Bubble and particle dynamics in a gas-solid fluidized-bed*

We experimentally investigate the dynamics of gas and solid phase (buoyancy-driven particle mixing) in two-dimensional fluidized-bed while varying the gas flux, which is measured by the combination of high-speed 2-phase PIV and PTV. To ensure the stage of fluidization, the pressure drop across the bed is also measured together. For the particle we use spherical glass bead (Geldart B-type, size: 500 μm, density: 2500 kg/m³), and the gas flux is varied from 3 to 9 m³/h. In the considered range, the fluidization regime covers from minimum- to fast-fluidization regimes with increasing the gas flux. It is found that solid-particles are globally carried upward at the core region but fall near the sidewalls, depending on the gas flux. On the other hand, the rising bubbles in the bed locally interfere with the particles, resulting in non-uniform fluidization (agglomeration, particle deceleration), which is exacerbated with increasing the gas flux. The statistical analysis on the bubble size in the bed shows that the equilibrium between bubble coalescence and break-up determines the maximum stable bubble size. The effect of different particle size on the bubble dynamics will be discussed additionally.