It is proposed that scaling of three-phase fluidized bed hydrodynamics can be
carried out based on geometric similarity and matching of a set of five dimensionless
groups: (i) the M-group, M=g-Δρ-μ[sub L]⁴/(ρ[sub L]²-σ³); (ii) an Eotvds number, Eo=g-Δρ-d[sub p]²/σ;
(iii) the liquid Reynolds number, Re[sub L] = ρ[sub L]-d[sub p]-U[sub L]/μ[sub L]; (iv) a density ratio, β[sub d]= ρ[sub p]/ ρ[sub L]; and (v)
a superficial velocity ratio, β[sub u]=U[sub g]/U[sub L]. These were varied in an experimental study
where four dimensionless hydrodynamic parameters were measured: (i) gas hold-up, ε[sub g];
(ii) bed expansion ratio, β[sub be]; (iii) the ratio of mean bubble diameter to particle diameter,
d[sub b]/d[sub p]; and (iv) the ratio of mean bubble rise velocity to gas superficial velocity, U[sub b]/U[sub g] .
This approach was validated experimentally by matching the dimensionless operating
conditions from a kerosene-nitrogen-ceramic three-phase system with those in an
aqueous magnesium sulphate solution-air-aluminum particle fluidized bed. There was
good agreement between the gas hold-ups and bed expansion ratios in the two systems.
A pilot-plant scale cold-flow co-current upwards-flowing three-phase fluidized
bed column of inside diameter 292 mm was built and operated using three different
liquids (tap water, an aqueous 44 mass % glycerol solution, and an aqueous 60 mass %
glycerol solution), air, and cylindrical aluminum particles of diameter 4 mm and length
10 mm. The fluids and solids were carefully selected to result in dimensionless group
values in the range of those of an industrial hydroprocessor. Specially built conductivity
probes and pressure transducers were used to measure the hydrodynamic properties for
different gas and liquid superficial velocities. Special attention was required to provide
for drift and calibration when recording and analyzing data from the conductivity probes.
Gas hold-ups were in the range of 5 to 20% by volume and were correlated as a function
of liquid-phase Reynolds number and superficial velocity ratio. The gas hold-ups were a
strong function of the velocity ratio with little influence of the liquid-phase Reynolds
number. Bed expansion, in the range of 0-200%, was similarly correlated. Although bed
expansion was dependent on the velocity ratio, the liquid Reynolds number had a much
more significant influence. Bubble rise velocities, pierced chord lengths, and frequencies
were also determined for a range of operating conditions
A new approach for estimating gas hold-up based on the gas-perturbed liquid
model, using calculated values of interstitial liquid velocity, was also developed. This
approach gave favorable agreement with gas hold-up measurements based on pressure
drops.Applied Science, Faculty ofChemical and Biological Engineering, Department ofGraduat
