LU92769B1

LU92769B1 - Pelletizing device

Info

Publication number: LU92769B1
Application number: LU92769A
Authority: LU
Inventors: Charles Steichen; Patrick Hutmacher
Original assignee: Wurth Paul Sa
Priority date: 2015-07-10
Filing date: 2015-07-10
Publication date: 2017-01-30

Abstract

The invention provides a pelletizing device (10) for producing pellets of agglomerated material, in particular for producing iron ore pellets for use in metallurgical furnaces. Such a pelletizing device (10) has an inlet end (20) for receiving raw material and an outlet end (24) for discharging formed pellets. The pelletizing device (10) comprises a pelletizer belt (12) mounted between a first primary drum (14) and a second primary drum (16), the first and second primary drum (14, 16) having their axes arranged in a direction generally parallel to a flow direction (18) of the raw material through the pelletizing device (10) from the inlet end (20) towards the outlet end (24) such that a direction of movement of the pelletizer belt (12) is essentially perpendicular to the flow direction (18) of the raw material through the pelletizing device (10). The first primary drum (14) is arranged at a lower height than the second primary drum (16) such that an upper run (30) of the pelletizer belt (12) is arranged at an angle of inclination with respect to the horizontal. At least one of the first and second primary drums (14, 16) is driven such that the upper run (30) of the pelletizer belt (12) carries the raw material up towards the second primary drum (16). The angle inclination and/or the pelletizer belt velocity is chosen such that material is allowed to roll back down towards the first primary drum (14). (Fig.1)

Description

Pelletizing device

Technical Field [0001] The present invention generally relates to a pelletizing device for producing pellets of agglomerated material, in particular for producing iron ore pellets from iron ore fines or metallurgical slag for use in metallurgical furnaces.

Background Art [0002] The formation of raw iron ore pellets, also known as pelletizing, has the objective of producing pellets in an appropriate band of sizes. Both mechanical force and thermal processes are used to produce the correct pellet properties. From an equipment point of view there are today two alternatives for industrial production of iron ore pellets: the pelletizing drum and the pelletizing disk.

[0003] Pelletizing drums generally receive raw material at an inlet end and discharge formed pellets at the opposite outlet end. As the drum rotates, the material is entrained upwards by the inner wall of the drum and then drops back down through gravity, while moisture is added to encourage particles to stick together. As the material progresses through the drum in direction of the outlet end, the size of the formed pellets gradually increases. The material in encouraged to flow through the drum in direction of the outlet end by either arranging a cylindrical drum with its axis inclined downwards, as e.g. disclosed in US 3,420,656, or by providing a cylindrical drum with internal protrusions, as e.g. disclosed in US 3,161,707 or GB 1,233,618, or by providing a drum having a diameter increasing in direction of the outlet end, as e.g. disclosed in US 3,154,806.

[0004] Pelletizing disks, on the other hand, are generally in the form of a large : inclined dish with a circumferential side wall for retaining the material. Raw material is fed onto the dish and is entrained upwards by the rotating dish. The material subsequently falls back down to a lower portion of the dish through gravity, while moisture is added to encourage particles to stick together. With each such cycle, the pellets increase in size.

The side wall of the pelletizing disk is dimensioned such that, once the pellets have reached a predetermined size, they fall over the edge of the side wall. An example of such . .. a pelletizing disk is shown in a rather simple form in GB 811,610 and in a more elaborate form in US 8,808,590. The pelletizing disk disclosed in US 8,808,590 has adjustable side walls allowing to vary the effective height of the sidewall, thereby allowing to adjust the size of the pellets discharged from the disk.

[0005] The known pelletizing drums and disks are generally rather cumbersome in view of their large size. Also, regular maintenance, which is required due to material sticking to the pelletizing device, may be lengthy and costly. Indeed, large dimensions, inefficient use of total volume, sticking problems in rotating drums, complicate construction due to inclination system and relatively large dimensions for quite allow productivity in rotating disks are only some drawbacks of these known devices.

Technical Problem [0006] The object of the present invention is to provide an alternative to the currently ,-T known pelletizing devices, alleviating at least some of the drawbacks thereof. This object is achieved by a pelletizing device as claimed in claim 1.

General Description of the Invention [0007] The invention provides a pelletizing device for producing pellets of agglomerated material, in particular for producing iron ore pellets for use in metallurgical furnaces. Such a pelletizing device has an inlet end for receiving raw material and an outlet end for discharging formed pellets. The pelletizing device comprises a pelletizer belt mounted between a first primary drum and a second primary drum, the first and second primary drum having their axes arranged in a direction generally parallel to a flow direction of the raw material through the pelletizing device from the inlet end towards the outlet end such that a direction of movement of the pelletizer belt is essentially perpendicular to the flow direction of the raw material through the pelletizing device. The first primary drum is arranged at a lower height than the second primary drum such that an upper run of the pelletizer belt is arranged at an angle of inclination with respect to the horizontal. At least one of the first and second primary drums is driven such that the upper run of the pelletizer belt carries the raw material up towards the second primary drum. The angle inclination and/or the pelletizer belt velocity is chosen such that material is allowed to roll back down towards the first primary drum.

