1. Introduction
Cyclone separators have been used in the United States for about 100 years, and are still
one of the most widely used of all industrial gas-cleaning devices. The main reasons for
the wide-spread use of cyclones are that they are inexpensive to purchase, they have no
moving parts, and they can be constructed to withstand harsh operating conditions.
Typically, a particulate-laden gas enters tangentially near the top of the cyclone, as
shown schematically in Figure l. The gas flow is forced into a downward spiral simply
because of the cyclone's shape and the tangential entry. Another type of cyclone (a vaneaxial
cyclone - see right panel of Figure 1) employs an axial inlet with fixed turning
vanes to achieve a spiraling flow. Centrifugal force and inertia cause the particles to
move outward, collide with the outer wall, and then slide downward to the bottom of the
device. Near the bottom of the cyclone, the gas reverses its downward spiral and moves
upward in a smaller inner spiral. The cleaned gas exits from the top through a "vortexfinder"
tube, and the particles exit from the bottom of the cyclone through a pipe Sealed
by a spring-loaded flapper valve or rotary valve.