Modeling and analysis of carbon dioxide permeation through ceramic-carbonate dual-phase membranes

A theoretical model has been developed for CO(2)/O(2) permeation through a dual-phase membrane consisting of mixed-conducting oxide ceramic (MCOC) and molten carbonate (MC) phases. Somewhat simpler theoretical CO(2) permeation equation is obtained for the special case or pure CO(2) permeation case, i.e., oxygen partial pressure in the feeding gases is zero or electronic transference number of the MCOC phase is zero. The results show that CO(2) permeation flux is much improved by involving oxygen permeation, which is more than one order of magnitude higher than the corresponding CO(2) permeation flux for a pure CO(2) permeation case. The fluxes of CO(2) and O(2) increase with increasing O(2) partial pressure in the feeding gases. Both the CO(2) and O(2) permeation fluxes increase with increasing electronic conductivity (sigma(h center dot)) of the MCOC phase. The CO(2) permeation flux increases with increasing ionic conductivity (sigma(v center dot center dot)) of the MCOC phase at a low electronic conductivity, i.e., sigma(h center dot) <= 0.1 S/cm, while decreases with an increase of sigma(v center dot center dot) at a high electronic conductivity, i.e., sigma(h center dot) > 1 S/cm. For pure CO(2) permeation, the CO(2) permeation flux increases with the increase of sigma(v center dot center dot) and decreases with increasing molten carbonate volume fraction. An ordered ceramic pore structure benefits CO(2) and O(2) permeation. The modeling results are compared with experimental data, and a reasonable agreement is obtained between modeling and experimental data. (C) 2009 Elsevier B.V. All rights reserved.