Development of La0.6Sr0.4Co0.2Fe0.8O3-δ mixed ionicelectronic conducting ceramic membrane for oxygen separation
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Date
2015-06-01
Authors
Siti Salwa Hashim
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Abstract
This study focuses on the preparation of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) membrane for oxygen separation at low sintering temperature by using 83.3 mol% CuO-16.7 mol% TiO₂ mixture (0-3 wt.%) as additives. The effect of the additives on the sintering behavior, crystal structure, microstructure, Young’s modulus, flexural strength and oxygen permeation flux of the LSCF membrane have been investigated. The crystal structure of the LSCF membrane has not been affected by the CuO-TiO2 mixture addition. The addition of 1 wt.% CuO-TiO2 mixture has reduced the sintering temperature of the LSCF membrane by 200°C. The LSCF membrane with 1 wt.% CuO-TiO2 mixture sintered at 1100°C has obtained a relative density of over 94% with high flexural strength and Young’s modulus. Its oxygen permeation flux at 600°C is also the highest (0.079 ± 0.001 ml/cm².min); which
is about 1.8 times higher than the pure LSCF membrane sintered at 1300°C (0.044 ± 0.003 ml/cm².min). The LSCF membrane with 1 wt.% CuO-TiO2 mixture sintered at 1100°C has been chosen for further oxygen permeation performance studies at different conditions. The experimental results show that the oxygen permeation flux increases with the increase of temperature, oxygen partial pressure in the feed side and sweep gas flow rate; and decreases with the increase of membrane thickness. For the 1.10 mm thick membrane, the optimum experimental conditions for oxygen permeation flux have been found to be 600°C temperature, 1 atm oxygen partial pressure in the feed side and 100 ml/min sweep gas flow rate. The oxygen permeation flux of 0.180 ± 0.02 ml/cm².min has been obtained using
these co-optimized experimental conditions. The oxygen permeation parameters have been determined from the experimental data by proposing a suitable mathematical model. The predicted data have been compared with the experimental data in order to validate the proposed model. Good agreement has been achieved between predictions and experimental data. The proposed model also indicates that in the 1.10-2.70 mm thickness range used in the present study, the oxygen flux is predominatly controlled by bulk diffusion mechanism across the membrane.