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Discrete element modelling to predict the behavior of coal particles during flow
Dissertation (MEng (Metallurgical Engineering))--University of Pretoria, 2015.
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2026
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| _version_ | 1867613516972687360 |
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| access_status_str | Open Access |
| author2 | u28213867@tuks.co.za |
| author_browse | u28213867@tuks.co.za |
| author_facet | u28213867@tuks.co.za |
| collection | Thesis |
| description | Dissertation (MEng (Metallurgical Engineering))--University of Pretoria, 2015. |
| format | Thesis |
| id | oai:repository.up.ac.za:2263/110143 |
| institution | University of Pretoria (South Africa) |
| language | English |
| last_indexed | 2026-06-10T12:37:24.077Z |
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| provenance_str_mv | Harvested via OAI-PMH from UPSpace — University of Pretoria Institutional Repository |
| publishDate | 2026 |
| publishDateRange | 2026 |
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| source_str | UPSpace — University of Pretoria Institutional Repository |
| spelling | oai:repository.up.ac.za:2263/110143 Discrete element modelling to predict the behavior of coal particles during flow u28213867@tuks.co.za Blignaut, L. DEM Modelling Particle flow Dissertation (MEng (Metallurgical Engineering))--University of Pretoria, 2015. Coal used for power generation has to adhere to an additional requirement of being able to pass through chutes, transfer points, hoppers and other handling systems with little or no difficulty, so as to ensure efficient transportation thereof through processing until delivery. However, this is not observed when coal fines are considered. Various handling difficulties, such as irregular flow and decreased flow capacities, occur as a result of the formation of dead zones, piping and arching. The increasingly current need to focus more on fine processing has also increased the need for understanding fines handling. The true behaviour of a material during handling can only be understood by means of experience or by evaluating the handling performance, which requires extensive financial resources as well as time. However, if a discrete element model is readily available with which the handling performance can be assessed easily and quickly, it would result in improved plant operations as well as aid in hopper and chute design. This project investigates the use of discrete element modelling as a tool to assess the degree of handling or handleability of two South African coals. In this work experimental determinations are compared to that of the numerical discrete element model in order to fine tune the model to accurately simulate the flow behaviour of these coal fines. The importance of material characterisation prior to the set-up of such a numerical model is also investigated. In literature these material properties are manipulated to simulate real material behaviour and rarely experimentally determined. In this investigation the effects of pressure, aeration and oxidation within the hopper is not considered as it involves the initial basic evaluation of using discrete element modelling as a tool to assess the degree of handling of coal fines. Therefore the tests are only conducted on laboratory scale testing. Proper material characterization for the use in numerical modelling was conducted for the Landau colliery coal and the Leeuwpan colliery coal in the duff size fraction (-8 mm +1 mm). The material properties such as the coefficient of static friction, coefficient of rolling friction and coefficient of restitution were determined for various conditions that are of importance in each ii case, for instance the influence of size and shape as well as moisture content. These experimentally determined properties were then used as inputs into the numerical model as opposed to other work where these properties are manipulated to evaluate the importance of material characterization in the validation of the numerical models. Material characterization work revealed some insight regarding the bulk density, coefficient of static friction, coefficient of rolling friction, coefficient of restitution and the angle of repose measured. The bulk density showed a decrease with decreasing particle size, which opposes that found by Moore (1988) on Australian coals with lower ash contents than the South African coals investigated by this work. The coefficient of static friction increased with a decrease in particle size, with the Landau coal delivering a larger coefficient of static friction than the Leeuwpan coal for the finer fractions investigated. The coefficient of rolling friction increased with increasing size fractions larger than 4.8 mm, therefore more work on size fractions below 4.8 mm is necessary to endorse this relationship. Leeuwpan fractions had larger coefficient of rolling friction than the Landau coal, which is due to the varying ash contents of these coals. The coefficient of restitution values (coal on coal interaction) obtained for Landau coal was larger than that for Leeuwpan coal for all sizes, fractions and shapes investigated, which implies that the varying ash contents of these coals cause different flow behaviour. The coefficient of restitution for coal on coal interactions delivered larger values than for the coal on steel interaction, which emphasizes the importance of the wall material in flow behaviours experienced. The angle of repose increased with an increase in the added moisture content of both coals for all the size fractions investigated, which supports that moisture content worsens the degree of handling of a coal as in accordance to the work by Brown and Miles (2004). Upon comparison between the numerical model and the experimental tests, an accuracy of 95 percent was achieved, which is much more significant than previously obtained, according to Grima (2011). Furthermore, as the hopper was being filled, segregation of particles was clearly observed within the hopper. Segregation is known to occur as bins and hoppers are filled and just as readily on discharge from the bins or hoppers, but this has not been visually experienced for real world scenarios as is the case with filling of the hopper of this numerical model. iii It is concluded from this work that discrete element modelling can indeed be used as an effective tool to assess the handleability of various coals as shown by the results obtained from the two South African coals with varying ash contents. The numerical model was properly validated by simple experimental tests, as well as material characterization tests such as the determination of the coefficient of static friction, coefficient of rolling friction and coefficient of restitution. The errors found between the numerical and experimental work were reduced to less than 5 percent. Discrete element modelling is further deemed as very useful in providing additional information, such as visually revealing the effects of segregation within a hopper. Materials Science and Metallurgical Engineering MEng (Metallurgical Engineering) 2026-05-15T17:26:26Z 2026-05-15T17:26:26Z 15/09/21 2015 Dissertation http://hdl.handle.net/2263/110143 en application/pdf |
| spellingShingle | DEM Modelling Particle flow Discrete element modelling to predict the behavior of coal particles during flow |
| title | Discrete element modelling to predict the behavior of coal particles during flow |
| title_full | Discrete element modelling to predict the behavior of coal particles during flow |
| title_fullStr | Discrete element modelling to predict the behavior of coal particles during flow |
| title_full_unstemmed | Discrete element modelling to predict the behavior of coal particles during flow |
| title_short | Discrete element modelling to predict the behavior of coal particles during flow |
| title_sort | discrete element modelling to predict the behavior of coal particles during flow |
| topic | DEM Modelling Particle flow |
| url | http://hdl.handle.net/2263/110143 |