Application of dense-medium in an enhanced gravity separator for fine coal cleaning

Dense-medium separators have proven to be the most efficient processes for removing the undesirable gangue material from run-of-mine coal. The application of high-pressure feed injection into dense-medium cyclones to provide an elevated centrifugal force has recently been found to allow efficient separation performances for the treatment of fine coal (i.e., < 1000 mu m). However, high-pressure injection requires specialized pumps and results in relatively high maintenance requirements. A test program has been conducted to evaluate the potential cleaning of 1000 x 44 mu m fine coal using dense-medium in an enhanced gravity separator (EGS), which mechanically generates an enhanced gravity field. Test results indicate that the use of dense-medium in an EGS resulted in an 8% weight unit increase in mass yield compared to the use of water-only for the treatment of an easy-to-clean Illinois No. 6 fine coal sample. For a difficult-to-clean coal, the mass yield improvement was significantly greater at nearly 20% by weight. From the treatment of four different coal samples, organic efficiency values greater than 90% were obtained over the entire range of product quality values. These findings are reflective of the highly efficiency, low density separations provided by the dense-medium as indicated by probable error values below 0.05. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.