GENERAL CYCLONE SIZING
This article is meant as a general backup and further explanation of
the information and sizing found
in the SDM Cyclone spreadsheet found at (http://www.smartdogmining.com/tools/Software/)
Specific cyclone operations, such as dense medium cyclones
are covered in separate articles.
Cyclone operation is based on having a feed, a mixture of
solids and a liquid carrying phase, enter the cyclone under
pressure, either pumped or by gravity.
This feed enters the body at a tangent.
As the feed enters the body, a rotation of the slurry begins,
causing centrifugal forces to act on the particles forcing them
towards the wall. As
additional slurry enters the body of the cyclone the particles
migrate downward towards the cone section.
Smaller and lighter particles migrate at a slower rate due to
hindered settling and may move back towards the center.
At the center of the cyclone a counter rotating central core
is established by the rotating action of the slurry.
This central core (vortex) is discharged through the vortex
finder as "overflow".
The mass along the wall is discharged through the apex or spigot as
"underflow".
Classifying cyclones separate predominately based on the
differential size of the particles, with the finer sized going to
overflow and the coarser particles going to underflow.
Water-only or Hydro-cyclones separate based on differential
specific gravity, with the lighter particles going to overflow.
Dense (heavy) medium cyclones accentuate the gravity
separation by using a separating media of known and controlled
specific gravity.
Standard Cyclone Configuration

Dimensions Standard cyclone dimensions (classifying) are based on
the following relationships:
Cyclone diameter
=
D
Feed inlet area
=
I = w *h
≈ 0.20D
Vortex finder diameter
=
d
≈ 0.43D
Apex opening diameter
=
a
≈ 0.15D
Apex cone angle
=
ca
≈ 20 degrees
Body length
=
B
≈ 0.60D
Feed pressure
=
P
The standard method of writing cyclone dimensions is as follows:
d - .20D - .43D - .15D - 20deg. - .60D
EQUIPMENT SIZING
The basic cyclone capacity is based on the above standard
dimensions. Changing
these dimensions will result in a change in capacity and cyclone
performance.

Capacity Factors
-
Feed: Capacity change is
directly proportional to the square root of the head divided by
10 when head is in meters, and divided by 32.8 when head is in
feet. P = head
(m)/10 or head (H) 32.8 or lbs/in2
-
Cyclone diameter:
Cyclones small thru 10" to 14" diameter have an increased
capacity per unit volume, cyclone larger than 10" to 14"
diameter have a decreased capacity per unit volume.
-
Inlet Area: Capacity is
directly proportional to "I" in centimeters.
-
Vortex diameter:
Capacity is directly proportional to "V" in centimeters.
-
Apex diameter: An
extremely large apex will result in increased capacity,
otherwise the apex diameter has no influence on capacity.
-
Length of body: A change
of 1.0D in length will change capacity by 10%.
-
Cone Angle: Standard
capacity is for 20 degrees.
A 10 degree cone will increase capacity by 10%, and a 60
degree cone will decrease capacity by 10%.
-
Slurry viscosity:
Capacity will vary directly with viscosity.
-
Roughness of casting:
Rough castings tend to give increased capacity.
Capacity Example:
For a standard 14" diameter classifying cyclone, or 350 mm
350-70 - 150 - 2.25 - 20 - 230 for h = 10 Meters
Feed capacity = 70 * (10 * 150) 1/2 = 103 cubic meter/hour = 453 g/m
at 15 psi
Changing the head to 50 feet = (50/32.8)**.5 x 453 = 560 g/m
More precise calculations for other cyclone configurations can be
done using the SDM Cyclone spreadsheet found at (http://www.smartdogmining.com/tools/Software/default.html)
Performance
Classification performance is the sharpness of separation for
producing a desired mesh size product.
Classification is dependent on the specific gravity of the
solids, with higher specific gravity particles producing finer size
separations and also more precise separations.
Classification is also dependent upon the feed concentration
with higher solids concentrations producing coarser separations.
-
Feed pressure: Size of classification is inversely proportional
to the fourth root of the feed pressure for a certain cyclone.
The effect is probable less for relatively large
cyclones and may be greater for relatively small cyclones.
-
Cyclone diameter: The mesh of classification is proportional to
the square root of the cyclone diameter for the same pressure
and same geometric shape.
-
Body length of Cyclone: Additional cylindrical body length will
decrease the size of classification.
A decrease in mesh of classification of about 30% can be
obtained by increasing the body length of a given cyclone.
-
Cone Angle: A 20o Cone
angle is standard.
Reducing the cone angle to 10o will
result in a significant decrease in the size of classification
and a sharper separation.
Increasing the Cone angle to 60o will
result in a coarse classification.
The 60o Cone
angle is not suitable when the feed concentration is above 20%
by volume due to poor separation efficiency.
-
Vortex Diameter: When all other dimension remain constant a
decrease in size of classification of about 30% can be obtained
by decreasing the vortex diameter.
-
Feed Inlet Diameter: When all other dimensions remain constant a
decrease, size of classification can be obtained by decreasing
the feed inlet diameter.
More precise calculations for other cyclone configurations can be
done using the SDM Cyclone spreadsheet found at (http://www.smartdogmining.com/tools/Software/default.html)
CLASSIFYING CYCLONES
Factors effecting mesh of classification.
Feeds solids concentration: The size of classification remains
constant up to about 7% solids by Volume.
Increasing the feed concentration above 7% by Vol. will
result in a coarser classification.
Also the efficiency of separation decreases as the feed
concentration is increased.
Specific Gravity of solids: The mesh of classification
decreases as the Sp.Gr. of the solids increase.
When the mesh of classification is known for sand (Sp.Gr. =
(2.65). The mesh of
classification for magnetite (Sp.Gr. = 5.0) can be calculated:

Coal at 1.40 Sp.Gr. will be classified about 3.5 times coarser than
sand.
The classification for coal is not as sharp as for sand or
magnetite. This is due
to the large difference in Sp.Gr. of the coal particles.
All the sand particles will have a Sp.Gr. of 2.60 to 2.70.
Coal particles of the same size will vary in Sp.Gr. from less
than 1.3 to 2.70 for sand and slate and up to 5.0 for free pyrite
particles. Therefore
fine heavy particles will report to the underflow and coarse light
particles will report to the overflow.
Viscosity of feed slurry: Feed solids concentration directly
effect viscosity, particularly minus 325 mesh particles.
Also temperature of slurry will effect viscosity and mesh of
classification. A finer
classification will be obtained at 110oF
than at 70oF
when all other factors remain unchanged.
It is not possible to classify sand particles coarser than
about 200 microns and coal particles (Sp.Gr. 1.40) coarser than
about 300 microns with a cyclone.
Sand particles can be classified at about 40 microns (325
mesh) with an 8" cyclone and about 60 microns with 14" cyclone.
The 95% point mesh of classification for 28M x 0 Raw Coal or
water only cyclone C.C. will be approximately as follows:
Calculations for other cyclone performance for alternative
cyclone configurations can be done using the SDM Cyclone spreadsheet
found at (http://www.smartdogmining.com/tools/Software/default.html)