The most common scale‐up methodology for gas‐solid fluidized bed reactors that has been reported in the literature is based on matching the dimensionless groups. This scale‐up methodology in the literature has been validated by only measuring global hydrodynamic parameters (overall holdups and pressure drop, etc.) without details. Therefore, in this work, we have applied advanced non‐invasive measurement techniques, gamma‐ray computed tomography (CT) and radioactive particle tracking (RPT) techniques, for the first time to evaluate such scale‐up methodology by measuring local hydrodynamic parameters. The results obtained demonstrate that the reported set of the dimensionless groups are not adequate in capturing all the interplay phenomena for achieving similarity in the local hydrodynamic parameters when the proposed set of dimensionless groups has been matched using two sizes of fluidized beds of 0.14 m and 0.44 m and sets of operating conditions. This finding confirms that the local measurements of the hydrodynamic parameters are essential for detailed assessment of scale‐up methodologies.

Many invasive and non-invasive techniques have been used to analyze the hydrodynamics of fluidized beds. In this study, the effect of superficial gas velocity and bed particle density on the hydrodynamics of gas-solid fluidized beds was investigated by using a cylindrical plexiglas fluidized bed column, 14 cm in diameter. Air at room temperature was used as the fluidizing gas and two different Geldart type-B particles were used: glass beads and copper particles with material densities of 2.5 and 5.3 g/cm 3 , respectively, with the same size particle, 210 lm. To measure the time-averaged cross-sectional gas and solid holdup distribution, gamma ray computed tomography was used for the first time as a non-invasive technique instead of using X-rays (due to the height attenuation of the copper particles). The results show that gas holdup increases by increasing the superficial gas velocity, and decreasing the particle density increases the gas holdup in the bed.

The hydrodynamics observed in large‐scale gas‐solid fluidized bed reactors are different from those observed in smaller scale beds. In this study, the effect of bed diameter on the hydrodynamics of gas‐solid fluidized bed reactors has been investigated in two bubbling fluidized beds of 44 cm and 14 cm in diameter using an advanced non‐invasive radioactive particle tracking (RPT) technique. Compressed air at room temperature was used as the gas phase, and the solid was glass beads with a particle size of 210 μm (Geldart‐B) and density of 2.5 g · cm−3. Particle velocity field, Reynolds stresses, normal stresses, turbulent kinetic energy, and axial and radial eddy diffusivities were measured in two beds at gas velocities of 1.5 Umf, 2 Umf, and 3 Umf. Experimental results showed that the bed scales have a significant effect on some of these hydrodynamic parameters where the magnitude of solids velocity is much higher in the larger bed and the solids mixing and diffusion of particles are increased by increasing the column diameter.