Abstract
Experimental and modelling investigations of the hydrodynamics of the internal flow structure in the circulating particulate bed electrode (CPBE) are reported. The CPBE, a hybrid between an expanded packed bed and an entrained/fluidized bed, is particularly well suited for many electrochemical applications such as metal recovery and pollution treatments for metal containing effluents. This study deals with the fundamental hydrodynamics and particle dynamics of the CPBE. A mathematical model of the CPBE has been developed which successfully describes the motion of the particles and the fluid in the bed. It is shown that many of the flow characteristics of the circulating bed can be predicted using fundamental data. The validity of the proposed model was demonstrated by comparing predictions to experimental observations of several bed characteristics under various operating conditions.
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Abbreviations
- A :
-
cross-sectional area of the cell (m2)
- d p :
-
mean particle diameter (m)
- C D :
-
experimentally determined constant calculated by Haider and Levenspiel [26]
- C :
-
proportional constant in Equation 15
- CR :
-
circulation rate of solids (m3 s−1)
- D :
-
hydraulic diameter of the vessel (m)
- g :
-
gravitational constant (kg m s−2)
- G :
-
flow rate (kg s−1)
- H D :
-
height of the particles inside the descending layer (m)
- H R :
-
height of the particles inside the rising layer (m)
- L :
-
length (m)
- n :
-
Richardson and Zaki index (−)
- ΔP :
-
pressure drop (N m−2)
- Q :
-
inlet liquid flow rate (m3 s−1)
- R :
-
reaction force between the descending layer and the cell wall (kg m-¨)
- T :
-
total bed thickness (m)
- t D :
-
descending layer thickness
- t R :
-
rising layer thickness tan θ coefficient of friction (−)
- U l :
-
superficial liquid velocity (m s−1)
- U i :
-
a function of terminal velocity (equation 3) (m s−1)
- U t :
-
particle terminal velocity (m s−1)
- V :
-
interstitial velocity or actual velocity (m s−1)
- V 1 :
-
slip velocity in the rising layer (m s−1)
- V 2 :
-
slip velocity in the descending layer (m s−1)
- W :
-
width of the bed (m)
- ε:
-
bed voidage (the fraction of the total volume which is made up of the free space between the particles and is filled with fluid) (−)
- εI :
-
packed bed voidage before bed expansion (−)
- θ:
-
tilt angle (radians or degrees)
- ϱs :
-
solid density (kg m−3)
- ϱf :
-
fluid density (kg m−3)
- µfPf:
-
solution viscosity (kg m s−1)
- θs :
-
particle sphericity (−) Subscripts
- D:
-
descending layer
- L(f):
-
liquid (fluid) component
- R:
-
rising layer
- S:
-
solid component
- L:
-
liquid component
- T:
-
total depth of the bed
- P:
-
particles
- t:
-
terminal
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Dweik, B.M., Liu, C.C. & Savinell, R.F. Hydrodynamic modelling of the liquid-solid behaviour of the circulating particulate bed electrode. J Appl Electrochem 26, 1093–1102 (1996). https://doi.org/10.1007/BF00243733
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DOI: https://doi.org/10.1007/BF00243733