FIELD OF THE INVENTION
The present invention relates to a cyclone for dense medium separation
adaptable to be used in the dense medium separation of a fine coal (-2
+0.25mm) fraction. More particularly, the invention relates to a cyclone for
dense medium separation that has been developed to minimize turbulence within
the cyclone during the separation process.
BACKGROUND OF THE INVENTION
The flow behaviour of slurries within cyclones is quite complex. This has led
designers to rely on empirical equations for predicting performance of cyclones.
These empirical relationships are derived from an analysis of experimental data
and include the effect of operational and geometric variables. Different sets of
experimental data lead to different equations for the same basic parameters.
However, these empirical models suffer from the inherent deficiency of any
empirical model. That is, the model can only be used within the limits of the
experimental data from which the model parameters were determined. In view
of this shortcoming, mathematical models based on fluid mechanics are highly
desirable.
The numerical technique "Computational Fluid Dynamics (CFD)" herein means
the numerical treatment of the Navier-Stokes equations over a
structured/unstructured 3D grid within a cyclone body. Turbulence modeling is
achieved by both RSM (Reynolds Stress Model) and LES (Large Eddy
Simulations) in order to capture the high swirling flow patterns seen in dense
medium cyclones. CFD provides a means of predicting velocity profiles under a
wide range of development and operating condition. The numerical treatment of

the Navier-Stokes equations, the basic of any CFD technique, crept into the analysis
of cyclone behavior in the early 1980s. This resulted from the rapid improvement in
computers at that time and a better understanding of the numerical treatment of
turbulence.
The expression "fine coal dense medium separation process" herein means
separation of a fine coal material into dense and less high gravity fraction at a
predetermined cut point. In the process the particulate material is carried in a
dense liquid medium which typically comprises a mixture of water and particles of
dense material such as ultra fine magnetite.
At present, the dense medium cyclone (DMC) is one of the best pieces of
processing equipment for washing cola of -20+0.5mm size. Difficult washing
characteristics associated with, for example, many Indian coals are generally due to
the present of a high proportion of near-gravity material (NGM). This makes the
DMC an obvious choice for most Indian washiers. In order to produce low ash clean
coal from run-of-mine (ROM) coal, it is necessary to crush the ROM to fine sizes to
liberate ash & coal. One of the more efficient methods of beneficiating the
generated intermediate size fraction (-2+0.25 mm) fines is dense medium
operation is small diameter cyclones.
A known prior art dense medium cyclone is illustrated in figure 1. This conventional
dense medium cyclone 10 includes a cylindrical inlet chamber 11 into which a
mixture of medium and raw coal enters tangentially through an inlet 12, thus
forming a strong vertical flow. The refuse or high ash particles move along the wall
13 of the cyclone due to the centrifugal force, where the velocity is the least and is
discharged through the underflow orifice 14 or spigot. The lighter washer coal
moves towards the longitudinal axis 15 of the cyclone

due to the drag force where a high velocity zone exists and passes through an overflow
orifice or vortex finder 16, also sometimes termed as overflow chamber. With cyclone of
this type, entrainment of fine or slower setting particles occurs in the void spaces
between the coarser, or faster settling, particles discharged as the underflow.
Turbulence fluctuation inside the cyclone are also expected to be significant due to the
collision of the inlet stream with the rotating stream. Due to inadequate standard inlet
and body section design, these cyclones are associated with large short-circuit flow and
short residence time of the internal upward flow. The though put and performance is
limited by the flow through the axial outlet. For many applications therefore, cyclones of
this type are operated at a reduced feed rate, in order to obtain the required cut
between the low gravity fraction and high gravity fraction.
Similarly US prior art US 6596196 discloses a dense medium cyclone for separating
particles of varying sizes from within a fluid stream which is introduced into a cyclone
that includes a body, a side wall having upper and adjacent lower wall portion tapering
inwardly in a direction away from upper wall. The cyclone also includes a vortex finder,
which defining an overflow outlet that removes the remaining fluid and entrained
particles from the cyclone.
The vortex finder and the upper wall portion form a feed zone of decreasing cross
section area from inlet to the internal end of the vortex finder.
There us need to develop a new design for a DMC for the recovery of clean coal ash
(<8%) from high NGM coals, such as those seen in India. It would be particular
advantageous if a dense medium cyclone having increased efficiency could be devised
that is able able to product reduced ash content. It would also be advantageous if a
dense medium cyclone could be devised having an increased ability to separate out fine
particles efficiently.
A new improved improved development of DMC for efficient coal separation emphasizing
a fines fraction of -2 +0.25 mm has been development using a comprehensive CFD
model. In particular, a CFD model of the DMC which is capable of predicting the
performance of the cyclone has been development, using Fluent, by coupling component
models for the air-core, the magnetic medium Lagrangian particle tracking for particles
ranging in size from 0.25 to 2 mm. This has resulted in the invention described below.

