Fabrication, sealing and high pressure testing of tubular La2NiO4+δ membranes for air separation

Recent results achieved on fabrication of La2NiO4+δ membranes, sealing technology and performance in pressurized conditions are presented. Porous tubular membrane supports of up to 1 m length are prepared by ceramic extrusion. Asymmetric La2NiO4+δ membranes are prepared by coating dense selective layers of 10-15 μm thickness onto the porous supports. Glass ceramic seals in the system Na2O-CaO-Al2O3-SiO2 are currently being evaluated for joining the membranes with high temperature steel alloys coated with a corrosion resistance protective layer. By adjusting the composition of the glass system the thermal expansion coefficient is tailored to match that of the membrane and steel material. Good seal adherences towards these materials are obtained. Long term oxygen flux measurements (>4000 hours continuous operation) performed on symmetric (dense) La2NiO4+δ membranes are conducted under various conditions (atmosphere, temperature, pressure). The oxygen flux dependency on the oxygen partial pressure (pO2) is investigated by increasing the feed pressure and oxygen content. An asymptotic flux behavior is observed with increasing pO2. It is seen a significant increase in the flux (by a factor of 6) when increasing the feed pO2 from 0.8 to 2.4 bars while a less significant pO2 dependency is observed with further increase.