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Journal of the Southern African Institute of Mining and Metallurgy

On-line version ISSN 2411-9717
Print version ISSN 0038-223X

J. S. Afr. Inst. Min. Metall. vol.108 n.12 Johannesburg Dec. 2008




The effect of thermal drying on the mechanical strength of South African coals



M. Le Roux

School of Chemical and Minerals Engineering, North-West University, South Africa




The dewatering of coal, and particularly fine coal, continues to challenge coal prepatration engineers to find a cost-effective solution. With known world oil reserves being depleted daily, it is envisaged that the future price of coal may justify the use of thermal drying to achieve lower coal product moisture levels. The effect of exposure of the coal to elevated toemperatures on the mechanical strength of the coal was investigated. It was found that temperature does not play a major role in determining the volume breakage of a particle and that other variables such as orientation during impact has a much greater influence.
A double breakage mechanism was reported during the grindability tests. Surface, as well as volume breakage, occurs for the first 4 minutes while only surface breakage takes place thereafter. Due to this double breakage action, it was found that exposure to temperature does play a role in the amount of breakage and breakage rates during grindability tests. It was also concluded that a particle will break to an optimum size due to impact, after which only its surface will grind away as it is subjected to breakage forces.



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1. TAO, D., GROPPO, J.G. and PAREKH, B.K. Enhanced ultrafine coal dewatering using flocculation filtration processes. Minerals Engineering, vol. 13, no. 2, 2000 . pp. 163-171.         [ Links ]

2. ANDERSON, C.M., DEWALL, R.A., MUSICH, M.A. and RICHTER, J.J. Reducing the moisture in low-rank coals: The stability issues. Conference Article. ASME: New York. 1994. pp. 375-391.         [ Links ]

3. JLANHUI, H., MIGHOU, X., DUNXI, Y. and YUN, Y. Fragmentation by coal particles by thermal stresses during combustion. Journal of Huazhong University of Science and Technology. vol. 32, no. 5, 2004. pp. 78-80.         [ Links ]

4. RONG, R.X. Advances in coal preparation technology, vol. 2: Literature review on fine coal and tailings dewatering. JKMRC report on AMIRA Project P239C, University of Queensland. 1993. p. 30.         [ Links ]

5. FALCON, R.M.S. and SNYMAN, C.P. An introduction to coal petrography: Atlas of petrographic constituents in the bituminous coals of South Africa. Geological Society of South Africa. Johannesburg. 1986. p. 39.         [ Links ]

6. ESTERLÉ, J.S., KOLATSCHEK, Y. and O'BRIEN, G. Relationship between in situ coal stratigraphy and particle size and composition after breakage in bituminous coals. International Journal of Coal. vol. 49, nos. 2-3, 2002. pp. 195-214.         [ Links ]

7. SAHOO, R. and ROACH, D. Quantification of the lump coal breakage during handling operation at the Gladstone port. Chemical Engineering and Processing, vol. 44, no. 7, 2005. pp. 797-804.         [ Links ]

8. JEFFREY, L. Characterisation of the coal fields of South Africa. Colloquium on sustainability of coal. SAIMM, Sep 2004.         [ Links ]

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