The conventional circuit fine coal circuit typically incorporates spiral concentrators to treat nominal I x 0.15 rum material. Pilot and in-plant studies have been performed to determine the operating parameter values needed to achieve optimum separation performances when extending the lower limit of a conventional spiral concentrator to 44 mu m. Based on experimental and empirical data, a feed solids concentration of about 12% by weight is required with a feed rate of around 60 l/min per start. Under these conditions, 60%, of the ashforming minerals and 48% of the sulfur was rejected from the 2 10 x 44 mu m size fraction of a given coal source. (c) 2007 Elsevier Ltd. All rights reserved.