Analysis of the mechanism for bubble effect on the movement behavior of separation particle in gas–solid separation fluidized bed based on fluorescence tracing method

Gas-solid separation fluidized beds have attracted considerable attention for the separation of coal. However, during the separation of fine particles, the target particles tend to mix with the dense medium rather than undergo effective separation behavior. In this study, the influence of bubbles on particle motion and the mixing/separation behavior between particles and the dense medium was investigated using a novel fluorescent tracer method. Fluorescent tracer particles were developed by reacting fluorescein with epoxy resin and adding nano-zinc, which significantly improved both fluorescence intensity reducing the requirements for spatial and temporal resolution in the measurement process. Particle movement and bubble dynamics were analyzed through digital image analysis technology (DIAT). The results revealed that bubble-induced wake vortices exert an upward effect on particles, while the emulsion phase around the bubbles exerts a downward effect. A theoretical model describing the bubble effect on separation particles was constructed and validated, achieving prediction errors within 15%. Based on this bubble model, a revised separation density model for gas–solid separation fluidized bed was established to reflect the mixing/separation behavior of separation particles and dense medium, achieving prediction errors within 10%. For the effective separation of fine particles, creating dispersed or bubble-free fluidization regimes is critical.