OBJECTS OF THE INVENTION
It is therefore, an object of the present invention to propose CFD cyclone for dense
medium separation of a fine coal, which eliminates the disadvantages of prior art.
Another objection of the present invention is to propose CFD cyclone for dense
medium separation of a fine coal, which is capable of predicting the performance of
a cyclone and has been developed using fluent by coupling component models for
the air-core, the magnetite medium and coal particles.
A further object of the present invention is to propose CFD cyclone for dense
medium separation of a fine coal, which separates fine coal particles by enhancing
residence time of fine coal particles and minimizing recirculation zone inside the
cyclone.
A still further object of the present invention is to propose CFD cyclone for dense
medium separation of a fine coal, which minimizes short-circuiting and recirculation
zones inside the cyclone.
SUMMARY OF THE INVENTION
The present invention advantageously provides an improved dense medium cyclone
model which it is believed will exhibit an improved throughput relative to
conventional cyclones for fine coal beneficiation.
According to one aspect of the invention there is provided a cyclone for dense
medium separation including.

a cyclone body that defines an interior space having an inner wall surface;
a vortex finder including a lower end that extends longitudinally into upper region
of the interior space of the cyclone body;
an overflow outlet associated with an upper end of the vortex finder;
a feed inlet that is in fluid communication with the upper region of the interior
space of the cyclone body; and
an outlet associated with a lower region of the interior space;
wherein the inner wall surface of the interior space curves inwardly and
downwardly from the upper region of the interior space to the lower region of the
interior space.
According to CFD predictions, in conventional dense medium cyclone (as illustrated
in Figurel) a very high turbulent kinetic energy exists near the tip of vortex finer.
As expected, the sudden transition from a cylindrical section to a conical section
result in a clear source of turbulent fluctuations downwards through the cyclone
body. These fluctuations usually propagate a very high turbulent kinetic energy
near the bottom of the apex zone. Modifying the cylindrical-conical shape of the
conventional DMC to a rounded wall design as described in the immediately
preceding paragraph advantageously alleviates or avoids turbulent fluctuations due
to separation at the intersection of cylindrical conical sections. Further, throughput
in the design of the invention is advantageously high compared to the
conventional cyclones described above.
Furthermore, it is anticipated that the rounded wall design may significantly
increase the residence time of fine particles within the cyclone which would be
advantageous as would be appreciated by those in the art.

The curvature of the inner wall surface of the interior space preferable extends
substantially along the longitudinal length of the cyclone body. More particularly, in
a preferred embodiment the degree of curvature of the inner wall surface of the
interior space in longitudinal direction continuously increases from a lower end of
the vortex finder to the lower region of the interior space. More preferably the
associated with the lower region of the interior space.
The degree of curvature of the inner wall surface is not particularly limited and may
very from case to case. However, in a particular embodiment, the curvature of the
inner surface of the interior space increase from about 1 degree at the point
immediately below the feed inlet to about 20 degree at the outlet.
According to a particular embodiment of the invention, the vortex finder is provided
with an outer surface that tapers outwardly and downwardly into the upper region
of the interior space along the longitudinal axis of the cyclone body.
The degree of the taper of the outer surface of the vortex finder according to this
embodiment of the invention is not particularly limited. However, it is preferred that
the outer surface of the vortex finder tapers outwardly and downwardly at 9 degree
from the longitudinally axis of the cyclone body.
The overflow outlet may be positioned as desired relative to the lower end thereof
that extends longitudinally into the upper region of the interior space of the cyclone
body.
Generally it is prepared that the overflow outlet is disposed on the upper end of the
vortex finder and in alignment with the longitudinal axis of the cyclone body.

