FIELD OF THE INVENTION

The present disclosure relates generally to a pelletizing system. More particularly, the disclosure relates to a pelletizing system suitable for materials that may be sensitive to water or air.

BACKGROUND

Extrusion is a manufacturing process where a material, typically in the form of a melt, is pushed or drawn through a die with a desired cross-sectional profile. Extrusion may be used to create material of varying sizes and to this end; a cutter assembly may be used to cut the strands of different diameter into pieces of small length called pellets. A machine creating pellets in this manner is called a pelletizer and the process is called pelletization. On account of the high temperatures involved in the extrusion process, the pellets are to be cooled immediately.

Various systems have been evolved to cool the strands or the pellets. Some systems immerse strands from the extruder die in to water, followed by air drying and then cutting of the cooled strands to form the pellets. Other systems using die face cutting followed by immersing the pellets in flowing water or alternatively an underwater pellitizer may be employed where the cutter assembly is immersed in water.

Conventional underwater pelletizers include a die plate with one or more extrusion orifices for extruding strands of molten polymer or other extrudable materials. Such extruding strands are cut into pellets by rotating cutter blades. The cutter blades may be part of a cutter hub supporting multiple blades. The cutter blades along with the die plate are enclosed in a water box and immersed in flowing water. The flowing water cools and rigidities the extruding strands enabling the cutter blades to better shear the strands into pellets. In addition, cooling reduces the tendency of pellets to stick to each other (agglomerate) or to stick to other surfaces of the pelletizer. Finally, a pellet - water slurry is formed which is guided by the water flow for collection and subsequent drying of the pellets.

Underwater pelletizers fail to form pellets of extrudable materials which are sensitive to air or water. Many grafted polymers and cabling compounds are of such nature. Hence, there is a need for a system and a method for pelletization of materials that are reactive to water or air.

In addition, such pelletizing systems require significant quantities of flowing water along with cooling towers to cool the high temperature pellets. As a result, existing systems are bulky and occupy large space. There is also a need for a pelletizing system that does not require large floor space.

BRIEF DESCRIPTION OF DRAWINGS

Figure 1 is a schematic illustration of a pelletizing system in accordance with a first embodiment of the invention.

Figure 2 is a schematic illustration of a pelletizing system in accordance with a second embodiment of the invention.

Figure 3 is a side view of the pelletizing system of Figure 2, illustrating the extruder interface of the pelletizing system.

Figure 4 is a schematic illustration of the pelletizing system with an integrated bagging system.

SUMMARY

A pelletizing system for materials to be pelletized is disclosed. The pelletizing system includes a chamber defining a base and a material inlet positioned above the base.

The material inlet configured to receive the material to be pelletized. The chamber further includes a belt inlet and a belt outlet positioned substantially towards the base of the chamber.

The pelletizing system also includes a rotating metal conveyor belt configured to enter and exit the chamber by the belt inlet and the belt outlet respectively. The pelletizing system also includes a trough positioned outside the chamber and configured to hold a cooling fluid such that the rotating metal conveyor belt passes through the trough before entering the chamber by the belt inlet. The pelletizing system further includes a cutter assembly positioned at the material inlet for receiving the material to be pelletized and cutting the material into pellets such that the pellets formed by the cutter assembly fall through the chamber onto the metal conveyor belt.

In accordance with an embodiment, the pelletizing system includes a chamber defining a material inlet. The pelletizing system also includes a plurality of rotating metal conveyor belts positioned within the chamber with one belt positioned vertically below another belt. The pelletizing system further includes a cutter assembly positioned at the material inlet for receiving the material to be pelletized and cutting the material into pellets such that the pellets formed by the cutter assembly fall through the chamber onto at least one of the plurality of rotating metal conveyor belts.

In accordance with an aspect, the materials to be pelletized are received by the material inlet of the chamber and then passed to the cutting assembly to form pellets. The pellets formed by the cutting assembly fall through the chamber onto the rotating metal conveyor belt. The pellets maintain contact with the rotating metal conveyor belt for a pre¬determined time period sufficient to lower the temperature of the pellets. The metal conveyor belts are directly or indirectly cooled by a cooling fluid.

