Permeation model and experimental investigation of mixed conducting membranes

Abstract

A simple oxygen permeation model was developed based on the theoretical analysis of the role of interfaces of mixed conducting membranes. The developed model equations contain three resistance constants, which can be determined by correlating oxygen permeation flux to oxygen partial pressure on each side. A series of experimental measurements of oxygen fluxes of Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3À membranes over a wide range of temperature and oxygen partial pressures were tested for the regression of three resistance constants with good correlation (R > 0.997). With this model, the interfacial exchange resistances of each side can be well distinguished from the bulk-diffusion resistance under a wide-temperature range. The kinetics parameters, including interfacial exchange coefficients on each side and ionic diffusion coefficient, can be obtained through the three resistance constants. Parametric studies can predict the influences of membrane thickness, oxygen partial pressures on oxygen flux, distribution of permeation resistances, and characteristic thickness.

Comparative investigation of dual-phase membranes containing cobalt and iron-based mixed conducting perovskite for oxygen permeation

“…The second one is that the surface microstructure changes under oxygen permeation condition can speed up the oxygen exchange rates, which has been verified by our previous investigation [50]. The third is that the adsorption of CO 2 on membrane surface retards oxygen exchange rates and decreases the oxygen permeation flux [3,7,40,57]. For the SDC67-SCC33 membrane, the three factors exhibit their effects at different stages.…”

Oxygen permeability and CO2-tolerance of Ce0.9Gd0.1O2−δ – SrCo0.8Fe0.1Nb0.1O3−δ dual-phase membrane

“…It is interest to note that the two interfaces have different exchange constants under oxygen permeation process, and oxygen exchange kinetics on the permeate side is faster than that on the feed side. The difference could be resulted from the microstructure developing on interfaces during oxygen permeation [26]. Different surface morphologies on both sides of perovskite membranes after permeation test were observed [33,34].…”

“…However, the result shows that the oxygen permeation in the membrane with a thickness of 0.6 mm is still controlled by bulk diffusion. After obtaining the two interfacial exchange constants and the bulk-permeation resistance, the interfacial exchange kinetic coefficient k 0 and self-diffusion coefficient D s can be calculated through below equations (5)e(7) [26].…”

“…However, if the bulk transport is fast enough compared with the interfacial exchange reactions on the feed side and permeate side of membrane, the exchange reactions on both sides would be the rate determining step in oxygen permeation. To clarify the determining step of the oxygen permeation of CGO-SCFN DPM, oxygen permeation model proposed by Zhu et al [26] was adopted on the 80CGO-20SCFN membranes with the thicknesses of 0.6 mm and 1.0 mm. In the process of oxygen permeation measurement, the oxygen partial pressure of one side was kept constant while adjusting the oxygen partial pressure at the reverse side, and the oxygen permeation flux at 900 C in the two cases was recorded with the oxygen partial pressure.…”

“…It's also known that electronic conducting oxides such as SrCo 0.8 Fe 0.1 Nb 0.1 O 3Àd (SCFN) shows high oxygen permeability [25]. In addition, in 2012, Zhu et al [26] proposed a new oxygen permeation model based on the theoretical analysis by Virkar [27]. The model can well describe the permeation fluxes of oxygen transport membranes and easily distinguish the distribution of interfacial resistances on both sides and bulk resistance.…”