The feed inlet may take any suitable configuration. In a preferred embodiment,
however, the feed inlet includes an involute conduit that extends around a portion
of the circumference of an upper end of the cyclone body. More particularly, the
involute conduit preferably extends horizontally along the circumference of the
upper end of the cyclone body and includes a rear wall that curves inwardly and
that is conterminous with an inner wall surface of the upper end of the cyclone
body.
The upper region of the interior space may be in the form of substantially cylindrical
barrel that extends up to 1.23 Dc from the top of the cyclone body, compared to
0.67 Dc in conventional cyclones. The substantially cylindrical barrel merges with
and into the more rounded inner wall surface of the interior space of the cyclone for
handing higher throughputs compared with conventional cyclones. The overall
length of the cyclone is generally about 3.23 - 3.5 Dc which is effectively 1.23 m for
a 350 mm cyclone is generally about 3.23 - 3.5 Dc which is effectively 1.23 m for a
350 mm cyclone.
The improved inlet design described above, including the preferred form for the
vortex finder and the preferred form for the feed inlet, advantageously makes it
conceptually possible to minimize short-circuiting of the high gravity fraction into
the overflow. Further, this design advantageously provides high centrifugal forces in
the upper region of the interior space of the cyclone body.
BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS
Figure 1 is schematic cross section view of a DSM dense medium cyclone which is
known in the art;

Figure 2A and 2B are schematic cross sectional views of a dense medium cyclone in
accordance with the invention;
Figure 3 is a schematic view of the methodology of the developed CFD model used
to predict the performance of dense medium cyclones;
Figure 4 is a graph of the predicted comparative turbulent kinetic energy of prior art
cyclones and the illustrated in Figures 2A and 2B;
Figure 5 is a graph of the predicted comparative density contours of prior art
cyclones and the cyclone illustrated in Figures 2A and 2B; and
Figure 6 is another graph of the predicted comparative performance of prior art
cyclones and the cyclone illustrated in figures 2A and 2B.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE
INVENTION
Referring to Figures 2A and 2B, a cyclone 20 is illustrated that includes a cyclone
body 21 defined by a cyclone body wall 22. The cyclone body wall 22 has an inner
wall surface 23 that defines an interior space 24 within which the separation
process takes place.
A vortex finder 25 extends into an upper region 26 of the interior space 24 of the
cyclone body 21. The vortex finder 25 is axially orientated and includes an overflow
outlet 27 that is associated with its upper end.

A feed inlet 28 is provided that is in fluid communication with the region 26 of
the interior space 24. The feed inlet is involute, as best seen in figure 2B, in that
wall 29 of the feed inlet 28 is curved and coterminous with the inner wall surface
23 at an upper end 35 of the cyclone body 21. The feed inlet 28 provides a
means for the introduction of a fluid stream into the interior space 26 and will be
discussed in more detail below.
A spigot 30 in provided in a lower region 31 of the interior space 24 and provides
an axially directed outlet 32 for removing fluid and high density material from the
cyclone body 21. The diameter of the spigot 30 of the lower 31 may be
determined using the application of normal cyclone design criteria.
The inner wall surface 23 of the cyclone body wall 22 curves inwardly and
downwardly substantially along the length of the cyclone body21. The inner wall
surface 23 typically curves inwardly downwardly from the bottom of the feed
inlet 28 to the spigot 30 at a continuously changing cone angle of from 1° to 20°
relative to the longitudinal axis 33 of the cyclone body 21. The converging
rounded nature of the inner wall surface 23 is though to be important in
generating appropriate helical fluid flow pattern through the interior space 24 of
the cyclone body 21 to achieve a desired degree of separation.
The smaller angles in the upper region 26 of the interior 24 are thought to be
important when dealing with separation involving fine particles, for example of
less that 2mm. Angles of close to 20° near the spigot 30 in the lower region 31
of the interior space 24 are thought to avoid surging if any occurs, at high
throughput rates.

It is believed that the design of the invention will therefore permit a greater volume
of high gravity fraction to pass through the underflow outlet 32 compared with
conventional cyclones as briefly described above.
As noted above, the vortex finder 25 extends substantially axially into the upper
region 26 of the interior space 24 of the cyclone body 21. The vortex finder 25
defines an overflow outlet 27 which removes fluid and entrained particles from the
cyclone. The vortex finder 25 terminates with an internal end 34 which is positioned
at least a minimum distance below the feed inlet 28 of the cyclone 20. The upper
region 26 of the interior space 24 defined between the inner wall surface 23 at the
upper end 35 of the cyclone body 21 and the vortex finder 25 forms a feed zone of
the cyclone 20.
Referring to the feed zone of the cyclone 20, the inner wall surface 23 at the upper
end 35 of the cyclone body 21 extending from the top of the cyclone body 21 to the
just below the feed inlet 28 tapers inwardly and downwardly at an angle of
typically 6°. The vortex finder 25 includes an outer wall 36 that tapers outwardly
and downwardly towards its internal end 34. The illustrated vortex finder 7 tapers
outwardly towards at an angle of 9° relative to a longitudinal axis of the cyclone
body 21.
The combination of inward taper of the inner wall surface 23 at the upper end 35 of
the cyclone body 21, a curved portion of the inner wall 36 of the vortex finder 25
creates a feed zone of decreasing cross section area from the feed inlet 28 down to
the internal end 34 of the vortex finder 25. This has the effect of accelerating the
fluid and entrained medium and coal particles through this region, thereby
increasing centrifugal forces. Furthermore, the outer wall 36 of the vortex finder 25
is spaced a reasonable distance radially outwardly relative to

