Influence of CO_2 on the oxygen permeation performance and the microstructure of perovskite-type (Ba_(0.5)Sr_(0.5))(Co_(0.8)Fe_(0.2))O_(3-δ) membranes

摘要

The influence of CO_2 on the oxygen permeation performance of perovskite-type (Ba_(0.5)Sr_(0.5))(Co_(0.8)Fe_(0.2))O_(3-δ) (BSCF) membranes under different experimental conditions is presented. First, pure CO_2 was applied as the sweep gas at 875℃ yielding an immediate cessation of the oxygen permeation. In order to probe the reversibility of this stagnancy, several cycles of changing the sweep gas between helium and CO_2 were conducted. The analysis of the microstructure after permeation experiments were carried out by transmission electron microscopy (TEM), X-ray diffraction (XRD) as well as by scanning electron microscopy (SEM). It was found that both microstructure as well as oxygen permeation are recovered in a helium atmosphere. Additionally, long-time treatment with pure CO_2 for 72 h on the permeate side and the concentration effect of CO_2 in the sweep gas were accomplished showing that the perovskite structure is impaired only up to a depth of 50 μm. Further on, the impact of CO_2 on the feed side was examined by adding certain amounts of CO_2 to the feed air. It was found that the impact of CO_2 on the oxygen permeation applied in the sweep gas is superior to that applied on the feed gas.