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3.2 Heterogeneous Reactors 77

• hydrogenation of oils
• oxidation of liquids
• oxidation of pollutants dissolved in liquids
• polymerization reactions.

Fixed-bed r eactors Trickle-flow reactor (TFR): This is a tubular flow reactor with a
wn-flo concurrent dow of gas and liquid oer a fed-bed of catalyst (Figure 3.10). Liquid ix v
trickles down whereas the gas phase is continuous. This reactor is mainly used in catalytic
applications. Typical application examples of this reactor type are the follo HDS of wing:
heavy oil fractions and catalytic hydrogenation of aqueous nitrate solutions.
Packed Bubble Bed Reactor (BBR): This is a tubular flow reactor with concurrent up-
flow of gas and liquid (Figure 3.11). The catalyst bed is completely immersed in a contin-
uous liquid flow while gas rises as bubbles. Some applications of BBR are the catalytic
denitrification of aqueous nitrate solutions and the hydrogenation processes.
Reactors with moving solid phase Three-phase fluidized-bed (ebullated-bed) r eactor:
Catalyst particles are fluidized by an upward liquid flow, whereas the gas phase rises in a dis-
persed bubble regime. A typical application of this reactor is the hydrogenation of residues.

L

G

G

L

Figure 3.10 The trickle-bed reactor.

L
G

L

G
Figure 3.11 . The packed bubble bed reactor