A trickle-bed reactor uses the downward movement of a liquid and upward or downward movement of gas over a packed bed of catalyst particles to facilitate catalytic reactions. There are three basic types - conventional trickle beds with randomly packed catalyst, semi-structured beds with structured or monolithic catalyst, and micro-trickle beds with catalyst in microchannels. In operation, the liquid trickles down while the gas flows concurrently up or down, with various flow regimes depending on flow rates and properties. Examples of uses include liquid-phase hydrogenation in refineries, oxidation of compounds in wastewater, and wastewater treatment using biofilm on the packed bed surface.

1. Trickle-bed reactor
Gopika J Menon | S5 BT | Roll no. 20

2. What ?
• Chemical reactor that uses the downward movement of a liquid and
the downward (co-current) or upward (counter-current) movement of
gas over a packed bed of (catalyst) particles
• It is considered to be the simplest reactor type for performing catalytic
reactions where a gas and liquid (normally both reagents) are present
in the reactor and accordingly it is extensively used in processing
plants.

3. Basic configurations and operations
• It is classified into following types
a) Conventional tickle bed reactors: Comprising randomly packed beds
of porous catalyst particles.
b) Semi structures tickle bed reactors: Comprising non-randomly packed
particles or catalyst on structured packing or monolith reactors
comprising large number of small channels coated with catalyst layer.
c) Micro-tickle bed reactor: Comprising a number of micro-channel
packed with catalyst particles

4. Working
• The gas and liquid co-currently flow downward over
a fixed bed of catalyst particles.
• Concurrent down-flow of gas and liquid over a
fixed-bed of catalyst.
• Liquid trickles down, while gas phase is continuous
• In a trickle-bed, various flow regimes are
distinguished, depending on gas and liquid flow
rates, fluid properties and packing characteristics.

5. Rate of transport
• The basic reaction and transport steps in trickle bed reactors are
similar to slurry reactors. The main differences are the correlations
used to determine the mass transfer coefficients. In addition, if there is
more than one component in the gas phase (e.g., liquid has a high
vapor pressure or one of the entering gases is inert), there is one
additional transport step in the gas phase.

6. Mathematical expression

7. Examples
• Liquid-phase hydrogenation, hydrodesulfurization, and
hydrodenitrogenation in refineries (three phase hydrotreater)
• Oxidation of harmful chemical compounds in wastewater streams or of
cumene in the cumene process.
• Treatment of waste water trickle bed reactors are used where the
required biomass resides on the packed bed surface

8. Applications

9. Applications

10. Thank you