Oxyfuel processes represent a promising technique for carbon capture and storage since the related energy penalty is considered to be comparatively low. A possibility to separate the O(2) from air is the use of mixed ion electron conducting (MIEC) membranes. A favored membrane material is Ba(0.5)Sr(0.5)Co(0.8)Fe(0.2)O(3-delta) since its permeation rate is high. In the work at hand this membrane material has been studied experimentally to determine the coefficients of the Wagner equation. The experiments have been performed with membrane tubes considering the use of tubular membrane systems for industrial application in future oxyfuel power plants. 3- and 4-end operating conditions have been applied to provide an additional degree of freedom for the integration of the membrane module into the power plant process. Wagner constants C = 1.004 x 10(-8) mol/(cm s K) and K = 6201 K have been determined. A membrane model for Aspen Plus has been developed, which allows to calculate the heat and mass transfer in an oxygen membrane module. Calculations were performed based on data from oxyfuel membrane power plant simulations found in the literature. Compared to the 3-end concept the 4-end concept shows a higher net-efficiency together with a lower demand on membrane area. Depending on the operation mode and boundary conditions, the estimated specific membrane area is between 0.22 and 0.59 m(2)/kW(th). (C) 2010 Elsevier B.V. All rights reserved.