Design and study on dual-layer rotor cage for ultrafine powder classification

doi:10.11949/0438-1157.20250653

Abstract

Abstract:

Ultrafine powders are widely used due to their unique physical and chemical properties. Consequently, preparation of ultrafine powders with narrow and fine particle sizes is crucial to improve product performance. Without increasing energy consumption or equipment complexity, a double-layer rotor cage is designed and its effects on the flow field distribution and classification performance of the pneumatic classifier are investigated through numerical simulations and powder classification experiments. Simulation results show that the gravity-induced classification effect of the double-layered cage's induction cone causes the airflow in the annular zone to move downward near the outer edge of the cage, reducing radial velocity. This improves powder dispersion in the annular zone and reduces fine powder particle size. Classification experiments confirmed that the dual-layer rotor cage significantly reduces the fine particle size. Moreover, with increasing the length of the diversion cone, the fines exhibit smaller particle sizes, narrower size distribution, and more pronounced secondary classification effect.

Key words: powder, numerical simulation, pneumatic classifier, dual-layer rotor cage, secondary classification, dispersion

摘要：

超细粉体因其物化特性应用广泛，制备粒度分布窄而细的超细粉体是提升产品性能的关键。在不增加能耗和设备复杂度的前提下，设计了双层转笼结构，通过数值模拟与分级实验，分析了其对气力分级机流场及细粉产品分布的影响。模拟结果表明，双层转笼引流锥由于重力分级作用使环形区气流在近转笼外缘向下运动且径向速度减小，改善了环形区粉体分散性并减小了细粉粒径。物料分级实验结果验证，双层转笼显著减小细粉粒径，且随引流锥长度增加，细粉粒径更小、粒度分布更窄，二次分级效果更为显著。

关键词: 粉体, 数值模拟, 气力分级机, 双层转笼, 二次分级, 分散

CLC Number:

TQ 028.1

Xingshuai LI, Yuan YU. Design and study on dual-layer rotor cage for ultrafine powder classification[J]. CIESC Journal, 2025, 76(12): 6328-6338.

李兴帅, 于源. 用于超细粉体分级的双层转笼设计与研究[J]. 化工学报, 2025, 76(12): 6328-6338.

Figures/Tables 18

Fig.1 3D model of the turbo air classifier1—coarse powder collection chamber; 2—guide vane; 3—volut;e 4—rotor cage; 5—air inlet; 6—fine powder outlet; 7—feeding inlet; 8—spreading plate

Fig.2 Schematic diagram of rotor cage blade channels and particle classification

Fig.3 Design schematic of the dual-layer rotor cage

Fig.4 Cross-sectional view of the dual-layer rotor cage structure1—lower wheel frame; 2—rotor cage blade; 3—upper wheel frame; 4—diversion cone; 5—triangle bracket

Table 1 Particle size differential distribution of calcium carbonate raw material （mass-based）

颗粒粒径/μm	微分分数/%
<1	4.73
<1~≤3	7.01
<3~≤7	10.74
<7~≤15	17.49
<15~≤30	23.57
<30~≤40	13.59
<40~≤50	10.77
<50~≤60	7.81
<60~≤70	2.75
>70	1.54

Fig.5 Turbo air classifier classification system

Fig.6 Streamline diagrams of the classifiers with four different rotor cages (XOZ plane at Y=0)

Fig.7 Axial velocity curves in the annular region of the classifier with four different rotor cages at various axial heights

Fig.8 Radial velocity curves in the annular region of the classifier with four different rotor cages at various axial heights

Fig.10 Tangential velocity curves in the annular region of the classifier with four different rotor cages at various axial heights

Fig.10 Particle trajectories of 8 μm particle inside the four different classifiers

Fig.11 Particle trajectories of 12 μm particle inside the four different classifiers

Fig.12 Particle trajectories of 14 μm particle inside the four different classifiers

Fig.13 Particle trajectories of 16 μm particle inside the four different classifiers

Table 2 Cut sizes with four classifiers

转笼类型	分级粒径d₅₀/μm
转笼A	32.5
转笼B_0.5	24.6
转笼B_0.75	16.2
转笼B₁	12.2

Fig.14 Particle size differential distribution curves of fine powders for four different rotor cage structures

Fig.15 The Rosin-Rammler distribution function of fine powder on a double logarithmic scale for rotor cage A

Table 3 Average particle size D50 and particle size distribution index n of the fine powder for the four different rotor cages

转笼类型	平均粒径D₅₀/μm	粒度分布指数n
转笼A	10.49	1.138
转笼B_0.5	9.08	1.152
转笼B_0.75	7.34	1.173
转笼B₁	5.96	1.230

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