Fluid dynamic modeling of oxygen permeation through mixed ionic–electronic conducting membranes

Gozálvez-Zafrilla, José M.; Santafé-Moros, Asunción; Escolástico, Sonia; Serra, José M.

doi:10.1016/j.memsci.2011.05.016

Cited by 37 publications

(21 citation statements)

References 26 publications

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“…This effect was more pronounced with increasing temperatures, that is, if the flux was higher and concentration polarization problems were more likely to occur. Apart from the improvement in the fluid dynamics,16 a higher sweep flow rate has the additional effect of increasing the separation driving force, as the dilution of the permeated oxygen leads to an overall lower partial pressure of O 2 ( p O 2 ). Another important aspect is the use of higher pressures in the air feed to increase the production of oxygen.…”

Section: Resultsmentioning

confidence: 99%

Enhanced Oxygen Separation through Robust Freeze‐Cast Bilayered Dual‐Phase Membranes

et al. 2014

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Dual-phase oxygen-permeable asymmetric membranes with enhanced oxygen permeation were prepared by combining freeze-casting, screen-printing, and constraint-sintering techniques. The membranes were evaluated under oxyfuel operating conditions. The prepared membranes are composed of an original ice-templated La(0.6)Sr(0.4)Co(0.2)Fe(0.8)O(3-δ) support with hierarchically oriented porosity and a top fully densified bilayered coating comprising a 10 μm-thick La(0.6)Sr(0.4)Co(0.2)Fe(0.8)O(3-δ) layer and a top protective 8 μm-thick layer made of an optimized NiFe2O4/Ce(0.8)Tb(0.2)O(2-δ) composite synthesized by the one-pot Pechini method. Preliminary analysis confirmed the thermochemical compatibility of the three involved phases at high temperature without any additional phase detected. This membrane exhibited a promising oxygen permeation value of 4.8 mL min(-1) cm(-2) at 1000 °C upon using Ar and air as the sweep and feed gases, respectively. Mimicking oxyfuel operating conditions by switching argon to pure CO2 as a sweep gas at 1000 °C and air as feed enabled an oxygen flux value of 5.6 mL min(-1) cm(-2) to be reached. Finally, under the same conditions and increasing the oxygen partial pressure to 0.1 MPa in the feed, the oxygen permeation reached 12 mL min(-1) cm(-2). The influence of CO2 content in the sweep gas was studied and its reversible and positive effect over oxygen permeation at temperatures equal to or above 950 °C was revealed. Finally, the membrane stability over a period of 150 h under CO2-rich sweep gas showed a low degradation rate of 2.4×10(-2) mL min(-1) cm(-2) per day.

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Section: Resultsmentioning

confidence: 99%

Enhanced Oxygen Separation through Robust Freeze‐Cast Bilayered Dual‐Phase Membranes

et al. 2014

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“…Mass transport limitations in the gas phase combined with oxygen exchange of MIECs have been described in the literature before. Ben Mansour et al [9] and Gozálvez-Zafrilla et al [10] showed, through numerical modelling, that the steady-state flux measurements of a membrane setup were significantly influenced by mass transport in the gas phase. Also, for porous electrodes of MIECs in solid oxide fuel cells, gas transport limitations are well described [11].…”

