稀土金属修饰铁基载氧体深度还原抑制析碳机理研究

Chemical looping process is an efficient way to convert fossil fuels with inherent CO2 separation. Iron oxide is a suitable oxygen carrier candidate for chemical looping hydrogen generation. Currently, fluidized bed is commonly adopted as the fuel reactor. The gas slip in fluidization leads to incomplete conversion of fuel gases. The outlet CO2 stream is mixed with fuel gases. This proposal will employ a moving bed as an alternative fuel reactor with iron oxide as oxygen carrier. It aims to increase the fuel conversion and the CO2 concentration at the outlet stream. This proposal will combine the quantum chemistry simulation and the experimental test. The rare earth metals suitable for carbon deposition inhibition will firstly be selected by quantum chemistry analysis. The oxygen carrier then will be decorated with rare earth metals to inhibit the potential carbon deposition in the extended reduction process. The mechanism of carbon deposition growth and inhibition will be investigated. Different iron oxide oxygen carriers will be prepared. The impacts of temperature, fuel gas compositions, gas/solid flow rate, particle size on the reaction kinetics, fuel conversion, oxygen carrier reduction rate, CO2 outlet concentration will be analyzed based on the experiment and the simulation. The objective of this proposal is to provide the basic data and contributes to the current technologies of chemical looping hydrogen generation.

铁基载氧体是公认的适合化学链制氢的载氧体。化学链制氢需要铁基载氧体深度还原，还原过程存在两个问题：一是燃料转化不完全；二是析碳。本课题拟采用移动床作燃料反应器，提高燃料转化率，并制备稀土金属修饰铁基载氧体，研究载氧体析碳机理和抑制析碳方法，提高化学链制氢过程的二氧化碳捕集效率和浓度。本课题采用量子模拟与实验相结合的方法，通过量子化学模拟，筛选适合制备抑制析碳的稀土金属元素，修饰并制备不同的铁基载氧体；搭建移动床燃料反应器实验装置，对稀土修饰前后的铁基载氧体进行还原特性研究，考察温度、燃料气组分、气体/载氧体颗粒流速、粒径等因素对反应速率、燃料转化率、载氧体还原深度、二氧化碳浓度分布的影响，揭示铁基载氧体深度还原过程的析碳分布和规律，寻找抑制析碳方法。为开发适合化学链制氢的铁基载氧体制备技术提供基础数据和理论指导。

本研究围绕项目书开展了化学链制氢过程中铁基载氧体析碳特性研究，围绕提高燃料转化率以及化学链制氢过程的二氧化碳捕集效率和浓度为目标，制备了多种助剂以及稀土金属修饰的高效铁基载氧体，探究了载氧体析碳机理和抑制析碳方法，重点针对甲烷化学链制氢过程还原气体和铁基载氧体之间反应展开实验研究。在小型反应器中，考察了铁基载氧体与还原气体反应过程中载氧体析碳路径，分析了铁基载氧体内部和表面晶格氧迁移与积碳的关联关系，解析了不同载氧体以及反应条件下积碳（碳化物Fe3C、石墨碳、不定性碳和须状碳纳米管）的形态和积碳特性，通过不同表征手段发现了析碳迁移和分解途径；探讨了不同载体和反应条件对析碳的影响；同时探索了铁基载氧体的还原与甲烷干重整反应之间的耦合机制，为开发适合化学链制氢的铁基载氧体制备技术的进一步工业应用提供基础数据和理论指导。