Air Pollution Control 391wherem = radial velocity (in ds),
ps = density of particle (in kg/m3),
p = density of air (in kg/m3),
r = radial distance (in m),
o = rotational velocity (in rads),
d = particle diameter (in m), and
p = viscosity of air (in kg/m-s).The centrifugal acceleration is equal to the square of the tangential velocity divided by
the radius, or
2
rw 2-vtan --.
r
Substituting for ro2 in Eq. (20.5) yields
However,
where v is the settling or gravitational velocity, so that
The separation factor S for a cyclone is defined as
(20.6)(20.7)(20.8)S is dimensionless, and may take values from 5 to as high as 2500. A large separation
factor requires high tangential velocities, thus a small diameter and high velocity,
leading to large pressure drops across the cyclone. A large-diameter cyclone, on the
other hand, would have a small separation factor.
The pressure drop through a cyclone can be calculated by an empirical relationship
3950K Q2 Pp
TâAP =
where
(20.9)A P = pressure drop, in meters of water
Q = m31s of gas,