the overflow outlet 27 of the vortex finder 25. This also has the effect of
decreasing the cross sectional area of the feed zone for fluid flow between the
inner wall surface 23 and the outer wall 36 of the vortex finder 25.
The feed inlet 28, in more detail, includes an aperture through which feed is
introduced and an involute conduit 38 that extends around a portion of the
upper end 35 of the cyclone body 21. The involute conduit 38, at its outer wall
29, tapers inwardly as is shown in the drawings. Again, this has the effect of
accelerating the feed as it centers the cyclone body 21.
Generally, the ration of diameters di: d2 is about 2.25. It will be appreciated,
however, that the size and configuration of the inlet conduit 38 and associated
conduit opening 37 may typically be determined depending on the application on
the application to which the cyclone is being put according to tradition design
criteria.
In use, a fluid stream containing entrained coal particles enters via the opening
37 of the inlet 28 under pressure and flows helically down the cyclone body 21
towards the underflow outlet 32. The acceleration of the fluid and entrained coal
particles through the feed zone acts to reduce short circuiting flow direct to the
overflow outlet 27.
The rapid swirling flow of the fluid has the effect of displacing relatively heavier
particles towards radially outer positions in the interior space 24 of the cyclone
body 21, proximate to the cyclone body wall 22. Relatively lighter particles are
displaced to a radially inner position in the interior space 24. As a result, the
heavier particles tend to exit the cyclone via the underflow outlet 32.

A rapidly swirling core of air moves upwardly from the underflow outlet 32
through a central region of the interior space 24 towards the vortex finder 25
where it exits via the overflow outlet 27. This swirling core of air which very
unstable carries with it the relatively lighter particles.
The medium used for the dense media cyclone 20 depends on the actual mineral
separation being effected within the cyclone 20. For the treatment of fine coal,
ultrafine magnetite is typically used, for example having from 95% -99% of
particles below 53 micron
Typically, the cyclone according to the invention will have a diameter in the
range of 100mm -350mm. By the term "cyclone diameter" is meant the
diameter of the cyclone body 21 at the upper end 35 of the upper wall portion.
Numerical experimental and pilot plant cyclones typically have a diameter of
350mm.
Generally, in a 350mm diameter diameter cyclone the total length is 1.2m, which
equates to 3.5 Dc. These sorts of cyclones are suitable for fine particle
separation where there is a high content of near gravity materials due t their
inherently high residence time of neutrally buoyant particles.
EXPERIMENTAL RESULT
In these comparative tests, a DSM (Dutch State Mine) cyclone was tested against
the CFD dense media cyclone of the invention.

A virtual test cyclone of 350 mm diameter, with an angle 20 degree slanted to
the horizontal plane and a dense medium made of ultra fine quality was used for
the simulations. The feed pressure to the cyclone used in simulations was in the
rage of 1 to 1.5 meter which is 9 to 13 times the cyclone diameter. The predicted
overflow and under flow of the cyclone were noted and used for the calculation
of product densities.
At the end of each completed case. The turbulence analysis has been done
before coal particle tracking process, to understand the flow structure and
swirling patterns inside the cyclone.
After each test case had been completed, the partition characteristics of the DMC
were modeled using Lagrangian particle tracking for particles ranging in size
from 0.25 to 2 mm. Partition numbers were calculated according to techniques
well known in the art.
The partition number (or coefficient) is basically an empirical measure of the
average probability of the particles in the respective density fraction reporting to
one or other of the products, for example to the cyclone underflow. The
partition curve describes the partition number as a function of the particle
densities. The efficiency of separation for a dense medium cyclone is usually
represented by the Ep value, which is calculated as follow
Ep =(D75-D25)/2
Where D75 is the density at which the probability of reporting to the underflow is
75%, and D25 is the density at which the probability of reporting to the
underflow is 25%.

