Enhanced coarse coal slime separation in a gravity–flotation coupled separator with up-flow feeding and dual-concentrate

A gravity – flotation coupled separator with up-flow feeding and dual-concentrate was developed to improve the recovery and selectivity in coarse coal slime separation. The separator combines flotation, cyclone separation, and gravity sedimentation. The optimal separation performance was achieved under the following conditions: slurry concentration = 100 g/L, feed flow rate = 4.411 m3/h, circulating rate = 3.125 m3/h, fifigfeeding air flow rate = 2 m3/h, frother dosage = 150 g/t and collector dosage = 1500 g/t. Two concentrates were obtained with ash contents of 7.48% and 11.56%. The partition coefficients of the 0.75–1 and 0.5–0.75 mm fractions were 88.42% and 95.92%, respectively, indicating the satisfactory recovery of coarse particles. The ash content in the tailings was 66.08%, indicating good selectivity. The diverging flow under the froth layer produced a coarse concentrate, which improved the recovery of the concentrate and reduced the flotation concentrate ash content. The total recovery of the concentrate blended with the + 0.25 mm fraction of diverging flow was 84.00%. Both up-flow and cyclone separation are beneficial for coarse particle recovery. The static separation cone is instrumental in improving the separation effect. Therefore, this wide-sized coal-slime separator facilitates the effective separation of both coarse and fine particles.