- Title
- Beneficiation of dense minerals through agglomeration
- Creator
- Borrow, Daniel James
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2020
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- This study was concerned with using a high internal phase water-in-oil emulsion as a method to selectively agglomerate and recover naturally hydrophilic particles. In the past, research into the area of selective agglomeration has been based on the use of an organic liquid as a binder. In the previous research, the organic liquid, typically a pure oil, preferentially wets hydrophobic particles and forms an agglomerated product. However, the oil requirements, and subsequent cost, made the process economically unviable. More recently, the development of a high internal phase water-in-oil emulsion has shown the potential to drastically reduce the overall organic liquid requirements. As the organic liquid in the high internal phase emulsion preferentially wets hydrophobic particles, all previous research has related to the separation of coal and mineral particles, where coal, being naturally hydrophobic is selectively recovered from the hydrophilic mineral matter. In this work, new feeds were introduced to examine the emulsion binder’s ability to recover naturally hydrophilic particles for the first time. To begin, silica powders were used as a feed source. Initial experiments indicated that in order for the emulsion binder, or pure oil, to recover silica particles, a collector must be added to render the particle surface hydrophobic. At the optimum collector dosage, a 16-fold reduction in organic liquid requirements was found when the emulsion binder replaced pure oil as the binding liquid. A model was produced showing the organic liquid requirements increasing linearly with the specific surface area of the feed powder. Unlike flotation, there was no decrease in recovery of ultrafine particles. It was found that the binder contains highly permeable oil films, approximately 30 nm thick. Driven via osmosis, water can be transported between internal and external aqueous phases. Positive osmotic pressure gradients resulted in net water movement in to the emulsion binder, while a negative gradient showed water being released. The direction and intensity of water transport significantly affected the agglomeration performance, with a positive osmotic force resulting in decreased organic liquid requirements. The permeability of the oil films allows the enhanced recovery of ultrafine material as the hydrodynamic resistance of an approaching particle is eliminated. The results from this investigation found that water permeation was directly influenced by the initial oil film thickness inside the emulsion. Following the development of the silica model and emulsion/film characterisation, magnetite particles were used as a new feed source. Investigations into the stability of the emulsion binder were carried out, with hydrophilic material being found to degrade the emulsion binder while conditioned, and therefore hydrophobic, magnetite resulted in emulsion stabilisation. Furthermore, it was found that when correctly conditioned, both the magnetite and silica required the same organic liquid dosage on a surface area basis. This finding allows the developed model to be used in determining the required binder dosage based only on the specific surface area of the hydrophobic material. With the successful development of the agglomeration process, a final investigation was carried out to study the potential for a continuous operation. In this work coal was used as the feed source. It was found that a flow constriction, provided by either a partially closed ball valve or an orifice plate, will provide the high shear environment in which the agglomeration process takes place. The process was found to successfully operate at superficial slurry velocities as high as 4.2 m/s. Overall, the work in this study has resulted in a method to rapidly recover naturally hydrophilic particles using a high internal phase water-in-oil emulsion. The work has provided the groundwork for further developments around mineral beneficiation and ultrafine particle recovery.
- Subject
- agglomeration; hydrophobic; silica; water-in-oil emulsion; emulsion; permeable film; stabilization; ultrafine particles
- Identifier
- http://hdl.handle.net/1959.13/1410929
- Identifier
- uon:36257
- Rights
- Copyright 2020 Daniel James Borrow
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 11 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 669 KB | Adobe Acrobat PDF | View Details Download |