- Title
- Hydrophobic-hydrophilic particle separation in a REFLUX™ flotation cell
- Creator
- Parkes, Siân Molly
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2024
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Flotation is employed industrially to recover and concentrate valuable minerals. As demand for these valuable minerals continues to surge, research into more efficient flotation technologies to enhance recovery and grade is crucial. For this research, two laboratory-scale flotation technologies, a REFLUX™ Flotation Cell (RFC™) and a mechanical cell, were used and operated in a continuous and batch configuration, respectively. The mechanical cell was used as a benchmark against which the performance of the RFC™ could be compared. The mechanical cell is well understood and readily available in most mineral processing laboratories. Rather than develop technology-specific models and hence scale-up relationships, a more generic performance ratio was developed, to assess any flotation technology, regardless of its size or configuration, to be compared and quantified against another. The basis of this comparison was the product flux that emerged from the upper surface of the flotation cell per unit of the feed concentration. The assessment was based on a wide range of feed suspensions sourced from a relatively pure chalcopyrite ore, deemed hydrophobic, and silica, deemed hydrophilic. The composition of the feeds applied in the assessment were varied significantly. The work was also extended to more applied chalcopyrite ores obtained from the industry. The performance measure showed the RFC™ outperformed the batch mechanical cell in recovering hydrophobic particles, particularly at lower solids concentrations, while strongly rejecting the hydrophilic particles. This performance was attributed to the hydrodynamics in the RFC™, especially the strong bubble-particle kinetics in the downcomer, and the counter-current washing applied to the rising bubbles in reducing the entrainment of the hydrophilic particles. From this work emerged the importance of reporting the selectivity alongside the performance measure. The selectivity measure used was based on the incremental recovery of the hydrophobic particles relative to the incremental recovery of the hydrophilic particles (Galvin et al., 1992). These measures were considered as a function of the particle size, and overall. The influence of the feed composition was explored using model hydrophobic and hydrophilic feed components of relatively pure chalcopyrite and silica, with the cell hydrodynamics fixed, and the overall solids concentration, or pulp density, at a very low level of 1 wt.% solids. The hydrophilic to hydrophobic feed mass ratio was varied from 1:1 up to 80:1. Regardless of the feed composition, the rate constants of the hydrophobic particles increased with particle size while the inferred rate constants of the hydrophilic particles decreased with particle size, covering 1 to 100 μm. Interestingly, the recoveries of the hydrophobic particles below 10 μm were reasonably constant for a given feed composition. The recoveries of the hydrophilic particles were similarly constant over the same size range. The work also showed the level of hydrophilic particle entrainment declined significantly with increasing wash water. Regardless of the mechanism, there was clear evidence the ultrafine hydrophilic silica hindered the adhesion kinetics of the hydrophobic chalcopyrite particles, leading to an apparent convergence in the hydrophobic and hydrophilic rate constants at a large hydrophilic to hydrophobic mass ratio. Conversely, the rate constants diverged as the hydrophobicity increased. This variation with the feed composition is contrary to first order kinetics, so warrants further investigation. The feed solids concentration, feed flux and gas flux were also systematically varied to investigate the impact on cell performance and selective mineral recovery. While the impacts were feed-specific due to the complexities of feed composition, mineralogy and chemistry, clear trends emerged. Hydrophobic particle recoveries increased with increasing particle size while hydrophilic particle recoveries remained low or began to decrease with increasing particle size. As the feed solids concentration was lowered from 27 to 0.05 wt.% solids, the recovery of hydrophobic particles increased while the recovery of hydrophilic material decreased. This led to increased performance ratios for the RFC™ of over 20-fold compared to the mechanical cell. A similar trend for hydrophobic particle recovery was observed as the feed flux decreased from 3 to 0.5 cm/s. However, for an industrial feed, the exceedingly low hydrophilic recoveries obtained at higher feed fluxes led to performance ratios of up to 40 for the overall feed and exceeded 100-fold at specific particle sizes. In general, a 1:1 gas to feed flux ratio was found to be optimal for hydrophobic particle recovery in the RFC™. However, higher gas to feed flux ratios enhanced the recovery of hydrophobic particles larger than 20 μm for certain feeds. The impact on hydrophilic particle recovery was less clear and varied depending on the ore type.
- Subject
- hydrophobic-hydrophilic particle separation; REFLUX™ flotation cell; valuable minerals; flotation
- Identifier
- http://hdl.handle.net/1959.13/1511320
- Identifier
- uon:56484
- Rights
- Copyright 2024 Siân Molly Parkes
- Language
- eng
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 16 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 478 KB | Adobe Acrobat PDF | View Details Download |