Section: Motivation and Initial Resultsmentioning

confidence: 99%

The Significance of Gas-Phase Mass Transport in Assessment ofk_chemandD_chem

Lohne

Søgaard

Wiik

2013

J. Electrochem. Soc.

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In this work, the validity of electrical conductivity relaxation (ECR) as a method for the assessment of chemical surface exchange, k chem , and bulk diffusion, D chem , coefficients is investigated with respect to mass transport limitations in the gas phase. A model encompassing both the oxygen surface exchange, mass transport in the bulk sample and the gas phase was set up and solved under different conditions using finite element software. It is found that the transport of oxygen in the gas phase is insufficient at low oxygen partial pressures, causing a concentration boundary layer at the sample surface to develop. This significantly decreases the driving force for oxygen exchange. The effect of mass transport limitations on the computed apparent transport coefficients is shown to be pronounced and surface exchange coefficients are shown to deviate as much as one order of magnitude from the set values. When mass transport limitations are pronounced, a discrepancy between oxidation and reduction values of the apparent k chem and D chem is evident and modelled apparent activation energies for k chem are shown to decrease significantly. The validity of the apparent transport coefficients can be improved by changing the experimental parameters, however the surface exchange coefficient is extremely sensitive to insufficient transport of oxygen in the gas phase and improvements are in general marginal. A criteria for the validity of D chem is introduced while no such measure could be introduced for k chem . The effect of experimental parameters and material properties on mass transport limitations are presented and general recommendations concerning the assessment of k chem and D chem are given.

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“…In this case, the gas phase mass transfer has a significant impact on the oxygen concentration profile, especially in the permeate side where oxidation reactions occur. Recent research has highlighted the importance of the gas phase mass transfer and the non-uniform oxygen chemical potentials next to the membrane surface [38].…”

Section: Gas Phase Mass Transfermentioning

confidence: 99%

“…By ignoring the effects of the gas phase mass transfer, it is assumed that the measurements at the points away from the vicinity of the membrane surface are the same as the local values near the membrane ((b) and (e) in Figure 1). Thus, while the resulting expressions may be sufficient for describing similar set ups, they are not general [38] and the local oxygen concentration profiles should be determined in order to recast these expressions in terms of the local values at the vicinity of the membrane surface.…”

Section: Gas Phase Mass Transfermentioning

confidence: 99%

Numerical simulation of ion transport membrane reactors: Oxygen permeation and transport and fuel conversion

Hong

Kirchen

Ghoniem

2012

Journal of Membrane Science

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Ion transport membrane (ITM) based reactors have been suggested as a novel technology for several applications including fuel reforming and oxy-fuel combustion, which integrates air separation and fuel conversion while reducing complexity and the associated energy penalty. To utilize this technology more effectively, it is necessary to develop a better understanding of the fundamental processes of oxygen transport and fuel conversion in the immediate vicinity of the membrane. In this paper, a numerical model that spatially resolves the gas flow, transport and reactions is presented. The model incorporates detailed gas phase chemistry and transport. The model is used to express the oxygen permeation flux in terms of the oxygen concentrations at the membrane surface given data on the bulk concentration, which is necessary for cases when mass transfer limitations on the permeate side are important and for reactive flow modeling. The simulation results show the dependence of oxygen transport and fuel conversion on the geometry and flow parameters including the membrane temperature, feed and sweep gas flow, oxygen concentration in the feed and fuel concentration in the sweep gas.

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Fluid dynamic modeling of oxygen permeation through mixed ionic–electronic conducting membranes

Cited by 37 publications

References 26 publications

Enhanced Oxygen Separation through Robust Freeze‐Cast Bilayered Dual‐Phase Membranes

Enhanced Oxygen Separation through Robust Freeze‐Cast Bilayered Dual‐Phase Membranes

The Significance of Gas-Phase Mass Transport in Assessment ofk_chemandD_chem

Numerical simulation of ion transport membrane reactors: Oxygen permeation and transport and fuel conversion

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Fluid dynamic modeling of oxygen permeation through mixed ionic–electronic conducting membranes

Cited by 37 publications

References 26 publications

Enhanced Oxygen Separation through Robust Freeze‐Cast Bilayered Dual‐Phase Membranes

Enhanced Oxygen Separation through Robust Freeze‐Cast Bilayered Dual‐Phase Membranes

The Significance of Gas-Phase Mass Transport in Assessment ofkchemandDchem

Numerical simulation of ion transport membrane reactors: Oxygen permeation and transport and fuel conversion

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The Significance of Gas-Phase Mass Transport in Assessment ofk_chemandD_chem