The Experiment Study Of Synthesis Parameters On The Cu-based Oxygen Carriers

Chemical looping air separation (CLAS) for oxygen production has the lowest energy consumption, about0.08kWh/m3, equal to that of26%of the low-temperature rectification process. It is friendly to the environment without releasing pollution gas. In CLAS, one of the key parts in CLAS is the study of the oxygen carriers, from the view of oxygen. carriers production, we study the effect of different methods and other preparing parameters on oxygen carriers performance to achieve the best preparation condition and supply the theoretical basis for practical application.Cu-based oxygen carriers has higher reactivity, larger ability of carring oxygen, which is hard to react with inert carriers, and not harmful to the environment. So, we chose the Cu-based oxygen carriers. The content of this paper is divided into three parts:oxygen carrier preparing, physical property characterization, chemical reaction perfoamance research. A variety of Cu based oxygen carriers were prepared by mechanical mixing method and sol-gel method; the inert carriers are Al2O3,Fe2O3,ZrO2,TiO2,SiO2, the initial sintering temperatures were:850℃,900℃,950℃,1050℃, stiring time is6h,8h. The mass ratio CuO vs inert carriers were4:6,6:4,8:2. Then we tested the physical properties:the phase compisiton determined by XRD, the surface morphology tested by SEM, the specific surface area measured by BET, and the mechanical strength by the testing machine. Besides, we studied the chemical reaction performance by the STA409PC, and the effect of different preparing parameters on the reduction and oxidation of oxygen carriers at reduction temperature900℃and oxidation one700℃, to achieve the best preparing codition. Finally, we do a research on the recycle reaction stability and the performance of the fresh oxygen carriers and the post-reaction ones.The results are as follows:(1) The results of the phase compisiton show that:CuO and Al2O3, CuO and Fe2O3generate the spinel compound CuAlO2and CuFeO4without releasing oxygen, so we select ZrO2,TiO2,SiO2.When the temperature is as high as1050℃, the Cu-based oxygen carriers melt and the part of CuO decomposites into Cu2O. So the appropriate sintering temperatures850℃,900℃,950℃.The datas of BET show that higher temperature and less content of the inert carriers, the smaller the specific surface area and the higher the mechanical strength are. The speicific surface area relationship of oxygen carriers with the three inert carriers is CuO/ZrO2>CuO/TiO2>CuO/SiO2, while the relationship of mechanical strength is CuO/TiO2>CuO/SiO2>CuO/ZrO2.(2) Thermogravimetric experiment results are as follows:with increasing string temperature, the reduction performance decreases. However, it has little influence on the oxidation performance. Longer string time has no evident effect on the reduction and oxidation performance. The reduction performance of three inert carriers are different, and the following order is:CuO/ZrO2>CuO/TiO2>CuO/SiO2, the oxidation performance is opposite to that of the reduction. The oxygen carriers with ZrO2and TiO2are higher than the pure CuO in the reduction and oxidation performance, while CuO/SiO2is lower than pure CuO. With more CuO and the less inert carriers, the reduction and oxidation performance decrease. For the mechanical mixing and sol-gel method, the effect on the chemical reaction depends on the inert carriers. For CuO/ZrO2and CuO/SiO2, that of mechanical mixing is better than that of sol-gel method, opposite to the CuO/TiO2.(3) In this paper, through the23cycles reaction of the CuO/TiO2oxygen carriers, we find that reduction and the oxidation of CuO/TiO2is not reduced which indicated that the Cu-based oxygen carriers had the good stability and is suitable for the chemical looping air separation for oxygen actually. Meanwhile, we analyze the performance of the oxygen carrier after23recycled reactions, we conclude that the phase compisiton in oxygen carrier are CuO and the inert carrier TiO2and the reduced Cu2O can be oxidized completely; the sintering phenomenon does not happen on the surface of the oxygen carrier, but the oxygen carrier surface is more compact, large pores become smaller, the specific surface area should decrease, which is not proved because the amount of the TGA is not sufficient for the BET test. The mechanical strength is lower than the fresh oxygen carrier, but it is still enough for CLAS.