Inertial separators like cyclones use centrifugal force to separate particles from an air stream. Cyclones are commonly used inertial separators that impart a cyclonic motion to the air via tangential inlets or internal vanes. Larger particles are thrown against the outer walls and collected while cleaned air exits through the center. Cyclones are effective for particles above 10 μm but have lower collection efficiency than other devices. Their simple design means lower costs than other options.

1. Inertial separators
• Inertial separators are widely used for the collection of medium-sized and
coarse particles.
• Their relatively simple construction and absence of moving parts means
that the capital and maintenance costs are lower than the other control
devices available in the particulate control industry.
• However, the efficiency is not as high and thus inertial separators are usually
used as pre cleaners upstream of the other control devices to reduce the
dust loading and to remove larger, abrasive particles.

2. general principle of inertial separation
•The general principle of inertial separation is that
the particulate-laden gas is forced to change
direction.
•As the gas changes direction, the inertia of the
particles causes them to continue in the original
direction and be separated from the gas stream

3. centrifugal collectors
• Cyclones and centrifugal collectors are utilized in various industries
such as chemical, coal mining and handling, combustion fly ash,
metal melting, metal working, metal mining, rock products, plastics
and wood products.
• Common uses of cyclones and inertial separators are the collection
of grinding, crushing, conveying, machining, mixing, sanding,
blending and materials handling dust and for particle collection.

4. Cyclones
• Cyclones are the most common type of inertial separators.
• Cyclone separators are gas devices that employ a centrifugal force generated by a
spinning gas stream to separate the particulate matter, which could be solid or
liquid, from the carrier gas.
• The separator unit may be a single large chamber, a number of small tubular
chambers in parallel or series, or a dynamic unit similar to a blower.
• Units in parallel provide increased volumetric capacity while units in series provide
increased removal efficiency.

5. Cyclone separators Classifications
• Cyclone separators can be classified as vane-axial or involute. The only difference between these
two is the method of introducing the gas into the cylindrical shell in order to impart sufficient
spinning motion.
• In the simple dry cyclone separator, shown in Figure , the circular motion is attained by a
tangential gas inlet.
• The rectangular inlet passage has its inner wall tangent to the cylinder and the inlet is designed
to blend gradually with the cylinder over a 180-degree involute.
• Figure shows a vane-axial cyclone. In this case, the cyclonic motion is imparted to the axially
descending dirty gas by a ring of vanes. In either case, the operation depends upon the inertia of
the particles to move in a straight line even as the direction of the gas stream is changed.

6. centrifugal force
• The centrifugal force due to a high rate of spin flings the dust particles to the outer
walls of the cylinder and the cone.
• The movement of the particles across the gas stream can be seen in Figure.
• The particles then slide down the walls and into the storage hopper.
• The cleaned gas reverses its downward spiral and forms a smaller ascending spiral.
• A vortex finder tube that extends downward into the cylinder aids in directing the
inner vortex out of the device.

7. cyclone separator
• The cyclone separator is usually employed for removing particles 10 μm in
size and larger.
• However, conventional cyclones seldom remove particles with an efficiency
greater than 90 percent unless the particle size is 25 μm or larger. High
efficiency cyclones are available and are effective with particle sizes down to
5 μm.
• A high-volume design sacrifices efficiency for high rates of collection.

9. collection efficiency
• For cyclones to have good collection efficiency, proper installation procedures are
of primary importance.
• The cyclone collector must be airtight in order to eliminate re entrainment of the
particles back into the gas stream.
• Therefore, while installing equipment such as access doors, inlet and outlet
plenums and dust disposal features these areas must be completely sealed.
• Any leakage in the cyclone collector can cause a 25 percent or more loss in the
collection efficiency.

10. Erosion and Fouling
• Erosion and Fouling of cyclones are problems that seriously affect
the cyclone collection efficiency and are encountered during the
operation and maintenance activities.
• Erosion in cyclones is caused by the striking or rubbing of dust
particles on the inside wall of the cyclone.
• Erosion increases with high dust loadings, high inlet velocities, high
particle specific gravity values and the strike angle.

11. cylindrical shell
• The area of the cylindrical shell opposite to the inlet may
experience excessive wear if the gas contains large dust particles.
• Welded seams in the cyclone design are also areas that tend to
be susceptible to erosion because of surface irregularities.
• Choosing the proper cyclone diameter size can control erosion.

12. Design options
• Further, using thicker material in the cone area and abrasion
resistant removable wear plates (linings) at the strike zone are good
design options that help in controlling erosion.
• Fouling of a cyclone collector occurs on account of the plugging of
the dust outlet or dust build up on the cyclone walls.
• Plugging of the dust outlet occurs by large pieces of material
becoming lodged in the outlet thereby forming an obstruction
about which small particles can build up.

13. large-diameter cyclones
• These conditions can lead to re entrainment of the dust into the gas stream.
• For large-diameter cyclones, an axial cleanout opening with a bolted cover
plate in the top of the outlet pipe can be provided so that a rod can be
inserted to clear a blockage.
• Material build up on the cyclone walls is a function of the dust.
• Soft, fine dust has a tendency to build up on the cyclone walls.

14. cohesive and adhesive forces
• Particles below 3 µm in diameter possess inherently greater
cohesive and adhesive forces.
• Condensation of moisture on the cyclone walls also contributes
to the accumulation of material on the walls. Wall smoothness
can help to reduce the amount of material build up.
• Electropolishing of walls has been a successful method in
minimizing build up.

15. Collection efficiency
• Collection efficiency is a strong function of particle size and
increases with increasing particle size.
• Also, the efficiency is greater for particles with higher densities
than for lower densities.
• Figure shows the variation of the cyclone collection efficiency
with different particle sizes for different types of cyclones.