SINOPSIS

A Ba_0.2Sr_0.8Co_0.8Fe_0.2O_3−δ (BSCF) perovskite-type oxide with mixed electronic and oxygen ionic conductivity at high temperatures was used as an oxygen permeable membrane. Oxygen permeation flux of the membranes was determined at different temperatures, feed flow rates and helium flow rates between 650°C and 950°C, 100 and 200 cm³/min and 40 and 80 cm³/min, respectively. It was found out that increasing helium flow rate increases oxygen permeation flux of the membranes and this is due to the fact that oxygen partial pressure decreases in the permeate side with increasing helium flow rate. However, it was also found that oxygen permeation flux can also be affected by air flow rate in the feed side. At air flow rates higher than 150 cm³/min, sensitivity of oxygen permeation flux is much less than that at lower air flow rates. Although x-ray diffraction (XRD) and x-ray disperse spectroscopy (EDS) showed that the surface of the BSCF membrane exposed to air for 75 h is almost similar to the surface of the fresh membrane in composition and structure, there are differences between the fresh membrane surface and the surface exposed to helium. Scanning electron microscopy SEM images of the used membrane surfaces exposed to air and helium were also compared with the fresh membrane.