The effect of feed-coal particle size on the separating characteristics of a gas-solid fluidized

The separating performance of a pilot dry beneficiation system using a gas-solid fluidized bed was investigated with coal from South Africa. The coal used for the study has a low inherent moisture content, a moderate ash content, a moderate volatile content, a low sulphur content and a high calorific value. Its washability is moderate. Experimental results show that the separating quality of the fluidized bed drops gradually as the feedcoal particle size decreases. The probable error, E, values for 50-25 mm, 25-13 mm and 13-6 mm coals were 0.04 g/cm3, 0.06 g/cm3 and 0.09 g/cm3, respectively. The cause of the differences in separating characteristics was analysed by particle dynamics and numerical modelling. Furthermore, the pilot fluidized bed was employed to separate 50-6mm coal. In this experiment the coal ash content was reduced from 23.74% to 11.79%, with a probable error, E, value of 0.07 g/cm3 and a recovery efficiency of 98.26%. This indicates that the fluidized bed is applicable to the separation of coal from South Africa and has good separating performance and wide applicability. © The Southern African Institute of Mining and Metallurgy, 2010.