类钙钛矿氧化物中低温下化学链制氧机理的研究

Chemical looping air separation (CLAS) is a novel air separation technology for the production of pure oxygen. The features of CLAS are energy-extensive, cost-effective and operation-simple. The oxygen releasing and absorbing properties of oxygen carriers with high temperature and high anti-agglomeration are the focus of the current study. The industrial waste heat with temperatures of lower than 400℃is abound. Perovskite oxide of YBaCo4O7+δ is used as oxygen carrier and the oxygen absorbing and releasing property between 200~400℃ are investigated in this project. The aim of this project is to produce oxygen using low temperature waste heat. In order to improve the oxygen transport capacity, oxygen releasing and absorbing rates and reduce the oxygen releasing and absorbing temperatures, the elements of Y and Co in YBaCo4O7+δ are replaced by other elements partially or fully. The effects of preparation methods, preparation parameters, the doping element types, and element adding ratios on phase formation and property of Y1-xRxBaCo4-yMyO7+δ will be investigated. The physical and chemical parameters of Y1-xRxBaCo4-yMyO7+δ will be measured and the parameter database will be established. The thermodynamic and kinetic analysis on oxygen releasing and absorbing of Y1-xRxBaCo4-yMyO7+δ will be done and the kinetic models will be established. The coupling mechanism of temperature- velocity- concentration fields in the reactor and the process of strengthening will be studied by numerical simulation. The characteristics of oxygen carrier in the fixed-bed reactor under the state of complex heat and mass transfer, and chemical reactions will be investigated. The macroscopic kinetic model will be established.

化学链空气分离制氧技术，具有能耗低、成本低、操作简单的特点，目前的研究重点主要是高温、高抗烧结能力载氧体的吸放氧性能。针对工业领域大量存在的低温烟气余热，本项目以类钙钛矿氧化物YBaCo4O7+δ为对象，研究其在200~400℃的吸放氧特性，以实现利用低温余热制取氧气。为提高YBaCo4O7+δ在低温段的氧容量、反应速率以及降低吸、放氧温度，对Y位和Co位元素进行部分或全部替换；研究制备方法、制备参数、替换元素种类、替换比例等对Y1-xRxBaCo4-yMyO7+δ成相率及性能的影响并建立其热物性参数数据库；进行热动力学分析并建立反应动力学模型；采用数值模拟，研究反应器内温度场-速度场-浓度场耦合作用机制和过程强化机理；进行热态实验研究复杂传热、传质、流动和化学反应存在情况下，固定床反应器内载氧体的反应特性，建立宏观反应动力学模型。

化学链空气分离制氧技术具有能耗低、成本低和操作简单的优点。本项目以YBaCo4O7+δ为对象，开展了制备参数优选、掺杂元素及比例优选、吸氧与释氧反应本征动力学以及固定床内反应特性的研究。主要研究工作及其成果如下：(1) 开展载氧体制备参数优选实验研究，制备出了YBaCo4O7+δ晶体结构的载氧体，获得了最佳制备参数：固相反应法、煅烧温度为1100℃、煅烧时间为30h和冷却方式为空冷。(2) 元素掺杂可以提高载氧体的储氧能力、降低载氧体最大吸氧反应速率对应温度、提高载氧体最大释氧反应速率对应温度、提升载氧体吸氧与释氧反应性能。元素单独掺杂时，Ti、Dy的掺杂比例分别为5%、50%的载氧体反应性能最优；元素同时掺杂时，Ti、Dy的掺杂比例分别为5%、75%的载氧体反应性能最优。(3) 进行载氧体吸氧与释氧反应本征动力学研究，吸氧反应活化能为167.08~197.70kJ/mol，释氧反应活化能为285.74~324.87kJ/mol，元素掺杂不会改变载氧体吸氧与释氧反应过程的机理函数类型。(4) 进行载氧体吸氧与释氧反应性能研究，获得了最佳操作参数：吸氧反应温度为350℃、释氧反应温度为430℃、气体流量为200mL/min和氧气浓度为21%。(5) 进行载氧体吸氧与释氧反应宏观动力学研究，吸氧反应的活化能为17.18~20.70kJ/mol，释氧反应的活化能为23.11~31.55kJ/mol，得到了载氧体吸氧与释氧反应过程机理函数，建立了载氧体吸氧与释氧反应宏观动力学模型。(6) Y0.5Dy0.5BaCo4O7+δ和Y0.2Ti0.05Dy0.75BaCo4O7+δ载氧体的吸氧与释氧反应循环稳定性优于YBaCo4O7+δ和Y0.95Ti0.05BaCo4O7+δ载氧体。