DETAILED DESCRIPTION

For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.

It will be understood by those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not intended to be restrictive thereof. Throughout the patent specification, a convention employed is that in the appended drawings, like numerals denote like components.

Reference throughout this specification to "one embodiment" "an embodiment" or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase "in one embodiment", "in an embodiment" and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.

The disclosure provides for a pelletizing system. The disclosed pelletizing system occupies less floor space and is particularly suitable for materials not suitable for contact with air or water. Such materials may be sensitive to air or water at the extruding temperatures or there may be general adverse or unwanted effects on these materials while pelletizing in the presence of air or water.

In accordance with an aspect, the disclosure provides for the cooling of pellets by contact with a metal surface. Metal being a good conductor of heat is suitable for quickly cooling the pellets. A cooling fluid cools the metal surface directly or indirectly.

In accordance with another aspect, this disclosure provides for an inert and dry environment for pelletization of a material. Using an inert fluid such as dry nitrogen gas, dry air or liquefied nitrogen etc may provide the inert and dry environment.

Figure 1 is a schematic illustration of a pelletizing system in accordance with a first embodiment. The pelletizing system 100 comprises of a chamber 102 defining abase 130, a material inlet 128, a cutter assembly 108, a rotating metal conveyor belt 112 and a trough 120. The pelletizing system 100 may further comprise of a collecting bin 114, a brush 116, one or more sponge roller 122, one or more heated rollers 124 and a motor 110. The pelletizing system also comprises of an inlet 104 and an outlet 126 for an inert fluid.

The chamber 102 further comprises of a belt inlet 132 and a belt outlet 134 positioned substantially towards the base 130 of the chamber 102.

In accordance with an embodiment of the invention, the material inlet 128 is positioned above the base 130 of the chamber 102 and configured to receive the material to be pelletized. The material to be pelletized may be in the form of strands. The incoming material is passed to the cutter assembly 108. The cutter assembly 108 cuts the material received into pellets. The cutter assembly l0S is positioned at the material inlet 128 and is powered by motor 110.

The pellets formed by the cutter assembly 108 fall downward and land onto the rotating metal conveyor belt 112. The rotating metal conveyor belt 112 is positioned below the cutter assembly 108 of the chamber 102, The rotating metal conveyor belt 112 is configured to enter and exit the chamber 102 by the belt inlet 132 and the belt outlet 134 respectively. The rotating metal conveyor belt 112 transports the pellets to the collecting bin 114 for collection. The collection bin 114 may be positioned outside the chamber 102. Speed of the belt 112 is adjusted by factoring rate of material input and time required to cool the pellets.

Further, the heat absorbed by the rotating metal conveyor belt 112 from the pellets, results in heating of the rotating metal conveyor belt 112. The trough 120 is positioned outside the chamber 102 and configured to hold a cooling fluid such that the rotating metal conveyor belt 112 passes through the trough 120 before entering the chamber 102 by the belt inlet 132.

In accordance with an embodiment, the cooling fluid contained in the trough 120 may be water. Alternatively, if the material being pelletized is extremely sensitive to the presence of water, a volatile cooling fluid like ethanol may be used to cool rotating metal conveyor belt 112.

Further, in accordance with an aspect the rotating metal conveyor belt 112 is operatively connected to at least one heated roller 124 and at least one sponge roller 122 positioned outside the chamber 102 and configured to remove water or cooling fluid present on the rotating metal conveyor belt 112.

In accordance with an embodiment, the heated roller 124 and the sponge roller 122 are configured for drying the rotating metal conveyor belt 112 after it has passed through the trough 120 of cooling fluid. This prevents any water or cooling fluid from entering the chamber 102 through the rotating metal conveyor belt 112.

In accordance with an embodiment of the invention, any pellets sticking to the rotating metal conveyor belt 112 are scraped by the brush 116 to fall into the collecting bin 114. The brush 116 is positioned proximate to the belt outlet 134 of the chamber 102.

