Research On Properties Of Copper-based Composite Oxygen Carrier Based On Chemical Looping Air Separation

As an important chemical raw material,oxygen is widely used in industrial production and daily life,and its demand is increasing year by year.At present,the commonly used air separation oxygen production technology has the problems of high energy consumption and high cost.Chemical looping air separation is a kind of new production oxygen technology based on chemical looping combustion.The technology has high purity oxygen and low energy consumption,which is only 26%of deep cooling method.CLAS conforms to the development requirements of China's energy saving and emission reduction and has wide development prospects.Studying on the performance of oxygen carriers has become the most important part in CLAS.Preparation oxygen carrier with good reaction performance,sintering resistance,low cost and environmental protection has been the focus of research and attention.Currently,the study of oxygen carrier performance is mostly through experimental method,but the study on the mechanism of its microcosmic reaction is few.So in the paper,Cu-Mn based and Cu-Fe based composite oxygen carriers are the research objects,aiming at solving the disadvantages of single metal oxygen carrier used alone.Combining the experimental method and theory research,from both macroscopic and microscopic aspects,the performance of Cu-based composite oxygen carriers is studied.The main contents and conclusions of this paper are as follows:(1)Cu-based composite oxygen carriers prepared by mechanical mixing method are tested chemical performance using the thermal gravimetric analysis and the obtained results are as followed:The best ratios of CuO/Mn2O3/ZrO2 are 1.5:1:1,2:1:1 and CuO/Fe2O3/ZrO2 is 2:1:1;With the increase of heating rate,the reaction temperatures are increased,the reaction time is shortened and the reaction rate is increased.With the increase of oxygen concentration,the temperatures of reduction reaction are increased,the reaction time is shortened and the reaction rate is increased.Oxygen concentration has little effect on the oxidation reaction.With the increase of reaction temperature,the reaction time is shortened and the reaction rate is increased.After 15 cycles,the reaction volumes of reduction reaction and oxidation reaction basically remain unchanged,it illustrates that oxygen carriers have good reaction property and cycle stability.(2)Based on phase analysis,surface morphology and energy spectrum analysis,the changes of physical properties are studied before and after reaction and the obtained results are as followed:In the process of preparation,the active ingredients do not react with inert carrier.CuO respectively reacts with Mn2O3 and Fe203 to form CuxMn3-xO4 and CuFe2O4 which have the oxygen release property.The relationship between the sintering properties of three kinds of oxygen carriers is:Cu/Fe/Zr 2:1:1>Cu/Mn/Zr 2:1:1>Cu/Mn/Zr 1.5:1:1.(3)On the basis of the experimental data in TGA,the reduction and oxidation reaction mechanism model of Cu-based composite oxygen carriers is filtered.In the reduction process,the chemical reaction model of Cu/Mn/Zr 1.5:1:1 and Cu/Mn/Zr 2:1:1 is chemical reaction C2,Cu/Fe/Zr 2:1:1 is shrinking core model R2.In the oxidation process,the chemical reaction model of three oxygen carriers is nucleation and nuclei growth model A1.The activation energy and the pre exponential factor can be solved and the dynamic model can be established,which can improve the theoretical basis for the following related research and industrial application.(4)Based on density functional theory,the mechanism of CuO cluster adsorption on Mn3O4 and Fe2O3 model is studied at the micro-level and the obtained results are as followed:The adsorption energy of cluster on Mn3O4and Fe2O3 surfaces are-3.749eV and-6.136eV respectively.CuO/Fe2O3 model has better stability and sintering resistance.Furthermore,after adsorption,the bond length of Cu-O becomes longer,the electron of CuO cluster transfer.The peak of density of states is decreased,and it has delocalization near the Fermi level.The activity of cluster is increased.