Impact of the Fluidized Bed Flotation Hydrodynamics on Bubble Interfacial Film Rupture and Coalescence

Fluidized bed flotation devices, such as the Eriez HydroFloat®, were specifically developed for efficient coarse particle recovery. The low-turbulence environment in fluidized bed flotation minimizes particle detachment and enhances coarse particle recovery. The hydrodynamic environment of fluidized bed flotation represents a significant departure from that of conventional mechanical flotation cells. In this environment, bubble size and bubble coalescence are substantially affected. Larger bubbles are necessary to improve buoyancy for heavier particles, and bubble-to-bubble collision rates are considerably reduced under quiescent conditions. This work aims to understand coalescence mechanisms and how frother dosage and type influence them within the novel hydrodynamic environment created by fluidized bed flotation. To establish the practical relationship between process chemistry and hydrodynamics, we examine bubble size as a function of coalescence, which is influenced by fluidized bed hydrodynamic parameters (such as airflow) and chemical parameters (such as frother concentration and type). Results indicate that fluidized bed flotation follows trends previously established for conventional flotation. However, significantly higher frother dosages are required to achieve the critical coalescence concentration (CCC) in a fluidized bed environment. Additionally, unlike in conventional flotation, superficial gas velocity (Jg) has a weaker impact on CCC. This study proposes a new methodology and model for numerically determining the CCC, offering a more accurate and objective estimation than conventional visual approximation methods. The detailed methodology presented in this paper has been applied to evaluate CCC across all conducted tests.