This document describes the results of the activities carried out for the creation of a planar membrane module for the separation of oxygen at high temperature and its efficient production in industrial settings.
In particular, the results relating to the experimental activities carried out for the creation of 60 x 60 mm membrane elements with a channel structure, which are necessary for the sweep gas supply, are reported. First of all, permeation tests in helium at room temperature were conducted on the half-cells, which highlighted adequate density values in line with those previously obtained on smaller samples. The half-cells were joined using a ceramic paste based on LSCF powders and then heat-treating them at 1200 °C by applying a load of ~ 400 g to improve the final component’s flatness and robustness. The samples were reworked to open the channels and the porous side surfaces were sealed using a specially developed ceramic paste to ensure gas tightness of the membrane element. SEM observations confirmed the success of the process developed for the production of ceramic components.
In parallel, long-term permeation tests were conducted on small-scale samples to assess the stability of the materials produced during operation at the set temperature. After approximately 700 hours of exposure at 950 °C in air, the tested membrane did not show significant variations either in terms of permeated oxygen flux or defectiveness of the dense layer, and the post-exercise microstructural characterization did not highlight any degradation of the material .
Starting from the experimental results, a CFD model capable of describing the influence of the operating conditions on the performance of the membrane element was developed, which was also used to conduct a sensitivity analysis for different temperature conditions.
Taking into account the geometry of the membrane element and the constraints due to the need to separate the process gas (air) from the permeated oxygen, the housing containing the ceramic component was designed. The membrane element must be installed inside the Inconel 625 case via an appropriate joint system that guarantees adequate gas tightness. A glass-ceramic material potentially suitable for coupling the metallic material with the LSCF membrane was developed and tested, whereas additional tests were conducted with a commercial glass-ceramic: in the first case, problems relating to the evolution of Inconel at high temperatures arose, whereas in the second case, there were difficulties in joining the LSCF due to a different thermomechanical behavior compared to the joining material. These critical issues could be resolved by replacing the metallic material or identifying an alternative ceramic material.