CLIAMS:WE CLAIM:
1. A cyclone separator (1) comprises of a cylindrical body (5) which incorporates a plurality of vortex finders (2,3,4) provided at the top of the separator, an inlet (6) for tangential entry of a heterogeneous mixture of feed particles, an overflow discharge opening, an underflow discharge opening and a plurality of output pipes, said cyclone separator (1) produces three overflow streams, namely an inner overflow, a middle overflow and an outer overflow which exit through the overflow discharge opening, said plurality of output pipes collect particles of different size ranges from said three overflows at one go.

2. The cyclone separator (1) as claimed in claim 1, wherein said plurality of vortex finders comprise of at least a first vortex finder (2), positioned co-axially within at least a second vortex finder (3), said first and second vortex finders (2, 3) being further positioned co-axially within at least a third vortex finder (4), said first, second and third vortex finders (2, 3, 4) being selected so as to have an increasing diameter inside the cyclone separator (1) in that order.

3. The cyclone separator (1) as claimed in claim 1, wherein said first, second and third vortex finders (2, 3, 4) are disposed at an increasing depth inside the separator (1), in that order.

4. The cyclone separator (1) as claimed in claims 1 and 2, wherein said first, second and third vortex finders (2, 3, 4) have the same length.

5. The cyclone separator (1) as claimed in claim 4, wherein the number and the diameter of the vortex finders to be provided within the separator are selected depending upon the size of the particles to be processed by the separator.

Dated this 11th Day of November 2014

(Monaj Saha)
IN/PA-1884
OF SS DATTA & ASSOCIATES
APPLICANTS’ AGENT
,TagSPECI:FIELD OF THE INVENTION
The present invention in general relates to cyclone separators which are prevalent in a wide range of industries like mineral processing, coal washing and chemical industry including petroleum and petrochemical industries and many more. More particularly, the present invention relates to a cyclone separator which reduces the chances of over-grinding of fine particles for classification and enables recovery of material having different particle size / density from a heterogeneous mixture / feed in a single stage.

BACKGROUND OF THE INVENTION
The hydro cyclone or cyclone separator is one of the most important and often used units operating in mineral processing plants and many other similar plants. It is a key component in closed-mill grinding circuit. However, despite its popularity, some inherent problems associated with its operation remain unresolved for years. One problem is that about 30% to 40% of the fines report to the underflow of the cyclone instead of reporting to the overflow. These fines get re-circulated resulting in unnecessary over-grinding, which adds to the milling cost and adversely affects the efficiency of the downstream process.
Another vital problem with cyclone separators known in the art is that dense minerals, which are also most valuable, tend to concentrate in the underflow even though they may be fine and liberated enough to pass to the downstream process via cyclone overflow. As the underflow subsequently reports to the grinding mill, these dense minerals result in being over-ground. This adds unnecessarily to the cost of grinding and may also adversely affect the efficiency of downstream processes.
Furthermore, multistage cyclone separation is required in the prior arts to separate various discrete particle sizes or density classes from a heterogeneous feed, as the device is essentially capable of generating only two products in a single stage. This adds to operating costs, maintenance costs and downstream processing costs resulting in over pricing.
Accordingly, there is a need for a cyclone separator which by virtue of its design overcomes the drawbacks in conventional cyclone separators effectively.
The present invention meets the aforesaid long felt need and other needs associated therewith.

OBJECTS OF THE INVENTION
The principal object of the present invention is to provide a cyclone separator which substantially reduces the chances of over-grinding of fine particles in the classification circuit and also enables recovery of material having different particle sizes / density from a heterogeneous mixture / feed in a single stage.
Another object of the present invention is to provide cyclone separator which ensures that there is substantial reduction in overall operating costs, maintenance costs and downstream operating costs.
A further object of the present invention is to provide a cyclone separator which ensures substantially better classification efficiency through multiple vortex finders incorporated within it.
How the foregoing objects are achieved will be clear from the following description. In this context it is clarified that the description provided is non-limiting and is only by way of explanation.

SUMMARY OF THE INVENTION
A cyclone separator comprises of a cylindrical body which incorporates a plurality of vortex finders that are provided at the top of the separator, an inlet for tangential entry of a heterogeneous mixture of feed particles, an overflow discharge opening, an underflow discharge opening and a plurality of output pipes.
It produces three overflow streams, namely an inner overflow, a middle overflow and an outer overflow which exit through the overflow discharge opening. The plurality of output pipes collect particles of different size ranges from the three overflows at one go.
The plurality of vortex finders comprise of at least a first vortex finder, positioned co-axially within at least a second vortex finder, said first and second vortex finders being further positioned co-axially within at least a third vortex finder. The first, second and third vortex finders are selected so as to have an increasing diameter inside the cyclone separator in that order.
The first, second and third vortex finders are disposed at an increasing depth inside the cyclone separator, in that order. The first, second and third vortex finders can have the same length.
The number and the diameter of the vortex finders to be provided within the separator are selected depending upon the sizes of the particles to be processed by the separator.

