Abstract

CHAGWEDERA, K.M.; BADA, S.O.  and  FALCON, R.M.S.. Evaluation of alternative solid media for coal beneficiation using an air dense-medium fluidized bed. J. S. Afr. Inst. Min. Metall. [online]. 2018, vol.118, n.8, pp.883-890. ISSN 2411-9717.  http://dx.doi.org/10.17159/2411-9717/2018/v118n8a12.

A study was carried out to identify alternative dense media with potential for use in coal beneficiation in South Africa. Magnetite, pyrrhotite, silica sand, granulated blast furnace slag, and coal discards were tested. Magnetite and pyrrhotite provided the most uniform and stable bed densities, with bed density variation less than 0.7% and standard deviation less than 0.0025 g/cm³. A 100% magnetite bed yielded a product with an ash content of about 20.30% and calorific value of about 25.24 MJ/kg from a feed coal of size fraction -13 +6 mm and ash content of 39.27%. A cleaner coal product containg about 14.50% ash and with calorific value of 27.30 MJ/kg was obtained from a bed of pyrrhotite and magnetite blend at a weight ratio of 40:60. The same blend reduced the total sulphur content from 2.49% in the feed coal to about 0.41% at a cut density of 1.63 g/cm3 at a probable error (Ep) of 0.083. The beneficiation of coal in a pure magnetite bed was not as effective as with the pyrrhotite-magnetite mixed bed.

Keywords : air separation; dense medium; fluidized bed; separation efficiency; bed stability.

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