超声空化效应对细粒尾矿的增渗作用

doi:10.16265/j.cnki.issn1003-3033.2024.05.0014

摘要/Abstract

摘要：

针对细粒尾矿的渗透性较弱,容易导致尾矿坝浸润线抬升和降低尾矿坝安全系数的问题,提出采用超声空化的方法改善尾矿的渗透性。首先,采用计算流体动力学(CFD)软件模拟空化泡溃灭的过程;然后,根据空化阈值和换能器的声压计算结果选定试验使用的换能器,频率范围为20~40 kHz,功率为60 W,并通过染色试验证实尾矿试样中存在超声空化效应;最后,使用自制变水头渗透仪与选定的换能器,针对不同细粒含量的尾矿试样,开展超声增渗试验,并利用核磁共振仪检测增渗前后试样的孔隙结构变化。研究结果表明:得到的空化泡半径变化曲线与R-P方程拟合曲线吻合度较高,证明模拟结果的有效性;当气泡直径大于50 μm时,低频超声的空化效果更好,当气泡直径小于25 μm时,高频超声的空化效果更佳;细粒含量相同时,尾矿试样的渗透系数增长率随超声的频率增大而增加;超声频率相同时,细粒含量多的尾矿试样渗透系数增长率更高;超声作用后,尾矿试样中0~10 μm的孔隙占比降低,降幅随频率的增加而增加;10~20 μm的孔隙占比变化趋势不明显;20~40 μm的孔隙占比增加,增幅随频率的增加而增加;>40 μm的孔隙占比增长较少。对于不同孔隙占比的尾矿,施加相应频率的超声信号可获得更显著的增渗效果。

关键词: 超声空化, 细粒尾矿, 增渗, 渗透系数, 数值模拟, 孔隙, 核磁共振

Abstract:

The weak permeability of fine-grained tailings can cause the leaching line of the tailings dam to rise and reduce the safety factor of the tailings dam, an ultrasonic cavitation approach was proposed to enhance the permeability of the tailings. Firstly, computational fluid dynamics (CFD) software was used to simulate the cavitation bubble collapse process. Then, the transducer used for the experiments was selected based on the cavitation threshold and the simulated sound pressure, with a frequency range of 20-40 kHz and a power of 60 W. Moreover, the presence of ultrasonic cavitation effects in the tailings samples was confirmed by staining tests. Finally, ultrasound-enhanced permeability tests were performed on tailings samples with different fine particle contents using a self-made variable head permeameter and the selected transducer. A nuclear magnetic resonance instrument was used to determine the pore structure changes before and after penetration enhancement. The results showed that the obtained cavitation bubble radius change curve was consistent well with the Rayleigh-Plesset(R-P) equation fitting curve, proving the validations of the simulations. Low-frequency ultrasound had a better cavitation effect when the bubble diameter was larger than 50 μm, whereas high-frequency ultrasound was more effective when the bubble diameter was less than 25 μm. When the fine particle content was kept constant, the permeability coefficient growth rate of the tailings samples increased as the ultrasound frequency increased. When the ultrasonic frequency was kept constant, the tailings samples' permeability coefficient growth rate with higher fine particles was higher. After the ultrasound treatment, the proportion of 0-10 μm pores in the tailings sample decreased, and the decrease became larger with the increase in frequency. There was no clear trend for the proportion of pores between 10-20 μm, while the proportion between 20-40 μm increased, and the increase became larger with the increase of frequency. The proportion of pores larger than 40 μm increased relatively small. For tailings with different pore proportions, appropriate ultrasound signals of corresponding frequencies can significantly enhance the permeability enhancement effect.

Key words: ultrasonic cavitation, fine tailings, permeability enhancement, permeability coefficient, numerical simulation, pore space, nuclear magnetic resonance

中图分类号:

X936
TD926.4

何文, 卢博凯, 石文芳, 祝思雨, 刘金朋. 超声空化效应对细粒尾矿的增渗作用[J]. 中国安全科学学报, 2024, 34(5): 91-100.

HE Wen, LU Bokai, SHI Wenfang, ZHU Siyu, LIU Jinpeng. Enhanced permeation effect of fine-grained tailings by ultrasound cavitation[J]. China Safety Science Journal, 2024, 34(5): 91-100.

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试验序号	C_u	颗粒含量/%				D50/μm
试验序号	C_u	-0.5~+0.1 mm	-0.1~+0.075 mm	-0.075~+0.005 mm	-0.005 mm	D50/μm
1—4	5.62	12.19	13.92	68.22	5.67	59.8
5—8	5.46	16.28	23.32	57.26	3.14	80.6
9—12	5.31	23.42	36.62	37.63	2.33	98.8
13—16	5.42	31.03	45.97	21.26	1.74	128.5