The steeper the partition curve, or the smaller the Ep value, the better the
separation. The partition curves for the experiments conducted are shown in
Figure 6.
The numerical experiments clearly demonstrate that the CFD cyclone delivers
superior performance to the DSM cyclone.
According to CFD predictions, as shown in Figure 4, it is interesting to note that
in the conventional dense medium cyclone a very high turbulent kinetic energy
exists near the tip of vortex finer. As expected, the sudden transition from the
cylindrical body to the conical section is a clear source of turbulent fluctuations
down the cyclone body. These fluctuations usually propagate a very high
turbulent kinetic energy near the bottom of the apex zone. Modifying the
cylindrical- conical shape to a curved wall design minimizes the turbulent
fluctuation due to separation at the intersection of cylindrical-conical body.
Further, the throughput is high in this conceptual design compared with the
conventional cyclones.
Certain embodiments of the CFD cyclone further provides an extended barrel
length up to 3.25-3.5 Dc and this extended section mostly merged with rounded
wall cyclone section. This arrangement provided an extra space for handling
higher throughput compared to the convention cyclone.
Also according to embodiments of the CFD cyclone there may be included an
outside tapered (9 degrees) thick vortex finder. With improved inlet chamber
design conceptually it is possible to minimize the short-circuiting of high gravity
fraction into overflow. Further, this vortex finder design provides high
centrifugal forces

The CFD predictions indicate that magnetic segregation is very significant in the
conventional DSM cyclone compared to the CFD cyclone, as shown in Figure5.
Unlike the conventional DSM cyclone, an almost uniform radial segregation of
magnetic can be observed in the CFD cyclone. Hence the low density differential
between overflow and underflows as provided in the table below.

It is observed that the CFD cyclone is able to separate fine coal particles (-
2+0.25 mm) more sharply than conventional DSM design, with reference to
Figure 6. A significant improvement in minimizing the short-circuiting to
overflow observed in new design. Overall performance of the CFD cyclone
design is much improved for the fine coal fraction compared to DSM design.
This was attributed to minimization of turbulent fluctuations, flow reversals and
short-circuiting flow.
The CFD cyclone design produced a lower Ep and therefore a higher efficiency
that the DSM design. The increase in efficiency was particularly pronounced for
very fine particles (0.5 mm 0.25 mm). The lower density difference between
overflow and underflow for the CFD cyclone indicates that uniform magnetite
segregation is being generated inside the cyclone.

Dense medium cyclone play a critical role in the beneficiation of coals. Any
increase in Separation efficiency of the equipment employed will avoid loss of
coal particles in rejects. The CFD cyclone design is expected to increase the
cyclone efficiency and thereby increase clean coal yields from washeries. The
comparison of efficiency curve of the CFD cyclone design vis-a vis the
conventional DSM design indicates a significant improvement in separation. Also,
as the equipment is specially designed to treat intermediate size coal (-2+0.25
mm) separately it enables a decrease in the overall ash content in the clean coal
from the washeries. The lower ash in clean coal and, hence, lower coke ash is
expected blast furnace productivity quite significantly.
It will of course be realized that the above has been given only by way of
illustrative example of the invention and that all such modification and variations
thereto as would be apparent to those of skill in the art are deemed to fall within
the broad scope and ambit of the invention as herein set forth.

WE CLAIM:
1. A cyclone for dense medium separation comprising:-
an inverted conical shaped
cyclone body (21) which provides an interior space (24) having an
inner wall surface (23), the inner wall surface (23) comprising an upper region
(26), and a lower region (31);
a vortex finder (25) including a lower end that extends along a
longitudinal axis of the cyclone into an upper region of the interior space of the
cyclone body (21);
an overflow outlet (27) associated with an upper end of the vortex
finder (25);
a feed inlet (28) that is in fluid communication with the upper region of
the interior space of the cyclone body (21);
an underflow outlet (32) associated with a lower region of the interior
space (24) and
characterized in that the inner wall (23) surface of the interior space
(24) curves inwardly and downwardly from the upper region (26) of the interior
space (24) to the lower region (31) of the interior space (24).
2. The cyclone as claimed in claim 1, wherein the degree of curvature of the
inner wall surface (23) of the interior space (24) in the longitudinal direction
continuously increases from a lower end of the vortex finder (25) to the lower
region of the interior space (24).
3. The cyclone as claimed in claim 1, wherein the degree of curvature of the
inner wall surface (23) of the interior space (24) in the longitudinal direction
continuously increases from a point immediately below the inlet (28) to the
underflow outlet (32) associated with the lower region of the interior space (24).

