Detailed simulations of industrial‐scale fluidized beds such as the FINEX process are still unfeasible due to the wide range of spatial scales. Due to the computational limitations it is common to apply coarse grids, which do not resolve all relevant structures. In our previous study (Schneiderbauer, AIChE J. 2017, 63, 3562), we have presented subgrid models, which enable the coarse grid simulation of dense large‐scale gas–solid flows. Herein, these corrections are applied to a parcel‐based the dense discrete phase model (DDPM), allowing to study the hydrodynamics of the FINEX process. Furthermore, the parcel approach is augmented by an unreacted shrinking core model (USCM) to account for the direct reduction of the iron ore particles by the reducing agents of H₂ and CO. This DDPM model is tested first for a cold pilot‐scale fluidized bed, and second, the USCM approach is validated for the direct reduction in a lab‐scale fluidized bed. Finally, the model is applied to the FINEX process. The results show fairly good agreement with measurements of the average bed voidage and with experimentally determined particle size distributions. The results further indicate that fines are immediately reduced, whereas the reduction of the largest ore grains takes considerably longer.

中文翻译：

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工业规模流化床中铁矿石还原的计算流体动力学模拟

由于空间尺度的范围很广，对工业规模的流化床（如FINEX工艺）进行详细的模拟仍然不可行。由于计算上的限制，通常会应用不能解决所有相关结构的粗网格。在我们以前的研究（Schneiderbauer，AIChE的Ĵ。2017年，63（3562），我们介绍了子网格模型，该模型可以对密集的大规模气固流进行粗网格模拟。在这里，这些校正应用于基于包裹的密集离散相模型（DDPM），从而可以研究FINEX过程的流体动力学。此外，未反应的收缩核心模型（USCM）增强了包裹方法，以说明H ₂的还原剂对铁矿石颗粒的直接还原DDPM模型首先在冷中试规模的流化床中进行了测试，其次，USCM方法已针对直接减少实验室规模的流化床进行了验证。最后，将模型应用于FINEX流程。结果表明与平均床空隙率的测量和实验确定的粒度分布相当吻合。结果进一步表明，细粉立即被还原，而最大的矿石颗粒的还原则花费更长的时间。