In packed-bed scrubbers, the gas stream is forced to follow a circuitous path through the packing material,
on which much of the PM impacts. The liquid on the packing material collects the PM and flows down the
chamber towards the drain at the bottom of the tower. A mist eliminator (also called a “de-mister”) is typically
positioned above/after the packing and scrubbing liquid supply. Any scrubbing liquid and wetted PM entrained
in the exiting gas stream will be removed by the mist eliminator and returned to drain through the packed bed.
In a packed-bed scrubber, high PM concentrations can clog the bed, hence the limitation of these devices to
streams with relatively low dust loadings. Plugging is a serious problem for packed-bed scrubbers because
the packing is more difficult to access and clean than other scrubber designs. Mobile-bed scrubbers are
available that are packed with low-density plastic spheres that are free to move within the packed bed. These
scrubbers are less susceptible to plugging because of the increased movement of the packing material. In
general, packed-bed scrubbers are more suitable for gas scrubbing than PM scrubbing because of the high
maintenance requirements for control of PM (EPA, 1998)