Abstract Scale-up studies of fluidized beds are important for numerous fields. Fluidization in a multi-ring inclined nozzle spout-fluid bed (MRIN spout-fluid bed) is one of the most critical factors that affect the coating efficiency and uniformity of tri-structural isotropic (TRISO) nuclear particles in the fluidized bed chemical vapor deposition (FB-CVD) process. In this work, the flow pattern similarity principle was proposed to scale up a specially designed spout-fluid bed, which was aimed at maintaining the gas-solid contact efficiency, and was validated by electrical capacitance tomography (ECT) measurements. First, the traditional ECT method was developed for the specially designed MRIN spout-fluid bed according to the filling method. Then, the reconstruction algorithms were updated using the alternating direction multiplier method (ADMM) by introducing optimization constraints. The fluidization laws were investigated for different superficial gas velocities and distributor structures. We found that the gas distributor structure affected the merge point of the jets, which played an essential role in fluidization pattern changes. The statistically-based coefficient of variation (Cv) was proposed to distinguish the different flow patterns. Multi-ring spouting was then selected as a typical flow pattern for good fluidization and mixing, where the Cv ranged from 0.25 to 0.65. Then, the optimal design principles for the enlarged spout-fluid bed gas distributor were obtained. We determined that a smaller nozzle diameter (0.71d 0), larger nozzle spacing (1.12x 0), and slightly inclined angle (1.50θ 0) could improve fluidization, and that nozzle spacing was the most important factor. This study may be beneficial for the industrial design of the FB-CVD process and for the fabrication of high-density nuclear fuel particles. Additionally, it could be presented to a more general audience for scaling-up fluidized beds with a complex distributor, which would be beneficial for the fluidization research community.

中文翻译：

---

多环斜喷嘴喷口流化床电容层析放大实验研究

摘要 流化床的放大研究对许多领域都很重要。多环倾斜喷嘴喷口流化床（MRIN喷口流化床）中的流化是影响流化床化学气相沉积中三结构各向同性（TRISO）核粒子包覆效率和均匀性的最关键因素之一（FB-CVD）工艺。在这项工作中，提出了流动模式相似性原理来扩大专门设计的喷口流化床，旨在保持气固接触效率，并通过电容断层扫描 (ECT) 测量进行验证。首先，针对专门设计的 MRIN 喷口流化床，根据填充方法开发了传统的 ECT 方法。然后，通过引入优化约束，使用交替方向乘法器方法 (ADMM) 更新了重建算法。研究了不同表观气体速度和分布器结构的流化规律。我们发现气体分布器结构影响射流的汇合点，这对流化模式的变化起着至关重要的作用。提出了基于统计的变异系数（Cv）来区分不同的流动模式。然后选择多环喷口作为良好流化和混合的典型流动模式，其中 Cv 范围为 0.25 至 0.65。进而得出扩大喷口-流化床气体分布器的优化设计原则。我们确定较小的喷嘴直径 (0.71d 0)，较大的喷嘴间距 (1. 12x 0）和略微倾斜的角度（1.50θ 0）可以改善流化，其中喷嘴间距是最重要的因素。该研究可能对FB-CVD工艺的工业设计和高密度核燃料颗粒的制造有益。此外，它可以呈现给更广泛的受众，以扩大具有复杂分配器的流化床，这将有利于流化研究界。