Turbulence-driven microbubble hydrodynamics and collision mechanisms for enhanced fine coal flotation

Flotation of fine coal is often limited by low particle – bubble interaction. We quantify the hydrodynamics and kinetics of a Turbulent Microbubble Flotation Cell (TMFC) using computational fluid dynamics (CFD) coupled with a population balance model (PBM) and targeted experiments. In the TMFC, turbulent kinetic energy in the impeller region increases to 0.25 m2·s−2, while gas holdup rises to 60%. The Sauter mean bubble diameter stabilizes at d32 = 2.5–3.5 mm (Xiqi laboratory cell, XFD: 4.0 mm). A collision model indicates higher particle – bubble collision probability in the impeller – stator zone (TMFC maximum > 0.0025) than in the XFD (0.0009). Under matched operating conditions, the corrected flotation rate constant is markedly higher for the TMFC; at 1000 rpm, Km = 0.51 min−1 versus 0.04 min−1 for the XFD (12.8×). These quantitative results show that the TMFC sustains stronger turbulence, more uniform gas dispersion, and smaller, more stable bubbles, which together enhance interaction frequency and fine-particle recovery.