元素掺杂对钙钛矿型透氧膜抗二氧化碳腐蚀性能的研究

发布时间：2018-03-16 02:31

  本文选题：透氧膜　切入点：掺杂　出处：《上海大学》2015年硕士论文　论文类型：学位论文

【摘要】：混合离子-电子导体钙钛矿型透氧膜(MIEC)主要应用在高温气体分离和膜催化反应中。在一定温度及氧势梯度作用下,空气中的氧会以氧离子形式从高压氧侧通过氧空位迁移到低压氧侧,如果将透氧膜反应器与整体煤气化联合循环发电系统耦联,一方面可以通过向化石燃料提供高纯氧促进富氧燃烧,提高能量利用效率,另一方面可以降低生产成本,且有利于CO2的捕获和存储。理想透氧膜材料不仅需要较高的透氧量,同时还应兼具良好的结构稳定性和优异的化学稳定性能。然而,对于该技术的实际生产应用来说,在高浓度CO2气氛下工作的透氧膜材料容易受CO2的毒化腐蚀,进而影响膜材料的透氧率和稳定性。因此,开发抗CO2腐蚀性能的混合导体透氧膜材料是实现富氧燃烧及整体煤气化联合循环发电技术高效应用的基础和前提。本文以具有高离子电导率和高透氧能力的Ba Co0.88Nb0.12O3-δ(BCN)材料作为研究基础,对BCN材料在A位和B位进行元素掺杂替代,并采用固相反应合成制备透氧膜材料Ba1-x Lax Co0.88Nb0.12O3-δ(BLCN)及Ba0.8La0.2Co0.88-x Fex Nb0.12O3-δ(BLCFN),探究元素掺杂替代对BCN材料的透氧性能、透氧速控步骤、结构稳定性等方面的影响。研究发现,在850°C下,BLCN材料随着La掺杂量增加透氧量逐渐降低。供氧侧通入不同浓度O2时,透氧量随氧气浓度的增加而增加。通过Wagner公式进行数据拟合得到参数0n0.5,表明其透氧控制步骤主要由表面交换和体相扩散控制。对于BLCN材料,在850°C下经不同浓度CO2气氛吹扫一定时间后,XRD结果显示BLCN膜材料的结构稳定性随La掺杂量的提高而增强。在5%CO2吹扫下,BLCN材料表面均无明显碳酸盐生成,在纯CO2气体吹扫下,La掺杂含量较低的膜片表面有少量碳酸盐生成,而掺杂含量较高的BLCN膜材料在5 h后仍未发生明显变化,在静态CO2气氛条件下表现出了优异的抗CO2腐蚀性能。进一步探究BLCN膜材料的透氧能力发现,纯CO2气氛吹扫后,La含量的增加使得膜片抗CO2腐蚀能力增强。其中,BCN及低La掺杂的BLCN(x≤0.2)来说,透氧率很快下降为0,而BLCN-0.5膜材料透氧量由CO2切换前的0.67m L·cm-2·min-1逐渐稳定在0.46 m L·cm-2·min-1。BLCN膜片抗CO2腐蚀能力的提高主要归因为La含量增加后金属-氧键能的提高和更稳定的钙钛矿结构。为了进一步改善BLCN膜材料抗CO2腐蚀性能,在BLCN-0.2的基础上通过B位掺杂一定比例的Fe元素制备Ba0.8La0.2Co0.88-x Fex Nb0.12O3-δ(BLCFN)透氧膜。结果显示,静态条件下,在850°C下纯CO2分别吹扫5 h后BLCFN材料均未生成明显的碳酸盐。与BLCN相比,同等条件下BLCFN表现出了更强的抗CO2腐蚀能力。BLCFN-0.2膜片在900°C下经纯CO2气氛吹扫110 h后透氧量由0.96m L·cm-2·min-1,下降并稳定在0.31 m L·cm-2·min-1。表明A位基础上对B位进行Fe元素的掺杂更加有利于透氧膜片在CO2气氛下的长期透氧稳定性能。
[Abstract]:Mixed ion-electron conductor perovskite-type oxygen permeable membrane (MIEC) is mainly used in high temperature gas separation and membrane catalytic reaction. Oxygen in the air will migrate from the hyperbaric oxygen side through the oxygen vacancy to the low pressure oxygen side in the form of oxygen ions. If the oxygen permeable membrane reactor is coupled to the integrated coal gasification combined cycle power generation system, On the one hand, it can promote oxygen-enriched combustion by providing high purity oxygen to fossil fuels and improve energy utilization efficiency. On the other hand, it can reduce the production cost and be beneficial to the capture and storage of CO2. At the same time, it should also have good structural stability and excellent chemical stability. However, for the practical application of this technology, the oxygen permeable membrane materials working in high concentration CO2 atmosphere are vulnerable to CO2 poisoning corrosion. Thus, the oxygen permeability and stability of the membrane materials are affected. The development of mixed conductor oxygen permeable film with CO2 corrosion resistance is the basis and prerequisite for the efficient application of oxygen-enriched combustion and integrated coal gasification combined cycle power generation technology. This paper deals with Ba Co 0.88 NB 0.12 O 3- 未 BCNs with high ionic conductivity and high oxygen permeability. Materials as a basis for research, The oxygen permeable membrane materials Ba1-x Lax Co 0.88 NB 0.12 O 3- 未 and Ba0.8La0.2Co0.88-x Fex NB 0.12 O 3- 未 were prepared by solid state reaction. The oxygen permeability and oxygen permeability of BCN materials were investigated. It is found that the oxygen permeability of BLCN decreases with the increase of La doping at 850 掳C, and when oxygen supply side passes through the oxygen supply side with different concentrations of O2, The oxygen permeation rate increases with the increase of oxygen concentration. The parameter 0n0.5 is obtained by fitting the data from Wagner formula, which indicates that the oxygen permeation control step is mainly controlled by surface exchange and bulk diffusion. For BLCN materials, The results showed that the structural stability of BLCN films increased with the increase of La doping content after blowing in different concentration of CO2 atmosphere for a certain time at 850 掳C. there was no obvious carbonate formation on the surface of BLCN films swept by 5CO 2. A small amount of carbonate was formed on the surface of the film with low La doping content in pure CO2 gas swept down, while the BLCN film material with high doping content did not change obviously after 5 h. Under the condition of static CO2 atmosphere, the excellent corrosion resistance to CO2 was demonstrated. Further study was made on the oxygen permeability of BLCN film. The increase of La content in pure CO2 atmosphere increases the corrosion resistance of the film to CO2, especially for BLCN(x 鈮，

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