In order to efficiently clean fine coals, enhanced gravity separators, such as Knelson concentrator, have been developed. Although the Knelson concentrator has not been applied yet in industrial scale for fine coal cleaning, different investigations have been conducted in recent years. In this study, an oxidized coal with high sulphur was subjected to cleaning process by Knelson concentrator after being classified into the size fractions of -106 mu m, -300 + 106 mu m and -500 + 300 mu m. Experimental variables were coal particle size, bowl speed and fluidizing water pressure. Maximum combustible matter recovery, pyritic sulphur rejection, and ash rejection were achieved to be 99.13%, 91.60%, and 60.94%, respectively. The highest separation efficiency for the pyritic sulphur and ash was determined to be 67.91% and 39.53%, respectively. These corresponded to the removal of 70.45% of pyritic sulphur with combustible matter recovery of 97.46% and removal of 45.96% of the ash with combustible matter recovery of 93.57%. Coal particle size, bowl speed and fluidizing water pressure were determined to affect the separation performance with a close interaction between them. (C) 2012 Elsevier B.V. All rights reserved.