Highly stable La0.6Sr0.4Co0.2Fe0.8O3-δ hollow fibre membrane for air separation swept by steam or steam mixture

Perovskite oxide ceramic membranes have the potentials for industrial oxygen production, particularly to replace the conventional expensive air separation units, which is of significance to improve the viability of the clean energy technologies like IGCC and Oxyfuel projects. In most of these applications, the steam presence is unavoidable thus requiring these membranes to be stable in the steam-containing atmosphere under high temperatures. In this work, La0.6Sr0.4Co0.2Fe0.8O3-alpha (LSCF) perovskite hollow Fibre membrane was prepared and tested for O-2 separation in the presence of steam in the sweep gas. Three membranes were successfully tested at temperature of 900 degrees C using the sweep containing 3%, 4-12% and 100% steam (balanced by helium) for 370, 200 and 500 h, respectively. In the long run, the steam can etch the membrane surface, as evidenced by the leaching of iron and the formation of strontium carbonate. This etching process however is too slow to cause substantial damage on the membrane performance. Using pure steam sweep, the LSCF membrane was operated at 900 degrees C for nearly 500 h without any sign of O-2 flux decay, compared favourably with Ba0.5Sr0.5Co0.8Fe0.2O3-alpha (BSCF) hollow fibre membranes, which only lasted for 90 h. In contrast to the severe poisoning effects of other acid gases like SO2 or NOx on the O-2 permeation through similar LSCF membrane, the detrimental effect of steam is negligible. In fact, the presence of minor steam less than 12% in the sweep is kinetically favourable for the surface oxygen exchange reactions, leading to the improvement of the O-2 flux. (C) 2015 Elsevier B.V. All rights reserved