The objective of this work was to investigate the behaviour of malleable metals in tumbling mills. Much of the work focused on lead: shots, flattened shots and fragments were ground in three different laboratory mills. Testwork with fragments was repeated in the presence of a brittle and harder mineral phase (95% silica, 5% lead) and for copper (100% copper). The transfer of particles across size classes and the loss of weight because of smearing on the mill shell and grinding media were measured. Microhardness tests confirmed that lead did not work-harden during grinding. / The transfer across size classes was modelled with various first order differential equations describing flattening, folding, cold-welding and actual breakage. Model parameters were estimated using a least-square minimization criterion. When more than one model was fitted to a given data set, the one whose phenomenological basis was closest to the dominant transfer mechanisms observed almost always yielded the best data fit. The dominant mechanism was very dependent on the type of metal ground, its particle size and shape, the grinding intensity generated by the tumbling mill and the presence of a hard, brittle phase. Flattening, responsible for the transfer to coarser size classes, generally dominated over folding, the mechanism accountable for the transfer to finer size classes (other than breakage). Breakage was favoured over flattening and folding when grinding finer and softer particles,in a high impact environment, or in the presence of a hard, brittle mineral phase. Loss of weight due to smearing significantly increased when grinding a softer mineral in a mill with a rough inner shell, or when particle breakage took place. / A methodology based on the Laboratory Knelson Concentrator was developed and tested to estimate the breakage function and gravity recoverability of gold flakes. Progeny from the breakage of gold particles was shown to be highly gravity recoverable, more than 90% above 0.025 mm. The breakage function was non-normalizable, with a large b$ sb{ rm i+1,i}$ component, because of folding.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.40217 |
| Date | January 1996 |
| Creators | Noaparast, Mohammad |
| Contributors | Laplante, Andre R. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Mining and Metallurgical Engineering.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001498926, proquestno: NN12451, Theses scanned by UMI/ProQuest. |
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