- Title
- Identification, characterisation and modelling of dynamic adhesion for optimised transfer system design
- Creator
- Carr, Michael
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2019
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- The depletion of favourable bulk material deposits in relation to their handleability is prompting the industry to consider mining material that may have comparatively less favourable flow properties. Typically found beneath the water-table, less favourable bulk materials frequently exhibit an increased clay and moisture content, leading to Wet and Sticky Material (WSM) and problematic behaviours regarding handleability. WSMs can have a significant impact in the materials handling stream due to the expensive downtime of processing equipment, which is attributed to the complex inter-particle and boundary adhesion mechanisms found within the bulk material. To better understand the characteristics of WSMs, new theoretical models are required and consequently developed within the scope of this research. For the identification of a WSM, a comprehensive study was undertaken where revised testing methods have been developed to attain quantifiable measurements for the problematic characteristics of bulk materials. The wall adhesion and inter-particle adhesion tests were developed and adapted for iron ore from existing methods that are typically used for fine powders. These tests have been performed in conjunction with a sweep of traditional flow property tests which were conducted on three iron ore samples. The three iron ore samples have been supplied from the Pilbara region of Western Australia and include; Upper Channel Iron Deposit (UCID), Lower Channel Iron Deposit (LCID) and the Denatured Zone (found between the UCID and LCID layers). The threshold moisture content for problematic behaviours were identified, where, Denatured was identified as the most problematic in relation to the adhesive strength it exhibits. To further understand the adhesive properties of the iron ore samples, a revised methodology for the estimation of bulk material adhesion determined from the extrapolation of the Instantaneous Yield Locus (IYL) produced from Jenike direct shear testing was undertaken. The predicted adhesion values from this methodology are compared to experimental measurements using an inter-particle adhesion tester where good correlation was found. Once the adhesive properties of each iron ore sample were identified, a theoretical model was developed and validated experimentally to define the dynamic adhesion of the bulk material samples. The developed model was able to predict the geometrical constraints where the identification of the effective angle at which the shear failure equates to a zero-bond depth was found for three typical wall liners used in industry. Following the identification of the dynamic adhesion geometrical constraints, it was observed by the author that the natural agglomeration of the iron ore samples assisted in the flow of the material through transfer systems. Additionally, it was also observed that the formed agglomerates reduced the amount of dust generated during transportation. An investigation was undertaken on the effects of agglomeration on the materials handling sector where the benefits of reduced build-up and a reduction of dust generation was shown. It was found that for an equivalent Run-of-Mine (ROM) iron ore moisture content, there was a significant reduction for the amount of build-up that commonly leads to potential blockages in industry. The final aspect of the presented research is the utilisation of numerical simulations for the prediction of problematic behaviours found in industrial systems. The characteristics of WSMs can be computationally expensive to model and with the development of the Discrete Element Method (DEM) in conjunction with the advancement in computational power over the past decade, it is now more feasible to model WSMs in DEM simulations. Three cohesion models capable of replicating WSMs are investigated where the potential to replicate problematic bulk material behaviours and computational solve times are analysed. The models used include; the Simplified Johnson-Kendall-Roberts (SJKR) model, Easo Liquid Bridging model and the Edinburgh Elasto-Plastic Adhesion (EEPA) model. In this study, the coupling of the SJKR and Easo Liquid Bridging models is proposed and used to predict problematic bulk material behaviour. Additionally, a calibration procedure is developed and undertaken where the parameters for each cohesion model are discussed in detail. A series of calibration simulations with systematic parameter variation was undertaken to define a set of calibration matrices. The developed calibration matrices resulted in the selection of a unique parameter setting, which can be used for the simulation of on-site applications to optimise plant geometry and other operational parameters. Finally, numerical modelling validation was undertaken using a lab scale vertical impact testing facility where good correlation between experimental and simulation results was found.
- Subject
- handleability; cohesion; adhesion; instantaneous yield locus; unconfined yield strength
- Identifier
- http://hdl.handle.net/1959.13/1414050
- Identifier
- uon:36695
- Rights
- Copyright 2019 Michael Carr
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 21 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 322 KB | Adobe Acrobat PDF | View Details Download |