High temperature air separation for oxyfuel-combustion by means of a ceramic membrane module

Abstract:
Among the different technology lines for Carbon Capture and Storage (CCS) from fossil fired power plants, the oxyfuel technology is assumed to be the most promising one. For oxyfuel combustion, fuel is combusted in a mixture of pure oxygen and recirculated flue gas in order to gain a flue gas with a high CO2 content (>90% dry). Since the main energy consumption for this measure is the oxygen production, usually done by cryogenic air separation, mixed ion electronic conducting membranes (MIEC) for air separation offer a high potential for reducing the energy penalty of this CCS technology. This type of process is investigated in the research project Oxycoal-AC. The overall efficiency of the oxyfuel process strongly depends on the integration on the membrane into the power plant process. Two different ways of membrane integration were investigated in process simulations, with and without contact to the recirculated flue gas. Since there are currently no flue gas stable membranes for this application available, the presentation focusses on the membrane integration without contact to the recirculated gas. It was shown that best energetic integration for a membrane unit in is achieved by applying feed air pressure of around 15 bar and using a slight vacuum on the permeate side at approximately 850°C. Simulation results will be shown in the presentation at hand. To demonstrate the membrane performance under the above mentioned conditions, a membrane module has been developed within the research project. To avoid sealing problems between the membrane and the module, a water cooled flange is used that encloses 15 m² of tubular membranes. With this area the module can provide more than 0.5 t/d of oxygen under the aimed process conditions. The module is to be installed in summer 2011. The presentation will show results of the testing phase regarding performance of the module as well as the stability of the membranes themselves under elevated pressure and temperature.

Keywords:
OTM, oxyfuel, ceramic membrane module, oxygen production

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