Sustainable Recovery of Fine Coal Slime Through Particle Size Classification and Reflux Flotation Cell Technology

Guided by the objectives of sustainable coal utilization and resource efficiency improvement, this study investigated the recovery of fine, high-ash coal slime using a Reflux Flotation Cell (RFC). Particle size analysis showed that the −0.074 mm fraction accounted for approximately 33.3% of the feed and exhibited poor flotation performance in conventional classification flotation, resulting in substantial combustible matter losses. To improve the recovery of this fine fraction, flotation experiments were conducted using the RFC. Under the optimum operating conditions, combustible matter recovery of the −0.074 mm fraction reached 89.92%, approximately 10 percentage points higher than that achieved by conventional flotation. The improved performance enhances the utilization of low-grade coal resources while reducing combustible matter losses to tailings. The superior separation performance of the RFC is attributed to its unique hydrodynamic characteristics. High-shear flow in the downcomer generates abundant microbubbles and promotes particle–bubble collisions, whereas the inclined channels accelerate gangue settling through the Boycott effect, improving the separation efficiency of fine particles. These results demonstrate that the RFC provides an effective approach for the sustainable recovery of fine coal slime and offers theoretical support for improving resource utilization and reducing solid waste generation in coal preparation.