INDURATION MACHINE

Abstract

An induration machine includes a travelling grate for transporting bulk material along a transport direction from a heating zone for heating and/or drying the material to a cooling zone for cooling the material by cooling gas. The machine includes a hood disposed over the travelling grate having a first hood section in the heating zone and a second hood section in the cooling zone; and two recuperation ducts for guiding used cooling gas from the second hood section to the first hood section.

The recuperation ducts are disposed on opposite sides of the hood, are laterally offset with respect to the hood, and are connected to the second hood section by a V-shaped gas collector duct. Each recuperation duct is connected to the first hood section by at least one gas supply duct and has at least one dust purge opening disposed in the lowermost part of the recuperation duct for purging dust from the recuperation duct.

Claims

1. An induration machine comprising: a travelling grate for transporting bulk material along a transport direction from a heating zone for heating and/or drying the material to a cooling zone for cooling the material by cooling gas; a hood disposed over the travelling grate having a first hood section in the heating zone and a second hood section in the cooling zone; and two recuperation ducts for guiding used cooling gas from the second hood section to the first hood section, wherein the recuperation ducts are disposed on opposite sides of the hood, are laterally offset with respect to the hood, and are connected to the second hood section by a V-shaped gas collector duct and each recuperation duct is connected to the first hood section by at least one gas supply duct and has at least one dust purge opening disposed in the lowermost part of the recuperation duct for purging dust from the recuperation duct.

2. The induration machine according to claim 1, comprising means for collecting dust purged from the recuperation duct.

3. The induration machine according to claim 1, wherein a purge duct is connected to each purge opening

4. The induration machine according to claim 1, comprising a plurality of burners for heating the material in the heating zone, which wherein the burners are directed downwards.

5. The induration machine according to claim 4, wherein at least some of the burners are directed vertically downwards and/or at least some of the burners are directed obliquely to the vertical direction

6. The induration machine according to claim 4, wherein at least some of the burners are disposed in the second hood section, at least some of the burners are disposed in at least one gas supply duct and/or at least one of the burners is disposed in at least one gas collector duct.

7. The induration machine according to claim 1, wherein at least one gas supply duct is aligned obliquely to the transport direction.

8. The induration machine according to claim 1, wherein at least one gas supply duct is a T-connection between the recuperation ducts and the first hood section.

9. The induration machine according to claim 1, wherein a cross-section of at least one recuperation duct increases towards the at least one gas collector duct.

10. The induration machine according to claim 1, wherein at least one recuperation duct comprises a plurality of successive duct segments along its length, which are arranged for individual exchange.

11. The induration machine according to claim 1, wherein the hood comprises a plurality of hood segments arranged for individual exchange.

12. The induration machine according to claim 1, wherein at least one recuperation duct and/or at least one gas supply duct comprises a valve element configured for influencing a gas flow.

13. The induration machine according to claim 1, further comprising a hoist positionable above the hood and above each recuperation duct.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The disclosure will now be described, by way of example, with reference to the accompanying drawings, in which:

[0030] FIG. 1 is a perspective view of an induration machine with a PhilAnt hood according to a first embodiment of the disclosure;

[0031] FIG. 2 is a top view of the induration machine from FIG. 1;

[0032] FIG. 3 is a sectional side view of the induration machine from FIG. 1;

[0033] FIG. 4 is a sectional front view of the induration machine from FIG. 1;

[0034] FIG. 5 is a sectional front view of an induration machine according to a second embodiment;

[0035] FIG. 6 is a sectional top view of a part of an induration machine according to a third embodiment;

[0036] FIG. 7 is a top view of a part of an induration machine according to a fourth embodiment;

[0037] FIG. 8 is a top view of a part of an induration machine according to a fifth embodiment; and

[0038] FIG. 9 is a sectional front view of an induration machine according to a sixth embodiment.

DETAILED DESCRIPTION OF THE DRAWINGS

[0039] FIGS. 1-4 show an induration machine 1 according to a first embodiment of the disclosure. The induration machine comprises two rails 3 of a travelling grate 2, on which a plurality of pallet cars 22 form an endless travelling grate chain. Underneath an upper run of the travelling grate 2, a plurality of wind boxes 4 are disposed, which are connected to the pallet cars in a gas-tight way. A hood 7 is disposed above the travelling grate 2 which forms a at least largely gas-tight seal above the travelling grate 2. The travelling grate 2 is adapted to transport iron ore pellets along a sequence of zones of the induration machine 1 and in particular from a firing zone 5, where drying of the green pellets is performed, along a transport direction T to a cooling zone 6. The drying process is performed under a first hood section 8 of the hood 7. In the cooling zone 6, dried pellets are cooled by an uprising gas stream which is introduced through the wind boxes 4, passes through the travelling grate 2 and enters the hood 7, or more specifically, a second hood section 9. As indicated in FIG. 3, the first hood section 8 and the second hood section 9 are separated by a vertically extending sealing wall 10.

[0040] Two recuperation ducts 11 are disposed laterally offset with respect to hood 7. As can be seen especially in FIG. 4, each recuperation duct is disposed in a similar vertical position as the hood 7. The recuperation ducts 11 are disposed on opposite sides of the hood 7 and designed symmetrically. Each of them is connected to the first hood section 8 by a plurality of gas supply ducts 14, which are aligned horizontally and transversally to the transport direction T. Furthermore, both recuperation ducts 11 are connected to the second hood section 9 by a V-shaped gas collector duct 15. The function of the recuperation ducts 11 is to guide used cooling gas from the second hood section 9 to the first hood section 8. The respective gas flow can be established or enhanced by fans with which are not shown in the figures.

