producing oxygen carrier by extrusion-spheronization method was established,and the iron ore and copper ore composite oxygen carriers were successfully prepared.Six kinds of natural aluminosilicates were used as inert carriers.According to their crushing strength,the montmorillonite and the pumice were selected as suitable inert carriers.The crushing strength of oxygen carrier Fe Cu-10M（the mass ratio of iron ore to copper ore was 8:2,and 10 wt.%montmorillonite was added）and Fe Cu-5P（the mass ratio of iron ore to copper ore was 8:2,and 5 wt.%pumices were added）can reach more than 2N.Then,the chemical looping combustion performance of Fe Cu-10M and Fe Cu-5P with coals in batch fluidized bed was investigated.The effects of reaction temperature,the oxygen to fuel ratio and the coal rank on the reactivity of oxygen carrier were studied.The crystal phase structure,microstructure,element distribution and particle size change of oxygen carrier particles were studied by XRD,SEM,EDX and particle size distribution.The results show that the spherical structure of Fe Cu-10M can be maintained in the multiple cycles,and no new crystal phase appeared and no original crystal phase was lost.Furthermore,the anti-sintering ability and long-term stability of the binary-ore（copper ore and iron ore）oxygen carriers prepared by extrusion-spheronization method were systematically investigated.Firstly,the proportion of inert carrier（montmorillonite）in oxygen carriers was evaluated,and four kinds of low-cost composite oxygen carriers with montmorillonite content of 10wt%～40wt%were prepared.Then,oxygen carriers with different contents of montmorillonite were subjected to 100 cycles of reduction/oxidation reaction with H₂/O₂ in a thermogravimetric analyzer.It was found that Fe Cu-10M could not only maintain high reactivity but also have good anti-sintering performance.Furthermore,a hundred cycle experiments of chemical looping combustion of coal were carried out in a batch fluidized bed to investigate the changes of reaction performance and wear rate for Fe Cu-10M.It was found that the combustion efficiency could be stabilized at more than 90%,and the average wear rate was 0.108%/h.Finally,the industrial scale production of low-cost composite oxygen carrier by extrusion-spheronization method was realized.In order to further reduce the raw material cost of oxygen carrier,the red mud（containing a lot of Fe₂O₃ and rich in Na）from the aluminum industry,was used to replace iron ore,and the red mud copper ore composite oxygen carrier RCu-10M（the mass ratio of iron ore to copper ore was 89.1:10.9,and 10 wt.%montmorillonite was added）was prepared on large-scale.Firstly,the effects of temperature and oxygen to fuel ratio on the reaction characteristics of RCu-10M were investigated in a batch fluidized bed.It was found that the CO₂ yield of RCu-10M could reach more than 94.5%at 950℃with an oxygen to fuel ratio of 2.0.Subsequently,100 cycles of redox reaction were carried out in a thermogravimetric analyzer,and the RCu-10M could maintain stable reaction performance without obvious sintering phenomenon.Finally,the reaction characteristics of RCu-10M with gaseous fuel were tested in a micro interconnected fluidized bed.The oxygen carriers could maintain stable circulating operation in the continuous operation for 100min,and there was no residual carbon deposition on the surface of the oxygen carriers after the reaction.