With reference to Figure 2, a pelletizing system 100 in accordance with a second embodiment is illustrated. The pelletizing system 100 comprises of a chamber 102 defining a material inlet 128. A plurality of rotating metal conveyor belts 138,140,142 is positioned within the chamber 102 with one belt positioned vertically below another belt. The cutter assembly 108 is positioned at the material inlet 128 for receiving the material to be pelletized and cutting the material into pellets such that the pellets formed by the cutter assembly 108 falls through the chamber 102 onto at least one of the plurality of rotating metal conveyor belts 138,140,142. Preferably, the plurality of metal conveyor belts 138,140,142 is arranged such that the pellets formed by the cutter assembly 108 falls on to the top most conveyor belt 142.

In the embodiment illustrated, three rotating metal conveyor belts 138,140,142 are provided within the chamber 102 one below the other. The belts 138,140,142 are positioned such that pellets are conveyed from one belt to a belt below it. In accordance with an embodiment, a belt may extend horizontally beyond the belt above it. Specifically, belt 140 extends horizontally to the left beyond the belt 142 above it and belt 138 extends horizontally to the right beyond belt 140 above it

In accordance with a further embodiment, the belts 138,140,142 may rotate at different speeds. By way of specific example of the three belts illustrated in figure 2, the top belt 142 may rotate at a relatively fast speed, the intermediate belt 140 may rotate at a moderate speed, while the lower most belt 138 rotates at a slow speed. The speeds of the belt may be adjusted to maintain sufficient contact time between the belts and the pellets. Moreover, in the example illustrated, consecutive belts may rotate in opposite direction so as to maximize contact time between the pellets and the belts.

Referring again to the example of Figure 2, pellets formed by the cutter fall on to the top belt 142 rotating in an anti-clockwise direction. The pellets are conveyed to the intermediate belt 140 rotating in the opposite direction and then on to the bottom belt 138 also rotating in the anti-clockwise direction.

Liquid cooled rollers 144 are used to cool the metal conveyor belts 138,140,142, By way of specific example, water-cooled rollers 144 are operatively connected to the metal conveyor belts 138,140,142 to cool the belts. The liquid cooled rollers 144 ensure that liquid or water does not directly contact the belt.

In another embodiment, the chamber 102 is maintained as an inert chamber 102. The inert chamber 102 is achieved by circulating an inert fluid such as dry nitrogen gas, dry air or liquefied nitrogen within the chamber 102.

With reference to the embodiment of Figure 1, the inert fluid flows out of the chamber 102 through the outlet 126 and is recycled to enter the chamber 102 again from the inlet 104. With reference to the embodiment of Figure 2, the inert fluid enters the chamber 102 through blower 146 and exits through an exit (not shown).

In accordance with an embodiment, the cutter assembly 108 may scatter the pellets up to various distances. The depth of chamber 102 is selected to be larger than the maximum range of the scattering pellets. This avoids the problem of pellets sticking to the wall of chamber 102.
In the embodiments illustrated, the rotating metal conveyor belt 112,138,140,142 is configured to rotate in a vertical plane. Alternatively, the rotating metal conveyor belts 112,138,140,142 may also be configured to rotate in a horizontal plane.

In another embodiment, the rotating metal conveyor belt 112,138,140,142 is coated with a non-sticking material to avoid the problem of pellets sticking to it. An example of a non-sticking material is Teflon. Alternatively, the rotating metal conveyor belts 112,138,140,142 may be coated with low friction material.

In another embodiment, the rotating metal conveyor belt 112,138,140,142 is provided with a profile or variations on its surface. The profiles or variations on the rotating metal conveyor belts 112,138, 140, 142 are in the form of projections or depressions to further limit agglomeration or sticking of the pellets on the rotating metal conveyor belts 112,138, 140, 142.

In accordance with an embodiment of the invention, the rotating metal conveyor belts 112,138,140^142 define openings through which an inert or cooling fluid may flow. Such an arrangement further cools the rotating metal conveyor belt and the pellets and helps avoid agglomeration of the falling pellets.

