Bjørnetun Haugen, Astri

Gurauskis, Jonas

Hendriksen, Peter Vang

Kaiser, Andreas

Ovtar, Simona

Online Research Database In Technology

                       General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.  • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal   If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.     Downloaded from orbit.dtu.dk on: Dec 21, 2017Oxygen permeation of dense dual phase tubular membranes supported on porousemagnesium oxideOvtar, Simona; Gurauskis, Jonas; Bjørnetun Haugen, Astri; Hendriksen, Peter Vang; Kaiser, AndreasPublication date:2015Document VersionPeer reviewed versionLink back to DTU OrbitCitation (APA):Ovtar, S., Gurauskis, J., Bjørnetun Haugen, A., Hendriksen, P. V., & Kaiser, A. (2015). Oxygen permeation ofdense dual phase tubular membranes supported on porouse magnesium oxide. Abstract from Summer schoolon Ionic and protonic conducting ceramic membranes for green energy applications, Valencia, Spain.OXYGEN PERMEATION OF DENSE DUAL PHASE TUBULAR MEM-BRANES SUPPORTED ON POROUSE MAGNESIUM OXIDE  Simona Ovtar, Jonas Gurauskis, Astri Bjørnetun Haugen, Peter Vang Hendriksen and Andreas Kaiser DTU Energy, Campus Risø, Technical university of Denmark Frederiksborgvej 399, 4000 Roskilde, Denmark Email: simov@dtu.dk  Keywords: Oxygen permeating membrane, dual phase composite, dense thin membrane, supported membrane     Acceptor doped ceria is an alternative to the perovskite based mixed ionic and electronic conductive oxygen sepa-ration membranes, because of the high ionic conductivity at low temperature and wide oxygen partial pressure (pO2) stability range. For gadolinium doped ceria (CGO) the ionic conductivity at 900 oC is 0.155 S/cm, but the electronic conductivity is only 6.8 x 10-4 S/cm [1]. The oxygen permeation flux in CGO membranes is therefore limited by the electronic conductivity, thus it is expected that better performance can be achieved if the electronic conductivity can be enhanced. Two different routes to increase the electronic conductivity have been extensively studied [1, 2]. The first is aliovalent substitution, for example with Pr, where the p-type electronic conductivity is significantly increased [1]. The second is adding a second phase with high electronic conductivity to the CGO [2]. An advantage of forming such a composite is greater flexibility in combining high ionic and high electronic conductivity.  In this study, a dual phase membranes consisting of Ce0.9Gd0.1O2- as a high ionic conductor and (La0.6Sr0.4)0.98FeO3- (LSF) as a high electronic conductor were investigated. The LSF was chosen due to a high stability in low pO2. Samson et al. [2] showed that for 1 mm thick pellets oxygen permeation flux of composite CGO-LSF is larger than for pure CGO. The oxygen permeation flux can be increased by reducing a membrane thickness. Further-more, parallel studies of the oxygen transport properties in the CGO-LSF composites have shown that the limiting thickness below which the process is limited by surface exchange rather than bulk diffusion is 70 m. Therefore, in this study, the main focus was on the preparation of thin dense CGO-LSF composite membranes with thickness between 10 and 30 m on a tubular porous support. The first step in the production of membranes was manufacture of a tubular porous support of MgO by thermo-plastic extrusion. Different poreformers (like graphite and polymethyl methacrylate) were used as sacrificial particles to form connected macro-pores. The tubular porous supports with open porosity around 40 % and with interconnected channels of 0.3 – 0.5 m have been produced [3]. The second step was application of active layers on the porous sup-port. Three different layers with a thickness between 5 and 30 m were applied on one side of the porous support by dip coating. The layers prepared from ethanol based slurries with or without poreformers were porous CGO, dense CGO-LSF composite and porous CGO layer [4]. After final calcination and sintering of the membranes an additional infiltra-tion was carried out. The inner porous CGO layer was infiltrated by a precursor solution of nano-CGO to increase the active surface area, and the outer porous CGO layer was infiltrated with an electronic conductor like La0.6Sr0.4CoO3-, LaNi0.6Co0.4O3- or LaCoO3-. The oxygen permeation flux of the tubular membranes was measured using a constant air flow on the outside of the membranes, and vacuum or a flow of different gasses (N2, CO2, H2, and CH4) on the inside. The membranes were tested in the temperature range between 700 oC and 850 oC. Long term tests on the stability of the membranes in CO2 and high reducing conductions were also carried out.  The oxygen permeation flux for a 10 m thick dense CGO-LSF composite membrane layer on the MgO porous support in N2 at 850 oC was 2.1 mlcm-2min-1, with the activation energy of 24 – 37 kJ/mol. The oxygen permeation flux strongly depends on the pO2 difference between the inside and outside of the membrane, and for humidified H2 (pO2 = 1.5 x 10-14 atm.) at 850 oC for the same membrane the flux of 15 mlcm-2min-1 was measured. The long term stability tests in CO2 and H2 showed that an initial degradation took place, followed by stable flux after 80 h or 200 h, respec-tively. The high oxygen permeation flux and fair stability show that the MgO supported thin dense CGO-LSF tubular membrane is a promising candidate for an oxygen separation process, combustion reactions or partial oxidation reac-tions.  References [1] C. Chatzichristodoulou et al., Phys. Chem. Chem. Phys. 13 (2011) 21558 [2] A. J. Samson et al., J. Membr. Sci. 470 (2014) 178 [3] D. Ramachandran et al., Ceram. Int. (2014) 10465 [4] J. Gurauskis et al., ECS Transactions 64 (2014) 251 

Oxygen permeation of dense dual phase tubular membranes supported on porouse magnesium oxide

http://orbit.dtu.dk/ws/files/116777427/Ovtar_abstract2.pdf

Oxygen permeation of dense dual phase tubular membranes supported on porouse magnesium oxide

Abstract

Similar works

Full text

Available Versions

Online Research Database In Technology