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176 3. Heterogeneous Processes and Reactor Analysis

where
1H
K A o
1 1 1 (3.387)

Ka ( ) k a ( ) k C
LG A f u A b m BS
L
and
( R ) C o (3.388)
K
B B BL
where:
1
o
K
B
1 1 (3.389)

k C
ka ( )
fu B b m AS
ed b eactor s Material balances for pacubble bed r k
In general, the material balances and the corresponding solutions for trickle and b ubble
bed reactors are the same, under the assumption that the plug-flow condition holds for both
phases. Of course, the appropriate correlations should be used for the estimation of mass
v
we
transfer coeficients. Ho in packed bubble bed reactors, the liquid-phase is fre-
f
,
er
quently found in a complete mixed state, and thus some adjustments hae to be made to v
the aforementioned models. Two special cases will be presented here.
Continuous flow of both phases in upflow and complete mixing of phases For packed
bubble columns (upflow of both gas and liquid phases), under the assumption of complete
mixed flow, the backmixing model of Ramachandran and Chaudhari (1980) is applicable.
v The releant equations are presented in Section 3.5.1 for the continuous flow of gas and
ed-flo slurry phases in complete mixw conditions (slurry CSTR reactor).

w with r Continuous flow of both phases in upfloecycling of liquid-phase For packed
bubble columns and trickle beds, under the assumption of complete recycling of the liq-
uid-phase, the solutions are the same as in slurry bubble columns and slurry CSTR with
batch and reacting liquid-phase (see Section 3.5.1) (Ramachandran and Chaudhari, 1980).
In this operation, V / V R is greater than unityycling is useful when the per-pass con- . Rec
L
version of the liquid phase is very small.

3.7.3 Hydraulics

Pressure drop in trickle-bed reactors
The two-phase pressure drop P GL Z can be related to the pressure drops of each
phase P G Z and P L Z . According to Larkins et al . (Larkins et al ., 1961; Perry and
Green, 1999),