Patent ID: 6767527
Filing Date: 2004-07-27
Classification: B01D,C01B,E21B,F23L,Y02E,Y02P

Abstract:
An energy efficient method for recovering substantially all carbon dioxide generated in a combustion process which includes an application of sweep gas in combination with a mixed conducting membrane, characterised in that said 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 pre-heated air stream fed to the retentate side of said membrane, b) the sweep gas containing oxygen is applied as oxidant in a combuster in said first stage to which a carbon containing fuel is separately fed and combusted, c) pre-heated combustion products of step b) containing CO2, H2O and a low concentration of O2 are used as sweep gas to pick up oxygen on the permeate side of a second mixed conducting membrane in a second stage downstream the combuster in step b) which is capable of separating oxygen from a pre-heated air stream fed to the retentate side of said second membrane, d) the concentration of oxygen in the sweep gas of step c) is increased in the second membrane in said second stage (step c) to a sufficiently high level to be used as oxidant in the combuster in said second stage to which a carbon containing fuel is separately fed and combusted, and e) the steps c)-d) are repeated in one or more stages, where each stage includes a membrane and a combustor.