Numerical Modeling of CO2 Splitting in High-Temperature Solar-Driven Oxygen Permeation Membrane Reactors

H2/CO production via H2O/CO2 splitting powered by concentrated solar energy is a promising pathway for energy conversion/storage. Oxygen permeable membrane reactor serves as an alternative reactor concept for realizing this chemical path with the advantages of continuous production, easy integration, and high product selectivity. In this paper, a mathematical model of steady-state mass and heat transfer coupled with reaction kinetics in the oxygen permeation membrane reactor was established. CO2 splitting in the ceria membrane reactor was simulated and the effects of various factors, including inert/CO2 flow configurations, reaction conditions, and geometric parameters of the membrane, on the CO2 conversion process, were studied. The increase of operating temperature could effectively improve the CO2 conversion ratio, and the effect of decreasing the oxygen pressure of the inert gas is very limited. The oxygen accumulation in the inert gas could lead to considerably high inert demand. Furthermore, conversion-limiting factors were studied under different conditions and there are two critical rate constants of reactions signifying a transition from a chemical kinetics limited conversion to oxygen diffusion limited conversion. This work helps guide reactor design and operate toward achieving the maximum CO2 conversion ratio.