4. The cyclone as claimed in claim 1, wherein the degree of curvature of the
inner wall surface (23) of the interior space (24) increases from about 1 degree
at the point immediately below the feed inlet (28) to about 20 degree at the
underflow outlet (32).
5. The cyclone as claimed in claim 1, wherein the vortex finder (25) is provided
with an outer surface (36) that tapers outwardly into the upper region (26) of
the interior space along the longitudinal axis of the cyclone body (21).

6. The cyclone as claimed in claim 5, wherein the outer surface (36) of the
vortex finder (25) tapers outwardly and downwardly at 9 degree from the
longitudinal axis (33) of the cyclone (21).
7. The cyclone as claimed in claim 6, wherein the overflow outlet (27) is
disposed on the upper end of the vortex finder (25) and in alignment with the
longitudinal axis (33) of the cyclone body (21).
8. The cyclone as claimed in claim 1, wherein the feed inlet (28) includes an
involute condition (38) that extends around a portion of the circumference of an
upper end (35) of the cyclone body (21).
9. The cyclone as claimed in claim 8, wherein the involute conduit (38) extends
horizontally along the circumference of the upper end (35) of the cyclone body
(20) and includes a rear wall (29) that curves inwardly and that is coterminous
with an inner wall surface of the upper end (35) of the cyclone body (21).
10. The cyclone as claimed in claim 1, wherein the upper region (35) of the
interior space (26) is in the form of a substantially cylindrical barrel that extends
up to 1.23 Dc from the top of the cyclone body (21) and that merges with and

into curved inner wall surface (23) of the interior apace (24) of the cyclone body
(21).
11. The cyclone as claimed in claim 1, wherein cylinder diameter is meant the
diameter of the cyclone body (21) at the upper end (35) of the upper end
portion can be in the range of 100 m-350 m.
12. The cyclone as claimed in claim 1, where in the total length can be in the
range of 1.2 mm to 1.5 mm.

13. The cyclone as claimed in claim 1, wherein the ration of the diameter of
feed inlet (28) to the diameter of conduit (38) can be 2.25 to 2.50.
14. The cyclone as claimed in claim 1, wherein a rapidly swirling core of air
moves upwardly from the underflow outlet (32) through a central region of the
interior space (24) towards vortex finder (25) from where it exists via the
overflow outlet (27).
15. The cyclone as claimed in claim 1, wherein the medium used for dense
medium cyclone depends on the actual mineral separation being effective in the
range 95% - 99% particles below 53 microns.
16. The process of performing the cyclone as claimed in claim 1 comprising:-
- a fluid stream containing entrained coal particles enters via the opening
(37) of the inlet (28) under pressure;
- flows helically down the cyclone body (21) towards underflow outlet
(32); and

- the accelerating of the fluid and entrained coal particles through the feed
zone acts to reduce short circuiting flow direct to the over flow outlet (27).
17. The process of performing of cyclone as claimed in claim 16 where in the
rapid swirling flow of the fluid has the effect displacing relatively heavier particles
towards radially outer position in the interior space (24) cyclone body wall (21)
proximate to the cycle body wall (22) and relatively lighter particles are displace
to a radically inner position in the interior space (24) which results the heavier
particles tend to exit the cyclone via the under flow outlet (32).
18. The process of performing of cyclone as claimed in claim 16, where in a
rapidly swirling core of air moves upwardly from the underflow outlet (32)
through a central region of the interior space (24) towards the vortex finder (25)
where it exists via the overflow outlet (27) and this swirling core of air which is
very unstable carrier with it the relatively lighter particles.

ABSTRACT

Title : CYCLONE FOR DENSE MEDIUM SEPARATION
The invention relates to a cyclone for dense medium separation comprising a
cyclone body (20) that defines an interior space (24) having an inner wall surface
(23); a vortex finder (25) including a lower end that extends longitudinally into
an upper region of the interior space of the cyclone body (20), an overflow
outlet (27) associated with an upper end of the vortex finder (25), a feed inlet
(28) that is in fluid communication with the upper region of the interior space of
the cyclone body (21), an underflow outlet (32) associated with a lower region of
the interior space (24); wherein the inner wall (23) surface of the interior space
(24) curves inwardly and downwardly from the upper region (26) to the lower
region (31).