Hydrodynamic study of gas–liquid-solid mini-fluidization based on fluorescence PIV.

• Gas-liquid–solid flow fields in mini-fluidized bed were studied by Fluorescence PIV. • Bubbles rise as straight line and S-shaped spiral trajectory in mini-fluidized bed. • Superficial gas velocity has a greater influence on bubble radial movement. • Divergence and vorticity of the liquid flow field were analyzed. • Particle's radial motion is caused by entraining of bubble vortex and surface force. The fluorescence-based tracer particle image velocimetry (fluorescence PIV) was used to obtain the flow regimes transition, bubble size and velocity, liquid and particle flow field characteristics of the 1 ∼ 3 mm GLSMFBs and 93 ∼ 195 μm glass beads. When the bed-to-particle diameter ratio increased, the bubble size and velocity distribution tended to be more concentrated. Bubble rose as straight line and S-shaped spiral trajectory. The divergence and vorticity of the flow field were preliminarily quantified. There showed a close relationship between the macroscopic hydromechanical behaviors such as bubble size and velocity and the mesoscopic behaviors such as the movement and development of vortices. The upward drag force of liquid and bubble on particles mainly affected the particle axial velocity, while the particle radial motion was mainly caused by bubble wake and surface force among particles. The results provide theoretical reference for the design and optimization of GLSMFB reactors. [ABSTRACT FROM AUTHOR]