Study on stress evolution and hopper design of ultrafine powder under aeration conditions

doi:10.11949/0438-1157.20250115

Abstract

Abstract:

Ultrafine powders play a crucial role in promoting technological development and improving product performance in various industries. However, due to their small particle size, large specific surface area, and strong inter-particle forces, ultrafine powders often exhibit poor flowability, creating challenges for mass-flow hopper design. This paper uses two kinds of ultrafine powders as experimental materials, and uses the PT-X powder comprehensive property tester and FT4 powder rheometer to characterize the powder fluidity through the angle of repose method, Hausner ratio (HR) method, shear test method, etc. Furthermore, by conducting experiments of aerated discharge, the effects of aeration, hopper outlet diameter, and powder properties on flow behavior of ultrafine powders were studied. Finally, based on the Jenike theory, the stress evolution and hopper design of ultrafine powder under aeration were investigated, and the critical flow equation for powder in the aerated hopper was established, yielding the functional relationship between the critical hopper outlet diameter and aeration volume/superficial velocity of mass-flow hoppers. The proposed aeration-coupled design method provides both theoretical foundations and practical guidelines for optimizing ultrafine powder hoppers.

Key words: ultrafine powder, aeration, stress evolution, hopper design

摘要：

超细粉体在推动技术发展和提高各个行业的产品性能方面发挥着关键作用。但是，由于粒径小、比表面积大、颗粒间作用强等特点，超细粉体流动性较差，这对质量流料仓的设计提出了挑战。以两种超细粉体为实验物料，借助PT-X粉体综合特性测试仪和FT4粉体流变仪，通过休止角法、豪斯纳比率（HR）法、剪切测试法等对粉体流动性进行表征；开展了粉体料仓通气下料实验，探讨了料仓通气、出口直径、粉体物性等对下料流动的影响；最后，在Jenike理论基础上，开展通气作用下超细粉体应力演变分析与料仓设计研究，耦合通气作用修正了料仓内粉体临界流动方程，推导出质量流料仓临界出口直径与通气量/表观气速的函数关系。本研究提出的耦合通气作用的粉体质量流料仓设计方法，为超细粉体料仓设计提供了理论依据和实践指导。

关键词: 超细粉体, 通气, 应力演变, 料仓设计

CLC Number:

TH 122

Luming CHEN, Yingli LIU, Haifeng LU, Qiaoyu GAN, Ying CHANG. Study on stress evolution and hopper design of ultrafine powder under aeration conditions[J]. CIESC Journal, 2025, 76(8): 3853-3863.

陈路明, 刘英莉, 陆海峰, 甘巧玉, 常颖. 通气作用下超细粉体应力演变与料仓设计研究[J]. 化工学报, 2025, 76(8): 3853-3863.

Figures/Tables 14

Fig.1 Flow patterns of hopper discharge

Table 1 Physical properties of powders

参数	模拟剂A	模拟剂B
d_sv/μm	1.02	14.7
M_c/%	0.32	0.48
ρ_p/(kg/m³)	1312	1500
ρ_b/(kg/m³)	210	435
ρ_t/(kg/m³)	450	693
AOR/(°)	40.3	46.0
k/(10^-12 m²)	18	11.7

Fig.2 Particle size distribution of experimental materials

Fig.3 SEM images of ultrafine powders

Fig.4 Schematic diagram of the aerated hopper discharge experiment

Fig.5 Shear test results under different pre-consolidation stresses

Fig.6 Discharge behavior of ultrafine powders under gravity and aeration conditions (simulation agent A，D=20 mm)

Fig.7 Effect of aeration on powder discharge (simulation agent A)

Fig.8 Comparison on discharge results of different ultrafine powders under aeration (D=20 mm)

Fig.9 Effect of hopper outlet on critical aeration volume/superficial velocity

Fig.10 Schematic diagram of arch stress analysis in the hopper

Fig.11 Effect of gas distribution coefficients on hopper critical outlet diameter predictions (simulation agent A)

Table 2 Design results of mass-flow hopper coupled with aeration condition

物料	$σ c 0$ /kPa	D/mm	Q_c/(L/min)	u_c/(m/s)	$D c'$ /mm
模拟剂A	1.82	20	4.0	0.21	21.64
		30	7.0	0.17	27.73
		50	9.0	0.08	53.22
模拟剂B	1.25	20	2.5	0.13	22.22
		30	3.0	0.07	31.24
		50	5.0	0.04	50.67

Table 2 Design results of mass-flow hopper coupled with aeration condition

物料	$σ c 0$ /kPa	D/mm	Q_c/(L/min)	u_c/(m/s)	$D c'$ /mm
模拟剂A	1.82	20	4.0	0.21	21.64
		30	7.0	0.17	27.73
		50	9.0	0.08	53.22
模拟剂B	1.25	20	2.5	0.13	22.22
		30	3.0	0.07	31.24
		50	5.0	0.04	50.67

Fig.12 Relationship between critical aeration superficial velocity and hopper outlet diameter

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