- Title
- Hydrodynamic fractionation of particles using inclined channels
- Creator
- Hunter, David
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2018
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Density‐based washability analysis is an important tool for determining how easily a given coal or mineral feed can be beneficiated, and also for analysing how well a separation unit is operating. However, the existing industry standard float‐sink method for measuring washability has serious limitations. The heavy liquids used are hazardous to operators, and the maximum upper densities are too low to be useful for most dense minerals. Hence the aim of this thesis was to develop a water‐based fractionation technique that could provide density‐based washability and partition data across a broad range of densities, covering both coal and iron ore. The challenge using water‐based fractionation methods is that particles settling in a fluid have a settling velocity dependent on both their size and density, rather than density alone. However, previous research has shown that when there is laminar flow in an inclined channel, the dependency of elutriation velocity on size is greatly diminished as the particles experience a local fluid velocity that is roughly proportional to their size. Hence, this thesis has investigated the use of a set of parallel inclined channels mounted above a fluidised bed (a REFLUX™ Classifier) to perform density‐based batch fractionation. Samples were fluidised at successively higher flowrates to fractionate them into flow samples of progressively high density particles. These samples were then analysed to determine their density, grade or ash content, providing the data necessary for washability and partition analysis. Initial work focussed on coal, building on previous work that showed water‐based fractionation gave excellent agreement with float‐sink yield‐ash curves for the size range ‐ 0.25 +0.038 mm. The effective maximum size was extended up to 16 mm by using aqueous glycerol solutions to lower the required flowrates and help preserve laminar flow conditions. Agreement with the float‐sink curve was within 1 %. When applied to feed, product and reject samples in the 0.25 to 1.4 mm size range, the partition curve could be established within 2 % RSMEs of the float‐sink determined partition curve. The focus then shifted to higher density iron ore in the size range 0.038 mm to 2.0 mm. After exploring a wide a range of methods, two different approaches for obtaining the washability and partition data were investigated in more detail. The first approach used a combination of flowrate measurements, laser particle sizing and water‐based pycnometry measurements in combination with theory to calculate the particle density distribution from the hydrodynamics of the system. The second proposed that due to the relationship between density and grade, density‐based fractionation could be thought of as grade‐based fractionation. Hence, grade‐based partition curves could be produced from assay data on fractionation samples. Furthermore, it was recognised that the washabilities of a feed, product and tailings (reject) stream from a continuous separation are all mathematically linked by a single partition curve. A two‐parameter partition curve was assumed, and an algorithm was developed which uses a least‐squares error mass balancing approach to produce a partition curve and consistent set of three washabilities that best match the experimental data. A difficulty with developing a density‐based fractionation technique for high density minerals is the lack of any benchmark method for validation. Hence, batch fractionations were simulated on a model set of feed, product and tailings distributions linked by a known partition curve. The algorithm was then applied to these simulated fractionation samples to recover the washability and partition curves. The results showed that determination of the ρ₅₀ was quite robust regardless of the EpB of the fractionator. However, the determined Ep value had an error that depended on the EpB of the fractionator. Provided the EpB of the fractionator was below 0.4 g/cm³, the Ep of the separation was able to be determined quite accurately, giving partition curves having an RSME of less than 4.26 wt.% relative to the true curve. Hence, provided the fractionator is sufficiently accurate, the fractionation algorithm provides excellent agreement with both the partition and washability curves. In summary, this body of work has led to the establishment of a validated method for producing accurate washability and partition data for low density coal. A technique was also developed for density‐based fractionation of high density minerals, but conclusive validation was not achieved. Simulated results suggest that this technique could provide washability and partition data with a similar degree of accuracy as for coal. However, it is recommended that further research be conducted in order to confirm the simulated results. Ideally what is needed is a feed consisting of a mixture of model particles of different densities which are able to be easily analysed to determine their relative amounts in the product and reject samples.
- Subject
- fractionation; REFLUX Classifier; density; mineral; beneficiation
- Identifier
- http://hdl.handle.net/1959.13/1391000
- Identifier
- uon:33152
- Rights
- Copyright 2018 David Hunter
- 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 | 610 KB | Adobe Acrobat PDF | View Details Download |