Ultrafine coal cleaning using spiral concentrators

The conventional circuit fine coal circuit typically incorporates spiral concentrators to treat nominal 1 × 0.15 mm 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 μm. 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 ash-forming minerals and 48% of the sulfur was rejected from the 210 × 44 μm size fraction of a given coal source.