Experimental investigation of multi-phase hydrodynamics and bubble-particle interactions in a Wemco 56 flotation cell

Performance of flotation cells heavily relies on their hydrodynamics inside cells and interactions among the solid, liquid and gas phases. The flotation process in conjunction with the bubble-particle interactions in three-phase flow were experimentally investigated in an industrial Wemco 56 cell. Various methods were developed to measure and analyse the flotation process, in which the velocity field of liquid phase was measured using Particle Image Velocimetry (PIV). Particle/Droplet Image Analysis (PDIA) technique was developed to capture and measure bubble sizes, while a conductivity-based probe system was designed to evaluate the mixing status of solid, liquid and gas phases. The flotation kinetics were found relatively inhomogeneous and anisotropic in most regions, while possible flow short-circuiting was identified near bottom corner of the tank. The bubble mix was found insufficient near the cell bottom, although void fractions near the bottom slightly increased after adding particles. The investigation revealed significant impacts of the solid phase, which stimulated bubble to breakup and reattach more actively and promoted bubbles to penetrate further downwards to the bottom. A solid deposition layer of 30 mm was observed near bottom of the Wemco 56 cell, which requires optimisation of draft tube and false bottom designs.