Characterisation of the multiphase fluid dynamics of the CoarseAIR™ fluidised bed flotation cell using the Large Modular Array (LaMA) for positron emission particle tracking (PEPT)

Fluidised bed flotation cells (FBFCs) present a compelling solution for coarse particle flotation, enabling an increase in the target particle size in comminution circuits, with the corresponding energy savings. Despite their potential and strong industrial interest, the three-phase fluid dynamics of large-scale FBFCs remain unexplored due to measurement complexities and size restrictions. This paper presents the first quantification of the fluid dynamics of the CoarseAir™-100, a 2 m tall laboratory-scale FBFC. Measurements were obtained using positron emission particle tracking (PEPT), a non-invasive technique that tracks the motion of a radiolabelled tracer. Leveraging the Large Modular Array (LaMA) PEPT system, consisting of 48 buckets, each housing four detector blocks, this study is the largest PEPT experiment to date. Particle tracks of hydrophobic and hydrophilic tracers were obtained under different fluidisation and airflow rates. Hydrophobic tracers exhibited buoyant behaviour despite their large size of up to 700 μm, while hydrophilic tracers engaged in recirculation patterns with rapid downward motion near the walls. The intricate motion of particles in the lamella plates was experimentally quantified, revealing an average path tortuosity of 7.3, providing essential information for design. These results represent a major advance in our understanding of fluidised bed flotation cells, contributing to the refinement of design and scale-up strategies for FBFCs.