Abstract The successful application of fixed bed chemical looping hydrogen in industrial scale demands highly stable oxygen carrier pellets. The goal of this work was the realistic long-term characterization of the pelletized oxygen carriers in a fixed bed reactor environment. TGA characterization of an iron-based powder sample containing 5 wt% Al2O3 for 100 cycles showed fast reaction speeds and high oxygen exchange capacity. Characterization of the same sample as pellets in a fixed bed reactor revealed a high temperature gradient, decreased oxygen exchange capacity and a rapid increase in system pressure due to powder formation. The pellet lifetime was prolonged to 100 redox cycles when the material was stored in reduced state at the respective operating temperature. The increased stability of the reduced material could be attributed to the higher crushing strength of the iron and wustite phase in contrast to magnetite. The increase of the inert portion and of the pellet calcination temperature led to an improved starting material durability but did not influence the mechanical stability after 100 cycles. The results of this study indicate that the long-term redox cycling seems to outweigh the impact of oxygen carrier preparation methods that may be overvalued in the long run.

中文翻译：

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制造方法对用于固定床化学循环氢气长期运行的球团铁基氧载体性能的影响

摘要 固定床化学循环氢气在工业规模上的成功应用需要高度稳定的氧载体颗粒。这项工作的目标是在固定床反应器环境中对粒状氧载体进行现实的长期表征。含有 5 wt% Al2O3 的铁基粉末样品经过 100 次循环的 TGA 表征显示出快速的反应速度和高的氧交换能力。同一样品在固定床反应器中的表征显示出高温梯度、氧交换能力降低以及由于粉末形成导致的系统压力快速增加。当材料在相应的操作温度下以还原状态储存时，颗粒寿命延长至 100 次氧化还原循环。与磁铁矿相比，还原材料的稳定性增加可归因于铁和方铁体相的抗压强度更高。惰性部分和球团煅烧温度的增加导致原材料耐久性的提高，但不影响 100 次循环后的机械稳定性。这项研究的结果表明，长期氧化还原循环似乎超过了从长远来看可能被高估的氧载体制备方法的影响。