Analysis on Chemical Reaction Kinetics of CuO/SiO2 Oxygen Carriers for Chemical Looping Air Separation

Chemical looping air separation (CLAS) offers an energy-efficient and cost-effective option for oxygen generation in several advanced power generation systems, such as integrated gasification combined cycle (IGCC), oxy-fuel combustion, and solid oxide fuel cells (SOFCs). In our previous study, CuO/SiO2 has been identified as one of the most efficient oxygen carriers for the CLAS process because of its higher reactivity, greater oxygen transport capacity, and lower inventory requirement. In the current study, the kinetic analysis of CuO/SiO2 oxygen carriers under a CLAS process environment has been conducted. The CuO/SiO2 oxygen carriers with a varying CuO content of 18-48 wt % were prepared by a dry impregnation method. The redox behavior was investigated under N-2 and air separately for the temperature range of 800-975 degrees C in a thermogravimetric analyzer (TGA). The reduction rate was found to increase gradually with an increasing temperature, while in contrast, a drop in the oxidation rate was observed. Furthermore, the chemical reaction kinetics of 18 wt % CuO/SiO2 for reduction and oxidation was attained by fitting various gas solid reaction mechanisms with the obtained experimental data. Among all studied gas solid reaction mechanisms, it was observed that the Avrami-Erofe'ev random nucleation and subsequence growth model (A2) and phase boundary reaction model (R2) fitted well with reduction and oxidation experimental data, respectively. In addition, relevant kinetic parameters, such as activation energy, pre-exponential factor, and reaction order, were also determined.