BRIEF DESCRIPTION OF THE ACCOMPNYING DRAWINGS
The nature and scope of the present invention will be better understood from the accompanying drawings, which are by way of illustration of a preferred embodiment and not by way of any sort of limitation. In the accompanying drawings:-
Figure 1 is a front view of a preferred embodiment of a cyclone separator according to the present invention.
Figure 2 is a top view of the cyclone separator, front view of which is shown in figure 1.
Figure 3 is a schematic view of the cyclone separator shown in figure 1.
Figure 4 is a flow diagram showing the procedure of calculating the orbit radius of different sized particles in the cyclone separator according to the present invention.

DETAILED DESCREPTION OF THE INVENTION
Having described the main features of the invention above, a more detailed and non-limiting description of a preferred embodiment will be given in the following paragraphs with reference to the accompanying drawings.
In all the figures, like reference numerals represent like features. Further, the shape, size and number of the devices shown are by way of example only and it is within the scope of the present invention to change their shape, size and number without departing from the basic principle of the invention.
Further, when in the following it is referred to “top”, “bottom”, “upward”, “downward”, “above” or “below” , “right hand side”, “left hand side” and similar terms , this is strictly referring to an orientation with reference to the apparatus , where the base of the apparatus is horizontal and is at the bottom portion of the figures. The number of components shown is exemplary and not restrictive and it is within the scope of the invention to vary the shape and size of the apparatus as well as the number of its components, without departing from the principle of the present invention.
All through the specification including the claims, the words “cyclone”, “cyclone separator”, “vortex finder”, ”vortex finder inserts” are to be interpreted in the broadest sense and include similar terminologies as known to persons skilled in the art. Further, the shape shown in different views are exemplary and not restrictive.
The present invention provides a cyclone separator comprising of a main body, a tangential inlet entry of particles, an overflow discharge opening, an underflow discharge opening and a plurality of outlet pipes for collection of particles of different size ranges as cyclone overflow. The separator has a plurality of vortex finders fitted at the top of the cyclone separator. Each vortex finder is fitted coaxially into another relatively bigger sized vortex finder. The number of vortex finders to be inserted is decided based on the number of discrete particle-size range products to be recovered through cyclone overflow which is primarily dependent either on the requirement of the downstream processes or on the specified size range to be used for a specific application. The diameters and the length of vortex finders depend on the specific size range of particles to be collected through each vortex finder and also on the overall capacity achievable for a single cyclone separator based on its cylindrical diameter and the size as well as density distribution of the feed material. All calculations are made based on proposed mathematical models which are described in detail in subsequent paragraphs.
Figure 1 is a view of a preferred embodiment of the cyclone separator (1) according to the present invention. It shows a first vortex finder (2) which is positioned within a second vortex finder (3). Both said first vortex finder (2) and said second vortex finder (3) are positioned within a third vortex finder (4). It also shows the cylindrical part (5) of the separator, within which the vortex finders (2, 3, 4) are arranged. The vortex finders (2, 3, 4) are co-axial and inserted within one another as explained above.
The vortex finders are arranged so as to have an increasing diameter and depth, from the first vortex finder to the second, from the second to the third and from the third to the fourth (not shown) and so on in that order. It is within the scope of the present invention that the vortex finders have the same length. There can be a plurality of vortex finders arranged in the manner as shown in figure 1. The embodiment in figure 1 has been shown to have only three vortex finders by way of example and not by way of any limitation.
Figure 1 also shows the tangential inlet (6) for the particles.
Figure 2 is a top view of the cyclone separator (1) with tangential inlet (6). It clearly illustrates that the first vortex finder (2) and second vortex finder (3) are coaxially inserted within each other and also within the third vortex finder (4).
Figure 3 is a schematic view of the cyclone separator (1) shown in figure 1. It shows the coaxial arrangement of the vortex finders (2, 3, 4) and also the orbits of rotation of four exemplary particle size d, c, b and with increasing grain size, in that order.
Figure 4 shows the procedure of calculating the orbit radius of different sized particles in the cyclone separator according to the present invention.
Referring back to figure 1, the vortex finders (2, 3, 4) are extended in the cyclone body to different depths and are arranged one within the other and therefore said vortex finders (2, 3, 4) have different diameters. This increases the selectivity and the collection efficiency of the multiproduct cyclone.
It is also within the scope of the present invention that vortex finders (2, 3, and 4) have the same length so that this arrangement should not disturb the air core that plays a significant role in particle classification.
Now referring to figure 2 which is a top view, the coaxial arrangement of the vortex finders (2, 3, and 4) becomes clear. This arrangement ensures that three product streams exit through the overflow, namely an inner overflow, middle overflow and an outer overflow. Output pipes (not shown) for collection of particles of different size ranges from these overflows are provided on the cyclone.
The multi product cyclone shown in figures 1 and 2 uses a smaller spigot size than in the conventional units in order to create crowding and to hinder settling conditions in the conical section. However it is not essential that a smaller spigot size than the conventional units has to be used always. It is primarily dependent on the feed material characteristics and the downstream process requirement.
At the top of the separator, three output pipes (not shown) are connected with three different collecting devices for collection of three products having different size ranges of particles.
Particles with heavier mass should rotate in a larger orbit and get discharged through spigot while finer and lighter particles which have an orbit of rotation similar to the diameter of vortex finder (4) and the two inserts (2, 3) are discharged through the top of the cyclone. Thus, the particles are discharged as a three-product stream comprising of outer overflow through (4), inner overflow through (2) and middle overflow through (3). It is, therefore, possible to separate particles of different size-ranges and of different density from a heterogeneous mixture at one go using this new multi product cyclone (1).
Figures 1 and 2 are views of a four-product cyclone separator. It should be understood from the forgoing description in general and also from the following description that the present invention includes a multi-product separator, which can have a plurality of vortex finders depending upon the requirement, which essentially works on the same principle. All the vortex finders can be arranged in the same manner as the vortex finders (2, 3, 4) already shown and explained.
The basic principle of the present invention and its functioning is now further explained with reference to figure 3. The design of a multi product cyclone according to the present invention is conceived on the basis of equilibrium orbit hypothesis. This is explained below:
It is assumed that under a given operating condition, a cyclone is fed with a mixture of four particle (a, b, c and d) and that the individual mass of these four particles decreases gradually i.e. ma > mb > mc > md. Based on the above mentioned hypothesis each particle class will then have different orbits of rotations inside the separator at a given operating condition which may be represented as in figure 3.
Now, as the orbital diameter of a particle ‘a’ merges with the cyclone diameter (5), this particle should report to the underflow. Similarly, the orbital diameter of particle ‘b’ is equal the diameter of the third vortex finder (4) and therefore, it should report to overflow. Another vortex finder (3) is inserted into the existing vortex finder (4) whose diameter is equal to the orbit diameter of particle ‘c’. Hence, the particle ‘c’ should be possible to be collected separately through vortex finder (3). Another vortex finder (2) is inserted into the vortex finder (3) and the particle “d” whose orbit of rotation is equal to the vortex finder diameter (2) will be collected through vortex finder (2) in overflow. Therefore, the particles ‘b’, ‘c’ and ‘d’ are collected separately through overflow by using vortex finders of different diameters in a single go. Similarly, separation of various particles in the overflow product may be possible by using vortex finders of various diameters simultaneously in the same manner and this is within the scope of the present invention. Selection of appropriate vortex finders for a given application is therefore critical as determination of orbital diameters of individual particle class is difficult. The present invention achieves this in a simple manner.
If a particle of mass m is revolving at a radius r with an angular velocity ?, it is subjected to a centrifugal force, Fc = m?2r, in a radial direction and to a gravitational force, Fg = mg, in a downward vertical direction. The ratio of the centrifugal to the gravitational force, G, is known as the relative centrifugal force;

