Study On The Oxygen Permeability Of Hollow Fiber Membranes Made Of High-concentration CO₂-Tolerant Perovskite Ceramic

This paper investigates the oxygen permeation flux of perovskite-type La_0.8Ca_0.2Fe_0.95Ag_0.05O_3-δ（LCF-Ag）and high-entropy La_0.3Ca_0.1Sr_0.2Bi_0.2Nd_0.2Co_0.3Fe_0.7O_3-δ（LCSBNCF）hollow fibers,with a focus on their performance under high CO₂ concentration.Their potential for use in oxygen-enriched combustion systems,which are known to be an effective way to save energy and enhance combustion efficiency,is being evaluated.Oxygen separation membranes with high oxygen permeability and CO₂tolerance are currently being designed and developed by researchers.This study contributes to that effort by examining the oxygen permeation capabilities of these two materials,which have shown promise in previous research:An asymmetric ceramic LCF-Ag hollow fiber oxygen-permeable membrane is prepared using the phase inversion-in-situ sintering technique.Results show that,compared to the traditional phase inversion-sintering method,the oxygen permeation flux of the membrane prepared using this technique increases by 26%.At 950℃,using 100 m L·min^-1of He as sweeping gas,the oxygen permeation flux increases from 1.487 m L·min^-1·cm^-2 to1.882 m L·min^-1·cm^-2,and the apparent activation energy is reduced by 20.6%.The membrane prepared by in-situ sintering has higher particle surface activity,which is more conducive to the adsorption,dissociation,and permeation of oxygen.The casting solution composition is optimized to form a highly asymmetric structure with a"three-layer sandwich"configuration.As a result,the oxygen permeation flux increases to 2.15 m L·min^-1·cm^-2,and the membrane operates stably for 200 hours without any decline under a high-purity CO₂ atmosphere.The results demonstrate that the highly asymmetric LCF-Ag hollow fiber membrane prepared using the phase inversion-in-situ sintering method has good tolerance to high-concentration CO₂.A multi-cation co-doping strategy is adopted by researchers to design a high-entropy perovskite-type La_0.3Ca_0.1Sr_0.2Bi_0.2Nd_0.2Co_0.3Fe_0.7O_3-δ（LCSBNCF）oxygen permeation membrane material in order to improve the oxygen permeation performance of perovskite ceramic oxygen permeation membranes and meet the low-temperature operation requirements of commercial applications.It is shown that LCSBNCF has more oxygen vacancies due to the co-doping of multiple oxygen ions leading to significant distortion of its structure,which is known as the"cocktail effect"compared to the parent material La_0.7Ca_0.16Sr_0.14Co_0.3Fe_0.7O_3-δ（LCSCF）.This membrane material has special oxygen desorption properties and low CO₂ adsorption capacity,indicating its excellent CO₂tolerance.The designed high-entropy LCSBNCF oxygen permeation material has a formation energy of 2.063 e V for oxygen vacancy and an oxygen diffusion energy of 0.975e V in bulk,which are significantly lower than those of the parent material,as shown by first-principles calculations.The high-entropy LCSBNCF hollow fiber membrane is prepared by researchers using a phase inversion-sintering technique.At 650℃,there is a relatively stable oxygen permeation flux.At 750℃,the oxygen permeation flux reaches 1 m L·min^-1·cm^-2,which meets the requirements for industrial production of 1 m L·min^-1·cm^-2.At 950℃,with high-purity CO₂ as the sweeping gas,the oxygen permeation flux reaches 4 m L·min^-1·cm^-2,which is significantly higher than that of traditional oxygen permeable membrane.After multiple cycles of heating and cooling experiments,the membrane still operates stably for1200 hours,and the oxygen permeation flux does not decrease significantly.It is shown that the designed high-entropy membrane material has more excellent CO₂ tolerance and high oxygen permeation ability.