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74 3. Heterogeneous Processes and Reactor Analysis

G

L

L

Figure 3.4 . A gas–liquid continuous-stirred tank reactor

Gas–liquid bubble column: This reactor is of tubular shape (Figure 3.5). The liquid
phase is agitated by the bubble rise of the gas phase. The gas phase flows through the reac-
tor upward at a constant rate. The liquid phase is continuous. This reactor could be of con-
tinuous type, if the liquid is flowing through the reactor continuously; or semibatch, if the
. liquid is stationary in the reactor

Two-phase fluid–solid heterogeneous reactors

eactors Agitated tank r eactor: Batch agitated r This is a batch stirred tank reactor . F or
liquid–solid systems, the liquid is agitated by a mechanical apparatus (impeller) and the
reactor is of tank shape. For gas–solid systems, the gas is agitated and rapidly circulated
through a fed-bed of solids. This reactor is basically an experimental one used for
ix
adsorption, ion e and catalysis studies. xchange,
eactor: Carberry r The gas flows continuously through the tank-type reactor whereas ,
the catalyst is placed in rotating baskets in the reactorThis reactor is also e . xperimental
and suitable for catalysis as well as for adsorption studies (Figure 3.6).

Fixed-bed reactors Fixed-bed reactor (FBR): Gas or liquid reactants flow at a constant
v ix rate oer a fed-bed of solids placed in a tubular vessel (Figure 3.7). The f ed-bed reac- ix
,
tor can be viewed as a semibatch reactor where the solid phase is fed and the fluid is ix
.
flowing continuously through the reactorThe operation is steady state for catalysis and
w- unsteady state for adsorption and ion exchange. Some applications of FBR are the follo
ing: HDS of naphtha, catalytic reforming, steam reforming, w-gas shift, methanation, ater
ammonia synthesis, and methanol synthesis. This contacting pattern is by far the most
common in adsorption and ion-exchange processes.
Monolith reactor: v This type of reactor is used eely for the abatement of automo- xtensi
biles exhaust emissions. The gas flows continuously through the reactor whereas the cat- ,
alyst is a continuous phase consisting of a ceramic support and the acti which is e phase, v
dispersed onto the support. The support is structured in many channels and shapes that
olume. achieve large catalytic surface at small vA typical application of monolith reactors
is the exhaust gas cleaning.