A method for recovering substantially all carbon dioxide generated in a
combustion process where the method comprises the following steps: a) a
sweep gas is used to pick up oxygen on the permeate side of a mixed
conducting membrane in a first stage which is capable of separating oxygen
from a hot air stream fed to the retentate side of the membrane; b) the
sweep gas containing oxygen is applied as oxidant in a combuster in the
first stage where a carbon containing fuel is combusted; c) hot combustion
products of step b) containing CO.sub.2, H.sub.2 O and a low concentration
of O.sub.2 is used as sweep gas in a membrane in a second stage downstream
the combuster in step b); d) the concentration of oxygen in the sweep gas
of step c) is increased in the membrane in the second stage (step c) to a
sufficiently high level to be used as oxidant in the combuster in the
second stage; e) and the steps c)-d) are repeated in one or more stages.
Furthermore, the present invention relates to use of the method in
different processes.
