Ceramic membranes

Gas separation

Separation of gases has numerous applications of relevance to sustainable energy systems, including manufacture of pure oxygen for oxygen blown power plants (facilitating CO2 removal from the waste stream) and separation of CO2 from biogas to upgrade it to biomethane. Our research addresses two technologies for gas separation: oxygen transfer membranes (OTMs), based on selective transport of oxygen ions through a gas tight ceramic membrane at high temperatures, and gas adsorption processes such as pressure
swing adsorption (PSA).

An Oxygen Transfer Membrane (OTM), based on functional ceramic materials, allows the separation of oxygen from air by the selective transport of oxide ions when operated at high temperatures. An OTM consists of a Mixed Ionic-Electronic Conductor (MIEC) which allows oxide ion diffusion through vacancies in the crystal lattice without external electrical circuits. This means that oxygen selectivity is infinite, apart from leakages through the membrane or the sealing. On both sides of the membrane, porous layers support the MIEC. These layers can contain suitable catalysts to increase the membrane efficiency.The research on OTMs ranges from fundamental research on mixed ionic-electronic conductors to processing, shaping and testing of planar or tubular components. Over the past few years competences have been built up for ceramic multilayer processing to achieve robust and high permeable supports in combination with dense layers and finely graded catalyst structures. We have successfully conducted a long-term test of the largest oxygen membrane module in Europe and demonstrated the use of oxygen membranes in conjunction with a biomass gasifier.

Potential applications for OTMs range from small-scale oxygen pumps for medical applications to large-scale usage in methane conversion, where methane is upgraded to higher value hydrocarbons (methanol, DME, synthetic diesel). Having cheap access to oxygen will also reduce the cost of transport fuels obtained from the gasification of biomass and in this way make CO2 neutral transport more economically competitive.

Another attractive use is for oxyfiring in fossil fuel power plants. When combustion takes place with pure oxygen, it is easy to separate the CO2 from the flue gas. Fossil fuel power plants are by far the biggest single sources of CO2 and contribute more than 40% of the total worldwide anthropogenic CO2 emission. Using Carbon Capture and Storage (CCS) from oxyfired fossil fuel power plants will make it possible to reduce CO2 emissions and allow future electricity supply to be more environmentally safe and sustainable.

Pressure swing adsorption is based on the fact that some materials adsorb specific gas molecules strongly. Materials which adsorb CO2 can be used to clean biogas which contains a mixture of methane and CO2. This is a well-established technology at large scale, but small-scale applications require novel adsorbents. For the gas adsorption technologies, the objective is to develop new materials and novel structuring methods (nanofibers or multilayer structures) for more efficient gas and heat transport. A main focus is to prove the advantages of nanofibers produced by electrospinning for gas adsorption processes.

Scientific topics of interest include:

  • Improving the properties of porous ceramic support structures using novel approaches such as sacrificial templates, freeze casting and phase inversion tape casting
  • Development and screening of mixed ionic-electronically conducting materials and composites
  • Electrospinning to achieve structured, high performance nanofiber adsorbents for multilayered gas separation and storage components.

Contact

Andreas Kaiser
Associate Professor
DTU Energy
+45 46 77 58 89