This report describes the results of the activities carried out to develop a planar membrane module for efficient separation of oxygen from air at high temperatures to integrate in industrial processes. Previous activities pointed out the opportunity to use membrane modules in different industrial processes, with potential and important advantages in terms of energy efficiency.

In order to spread the membrane technology in the industrial sector, it is important to achieve a proof of concept device to validate the oxygen transport membrane technology in real conditions. At the same time, innovative materials for the membrane manufacturing need to be identified, as well as a proper sealing system between the ceramic membrane and the metal case, able to ensure stability in the relevant operating conditions.

Dual-phase powders, e.g. 70CGO-30LSCF, have been identified in 2022 as an alternative material to standard LSCF. To optimize the manufacturing process of asymmetric membranes, in 2023 CGO powders have been calcinated, in order to reduce their specific surface area. The slurry obtained by using a CGO powder calcinated at 1000 °C showed a viscosity apparently suitable to be used for the tape casting technique, but not adequate to obtain defect-free tapes.

High temperature permeation tests have been performed in 2023 on a previously fabricated (in 2022) asymmetric dual-phase membrane: as expected, dual phase samples showed slightly lower performance than LSCF membranes, but still comparable. Moreover, these membranes exhibited excellent stability during long term test, also confirmed by SEM and XRD characterization.

Furthermore, in the 2023 joining tests have been carried out with a commercial glass-ceramic material and with a custom-made glass–ceramic sealant (named GC2). Specifically, in the first case, joining tests involving Inconel 625 alloy and dual-phase membrane 70CGO-30LSCF demonstrated that the chromium oxide, created during a preliminary heat treatment, reduces the chromium diffusion towards the glass ceramic and prevents the detachment of the metal-glass-ceramic interface.

In the second case, joining tests have been performed by depositing a custom-made glass-ceramic material by robocasting technique. After deposition, an intermediate drying treatment ensured good adhesion of the GC2 on both Crofer22APU and LSCF surfaces, thus generating a homogeneous interface.

Finally, a preliminary study on the development of metal-ceramic joins using brazing processes has been started.

The Report is available on the Italian site