Impact of Particle Size on the Selection of a Representative Bed Section for Poly-Dispersed Fixed Bed Reactors
Impact of Particle Size on the Selection of a Representative Bed Section for Poly-Dispersed Fixed Bed Reactors
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粒径对多分散固定床反应器代表性床段选择的影响
DOI：
10.11159/jffhmt.2023.004
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Armstrong L
中科院分区：
文献类型：
--
作者：
Armstrong L
计算流体力学(CFD)模型是固定床化学反应器设计、优化和放大的重要工具。然而，催化床结构的逼真表示和三维几何图形的网格质量对于提高CFD模型的精度至关重要。对于前者，计算机层析成像(CT)是一种无损的方法来绘制和生成实验固定床反应器的内部结构，使得实验和模拟之间能够直接一对一地耦合。在我们以前的工作中，我们分析了由筛分颗粒形成的高度分散的固定床反应器的内部结构。形成它们的粒子显示出大小、形状和取向的广泛范围。由于这些床的局部拓扑结构的复杂性，对其整个体积进行网格划分和模拟需要耗费大量的计算资源。为了减少这些，应该选择一个合适的样品截面，它准确地表示整个床层的体积孔隙度和径向孔隙度。这里量化了三个不同的样本切片，以求其准确性，确认由于全床高度不均匀的性质，样本选择是区分大小写的。此外，与较小的颗粒相比，较大的颗粒形成了更多的异质局部结构，因此需要更长的截面才能准确地表示整个床层。然后选择一个10%的截面进行网格划分，并求解其水动力剖面，以评估其网格独立性。计算结果强调了选择合适的床层截面和网格尺寸的重要性，以减少计算需求，最大限度地减少计算误差，并达到所需的解细节水平。
Computational Fluid Dynamics (CFD) models are a valuable tool for the design, optimization, and scaling-up of fixed bed chemical reactors. However, the realistic representation of the catalytic bed structure and the mesh quality of the 3D geometry is of paramount importance to improve the accuracy of CFD models. For the former, computed tomography (CT) is a non-destructive method to map and generate the internal structure of experimental fixed bed reactors, enabling a direct 1-to-1 coupling between experiments and simulations. In our previous work, the internal structure of highly poly-dispersed fixed bed reactors, formed by sieved particles, was analysed. The particles that formed them displayed a wide range of sizes, shapes, and orientations. Due to the local topological complexity of these beds, meshing and simulating their entire volume would lead to exhaustive computational demands. To reduce these, a suitable sample section should be selected, which accurately represents both the bulk and the radial porosity of the full bed. Three distinct sample sections were quantified here for their accuracy, identifying that, due to the highly heterogeneous nature of the full beds, sample selection is case sensitive. In addition, compared to smaller particles, larger particles form more heterogeneous local structures, thus requiring longer sections to accurately represent the full bed. A selected 10% section was then meshed, and its hydrodynamic profile resolved, to evaluate its mesh independency. The results highlight the importance of choosing a suitable bed section and mesh size to reduce the computational demands, minimise the computational errors, and achieve the desired level of solution detail.
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