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Studies of wetting film stability, froth stability and mineral flotation

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  • Nhan đề:
    Studies of wetting film stability, froth stability and mineral flotation
  • Tác giả: Yang, Bingyu
  • Chủ đề: 400403 Chemical engineering design ; 400406 Powder and particle technology ; 401904 Mineral processing/beneficiation ; Acoustic sound ; Carry rate ; Foam/froth dynamic stability ; Froth flotation ; Mass recovery ; School of Chemical Engineering ; Wetting film stability
  • Mô tả: Flotation is a physiochemical process that can be used to separate different substances based on the difference in their surface hydrophobicity. Hydrophobic particles will attach to bubbles and float to the froth phase, while the hydrophilic particles will be left behind (in the pulp phase). Flotation is widely used in mineral processing, wastewater treatment and papermaking. Due to the depletion and massive demand for minerals, improving the technology to improve the performance is necessary. An attempt to enhance the flotation performance was recently made using acoustic sound, and the flotation improvement was speculatively explained by the stabilization effect of the sound on foam film, increasing the froth stability. However, it remains unclear as to whether other factors, like a change in the bubble-particle interaction in the pulp phase, also contribute to the observed improvement of flotation performance with applying the sound. This thesis firstly investigates the impact of acoustic sound on bubble-particle interaction by studying the stability of thin wetting films. The results demonstrate that acoustic sound at certain frequencies and amplitudes can decrease the lifetime of the wetting film formed from pure water on the surface of a flat quartz substrate under various hydrophobicities and bubble sizes. The reduced lifetime was explained by faster liquid draining speed to reach the critical rupture thickness due to the pressure change in the presence of acoustic sound. The observed decreases in wetting film lifetime suggested enhanced bubble-particle interactions in the pulp phase, conducive to the improvement of flotation efficiency. Next, the dynamic foam/froth stability improvement under acoustic sound was investigated. The results illustrate that the use of acoustic sound with specific frequency and amplitude could increase the maximum foam/froth height (at steady state) and thus the dynamic froth stability at various experimental conditions, such as different reagent types and reagent concentration and superficial air velocity. Therefore, this result confirmed that the froth stabilization by acoustic sound would be important for understanding the observed improvement of flotation performance. Following the fundamental studies on wetting film stability and foam/froth stability, flotation tests with minerals in different flotation systems were conducted. Firstly, a semi-continuous flotation system with quartz particles incorporated with an underwater loudspeaker was used for the experiments. The loudspeaker was immersed in the pulp phase rather than in air above the flotation cell, so the noise level was substantially reduced. The tested parameters include feed volumetric flow rate, feed solid contents, reagent dosage and superficial air velocity. Results showed that by use of 350 - 400 Hz and a certain amplitude of acoustic sound would increase froth carry rate and mass recovery. Secondly, a series of batch mode experiments were completed in a mechanical flotation cell, and the results show that acoustic sound increased flotation recovery over a broad particle size range, especially a significant improvement for coarse particles was observed. In conclusion, fundamental studies of wetting film stability and dynamic foam/froth stability were investigated under acoustic sound. The results suggested that the acoustic sound could improve the bubble-particle interaction in the pulp phase and the froth stability in the froth phase. The acoustic sound could also increase froth carry rate in flotation and could improve flotation efficiency over a broad range of particle sizes, extending the upper limit of particle size for flotation. The present study provides a versatile method for improving the flotation performance at reduced reagent consumption and by utilizing existing flotation cells. Source: TROVE
  • Năm xuất bản: 2023
  • Ngôn ngữ: English
  • Nguồn: Trove Australian Thesis (Full Text Open Access)
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