Mechanisms of Droplet Removal
Droplets are removed from a vapor stream through a
series of three stages: collision & adherence to a target,
coalescence into larger droplets, and drainage from
the impingement element. Knowing the size distributions
as explained above is important because empiricalempirical
evidence shows that the target size - important in
the first step of removal - must be in the order of
magnitude as the particles to be removed. These
steps are shown schematically in Figure 3 for mist
elimination using a wire mesh mist eliminator.For fogs in which the bulk of the droplets are characterized
with submicron diameters, the energy to bring
about the collision with the target is derived from
Brownian Diffusion, the random motion of fine liquid
particles as they are
pushed about by
molecular action as
shown in Figure 4a.
Fog elimination with
so-called fiberbed
technology is beyond
the scope of this
manual.
For particles in the
mist region between
3-20 μm, knitted wire
mesh is themost common
type of mist
eliminator used and
interception is the
primary mechanism.