Hydrodynamics of shallow fluidized bed of coarse particles

The aim of the present study is experimental investigation of hydrodynamics of shallow fluidized bed of coarse particles. Air was fluidizing fluid. γ-Al2O3 particles of 1 mm and 1.8 mm in diameter and density of 1080 kg m−3 (both Geldart D) were used. Experiments were carried out in a column with rectangular cross-section area of 100 mm × 100 mm, at temperatures of 20 °C and 500 °C. Measurements of absolute and differential pressure fluctuations were employed. Standard deviation and amplitude spectra analysis were used to determine fluidization regimes. In the range of superficial velocities 0-4.5 m s−1, three different regimes were found: single bubble regime, rapidly growing bubble regime and turbulent fluidization. General qualitative characteristics of those regimes regarding bed structure were ascertained. Transition velocities between regimes were experimentally determined and compared with literature correlations. A new correlation for prediction the velocity at the beginning of turbulent fluidization in the coarse particle systems was proposed as follows: Rec = 0.326Ar0.52.