Moving Bed Reactors

Moving bed reactors are reactors in which the catalytic material flows along with the reactants and is then separated from the exit stream and recycled.

Dual Serial Tank MBBR System_new height.jpg

( Copyright of PEWE LLC, Camas, WA)

General Information

Moving bed reactors are catalytic reactors in which the catalyst moves through the reactor along with the reactants. They are open systems and operate at steady state .

The animation below shows the operation of a moving-bed reactor. Reactants (green) and catalyst (white) enter the top of the reactor and move through the vessel. Once at the bottom the catalyst (black) is removed and regenerated; products (blue) are removed from the reaction system and the catalyst is regenerated and brought to the top of the reactor.

Equipment Design

This animation shows the basic operation within a moving bed reactor. Solid catalyst pellets are continuously introduced at the top of the reactor, as are the fluid phase reactants. The catalyst and the fluid flow together down the reactor. The reaction takes place along the way, which establishes a concentration gradient. In some cases, a set of sampling access ports may be installed so that one may collect data on reactant and product concentrations. Heating coils or wraps can be included along the reaction chamber to mediate heat from the reaction.

Usage Examples

Moving bed reactors are frequently used in wastewater treatment processes. They can be tuned to the application by selecting specific  microbes, but these types of reactors are very effective  at nitrification, denitrification, and chemical oxygen demand (COD) reduction processes. Because moving bed reactors are also easy to build, it is also easy to scale the reactor to meet different wastewater demands.

(Copyright BioprocessH2O, Portsmouth, RI)



  • Easy to regenerate catalyst
  • Have plug flow characteristics
  • Low catalyst handling cost
  • High conversion rate
  • Good selectivity
  • Flow of solids not easy to maintain
  • Poor heat transfer characteristics
  • Fluid reactant may bypass catalyst bed
  • Solid distribution difficult to maintain
  • Stagnation may occur
  • Attrition, break-up of catalyst pellets due to impact against reactor walls, may occur


Process Engineered Water Equipment LLC , Camas, WA

BioprocessH2O , Portsmouth, RI


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Hill, Charles G., Jr. An Introduction to Chemical Engineering Kinetics and Reactor Design .      New York: John Wiley & Sons, Inc. 1977. Print.

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Trambouze, Pierre, Van Landeghem, Hugo, and Wauquier, Jean-Pierre. Chemical Reactors .      Houston: Gulf Publishing Company, 1988. Print.

Walas, Stanley M. Reaction Kinetics for Chemical Engineers . New York: McGraw-Hill Inc.,      1959. Print.


Sam Catalano

Alex Wozniak

Joel Holland