[0008] As the material progresses through the pelletizing device, it is moved upwards, transversally to the flow direction of the raw material through the pelletizing device. On its way upwards, the material comes into contact with material that is rolling back down through gravity. Because of the moisture content in the material, the latter sticks and forms slightly bigger lumps. As the material reaches a certain height and size, it roils back down through gravity. On its way towards the outlet end, the material moves up and down the pelletizer belt several times and the size of the lumps of material slowly increases until the desired pellet size is achieved at the outlet end.

[0009] Due to the belt velocity, the material starts to roll itself and the pelletizing process, also referred to as tumble agglomeration, can proceed.

[0010] One of the major advantages of the present pelletizing device is the free access from one side. Access to the surface on which agglomeration takes place is not hampered by the presence of an opposite surface, as would be the case in a pelletizing device of the pelletizing drum type. Preferably, a water injection system is provided for spraying water onto the material on the upper run of the pelletizer belt, thereby ensuring that the material has sufficient moisture to stick. The improved access not only facilitates the installation of such a water injection system, but also the monitoring of the amount of water injected.

[0011] Also, with respect to pelletizing drums and pelletizing disks, the overall size of the pelletizing device can be reduced.

[0012] The use of a belt as surface on which agglomeration takes place also has the particular advantage that sticking problems of material on that surface can be greatly reduced. Indeed, material is firstly less likely to stick to the belt surface. Furthermore, any ; material that does stick to the belt can be easily removed, i.e. by use of a scraper that may be arranged at or downstream of the second primary drum to clean the pelletizer belt.

[0013] A further important advantage of the present invention is the possibility of continuously charging raw material onto the pelletizer belt and thus produce pellets in a : continuous manner.

[0014] Preferably, the first and second primary drums have their axes arranged at an angle with respect to the horizontal, the axes pointing downwards in direction of the outlet end, thereby encouraging the material to flow from the inlet end towards the outlet end.

The angle of the axes of the first and second primary drums may be adjustable, which allows adjusting the stay time of the material on the pelletizer belt. This may be of . advantage to either adjust the size of the pellets or to accommodate for a change in . .... material and/or moisture content.

[0015] According to a preferred embodiment, the pelletizing device further comprises ' a plurality of secondary rollers arranged between the first and second primary drums for carrying the pelletizer belt, the secondary rollers being arranged with their axes parallel to . the axes of the first and second primary drums, the secondary rollers being arranged so as to form a concave section between the first and second primary drums. As the pelletizer belt rests on the primary drums and secondary rollers, the upper run of the pelletizer belt forms a concave agglomeration surface. Such a concave shape encourages the rolling of the material on the pelletizing device and thus the pellet formation. The concave section may e.g.be a section of a circle or oval.

[0016] Advantageously, the secondary rollers are arranged such that their position is adjustable, thus providing the possibility of adjusting the shape/inclination of the upper run and consequently pellet formation.

[0017] Preferably, both of the first and second primary drums are individually driven in synchronized manner so as to keep the upper run of the pelletizer belt in contact with the secondary rollers.

[0018] Furthermore, at least one guiding roller in contact with a return run of the . ; pelletizer belt may be provided; such a guiding roller being preferably arranged with its ... ... axis parallel to the axes of the first and second primary drums.

[0019] Preferably, the at least one guiding roller is arranged such that its position is adjustable, thereby allowing the guiding roller to be used for taking up any slack that may have been caused by the adjustment of the position of the secondary rollers.

Brief Description of the Drawings [0020] A preferred embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:

Fig.1 is a simplified perspective view of a pelletizing device according to the present invention;

Fig.2 is a schematic cut through the pelletizing device of Fig.1;

Fig.3 is a schematic cut through the pelletizing device of Fig.1 with the pelletizer belt in a different position;

Fig.4 is a simplified perspective view of the pelletizing device of Fig.1.

Description of Preferred Embodiments [0021] Fig.1 shows a preferred embodiment of a pelletizing device according to the invention. Such a pelletizing device 10 comprises a pelletizer belt 12 mounted between a first primary drum 14 and a second primary drum 16. As can be seen, the first and second primary drums 14, 16 are arranged such that their axes are generally parallel to the direction of flow of material through the pelletizing device. This direction is indicated by reference numeral 18. The pelletizing device 10 has an inlet end 20 where raw material is deposited from a charging belt 22 onto the pelletizer belt 12 and an outlet end 24 from where formed pellets are discharged from the pelletizer belt 12 onto a discharge belt 26.

