Study on the enhanced separation performance of refractory coal slime using a reflux flotation cell under high gas flux

Gas flux is a critical parameter governing fine mineral flotation performance. Unlike previous reflux flotation cell (RFC) studies based on ideal systems or froth wash water, this study investigated industrial raw coal slime. By regulating underflow discharge to control water recovery within 0.36–0.41, we revealed the enhancing mechanism of pure bubble dynamic kinetics while mitigating entrainment interference under high gas flux. Results show that within the gas flux range of 0.5–4.0 cm/s, the bubble surface area flux of the RFC reaches 46.88–282.35 s−1. At a gas flux of 1.0 cm/s, the RFC produces ash generally consistent with the traditional mechanical cell, but combustible recovery reaches 78.11%, 32.11 percentage points higher than the reference. Benefiting from bottom inclined plates in promoting phase separation, the system maintains effective separation at a gas flux of 3.0 cm/s, even after breaching the theoretical flooding threshold. Under experimental conditions, further increasing gas flux intensifies turbulence, offsetting the plates’ advantage and triggering a precipitous drop in combustible recovery to 54.54%. This research defines the hydrodynamic mechanisms and breakdown boundaries of the RFC, demonstrating its capability to operate beyond conventional hydrodynamic limits under the tested conditions.