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Highlights • First realization of planar, asymmetric membrane components for 4-end operation. • Design of the membrane component supported by FEM and CFD simulations. • Flexible process chain for the production of membrane components developed. • Fabrication of defect free membrane components by scalable processes. Abstract Membrane-based oxy-combustion is a promising technology for energy efficient combustion of carbon-containing fuels with the simultaneous opportunity to capture CO 2 from the resulting exhaust gas. However, oxy-combustion conditions result in special demands on the design of the ceramic membrane components due to the high pressure and temperature applied. Therefore, we have developed a planar membrane design for 4-end operation using asymmetric membranes of La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ. FEM and CFD simulations have been performed in order to develop an internal channel structure that allows withstanding pressures of 5 bar on the feed side while achieving the desired O 2 concentrations of 27% in the sweep gas, i.e. CO 2 , and an oxygen recovery rate from the feed gas of 86% at the same time. Due to the symmetric design of the membrane components, they are scalable and adaptable in size. This design has been realized in a process chain from powder to the final component consisting of thin 20 µm Membrane layer, support with 38% porosity, an inner channelled architecture and a thin (3–5 µm) porous activation layer. Particular emphasis was laid on scalable manufacturing processes in order to ensure transferability to industrial scale. The process chain is also applicable to other membrane materials suitable for any application of interest. Finally, the reproducible processing was successfully demonstrated by the fabrication of membrane components in lengths of 100 mm and widths of 70 mm. [ABSTRACT FROM AUTHOR]

Advanced concepts for oxygen transport membranes focus on thin layers supported by a porous substrate. To warrant long term reliable operation of such systems, an assessment of the mechanical stability of each membrane component is required. With respect to chemical stability, cerium oxide and doped cerium oxides are promising materials for this application. The present work addresses the mechanical properties of cerium oxide variants, aiming to elucidate properties of relevance to the manufacture of reliable cerium oxide components. In particular Ce0.8Gd0.2−yPryO2−δ membrane materials and the influence of an addition 2 mol% of CoO is assessed. Materials preparation and compositional variations are compared with respect to elastic modulus, hardness and fracture toughness, as characterized using depth sensitive indentation. Furthermore, the creep behavior of doped and undoped cerium oxides, that is important for the long term structural stability at temperatures relevant to the oxygen-membranes operation, is assessed and critically discussed. [ABSTRACT FROM AUTHOR]

Abstract: Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) exhibits high oxygen permeability, which is why it is being discussed for gas separation (oxygen transport membrane, OTM) in zero-emission power plants using oxyfuel technology when the membrane is operated in a clean environment, i.e. no flue gas contact. We investigate the influence of membrane processing on microstructure and oxygen permeation. Pure-phase BSCF powder is synthesized using a modified Pechini method. For comparison, commercially available powder is also used, synthesized by a solid-state reaction. Disk-shaped membranes of various microstructures, i.e. closed porosities and grain sizes, are prepared by uniaxial pressing and sintering of the powders processed in different ways. The powders and membranes are characterized by methods including BET, SEM, XRD, and DSC. The microstructures obtained by different sintering conditions are investigated by SEM and TEM. Sintering at 1150°C leads to incongruent melting of BSCF indicated by DSC. The liquid phase appears at three-phase boundaries grain–grain–air and consists of nearly pure cobalt oxide with small impurities of barium and strontium detected by TEM/EDX analysis. Oxygen permeation of the membranes is measured in an air/Ar gradient depending on temperature and membrane microstructure. The closed porosity of different processed membranes is varied between 2 and 15% with uniform grain sizes in the range of approx. 10μm. The average grain size is increased from 10 to 45μm by increasing the sintering temperature. Neither porosity nor the grain size significantly influences the oxygen permeation rate of 1-mm-thick disks in the investigated parameter range. [Copyright &y& Elsevier]

Asymmetric membranes of mixed ionic-electronic conducting perovskite-type oxides SrTi 1-x Fe x O 3- δ (STF, x = 0.3, 0.5 and 0.7) were prepared by inverse sequential tape-casting. Both porous support (~600 μm) and functional membrane layer (~20 μm) for a given membrane assembly were made from the same composition to ensure thermochemical compatibility between the layers. Oxygen fluxes were assessed in the range 650 -1020 °C, using either (non-pressurized) ambient air or pure oxygen as feed gas at the support side of the asymmetric membrane and argon as sweep gas. Notably, similar oxygen fluxes (~1.2 × 10−6 mol cm−2 s−1) are measured through the membranes of different compositions above 950 °C when using ambient air as feed gas. This observation is interpreted to reflect the major role of the support layer resistance in rate-limiting the oxygen fluxes through the STF asymmetric membranes, which conclusion is supported by comparison of the oxygen fluxes with those measured previously through asymmetric membranes of Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3-δ (BSCF) and La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ (LSCF). A simple diffusion-convection model is used to account for the observed gas phase polarization in the porous support layers limiting the oxygen fluxes. Image 1 • Asymmetric all-perovskite membranes were prepared by inverse sequential tape-casting. • Support layer resistances limit the oxygen fluxes when using air as feed gas. • Diffusion-convection simulations account for the observed gas phase polarization. [ABSTRACT FROM AUTHOR]

Highlights: [•] Membrane microstructure was analyzed using SEM and X-ray computer tomography. [•] Different limitations for the oxygen transport were identified. [•] The porous substrate has a significant influence on the permeation. [•] A model approach was developed to account for surface exchange. [•] The characteristic thickness is the governing factor for modeling oxygen transport. [ABSTRACT FROM AUTHOR]