Effects of Bi Substitution on the Cobalt-Free 60wt.%Ce0.9Pr0.1O2−δ-40wt.%Pr0.6Sr0.4Fe1−xBixO3−δ Oxygen Transport Membranes

The mixed ionic-electronic conducting (MIEC) oxygen transport membrane (OTM) can completely selectively penetrate oxygen theoretically and can be widely used in gas separation and oxygen-enriched combustion industries. In this paper, dual-phase MIEC OTMs doped with Bi are successfully prepared by a sol-gel method with high-temperature sintering, whose chemical formulas are 60wt.%Ce0.9Pr0.1O2−δ-40wt.%Pr0.6Sr0.4Fe1−xBixO3−δ (60CPO-40PSF1−xBxO, x = 0.01, 0.025, 0.05, 0.10, 0.15, 0.20). The dual-phase structure, element content, surface morphology, oxygen permeability, and stability are studied by XRD, EDXS, SEM, and self-built devices, respectively. The optimal Bi-doped component is 60wt.%Ce0.9Pr0.1O2−δ-40wt.%Pr0.6Sr0.4Fe0.99Bi0.01O3−δ, which can maintain 0.71 and 0.62 mL·min−1·cm−2 over 50 h under He and CO2 atmospheres, respectively. The oxygen permeation flux through these Bi-doped OTMs under air/CO2 gradient is 12.7% less than that under air/He gradient, which indicates that the Bi-doped OTMs have comparable oxygen permeability and excellent CO2 tolerance.

Pure oxygen separation from air using dual-phase SDC-SCFZ disc membrane: A modelling approach

Novel Ce0.8Sm0.2O1.9-SrCo0.4Fe0.55Zr0.05O3-δ (SDC-SCFZ) disc membranes consist of 25 wt.% SDC fluorite ionic conducting phase and 75 wt.% SCFZ perovskite mixed conducting phase, which is more promising than perovskite oxide SCFZ single-phase membrane in terms of the oxygen permeation flux. This work features a modelling approach to simulate the oxygen permeation fluxes of the SDC-SCFZ membrane. Simplified model equations from the Zhu model and Xu-Thomson model based on the limiting cases of surface exchange reactions and bulk diffusion are compared. The Zhu model is found to be more applicable for the membranes with overall good correlation and low sum of squared error. Furthermore, modelling studies revealed that the oxygen transport is limited by surface exchange reactions from 700 to 850 °C and a mixture of both limiting cases above 850 up to 950 °C. It is concluded that the membranes exhibit high oxygen permeation flux of up to 2×10−6 mol s−1 cm−2 at 950 °C with Pair of 5 atm and Po 2 of 0.005 atm. The optimum range of operating conditions of the membrane are found to be at 950 °C with minimum Pair of 1 atm and P11 2 lower than 0.025 atm.

A chemically and mechanically stable dual-phase membrane with high oxygen permeation flux

This contribution details our comprehensive efforts to design a chemically and mechanically stable dual-phase membrane with a high oxygen permeation flux.

Progress in Ce0.8Gd0.2O2−δ protective layers for improving the CO2 stability of Ba0.5Sr0.5Co0.8Fe0.2O3−δ O2-transport membranes

A promising way of overcoming BSCF limitations in real operation conditions are CGO protective layers deposited by RF magnetron sputtering, as they show an improvement in the oxygen permeation flux when using pure CO2 as sweep gas.

Numerical Investigation of Oxygen Permeation Through a Ba0.5Sr0.5Co0.8Fe0.2O3−δ Ion Transport Membrane With Impingement Flow

Ion transport membrane (ITM) is considered to be one of the promising techniques for the separation of oxygen from the air for clean energy applications. Studying flow configurations of gases around Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) membrane is presented and discussed in this paper. The effects of the sweep mass flow rate and impingement configurations for the gases flow in the feed and permeation sides have been investigated. In this regard, flow with single or double impingement and impingement with different angles have been simulated and analyzed in order to identify the configurations that would provide the maximum permeation flux. Results show that increasing the sweep flow rate, directly, increases the oxygen permeation flux. It is also found that, in case of single impingement, decreasing the distance between the nozzle and the membrane (H), directly, increases the oxygen permeation flux for constant sweep side nozzle (slot) width (D). The permeation flux increases from around 2.9–3.66 µmole/cm2 s for the ratio H:D from1:1 to 1:4 (i.e., decreasing H to one-fourth of its value). Results show that the double impingement flow gives lower results than the single impingements by about 35.7%. The results also revealed that the optimum configuration is the parallel flow with vacuum in the sweeping side, which gives the highest permeation flux with an increase of more than 41% from that of the parallel configuration with a sweeping gas. Using carbon dioxide as a sweeping gas is better than helium.