Page 133 - Adsorption, Ion Exchange & Catalysis- 2007, Elsevier - Copy

Else_AIEC-INGLE_cH003.qxd 7/13/2006 1:45 PM Page 129
3.4 Slurry Reactors 129

where
p the particle density ,
n the number of solid particles,
m s the concentration of catalyst in the slurry gcatalyst/cm3liquid. ,
ed-beds.
Note that α is equialent to v α for fThe liquid–solid interfacial area per unit ix
c
u
volume of reactor is
a a h (3.219)
t c,to c L
Mass transfer coeficients: gas bubble to liquid (k f fg )
Normally, ethe major mass transfer resistance ubble phase is a gas mixture, v en when the b
for slightly soluble gases is in the gas–liquid interf the mass transfer coef Thus, ace. f icient
in the liquid film around the bubble is the important one in gas bubble-to-liquid mass trans-
fer (Smith, 1981; T 1980). ybal, re
In the absence of mechanical agitation and for bubbles with diameter less than 2.5 mm
(the usual size range for slurry reactors), the following correlation of Calderbank is a ail- v
able (Smith, 1981):

 23 
g  13
k fg  L  0.31  fg L  (3.220)
 L D fg   2 L 
where
the difference in density between liquid-phase and gas b g/cm ubbles, 3
fg
µ L the viscosity of liquid-phase, g/cm s
L the density of liquid-phase, g/cm 2
g the acceleration of gra cm/s , vity 2
k fg the masstransfer coef cm/s. f icient,
D fg the liquid-phase dificient of the gas solute, cm fusion coef f 2 /s
v
Although the aboe correlation was deeloped for a column with no solids present, it has
v
been applied with some success to slurry bubble columns. Another correlation, presented
by Hikita et al. (1981), which was deeloped under ambient conditions in the absence of v
solid particles and for 0.042 u sG 0.38 m/s (bubble column), is the following (Hikita
et al ., 1981; Behkish, 2004):

ka fg Gtot s,G u u 
 1.76 
4 g  0.248 

 0.243 
 0.604 (3.221)
L
,
14.9  sG L   L 3   G   L 
g 
L  
 
  D fg 
L
L
L
L
where u sG is the superficial gas velocity and α GL,tot the gas-liquid interfacial area per unit
volume of reactor, as defined in eq. (3.230).
Another equation is the Akita–Yoshida correlation deried for bubble column reactors v
(Shah et al., 1982; Ramachandran and Chaudhari, 1984):
2
D fg 
 0.5 gD   0.62 gD  3 
k 0.6 L  L L h 1.1 (3.222)
fg GL,tot 2   
   2  G
D D  fg  L 
L L 
L