Oxygen permeation continued

Oxygen partial pressure between the two sides of the membrane is the driving force of oxygen permeation. Figure 3.1c shows a dual-phase MIEC membrane, which can be visualized as a dispersion of a continuous electronic conducting phase into an SE matrix. The electronic conducting phase is usually made from precious metal or metal oxides. 

Lao.sSrijGao.eFei.aOs+s [24] and SrFeCoo.sOx [65] were also successfully used as MIECM for POM more than 1,000 h. A membrane reactor based on a brown-millerite structure materials could be continuously operated for over one year under syngas atmosphere at 900°C [66]. The syngas production rate was 60ml/cm. min, and equivalent oxygen permeation flux was 10-12 ml/cm. min. The composition of the membrane was not specified in the literature. 

Figure 16.7 Low temperature oxygen separation from air Oxygen permeation flux through a BCFZ hollow fiber membrane as a function of time at 500 °C. At this temperature a continuous decrease of the oxygen flux is observed. For regeneration, the fiber was heated to 925 °C, kept at this temperature for 1 h in air, then cooled down to 500 °C for the next run. Experimental details Air flow rate on the shell side= 150 mL min He flow rate on the core side = 30 mL min 0.43 cm effective membrane area.

Finally, under prolonged shutdown conditions with the cell continually provided with fuel, both, the alcohol and oxygen permeate the membrane. These effects generate a transient condition in which fuel exists in both electrodes resulting in a reversal current, cathode poisoning and anode catalyst oxidation [100]. 

The most important consideration for a MIEC membrane is the delivery of a stable continuous transmembrane flux. This flux is central to membrane performance and therefore oxygen permeation studies in MIEC membrane characterization are fundamental. From an economic standpoint, an oxygen flux of 1 to 10 ml cm min (STP) has been cited as the requirement for future needs [25,26]. In order to provide a broad overview of this research area we will briefly outline synthesis and characterization methods applied to the MIEC perovskites before moving on to look at selected MIEC membranes currently used in laboratory-scale tests. 

Oxygen permeation of Lao.sSro.yCoOs-d, Solid State Ionics, Vol. 98, pp. 7-13 Crank, C. (1975). The mathematics of diffusion, 2" Edn., Clarendon Press, Oxford, pp.44-68 Ducroux, R. Fromont, M. Jean Baptiste, Ph. Pattoret, A. (1980). Mesures en continu de la redistribution de I oxygene sous gradient thermique dans UO2+X, / Nucl, Mat, Vol. 92, pp. 325-333... 

Figure 5.1 (Continued) (c) oxygen permeation through MIEC membrane (d) oxygen permeation through dual-phase membrane.

Continuous Multicomponent Distillation Column 501 Gas Separation by Membrane Permeation 475 Transport of Heavy Metals in Water and Sediment 565 Residence Time Distribution Studies 381 Nitrification in a Fluidised Bed Reactor 547 Conversion of Nitrobenzene to Aniline 329 Non-Ideal Stirred-Tank Reactor 374 Oscillating Tank Reactor Behaviour 290 Oxidation Reaction in an Aerated Tank 250 Classic Streeter-Phelps Oxygen Sag Curves 569 Auto-Refrigerated Reactor 295 Batch Reactor of Luyben 253 Reversible Reaction with Temperature Effects 305 Reversible Reaction with Variable Heat Capacities 299 Reaction with Integrated Extraction of Inhibitory Product 280... 

---