One of the crucial issues in the chemical looping technology lies in its bed material: the oxygen carrier. Particle size analysis of an oxygen carrier is important since in a fluidized bed the material can only work well within a specific size range. While the favorable size ranges for oxygen carrier materials have already been reported, none of the published studies has analyzed the particle size and shape of oxygen carriers in detail. Furthermore, the effect of oxygen carriers' oxidation degree on such properties has not been considered either. This study aimed to report the particle size and shape analysis of five iron-based oxygen carriers, one natural ore, one synthetic material, and three residue products, at different oxidation degrees using dynamic image analysis (DIA). The oxygen carriers were prepared at different mass conversion degrees in a fluidized bed batch reactor. The size distribution, sphericity, and aspect ratio of the oxygen carrier particles were examined experimentally using a Camsizer instrument. Our results show that the DIA method was successfully able to analyze the particle size and shape of our oxygen carriers with satisfying accuracy for comparison. The oxidation state of the investigated materials seems to only affect the particle size and shape of oxygen carriers to a minor extent. However, exposures to redox cycles in a fluidized bed reactor may alter the particle size and shape of most oxygen carriers.

中文翻译：

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多种氧化态铁基氧载体粒径和形状分析的新方法

化学循环技术的关键问题之一在于其床层材料：氧载体。氧载体的粒度分析很重要，因为在流化床中，材料只能在特定的粒度范围内良好地工作。虽然氧载体材料的有利尺寸范围已经被报道，但已发表的研究都没有详细分析氧载体的粒径和形状。此外，也没有考虑氧载体的氧化程度对其性能的影响。本研究旨在利用动态图像分析 (DIA) 报告不同氧化程度下五种铁基氧载体、一种天然矿石、一种合成材料和三种残留产品的粒径和形状分析。在流化床间歇反应器中以不同的质量转化率制备氧载体。使用 Camsizer 仪器对氧载体颗粒的尺寸分布、球形度和纵横比进行了实验检查。我们的结果表明，DIA 方法能够成功地分析氧载体的粒径和形状，并具有令人满意的比较精度。所研究材料的氧化态似乎仅在较小程度上影响氧载体的粒径和形状。然而，在流化床反应器中暴露于氧化还原循环可能会改变大多数氧载体的颗粒尺寸和形状。