In accordance with an embodiment of the invention, the rotating metal conveyor belt 112,138,140,142 is sufficiently long which allows for effective heat transfer and dissipation between the pellets and the belt.

In accordance with an embodiment, a cooling system is provided at the cutter assembly 108. The cooling system may be in the form of a forced air draft.

In accordance with an embodiment, one or more heat exchangers 150 may be provided for cooling the chamber 102. Specifically, the heat exchangers 150 may be used to cool the fluid circulated within the chamber 102 and the cutter assembly 108,

In accordance with an embodiment and as illustrated in Figure 2, a rotary valve 136 is provided at the outlet of the pelletizing system 100 for discharging cooled pellets from the chamber 102. The rotary valve 136 prevents significant losses of inert gases from the chamber 102 during exit of pellets.

The material inlet of the pelletizing system 100 may be integrally connected with an outlet of an extruder (not shown), which is preferred. With reference to Figure 3, a seal 152 may be provided to enclose the joint between the pelletizing system 100 and the outlet of the extruder (not shown). By way of example, a hydraulic seal may be provided. However, principles of the disclosure may equally be applied where the pelletizing system 100 is not integrally connected with the outlet of the extruder (not shown).

In accordance with an embodiment and as illustrated by Figure 4, the pelletizing system 100 may be provided with an integral bagging system 156 that permits the bagging of the pellets in the inert environment. The bagging system 156 may be configured to receive the pellets from the rotating metal conveyor belt 112,138, 140, 142 and pack the same in air tight packaging means for further storage or transport. As illustrated, pellets formed are conveyed from the pelletizing system 100 by a conveyor 154 to the bagging system 156.

SPECIFIC EMBODIMENTS ARE DESCRIBED BELOW

A pelletizing system comprising a chamber defining a base and a material inlet positioned above the base, the material inlet configured to receive the material to be pelletized, the chamber further including a belt inlet and a belt outlet positioned substantially towards the base of the chamber, a rotating metal conveyor belt configured to enter and exit the chamber by the belt inlet and the belt outlet respectively, a trough positioned outside the chamber and configured to hold a cooling fluid such that the rotating metal conveyor belt passes through the trough before entering the chamber by the belt inlet and a cutter assembly positioned at the material inlet for receiving the material to be pelletized and cutting the material into pellets such that the pellets formed by the cutter assembly fall through the chamber onto the metal conveyor belt.

Such pelletizing system(s), further comprising at least one heated roller positioned outside the chamber operatively connected to the metal conveyor belt; the heated roller configured for drying the rotating metal conveyor belt after it has passed through the trough.

Such pelletizing system(s), further comprising at least one sponge roller operatively connected to the metal conveyor belt; the sponge roller configured for drying the rotating metal conveyor belt after it has passed through the trough.

Such pelletizing system(s), wherein the cooling fluid in the trough is water.

Such pelletizing system(s), wherein the cooling fluid is a volatile liquid.

A pelletizing system comprising a chamber defining a material inlet, a plurality of rotating metal conveyor belts positioned within the chamber with one belt positioned vertically below another belt; and a cutter assembly positioned at the material inlet for receiving the material to be pelletized and cutting the material into pellets such that the pellets formed by the cutter assembly fall through the chamber onto at least one of the plurality of rotating metal conveyor belts.

Such pelletizing system(s), further comprising a plurality of liquid cooled rollers operatively connected to the plurality of rotating metal conveyor belts.

Such pelletizing system(s), wherein one belt extends horizontally beyond another belt.

Such pelletizing system(s), wherein the plurality of belts rotate at different speeds.

Such pelletizing systern(s), wherein the belt positioned below another belt rotates slower than the belt above it.

Such pelletizing system(s), further comprising a heat exchanger for cooling the air within the chamber.

Such pelletizing system(s), further comprising a rotary valve for discharging cooled pellets from the chamber.

