Method and apparatus for charging pallet cars of a traveling grate for the thermal treatment of bulk materials

Abstract

A method for charging pallet cars of a traveling grate for the thermal treatment of bulk material includes in a first step a first layer is applied as a hearth layer on a grate surface of the pallet car. In at least one second step a second layer at the same time or successively is applied as a side layer on two opposed side walls of the pallet car and a third layer is applied as green pellet layer between the side layers and on the hearth layer. The pellets used for the grate and the side layer differ in terms of their diameter and size distribution.

Claims

1. A method for charging pallet cars of a traveling grate for the thermal treatment of bulk material, in a first step comprising an application of a first layer as hearth layer on a grate surface of the pallet car and in at least one second step comprising the simultaneous or successive charging with a second layer as side layer on two opposed side walls of the pallet car and with a third layer as green pellet layer between the side layers and on the hearth layer, wherein the hearth layer includes fired pellets with a mean diameter between 10 and 20 mm, wherein the diameter of at least 85 wt-% of the pellets lies in the range between 10 and 20 mm, that the side layer contains pellet breakage and/or fired pellets of a mixture of two fractions A and B, wherein the material of fraction A has a mean diameter between 5 and 13 mm and the diameter of at least 85 wt-% of the material of fraction A lies in the range between 5 and 13 mm, wherein the material of fraction B has a mean diameter greater than 14 mm and the diameter of at least 85 wt-% of the pellets of fraction B is greater than 14 mm, and wherein the side layer consists of fraction A for between 0 and 100 wt-% and of fraction B for between 0 and 100 wt-%, and that the green pellet layer includes thermally untreated pellets with a mean diameter at least 2 mm greater than the mean diameter of fraction A.

2. The method according to claim 1, wherein the side layer contains between 20 and 90 wt-% of fraction A.

3. The method according to claim 1, wherein during and/or after charging with the side layer the side walls adjoining the side layer and/or a partition between side layer and green pellet layer and/or at least one device placed on and/or introduced into the side layer vibrates or vibrate.

4. The method according to claim 3, wherein the vibration has the natural frequency of the side walls.

5. The method according to claim 3, wherein after vibrating and/or passing the partition the side layer is filled up with pellet breakage and/or pellets of fraction A and/or B.

6. The method according to claim 1, wherein the hearth layer has a layer thickness between 3 and 10 cm.

7. The method according to claim 1, wherein the side layer has a layer thickness between 5 and 15 cm.

8. The method according to claim 1, wherein the pellets for hearth layer and side layer are taken from the total content of the pallet car after curing of the bulk material and recirculated to the charge.

9. A plant for charging pallet cars of a traveling grate for the thermal treatment of bulk material, comprising in a charging zone at least one chute for applying a first layer as hearth layer on a grate surface of the pallet cars and at least one second chute for charging with at least one second layer as side layer on two opposed side walls of the pallet car and a charging device for introducing a third layer as green pellet layer on the hearth layer and between the side layers, wherein the at least one chute for applying the hearth layer and the at least second chute for charging with the side layer is fed by two separate conveyor belts and further comprising a partition attached to the at least one second chute for charging with the side layer.

10. The plant according to claim 9, wherein the partition is aligned parallel to the direction of movement of the traveling grate at an angle in a range between the angle of the side wall and 85, and whose lower edge at least partly protrudes into the pallet car during operation of the traveling grate.

11. The plant according to claim 9, wherein the partition is aligned such that during operation it protrudes into the pallet car such that it ends exactly at the height of the surface of the hearth layer.

12. The plant according to claim 9, wherein at least one device for vibrating the side walls adjoining the side layer and/or a device for vibrating the partition is provided between side layer and green pellet layer and/or a device is provided for application on and/or introduction into the side layer.

13. The plant according to claim 9, wherein the at least one second chute is configured such that it also fills at a position at which the pallet car in operation of the traveling grate already has passed the partition and/or at least one device for vibrating the side layer.

14. The plant according to claim 9, further comprising first and second conveyor belts for the transport of material for charging pallet cars whereby the first conveyor belt conveys material for a hearth layer and the second conveyor belt conveys material for charging a side layer.

Description

(1) In the drawings:

(2) FIG. 1 shows the construction of a traveling grate,

(3) FIG. 2 shows the charging of a pallet car according to the invention, and

(4) FIG. 3 shows the charging of pallet cars according to the invention.

