【作者】 芮泽宝；

【导师】 林跃生； 李永丹；

【作者基本信息】 天津大学 ， 工业催化， 2010， 博士

【摘要】 本论文针对与三条二氧化碳捕集技术路线（即燃烧后脱碳、燃烧前脱碳和富氧燃烧技术）相关的两类气体,即CO₂和O₂,的分离和富集展开研究。选用致密离子导体膜和陶瓷吸附剂作为分离载体。第二章建立了一个分析CO₂/O₂渗透通过包含混合电子-离子传导氧化物陶瓷（MCOC）相和熔融碳酸盐（MC）相的双相膜模型。并推导出了描述一些特殊情况下纯CO₂的渗透模型。结果显示,当CO₂和O₂一起渗透时,CO₂的渗透通量比相应的纯CO₂渗透时的大一个数量级。CO₂和O₂的渗透通量都随着反应侧O₂分压和MCOC相的电子电导率(σ_h·)的增大而增大。当MCOC相的电子电导率很小时,例如σ_h·≤0.1 S/cm,CO₂的渗透通量随着MCOC相的离子电导率增大而增大;而当MCOC相的电子电导率很大时,例如σ_h·>1 S/cm,CO₂的渗透通量随着MCOC相的离子电导率增大而减小。对于纯的CO₂渗透过程,CO₂的渗透通量随着MCOC相的离子电导率增大而增大,随着MC相的体积分数的增加而减小。规则的陶瓷载体的孔结构有利于CO₂和O₂的渗透。第三章利用直接浸润法合成了致密的Bi_1.5Y_0.3Sm_0.2O₃ （BYS）- MC双相膜,并将其用于高温CO₂的选择性渗透分离。由于氧离子的传导相中的斜方六面体结构和立方萤石结构之间的可逆相变,在高温CO₂渗透实验的初始阶段,需要很长时间才能达到稳态渗透。CO₂在双相膜中的渗透通量随着温度的升高而增大（500-650℃）,其渗透活化能是113.4 kJ/mol。CO₂的渗透通量随着吹扫气流速的增大而增大（25-125 mL/min）。第四章推导了一个一维致密透氧膜反应器模型,并用其对膜反应器中甲烷部分氧化反应（POM）制合成气的过程进行了模拟。采用了燃烧-重整机理描述POM,并且考虑了重整产物H2和CO的氧化。结果表明:考虑重整产物氧化反应的模型比忽视产物氧化反应的模型更合理。如果在反应器中甲烷完全消耗,则将发生飞温。选定反应器进料温度作为主要参考指标考察反应器的各种操作性能和这种现象的关系,并且定义了临界进料温度（BIT）概念。模拟结果显示,当反应器进料温度接近BIT时,可以获得最佳的膜反应器操作性能。第五章利用模型分析了反应条件下离子或混合传导陶瓷膜的氧渗透性能。该模型考虑了不同的氧传输传导机理,例如p型或者n型传输膜,以及不同的化学反应速率。结果表明,无论对p或n型传导机理膜来说,当膜一侧有氧消耗反应发生时,反应侧氧分压随反应速率的增快而降低,而氧渗透通量随之增大。这些变化介于没有化学反应发生和反应达到平衡这两种极限情况之间,并在反应速率极慢或者极快时接近于这两种极限情况。反应速率的增快能导致p型膜的氧传输机理从p向n型转变,而这种转变能使氧渗透通量增大近30倍。第六章利用柠檬酸盐法制备钙钛矿结构SrCo_0.8Fe_0.2O_3-δ（SCF）,并利用其制备用于富氧燃烧过程中需要的高温O₂-CO₂气体混合物。当吸附剂在高温条件下暴露于CO₂气体流时,氧气将会从吸附剂内脱附出来,得到一个富含氧气的高温CO₂气体流。当SCF吸附剂在空气中再生时,氧气又会被吸附剂吸收。利用XRD和TGA分析结果鉴定了O₂脱附过程的碳酸盐化反应机理。最佳的氧气吸附和脱附温度分别为900和850℃。多次吸附/脱附循环实验显示SCF吸附剂具有很高的活性和循环稳定性。更多还原

