Ultrafine coal cleaning using spiral concentrators - ScienceDirectThe 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.spiral concentrator for coal,particle flow modelling on spiral concentrators - CSIRO CFDDec 8, 1999 . media for coal processing by increasing the fluid density above that of water. INTRODUCTION. The twisting open trough geometry of spiral concentrators is illustrated in Figure 1. Employed in the fine coal and heavy mineral processing industries, a slurry mix of fine. (75 - 3000 µm) particles and water is fed.