[0041] As a part of the gas flow exits through every gas supply duct 14, the total gas flow through the recuperation duct 11 decreases from the second hood section 9 along the length of the first hood section 8. This is taken into account by reducing the cross-section of the recuperation duct 11 in stages. A first part as a larger diameter, a second part has an intermediate diameter and a third part has a small diameter. Therefore, although the flow rate decreases significantly, the velocity of the gas flow decreases only moderately. Each recuperation duct 11 is tube-shaped with a circular cross-section as can also be seen in FIG. 4.

[0042] Apart from the openings towards the gas collector duct 15 and the gas supply ducts 14, it comprises a plurality of purge openings 16 disposed in a lower region 11.1 of the recuperation duct 11. From each purge opening 16 originates a purge duct 17 which extends vertically downwards. A valve 24, e.g. a double pendulum flap valve or a double cone valve, is disposed in each purge duct 17 in order to avoid unnecessary gas leakage through the purge duct 17. The cross-section of each purge duct 17 can be much smaller than the cross-section of the recuperation duct 11 which further helps to reduce the amount of gas that can exit through the purge duct 17. As used cooling gas is guided through the recuperation duct 11, it is laden with a considerable amount of dust, which could settle in the recuperation duct 11 and the gas supply ducts 14. This is largely prevented by the presence of the purge openings 16 through which dust is purged by gravitational pull from the recuperation duct 11. The valves 24 can be opened intermittently to allow dust to fall downwards through the purge duct 17. A box 18 is disposed at the lower end of each purge duct 17 to collect the dust from the recuperation duct 11. Instead of boxes 18 placed underneath the purge ducts 17, a conveyor system could also be used to transport the dust to a desired location. For instance, the dust could be reused in the production of new pellets or other recycling methods like briquettes or others.

[0043] As shown in the cross-sectional view of FIG. 4, the hood 7 has a rectangular cross-section in the first hood section 8, while the recuperation ducts 11 have a circular cross-section. Each of these elements has an outer shell made of metal with an inner lining of refractory material. In order to facilitate construction and maintenance of the induration machine 1, both the hood 7 and the recuperation ducts 11 comprises a plurality of duct segments 13 which are arranged for individual exchange. Likewise, the gas supply ducts 14 and the gas collector duct 15 may comprise a plurality of duct segments that are arranged for individual exchange. In other words, it is possible to remove and replace a single duct segment 13 without removing neighbouring duct segments. FIG. 4 shows by way of example a duct segment 13 of a recuperation duct 11 that is being moved by a hoist 19 which is mounted above the hood 7 and the recuperation ducts 11. Since the recuperation ducts 11 are disposed beside the hood 7 at approximately the same vertical position, a hoist beam 20 of the hoist 19 can be positioned at a relatively low height. Therefore, the hoist 19 can easily be placed within a building 24 of the induration machine 1.

[0044] In the embodiment shown in FIGS. 1-4, the necessary heat for drying the pellets in the firing zone 5 is generated by a plurality of burners 23 which are mounted to the ceiling of the first hood section 8. The burners 14 are directed vertically downwards.

[0045] FIG. 5 shows a cross-section front view of a second embodiment of an induration machine 1 which is largely identical to the first embodiment. In this case, however, the burners 23 are mounted to the gas supply ducts 14 and are directed obliquely to the vertical direction V. In particular, they are inclined towards the intended direction of the gas flow, i.e. towards the hood 7. This may help to support or enhance the gas flow. It should be noted that the burners 23 could alternatively be directed vertically downwards while being mounted to the supply ducts 14.

[0046] FIG. 6 is a cross-section top view of a part of an induration machine 1 according to a third embodiment, which is largely identical to the first embodiment. In this embodiment, a plurality of movable valve elements 21 are provided in the recuperation duct 11 and the gas supply ducts 14. Using these valve elements, the gas flow can be blocked, reduced or redirected in a desired way.

[0047] FIG. 7 is a cross-sectional top view of a part of an induration machine 1 according to a fourth embodiment, which differs from the first embodiment in that the gas supply ducts 14 are not aligned perpendicularly to the transport direction T, but obliquely. In other words, the gas supply ducts 14 are inclined towards the transport direction T, so that the gas flow from the recuperation duct 11 only has to undergo a minor change of direction as it enters the gas supply duct 14. This can also help to increase the gas flow.

[0048] FIG. 8 is a cross-sectional top view of a part of an induration machine 1 according to a fifth embodiment, which is largely identical to the fourth embodiment, but has a special configuration of the burners 23. One burner 23 is disposed on either side of the gas collector duct 15. This burner 23 is inclined laterally as well as longitudinally. Furthermore, several vertically aligned burners 23 are disposed in each recuperation duct 11 or hood 7. All of these burners 23 may be turned on only during a warm-up phase after a cold start of the induration machine 1. Furthermore, a plurality of burners 23 are disposed in the gas supply ducts 14. These are also inclined laterally and longitudinally, mostly in order to enhance a gas flow during normal operation of the induration machine. It is understood that the burner configuration shown here can be used with minimal adaption in any of the first, second or third embodiment.

[0049] FIG. 9 is a cross-sectional front view of an induration machine 1 according to a sixth embodiment. Here, the recuperation ducts 11 are also laterally offset with respect to the hood 7, but are disposed considerably higher than in the first embodiment. Also, the shape of the gas supply ducts 14 is different. In particular, each gas supply duct 14 is a T-junction that connects the recuperation ducts 11 and the hood 7 with each other. Also, by way of example, a hood segment 13 of the hood 7 is shown that is being moved by a hoist 19 which is mounted above the hood 7 and the recuperation ducts 11.