【Abstract】 This work focuses on high-temperature separation and enrichment of CO₂ and O₂, which are the most relevant separations with three CO₂ capture pathways: post-combustion capture, pre-combustion capture, and oxy-combustion, with dense ionic conducting membrane and ceramic sorbent.In chapter 2, a theoretical model is developed for CO₂/O₂ permeation through a dual-phase membrane consisting of mixed-conducting oxide ceramic （MCOC） and molten carbonate （MC） phases. Somewhat simpler theoretical CO₂ permeation equation is obtained for the pure CO₂ permeation case. The results show that CO₂ permeation flux （J CO₂） with involving oxygen permeation is more than one order of magnitude higher than the corresponding J CO₂ for a pure CO₂ permeation case. The fluxes of CO₂ and O₂ （J O₂） increase with increasing O₂ partial pressure in the feeding gases. Both J CO₂and J O₂ increase with increasing electronic conductivity (σ_h·) of the MCOC phase. J CO₂increases with increasing ionic conductivity (σ _V··) of the MCOC phase atσ_h·≤0.1 S/cm, while decreases with an increase ofσ _V··atσ_h·>1 S/cm. For the pure CO₂ permeation case, J CO₂ increases with the increase ofσ _V··and decreases with increasing MC volume fraction. An ordered ceramic pore structure benefits CO₂ and O₂ permeation.In chapter 3, a dense Bi_1.5Y_0.3Sm_0.2O₃ （BYS）-MC dual-phase membrane is synthesized by the direct infiltration method and used for selective permeation of CO₂ at high temperatures. Permeation takes a long time to reach a steady state at the initial stage due to the reversible phase change of the oxygen ions conduction phase between the rhombohedral structure and cubic fluorite structure. J CO₂increases with increasing temperature （500-650°C）, with apparent activation energy of 113.4 kJ/mol. J CO₂ increases with increasing sweep gas flow rate（25-125 mL/min）.In chapter 4, a one-dimensional dense oxygen permeation membrane reactor （DMR） model is developed to simulate the partial oxidation of methane （POM） to syngas. A combustion-reforming mechanism is adopted and the oxidation of reforming products, i.e. H₂ and CO, is considered. The results show that the model with incorporation of the product oxidation steps is more reasonable than those ignoring the product oxidation reactions. The model predicts that if methane is consumed completely in the reactor, a temperature runaway occurs. The reactor inlet temperature is chosen as a major factor to demonstrate the correspondence of the reactor performance and this phenomenon. A borderline inlet temperature （BIT） is defined. Simulation results show that when the reactor inlet temperature approaches to this value, an optimized reactor performance is achieved.In chapter 5, the oxygen permeation through oxygen ionic or mixed-conducting ceramic membranes under reaction conditions is examined with a model taking into account of different transport mechanisms, i.e. p-type and n-type transport, and finite reaction rate. It is demonstrated that with a reaction consuming oxygen in one side of the membrane, the oxygen partial pressure in the reaction side decreases, whileJ O₂ increases from the value of no reaction case to that of complete reaction case, with the increase of the reaction rate. The increase of reaction rate causes a transition of the transport mechanism from p-type to n-type, which leads to an increase of J O₂ by up to 30 times of magnitude.In chapter 6, perovskite-type SrCo0.8Fe0.2O3-δ（SCF） is prepared by a liquid citrate method and used to produce O₂-CO₂ gas mixture for oxyfuel combustion. O₂ is desorbed and an O₂-enriched CO₂ stream is obtained when SCF is exposed in a CO₂ stream at high temperature. O₂ is adsorbed when SCF is regenerated in an air stream. A carbonation-reaction mechanism for O₂-desorption is identified with the evidences of XRD and TGA analysis. Optimal temperatures for O₂ sorption and desorption processes are determined to be 900 and 850℃, respectively. Multiple sorption and desorption cycles indicate that SCF sorbent has high reactivity and cyclic stability.更多还原