The sedimentation of a spherical particle in an incompressible fluid in a centrifugal field may be written from the equation of motion as;

Where, and µ are particles diameter, particles density, fluid density and viscosity of the fluid respectively.
Through the detailed analysis of particle motion in fluid in a centrifugal force field, the correlations we arrive at for the terminal velocity under centrifugal force is
,
where, is the terminal settling velocity of the particle under a gravitational force field and is the centrifugal terminal settling velocity. The exponent ‘n’ depends on the particle Reynolds number and according to Hsu (1981, p383) n=1 for ; n=1/ 3 for & n=1/ 2 for
It is evident from the above equation that the centrifugal effect becomes more dominant over the particles gravitational settling velocity, as the size of the particle becomes smaller. The settling velocity of any particle class in a centrifugal force field, can therefore, be calculated by using these three sets of equations. The settling velocity of a particle under a gravitational force field can be calculated using appropriate free settling models or hindered settling models available in the literature.
For a particular cyclone geometry, the G force at a given operating condition, can be calculated by using the following equation proposed by Bradley.

Where, ‘a’ is a modifying factor for inlet losses approximated by where, ‘ ’ is the feed inlet diameter, ‘ ’ is the cyclone diameter, and ‘g’ is the gravitational acceleration and ‘n’ is a constant which normally varies between 0.5 and 0.8.
The average residence time of particles inside a cyclone is simply equal to the volume of the cyclone divided by the throughput. Summation of times integrated along the paths of fluids flow suggest that the effective residence time is approximately half of the values given by dividing volume by flow rate. The orbit diameters of each particle class ‘a’,’b’, ‘c’ and ‘d’ can, therefore, be, calculated based on the centrifugal settling velocity of the targeted particle class multiplied by the particle residence time. The procedure of calculating the orbit radius is shown in the flow diagram depicted in figure 4.
From the foregoing description it would be clear that all the objects of the present invention have been met.
The present invention has been described with reference to some drawings and a preferred embodiment purely for the sake of understanding and not by way of any limitation and the present invention includes all legitimate developments within the scope of what has been described herein before and claimed in the appended claims.