Oxygen transport through supported Ba0.5Sr0.5Co0.8Fe0.2O3−δ membranes

Integrated Heat Recovery System Based on Mixed Ionic-Electronic Conducting Membrane for Improved Solid Oxide Co-Electrolyzer Performance

The current state of mixed ionic-electronic conducting ceramic membrane technology presents significant advancements with potential applications in various fields including solid oxide electrolyzers, fuel cells, hydrogen production, CO2 reduction, and membrane reactors for chemical production and oxygen separation. Particularly in oxygen separation applications, optimal conditions closely align with the conditions of oxygen-rich air streams emitted from the anode of solid oxide co-electrolyzers. This paper describes and analyzes a novel integrated heat recovery system based on mixed ionic-electronic conducting membranes. The system operates in two stages: firstly, oxygen is separated from the anode output stream using mixed ionic-electronic conducting membranes aided by a vacuum system, followed by the heat recovery process. Upon oxygen separation, the swept gas stream is recirculated at temperatures near thermoneutral conditions, resulting in performance improvements at both cell and system levels. Additionally, an oxygen stream is generated for various applications. An Aspen HYSYS® model has been developed to calculate heat and material balances, demonstrating the efficiency enhancements of the proposed system configuration.

Sensitivity of Material, Microstructure and Operational Parameters on the Performance of Asymmetric Oxygen Transport Membranes: Guidance from Modeling

Oxygen transport membranes can enable a wide range of efficient energy and industrial applications. One goal of development is to maximize the performance by the improvement of the material, microstructural properties and operational conditions. However, the complexity of the transportation processes taking place in such commonly asymmetric membranes impedes the identification of the parameters to improve them. In this work, we present a sensitivity study that allows identification of these parameters. It is based on a 1D transport model that includes surface exchange, ionic and electronic transport inside the dense membrane, as well as binary diffusion, Knudsen diffusion and viscous flux inside the porous support. A support limitation factor is defined and its dependency on the membrane conductivity is shown. For materials with very high ambipolar conductivity the transport is limited by the porous support (in particular the pore tortuosity), whereas for materials with low ambipolar conductivity the transport is limited by the dense membrane. Moreover, the influence of total pressure and related oxygen partial pressures in the gas phase at the membrane's surfaces was revealed to be significant, which has been neglected so far in permeation test setups reported in the literature. In addition, the accuracy of each parameter's experimental determination is discussed. The model is well-suited to guiding experimentalists in developing high-performance gas separation membranes.

Comparison of the Simplification of the Pressure Profiles Solving the Binary Friction Model for Asymmetric Membranes

The gas flow through porous media including that of multiple species is frequently described by the binary friction model (BFM) considering the binary diffusion, Knudsen diffusion, and viscous flow. Therefore, a numerical simulation was performed on a microporous support of an asymmetric oxygen transport membrane. As its exact numerical solution is complicated and not always possible, the results of two different levels of simplification of the pressure profiles within the porous support are compared to the exact numerical solution. The simplification using a constant pressure equal to the gas pressure outside the support leads to a deviation by up to 0.45 mL·min⁻¹·cm⁻² from the exact solution under certain operating condition. A different simplification using a constant pressure averaged between the outside of the support and the support/membrane interface reduces this deviation to zero. Therefore, this is a useful measure to reduce computational efforts when implementing the Binary Friction Model in computational fluid dynamics simulations.