The present disclosure relates to solid oxide fuel cells (SOFCs)
exploiting gas separation devices in which a first gas mixture including
components A (for example hydrogen) and B (for example carbon dioxide) is
to be separated so that a first product of the separation is enriched in
component A, while component B is mixed with a third gas component C (for
example air, oxygen-enriched air or oxygen-depleted air) contained in a
displacement purge stream to form a second gas mixture including
components B and C, and with provision to prevent cross contamination of
component C into the first product containing component A, or of
component A into the second gas mixture containing component C. The
invention may be applied to hydrogen (component A) enrichment from fuel
cell anode exhaust, where dilute carbon dioxide (component B) is to be
rejected such as to the atmosphere by purging with cathode exhaust
oxygen-depleted air (as component C).