Such pelletizing system(s), wherein the rotating metal conveyor belt defines a plurality of openings through which a cooling or inert gas may pass.

Such pelletizing system(s), wherein the rotating metal conveyor belt is coated with a non-stick material.

Such pelletizing system(s), wherein the rotating metal conveyor belt is coated with a low friction material.

Such pelletizing system(s), configured to engage an outlet of an extruder and further comprising a seal to enclose the extruder outlet and the material inlet.

Such pelletizing system(s), comprising a cooling system at the cutter assembly.
Such pelletizing system(s), wherein the rotating metal conveyor belt includes a profile on its surface.

Such pelletizing system(s), wherein the profile on the rotating metal conveyor belt is in the form of projections or depressions.

Such pelletizing system(s), wherein the chamber is an inert chamber including an inlet and an outlet for an inert fluid.

Such pelletizing system(s), further comprising a bagging system configured to receive pellets from the chamber and package the pellets in a bag.

FURTHER SPECIFIC EMBODIMENTS ARE DESCRIBED BELOW

A process for forming pellets on a pelletizing system, the pelletizing system comprising a chamber defining a material inlet, a plurality of rotating metal conveyor belts positioned within the chamber with one belt positioned vertically below another belt; and, a cutter assembly positioned at the material inlet configured to receive the material to be pelletized; the method comprising;

feeding material to be pelletized to the pelletizing system through the material inlet of the chamber, cutting the material into pellets at the cutter assembly such that the pellets formed fall through the chamber on to at least one of the plurality of rotating metal conveyor belt and maintaining contact between the pellets and the plurality of rotating metal conveyor belts for a pre-determined time period sufficient to lower the temperature of the pellets.

Such process(s), further comprising passing an inert gas into the chamber to maintain an inert chamber.

Such process(s), wherein pellets are conveyed from a rotating metal conveyor belt to the rotating metal conveyor belt below it.

Such process(s), wherein the plurality of belts rotate at different speeds.

Such process(s), wherein the metal conveyor belt is cooled by a liquid cooled roller.

INDUSTRIAL APPLICABILITY

The pelletizing system 100 as disclosed above provides for a simple and efficient way of pelletizing the materials that are reactive to water or air. The pelletizing system 100 as disclosed, offers possibilities of space saving and reduced requirements for cooling fluid.

The pelletizing system 100 as disclosed provides an inert and dry environment for pelletization of the material. The pelletizing system 100 also provides for the inert gas or fluid to be recycled so that the inert gas or fluid can be re-circulated in the pelletizing system.

The pelletizing system 100 as disclosed provides for an effective way of cooling of the pellets by constituting the rotating conveyor belt 112 with a metal surface. The metal surface is a good conductor of heat and is suitable for quickly cooling the pellets.

While the first embodiment, discloses directly contacting the metal belt with a cooling fluid, the second embodiment discloses a system of cooling the belts using liquid cooled rollers. The second embodiment offers greater benefits for materials sensitive to moisture or cooling fluids.

While example embodiments of the invention have been illustrated and described, it will be clear that the invention is not limited to these embodiments only. Numerous modifications, changes, variations, substitutions and equivalents will be apparent to those skilled in the art without departing from the spirit and scope of the invention as described in the claims.

We Claim:

1. A pelletizing system comprising;

a chamber defining a base and a material inlet positioned above the base, the material inlet configured to receive the material to be pelletized, the chamber further including a belt inlet and a belt outlet positioned substantially towards the base of the chamber;

a rotating metal conveyor belt configured to enter and exit the chamber by the belt inlet and the belt outlet respectively;

a trough positioned outside the chamber and configured to hold a cooling fluid such that the rotating metal conveyor belt passes through the trough before entering the chamber by the belt inlet;

and

a cutter assembly positioned at the material inlet for receiving the material to be pelletized and cutting the material into pellets such that the pellets formed by the cutter assembly fall through the chamber onto the metal conveyor belt.

