Performance Study Of Cu-based Oxygen Carriers Used In Chemical Looping Oxygen Production

Oxygen is an important industrial chemical, and there is a widely used in industrial production and daily life. The traditional methods of generating oxygen have many defects in consumption, investment in equipment and operational aspects of the production. The chemical looping oxygen production (CLOP) is a new method of oxygen production which is based on the chemical-looping concept. The theoretical consumption of the CLOP process is just26%of the traditional cryogenic air-separation system and it has a very broad application prospects.The chemical looping oxygen production (CLOP) is a new technology of producing oxygen and oxygen carrier’s performance directly determines the system performance and efficiency. The study of the oxygen carrier’s performance is the key. Cu-based oxygen carriers have large ability of carrying oxygen, a big range of oxygen production’s temperature and it is not harmful to the environment. In this paper, five kinds of Cu-based oxygen carrier are prepared with different CuO contents using MgAl2O4、SiO2、ZrO2as inert supports by mechanical mixing method. The oxygen carriers prepared are:CuO-(60wt.%)MgAl2O4、 CuO-(50wt.%)MgAl2O4、CuO-(40wt.%)MgAl2O4、CuO-(60wt.%)ZrO2、CuO-(60wt.%)SiO2. The physical properties of the oxygen carriers were characterized, including XRD phase composition analysis, SEM-EDX surface morphology and energy spectrum analysis and BET surface area analysis. In order to simulate a small scale practical industrial application process a fixed bed reactor thermal test platform was set up. The effects of reaction temperature, gas flow, the mass of reactant, inter carriers and the additive proportion of inter carriers on the reduction reaction and oxidation reaction of Cu-based oxygen carriers were studied. Temperatures were950℃,975℃,985℃,100℃,1015℃in the reduction reaction process and gas flow rates were0.8L/min,0.9L/min,1.0L/min,1.1L/min,1.2L/min. Temperatures were800℃,850℃,900℃,950℃,1000℃in oxidation reaction process, and gas flow rates were0.7L/min,0.8L/min,0.9L/min,1.0L/min,1.1L/min. The mass of sample was50g,70g,90g respectively both in the process of reduction reaction and oxidation reaction. In addition, stability of the five kinds of oxygen carriers was investigated and analyzed through cyclic experiments. The conclusions are as follows:(1) The results of the phase composition analysis show that:the active components of prepared oxygen carriers do not react with the inter carriers; The results of surface morphology analysis show that:the active components and inter carriers are staggered in the prepared samples; The results of specific surface area measurements show that: CuO/MgAl2O4>CuO/ZrO2>CuO/SiO2and with the additive proportion of inter carriers increasing, the specific surface area increases.(2) Thermal test results show that:the reaction rates of oxygen carriers increase with increasing temperature in the range of950℃-1015℃during the reduction reaction process, and increase with increasing flow rates in the range0.8L/min-1.2L/min; the reaction rates of oxygen carriers decrease with increasing temperature in the range of800℃-1000℃during the oxidation reaction process, and increase with increasing flow rates in the range0.7L/min-1.1L/min; Reduction and oxidation reaction rates both increase with the increasing of the amount of oxygen carriers in a certain range; For the three kinds of oxygen carriers with same inert carriers, the reduction rates increase in the order of MgAl2O4>ZrO2>SiO2. However, the oxidation rates have little difference; Reduction and oxidation reaction rates both increase with the decreasing of inert carrier.(3) The result of cyclic experiments show that:CuO-(50wt.%)MgAl2O4and CuO-(60wt.%)SiO2have the cyclic stability under the condition that the temperature of reduction reaction is1000℃and the temperature of oxidation reaction is900℃; CuO-(40wt.%)MgAl2O4has the cyclic stability under the condition that the temperature of reduction reaction is985℃and the temperature of oxidation reaction is900℃; For CuO-(40wt.%)MgAl2O4、the rates of reduction reaction decrease under the condition that the temperature of reduction reaction is1000℃and the temperature of oxidation reaction is900℃. The reason is that the surface migration of CuO/Cu2O crystalline particles occurred at high reaction temperature, resulting in agglomeration of the oxygen carrier particles.