(61d) Flow Regimes in Gas-Liquid-Solid Mini-Fluidized Beds with Single Gas Orifice

Flow regimes and their transitions in the gas-liquid-solid mini-fluidized beds (MFBs) with single gas orifice were studied experimentally in this paper. The diameter of the fluidized beds varied from 3mm to 5 mm and the bed height was 50 mm. The ranges of superficial gas and liquid velocity were 1.96×10^-4 - 4.73×10^-3 and 5×10^-6-4.2×10^-2 m/s, respectively. Half-fluidization, slug, dispersed bubble and transport flow regimes in the three-phase MFBs were identified by analyzing minimum fluidization velocity, pressure drop, and entrainment velocity of solid particles based on experimental data of pressure drop and fluidization velocity as well as flow observations. The effects of solid particle and liquid properties, bed and gas orifice sizes, and static bed height on the flow regimes and transitions were investigated. Results show that the behavior of gas bubbles and wall effect affect the flow regimes and transitions. Obvious wall effect increases minimum fluidization liquid velocity in the liquid-solid mini-fluidized beds, which increases the transition liquid velocity between the half-fluidization and slug flow regimes. Moreover, wall effect makes Taylor bubble bigger at lower superficial liquid velocities due to the bubble coalescence and the transition boundaries expand. Solid particles aggregation, wall effect and bubble wake behavior are responsible for reduction of the minimum entrainment velocity of solid particles. Flow regime maps of the gas-liquid-solid MFBs were presented. Correlations were suggested for the flow regime boundaries.