Cyclone

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Cyclone
Reading Chap. 4

• Impactor, Stokes Number
• Cyclone Operation and Applications
• Standard Dimensions
• Lapple Theory
• Pressure Drop
• Arrangement, Discharge

http//aerosol.ees.ufl.edu/cyclone/section01.html
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Impactor
Stokes Number the ratio of stopping distance of
a particle to a characteristic dimension of the
obstacle. Its a particles persistence to the
size of the obstacle.
Q Does a smaller or a larger particle possess
higher persistence?
http//aerosol.ees.ufl.edu/cyclone/section03.html
3
Q How can we collect more smaller particles
using the same nozzle?
4
Cyclone Operation
Outlet
Inlet
Vortex Finder
Cyclone body
Cylinder
Cone
Dust Discharger
http//aerosol.ees.ufl.edu/cyclone/section05.html
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Axial Inlet
Bottom Inlet
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Cyclone Performance for Various Applications
Air Pollution Control Equipment, Theodore
Buonicore, CRC Press, 1988.
Any pattern?
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Standard Cyclone Dimensions
b

a

h

H
B
http//aerosol.ees.ufl.edu/cyclone/section06.html
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• General guidelines
• a lt S
• b lt (D-De)/2
• H gt 3D
• Cone angle 7o 8o
• De/D 0.40.5, H/De 8, S/De 1

Q Why?
Cyclones used for removing wood dust
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Lapple Theory (plug flow)
b
Number of effective turns

a

Gas residence time
Vi
h

Terminal velocity
H
Smallest collected diameter
B
Q How can we reduce the smallest size further?
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50 cut size
The collection efficiency of any size dpj
? ()
Overall efficiency
Q Is fj mass based?
Particle size ratio dp/dp50
Q Is the dp50 the median size of the size
distribution of the inflow particles? Q Is the
laminar flow assumption valid?
Penetration
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Pressure Drop
Number of gas inlet velocity head
Static pressure drop
Kc 16 for normal tangential inlet 7.5 for
one with an inlet vane
Power requirement
Q Cost?
Common ranges for pressure drops Low efficiency
cyclone 2-4 inch of water Medium efficiency
cyclone 4-8 inch of water High efficiency
cyclone 8-10 inch of water
Higher flow velocity results in a higher
efficiency at the cost of a higher pressure drop
(and hence power)
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Example 4-5

• Design a conventional Lapple cyclone to function
  as a pre-cleaner (? gt 70) on a gas stream that
  flows at 120 m3/min. ?P lt 3000 Pa. ?p 1500
  kg/m3, ?g 1 kg/m3, m 0.07 kg/m-hr (1.94410-5
  kg/m-s). Specify your final choice of body
  diameter, overall cyclone efficiency, inlet gas
  velocity and pressure drop (assuming Kc 14).

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Arrangement
Series
Q If each cyclones efficiency is 80, how much
is the total efficiency for this serial cyclone?
Parallel/ Battery
Q Advantages? Disadvantages?
Air Pollution Control Equipment, Theodore
Buonicore, CRC Press, 1988
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Discharge
Q What may happen to if equipped with a bad
discharge device?
Handbook of Air Pollution Control Engineering
Technology, Mycock, McKenna and Theodore, Lewis
Publishers, 1995.
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Quick Reflection