Cyclone dust collectors can be designed with either
large or narrow diameters depending on the application.
Small diameter cyclones have high dust collection
efficiencies at low dust loads (0.1 to 6 grains per
cubic foot) and high pressure drop of 6 to 10 inches
w.c. (water column). Owing to the small diameter they
have the tendency to plug at high dust loads. Large
diameter cyclones can handle high dust loads (50-100
grains per cu.ft) with low pressure drops (1.5 to
3 inch w.c.) efficiently. They are not very efficient
at low dust loads.
To improve efficiencies, design considerations are,
1. high narrow inlets reduce distances traveled
by dust to the wall and thereby improve collection
2. small diameters have higher forces than larger
3. smooth transition ensures maximum efficiency.
Use of expansion hoppers in dust discharge:
In high pressure drop cyclones, dust collecting at
the discharge point could be swept upward to the outlet
tube. This phenomenon occurs due to the powerful inner
vortex that is formed inside the main swirling stream
at the discharge point. Use of expansion hoppers allows
dust to be discharged through an airtight feeder.
Expansion hoppers effectively squeeze out moisture
in some heavy moisture applications.