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Institute of Energy and Climate Research

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Gas separation membranes

IEK-1 develops ceramic membranes for separating the greenhouse gas CO2, which is to be subsequently stored in order to prevent harmful emissions.

This new technology is called "carbon capture and storage" or CSS technology.

Inorganic membranes for gas separationTest equipment for the determination of oxygen permeation

Carbon capture and storage technology
In this research area, IEK-1 is concerned with the development of inorganic membranes for gas separation. These membranes will allow the separation of the technically relevant gases O2/N2, CO2/H2 and CO2/N2 sfor various fossil power plant concepts, in order to achieve a CO2 flow that is as pure as possible and free from residual gases and which is to be subsequently stored underground. In contrast to conventional separation methods, membrane processes have the advantage that they cause significantly lower losses in efficiency during separation than methods such as chemical gas scrubbing. This makes them particularly interesting for applications in power plants.

For each separation task, different ceramic membranes are developed at the institute. Among the different inorganic membrane types, a distinction is made between dense ion-conducting or mixed-conducting membranes and microporous crystalline or amorphous membranes.

All membrane types have development needs with regard to permeability, selectivity and stability. IEK-1 is concerned with the development and production of new materials and membrane coatings using different process technologies.

A class 1000 clean room has been in operation at the institute for the production of microporous coatings since 2005. As the membranes display particles and coating thicknesses in the nanometre range, it is essential to work under dust-free conditions. Otherwise dust particles, which are often as big as a millimetre or a micrometre, would create large holes in the coatings and destroy the membrane during the wet-chemical or physical deposition of the film.

The thin coatings are therefore produced under clean-room conditions, for example by the sol-gel route, using different methods such as spin coating, dip coating or vacuum slip casting.

Clean room - Spin CoatingDeposition of thin films via spin coating in the clean room

Production of thin layers under clean-room conditions via the sol-gel route with various production methods such as spin coating

Microporous gas separation membranes generally have a graduated structure, i.e. starting with a substrate with relatively large pores and then applying successive layers with ever finer particles, which creates the gradient in the porosity, up to and including pores in the nanometre range. The membrane layer deposited on this support structure is only a few nanometres thick. The figure below shows the entire structure of a gas separation membrane.

Entire structure of a gas separation membraneThe figure shows the entire structure of a gas separation membrane.

Production processes: Oxygen separation membraneOxygen separation membrane manufactured by means of film casting.

Cross-section through an oxygen membrane.Cross-section through an oxygen membrane.

In addition to the microporous gas separation membranes shown above, substantially thicker and dense oxygen-ion-conducting membranes are also developed. These membranes have a layer thickness of around 10 µm to 50 µm, the thickness of a human hair. For these membrane layers, coating techniques such as screen printing, vacuum slip casting, as well as film casting, are generally used.

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