[0022] As can be more closely seen of Fig.2, the pelletizing device further comprises a plurality of secondary rollers 28 arranged between the first and second primary drums 14, 16. The secondary rollers 28 are arranged so as to form a concave section between the first and second primary drums 14, 16. The area on the upper run 30 of the pelletizer belt 12 in which agglomeration of material takes place is schematically indicated by shape 32. Through moving the upper run 30 from the first primary drum 14 towards the second primary drum 16, the material within the shape 32 rolls as indicated by arrows 34. At least one guiding roller 36 is in contact with a return run 38 of the pelletizer belt 12.

[0023] In order to keep the upper run 30 of the pelletizer belt 12 in contact with the secondary rollers 28, the first and second primary drums 14, 16 are individually driven in synchronized manner with variable speed.

[0024] A water injection system 40 is provided for spraying water onto the material on the upper run 30 of the pelletizer belt 12. Any material sticking to the pelletizer belt 12 can be removed therefrom by means of a scraper 42 contacting the belt.

[0025] Fig.3 shows the pelletizing device of Fig.2 with a differently adjusted concave shape of the upper run 30. Indeed, the secondary rollers 28 are arranged such that their position is adjustable. Reference 28’ shows the same secondary rollers in a different position. The pelletizer belt 12’ thus presents a different shape. Consequently, the area on in which agglomeration of material takes place is schematically indicated by shape 32’. The guiding roller 36 is also arranged such that its position is adjustable, thereby taking up some slack and allowing the pelletizer belt 12, 12’ to rest on the secondary rollers 28, 28’ whatever the position of the latter.

[0026] Fig.4 shows the angle of inclination a between the horizontal and the axes of the primary drums 14,16 and guiding roller 36. The angle of inclination a is adjustable so as to control the rate at which materia! advances towards the outlet end 24.

Legend of Reference Numbers: 10 pelletizing device 30 upper run 12 pelletizer belt 32 agglomeration area 14 first primary drum 34 rolling movement of material 16 second primary drum 36 guiding roller 18 direction of flow of material 38 return run 20 inlet end 40 water injection system 22 charging belt 42 scraper 24 outlet end a angle of inclination 26. discharge belt 28 secondary roller

Claims

1. A pelletizing device for producing pellets of agglomerated material, in particular for producing iron ore pellets for use in metallurgical furnaces, wherein: the pelletizing device has an inlet end for receiving raw material and an outlet end for ' discharging formed pellets, the pelletizing device comprises a pelletizer belt mounted between a first primary drum and a second primary drum, the first and second primary drum having their axes arranged in a direction generally parallel to a flow direction of the raw material through the pelletizing device from the inlet end towards the outlet end such that a direction of movement of the pelletizer belt is essentially perpendicular to the flow direction of the raw material through the pelletizing device, the first primary drum is arranged at a lower height than the second primary drum such that an upper run of the pelletizer belt is arranged at an angle of inclination with respect to the horizontal, at least one of the first and second primary drums is driven such that the upper run of the pelletizer belt carries the raw material up towards the second primary drum, the angle inclination and/or the pelletizer belt velocity is chosen such that material is allowed to roll back down towards the first primary drum.

2. The pelletizing device according to claim 1, wherein the first and second primary drums have their axes arranged at an angle with respect to the horizontal, the axes pointing downwards in direction of the outlet end.

3. The pelletizing device according to claim 2, wherein the angle of the axes of the first and second primary drums is adjustable.

4. The pelletizing device according to any of the preceding claims, wherein the pelletizing device further comprises a plurality of secondary rollers arranged between the first and second primary drums for carrying the pelletizer belt, the secondary rollers being arranged with their axes parallel to the axes of the first and second primary drums, the secondary rollers being arranged so as to form a concave section between the first and second primary drums.

5. The pelletizing device according to claim 4, wherein the concave section is a section of a circle or oval.

6. The pelletizing device according to claims 4 or 5, wherein the guiding rollers are arranged such that their position is adjustable.

7. The pelletizing device according to any of claims 4 to 6, wherein both of the first and second primary drums are individually driven in synchronized manner.

8. The pelletizing device according to any of claims 4 to 7, further comprising at least one guiding roller in contact with a return run of the pelletizer belt, the at least one guiding roller being arranged with its axis parallel to the axes of the first and second primary drums.

9. The pelletizing device according to claim 8, wherein the at least one guiding roller is arranged such that its position is adjustable.

10. The pelletizing device according to any of the preceding claims, further comprising a water injection system for spraying water onto the material on the upper run of the pelletizer belt.

11. The pelletizing device according to any of the preceding claims, further comprising a scraper in contact with the pelletizer belt, the scraper being arranged at or downstream of the second primary drum.