The Beneficiation of Fine Coal by a Combination of Three-Product Cyclone and Fine Screen

A novel classified gravity system, comprised of a three-product cyclone and a fine high-frequency screen, was developed and tested for recovery of fine coal. The three-product cyclone is characterized by the primary cylinder and a secondary cyclone. The effects of major parameters of the secondary cyclone, such as vortex finder diameter, vortex finder length, and spigot diameter, were investigated by single-factor experiments. Regression models of the yield and ash content of clean coal were developed with statistical design of experiments and showed good correlations of experimental results. The regression models indicated that the spigot diameter had the largest impact on the yield and ash content of clean coal. It also indicated that spigot diameter and vortex finder diameter jointly affect performances of the three-product cyclone. The cylinder played a significant role in desliming of the feed, giving the secondary cyclone a better gravity-separation condition. Ash reductions of +0.150 mm fractions were all above 70%, which showed that the cyclone had significant effects on fine coal separation in the classified gravity system.