Mapping of Regimes
The Geldart Classification of Particles
Geldart came up with four clearly recognizable kinds of particle behavior. From smallest to largest particle, they are as follows:
Group C: cohesive, or very fine powders. Normal fluidization is extremely difficult for these solids because interparticle forces are greater than those resulting from the action of the gas.
Group A: aeratable, or materials having a small mean particle size and/or low particle density ( < ~ 1.4 g/cm3 ). These solids fluidize easily, with smooth fluidization at low gas velocities and controlled bubbling with small bubbles at higher gas velocities. FCC catalyst is representative of these solids.
Region A': Range of properties for well-behaved FCC catalyst; from Miyauchi et al.
Group B: sandlike, or most particles of size 40 μm < dp < 500 μm and density 1.4 < ps < 4 g/cm3. These solids fluidize well with vigorous bubbling action and bubbles that grow large.
Group D: spoutable, or large and/or dense particles. Deep beds of these solids are difficult to fluidize.
Region A', Miyauchi et al
Considering Squires’ criteria and observed industrial performance, Ikeda modified the criteria as shown in Table I
