Moving Bed

Moving Bed Reactor

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.

Moving Bed Reactor

( 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 a 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

The movie below shows the operation of a semi-batch reactor. In this example, an initial amount of reactants is charged into the reactor. The reactor is then started, and additional reactants are added continuously to the tank. The reactor is then allowed to run until the desired conversion is achieved, at which point the products and remaining reactants are removed from the tank and the process can be started once more.

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.

moving bed reactor2

(Copyright BioprocessH2O, Portsmouth, RI)


  • Easy to regenerate catalyst
  • Have plug flow characteristics
  • Low catalyst handling cost
  • High conversion rate
  • Good selectivity


  • High 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



  • Fish, Barry Brent. A Study of Moving Bed and Simulated Moving Bed Separators and Reactors. Ann Arbor, MI: UMI 1988. Print.
  • Fogler, Scott H. Elements of Chemical Reaction Engineering. 3rd ed. Englewood Cliffs, NJ: Prentice-Hall, 1998. Print.
  • Hill, Charles G., Jr. An Introduction to Chemical Engineering Kinetics and Reactor Design. New York: John Wiley & Sons, Inc. 1977. Print.
  • Perry, Robert H., and Don W. Green. Perry’s Chemical Engineers’ Handbook. 7th ed. New York: McGraw-Hill Inc., 1997. Print.
  • 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