2. A pelletizing system as claimed in claim 1, further comprising at least one heated roller positioned outside the chamber operatively connected to the metal conveyor belt; the heated roller configured for drying the rotating metal conveyor belt after it has passed through the trough.

3. A pelletizing system as claimed in claim 1, further comprising at least one sponge roller operatively connected to the metal conveyor belt; the sponge roller configured for drying the rotating metal conveyor belt after it has passed through the trough.

4. A pelletizing system as claimed in claim 1, wherein the cooling fluid in the trough is water.

5. A pelletizing system as claimed in claim 1, wherein the cooling fluid is a volatile liquid.

6. A pelletizing system comprising:

a chamber defining a material inlet,

a plurality of rotating metal conveyor belts positioned within the chamber with one belt positioned vertically below another belt; and

a cutter assembly positioned at the material inlet for receiving the material to be pelletized and cutting the material into pellets such that the pellets formed by the cutter assembly fall through the chamber onto at least one of the plurality of rotating metal conveyor belts.

7. A pelletizing system as claimed in claim 6 further comprising a plurality of liquid cooled rollers operatively connected to the plurality of rotating metal conveyor belts.

8. A pelletizing system as claimed in claim 6 wherein one belt extends horizontally beyond another belt,

9. A pelletizing system as claimed in claim 6 wherein the plurality of belts rotate at different speeds.

10. A pelletizing system as claimed in claim 9 wherein the belt positioned below another belt rotates slower than the belt above it.

11. A pelletizing system as claimed in claim 1 or 6 further comprising a heat exchanger for cooling the air within the chamber.

12. A pelletizing system as claimed in claim 1 or 6 further comprising a rotary valve for discharging cooled pellets from the chamber,

13. A pelletizing system as claimed in claim 1 or 6, wherein the rotating metal conveyor belt defines a plurality of openings through which a cooling or inert gas may pass.

14. A pelletizing system as claimed in claim 1 or 6, wherein the rotating metal conveyor belt is coated with a non-stick material.

15. A pelletizing system as claimed in claim 1 or 6, wherein the rotating metal conveyor belt is coated with a low friction material.

16. A pelletizing system as claimed in claim 1 or 6 configured to engage an outlet of an extruder and further comprising a seal to enclose the extruder outlet and the material inlet.

17. A pelletizing system as claimed in claim 1 or 6 comprising a cooling system at the cutter assembly.

18. A pelletizing system as claimed in claim 1 or 6 wherein the rotating metal conveyor belt includes a profile on its surface.
19. A pelletizing system as claimed in claim 18, wherein the profile on the rotating metal conveyor belt is in the form of projections or depressions.

20. A pelletizing system as claimed in any preceding claim, wherein the chamber is an inert chamber including an inlet and an outlet for an inert fluid.

21. A pelletizing system as claimed in any preceding claim further comprising a bagging system configured to receive pellets from the chamber and package the pellets in a bag.

22. A process for forming pellets on a pelletizing system, the pelletizing system comprising a chamber defining a material inlet, a plurality of rotating metal conveyor belts positioned within the chamber with one belt positioned vertically below another belt;

and, a cutter assembly positioned at the material inlet configured to receive the material to be pelletized; the method comprising:

feeding material to be pelletized to the pelletizing system through the material inlet of the chamber;

cutting the material into pellets at the cutter assembly such that the pellets formed fall through the chamber on to at least one of the plurality of rotating metal conveyor belt; and

maintaining contact between the pellets and the plurality of rotating metal conveyor belts for a pre-determined time period sufficient to lower the temperature of the pellets.

23. A process as claimed in claim 22 further comprising passing an inert gas into the chamber to maintain an inert chamber.
24. A process as claimed in claim 22 wherein pellets are conveyed from a rotating metal conveyor belt to the rotating metal conveyor belt below it.

25. A process as claimed in claim 22 or 24 wherein the plurality of belts rotate at different speeds.

26. A process as claimed in claim 22 wherein the metal conveyor belt is cooled by a liquid cooled roller.

27. A pelletizing system substantially as herein described with reference to and as illustrated in the accompanying drawings.