A fluidized-bed reactor is a combination of the two most common, packed-bed and stirred tank, continuous flow reactors. It is very important to chemical engineering because of its excellent heat and mass transfer characteristics. The fluidized-bed reactor can be seen below:
In a fluidized-bed reactor, the substrate is passed upward through the immobilized enzyme bed at a high enough velocity to lift the particles. However, the velocity must not be so high that the enzymes are swept away from the reactor entirely. This causes some mixing, more than the piston-flow model in the packed-bed reactor, but complete mixing as in the CSTR model. This type of reactor is ideal for highly exothermic reactions because it eliminates local hot-spots, due to its mass and heat transfer characteristics mentioned before. It is most often applied in immobilized-enzyme catalysis where viscous, particulate substrates are to be handled.