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| Home > Publications database > Membrane performance tests in flue gas of fossil power plants |
| Talk (non-conference) (Invited) | FZJ-2018-00713 |
2017
Abstract: Carbon capture and storage or utilization is a key technology to decrease CO2 emissions from conventional power plants, until cost efficient energy supply from renewable sources is possible. Membrane-based systems to capture CO2 from flue gas streams are considered a promising alternative to conventional absorption technology. Such an application sets a number of challenges towards the membrane, e.g. performance, stability, integrity, durability etc. For this reason, only experiments performed under real flue gas conditions could attest the membrane operation in a coal power plant.In the present work the effect of coal power plant exhaust gas on the performance of different kinds of membranes is investigated. Testing membranes in real flue gas represent a new approach, as testing under simulated flue gas conditions has already been undertaken. The exposure and performance experiments were carried out in a lignite-fueled and a hard-coal-fueled power plant, both offering significant variation in the flue gas compositions. A test rig was specially designed to enable the direct membrane contact with unconditioned flue gas inside the exhaust gas channel, while a second test rig was developed to test membrane samples with pre-treated (dehumidified and dust free) flue gas. Thanks to an integrated analythical system, the in-situ permeance and selectivity of the membrane can be continuously monitored. Different kinds of membranes have been tested including microporous silica based membranes with different modifications, as well as two kinds of polymeric membranes. The newer coal-fired power plants work under high water content of up to 30 vol.% and a relative humidity (RH) of 100 %. Gases (e.g. SO2, NOx) and alkaline species (e.g. Na, K) are dissolved in the present water resulting in highly aggressive condensate on the membrane surface and in the intermediate layers which inevitably leads to severe corrosion of all materials in contact with it. Under such condition, no membrane could be able to operate. Using the new test rig setup and pre-treating the flue gas to a low dew point and low relative humidity, the lifetime of the membranes could be significantly extended. In any case, also the operation under pre-conditioned flue gas is associated with some losses in selectivity and permeance for all tested membranes, for which the degradation mechanisms have to be still identified and understood.Aiming to achieve better comprehension of the individual damage mechanisms and the influence of the different functional layers, the gas flows in the membrane cell and the gas transport through the membrane assembly must be considered and better understood. By this, further development of the membranes would be significantly supported. Hence, the talk would give an outlook on forthcoming activities as the development of computational fluid dynamics models to map both the test cells and the different layers of the membrane.
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