| The key point of the oxygen permeable membrane technology, which can beintergrated with oxyfuel for power generation and CO2capture, is the development ofa kind oxygen permeable membrane material with high permeation flux andsustaining the poising of CO2. The dissertation presents a reasonable strategy for thedesign of dual-phase membranes and shows the experimental investigation of thedesigned membrane materials.The dual-phase membranes of75wt%Ce0.8Sm0.2O1.9-25wt%Sm1-xCaxCoO3（x=0、0.2、0.4）were investigated through the effects of calcium doping in the perovskitephase of dual-phase materials on the total conductivity, the stability under CO2atmosphere, permeation fluxes and permeation stability. The oxygen permeation ofthe Ca-doped dual-phase membranes is limited by both bulk diffusion and the surfaceexchange of oxygen molecules, while that of the Ca-free dual-phase membrane islimited by the electronic transport through membrane bulk. All the membranes can bestable in the CO2atmosphere. The permeation experiments showed that at x=0.4thedual-phase membrane shows the highest permeation flux up to0.19mL cm-2min-1at950oC when CO2was used as the sweeping gas.It was found that for the （100-y） wt%Ce0.8Sm0.2O1.9-y wt%Sm0.6Ca0.4CoO3（y=20、25、33） dual-phase membranes, the electronic conductivity and oxygen permeationflux increase with the content of the perovskite phase. Among the three membranes,66.7wt%Ce0.8Sm0.2O1.9-33.3wt%Sm0.6Ca0.4CoO3shows high stability and thehighest permeation flux up to0.55mL cm-2min-1at950oC when CO2was used as thesweeping gas. The value is the highest permeation flux reported in the literatures forthe dual-phase membranes employed for the purpose of integrated with oxyfuel process. The key reason is that the increase of perovskite content in the dual-phasesystem can significantly enhance the electronic conductivity and the dipolarconductivity and then increase the permeation flux.A comparative investigation of the dual-phase membranes made of Co-basedperovskite （Sm0.6Ca0.4CoO3） and Fe-based perovskite （Sm0.6Ca0.4FeO3） showed thatthe microstructure of the dual-phase membrane containing Fe-based perovskite isbetter than it containing Co-based perovskite when the mass fraction of perovskitephase is25%. As a result the Fe-containing dual-phase membrane has higherelectronic conductivity and oxygen permeation flux than the Co-containingdual-phase membrane. However, increase the Fe-based perovskite content to33.3wt%has no help to enhance the permeation flux of the dual-phase membrane,because the oxygen ionic conductivity of Fe-based perovskite is smaller than that offluorite phase oxide Ce0.8Sm0.2O1.9. |
PDF Full Text Request