Resumo

MOHANTA, S.; SAHOO, B.; BEHERA, I.D.  e  PRADHAN, S.. Effect of crushing on near-gravity material distribution in different size fractions of an Indian non-coking coal. J. S. Afr. Inst. Min. Metall. [online]. 2016, vol.116, n.2, pp.209-213. ISSN 2411-9717.  http://dx.doi.org/10.17159/2411-9717/2016/v116n2a12.

Run-of-mine coal contains particles of different sizes with different specific gravities, and when this coal is crushed, the amount of material present in a particular density class changes. This alters the washability characteristics of the coal, which affects the quantity, quality, and separation efficiency of the gravity-based coal washing process. The degree of difficulty in washing a typical coal at a particular specific gravity depends mostly on the amount of material occurring within ±0.1 specific gravity range, which is known as 'near-gravity material' at that particular specific gravity of separation. In this paper, two numerical indices, namely 'near-gravity material index' and 'index of washability', are used to quantify the distribution of near-gravity material in different density classes and to evaluate the degree of difficulty involved in the washing process. The results of this preliminary investigation indicate the uniform distribution of near-gravity material in all density classes for finer size fractions, whereas for coarser size fractions more near-gravity material is present in the lower density classes, making the washing process more difficult at a lower specific gravity of separation.

Palavras-chave : coal; coal cleaning; near-gravity material; index of washability.

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