(5) FIG. 1 already has been discussed in detail and represents the basic arrangement of a traveling grate, as it is also underlying the present invention.

(6) FIG. 2 shows a pallet car 3. Its frame 30 is equipped with rollers 31 and also includes cross-beams 32. On these cross-beams 32 the grate bars 33 are arranged.

(7) On these grate bars 33 the so-called hearth layer R is applied, which substantially extends as area above the grate surface of the pallet car 3 formed by cross-beams 32 and grate bars 33. According to the invention, the hearth layer R consists of fired pellets with a mean diameter between 10 and 20 mm, wherein the diameter of at least 85 wt-% of the pellets lies in the range between 10 and 20 mm.

(8) From the pallet car 3 two opposed side walls 34 extend from the grate surface at an angle , whose inner surfaces are parallel to the direction of movement of the traveling grate, which in FIG. 2 leads into the drawing plane.

(9) Via the depicted chutes 52, 52 a so-called side layer S can be applied on these side walls. According to the invention, this side layer consists of pellet breakage and/or pellets of two fractions A and B. Pellet breakage in the sense of the invention refers to parts of the fired pellets. Fraction A includes pellets with a mean diameter of 5 to 13 mm, wherein at least 85 wt-% of the pellets of fraction A have a diameter between 5 and 13 mm. Fraction B contains pellets with a mean diameter greater than 14 mm, wherein the diameter of at least 85 wt-% of the pellets of fraction B is greater than 14 mm. The side layer contains between 0 and 100 wt-% pellets of fraction A and for the other part pellet breakage and/or pellets of fraction B. As a result, a very high bulk density and hence low permeability can be produced in the side layer S.

(10) To ensure a bed of the side layer S extending uniformly on the side walls 34, partitions 41, 41 are used in general, which at an angle in the range between 85 and the angle , based on the grate surface, at least partly protrude into the pallet car 3. Preferably, they protrude into the pallet car 3 to such an extent that they end directly at the height of the surface of the hearth layer R. To be able to omit further fastening devices, the partitions 41 and 41 are attached to the chutes 52 and 52. The chutes 52 and 52 are charged with the material for the side layer S by the conveyor belts 62 and 62.

(11) Furthermore, vibration devices 42, 42 are provided, by which the side walls 34 can be vibrated, preferably in their natural frequency. Virtually exclusively the side layer S thereby is vibrated and compacted further, whereby its permeability can be lowered further. There are also provided vibration devices 43, 43 by which the partitions 41, 41 can be vibrated, which likewise serves a compaction of the side layer S. In addition, the vibration devices 44 and 44 either can be introduced into the side layer S by being designed for example as vibrating bars or they can act on the side layer S in the manner of a punch and thus further compact the same by vibration. What also is possible is the use of only one vibration device 42, 43 or 44 or any combination of these possibilities. Enclosed by the side layer S and the hearth layer R the green pellet layer G also is located within the pallet car, which contains the material to be cured, which preferably is configured as bed of green pellets.

(12) FIG. 3 shows the section of a traveling grate within the charging zone. A plurality of pallet cars 3.sub.n are arranged symbolically. The foremost pallet car 31 just passes through the charging zone with the hearth layer R, which is applied through at least one chute 51 which is charged via the conveyor belt 61. The pallet car 32 just passes through the charging zone with the side layer S, wherein the chute 52 is formed such that the partition 41 is attached to the same, which on passing of the pallet cars 3 at least partly extends into the pallet car below the chute 52 such that it extends substantially parallel to the side wall 34 and thus the side layer S can be piled up between side wall 34 and partition 41. The chute 52 is charged by means of the conveyor belt 62.

(13) In the configuration shown the discharge openings of chute 52 just like the opposed parallel chute 52, which is not shown, also protrude to the front beyond the front edge of partition 41, so that in the region which already has left behind the front edge of the partition 41, material can be introduced and thus sagged areas in the surface of the side layer S produced by the passage of the partition 41 in direction of movement of the traveling grate can be filled up.

(14) The pallet car 33 finally is in the position of being charged with the green pellet layer G via the charging device 53, which is charged by means of the conveyor belt 63.

LIST OF REFERENCE NUMERALS

(15) 1 pellet induration machine 2 hood 3 pallet car 4 traveling grate, pallet car chain 5 upper run 6 continuous conveyor 7 track roller of the pallet car 8 inner rail guide 9 outer rail guide 10 lifting or drive wheel 11 tooth gap 13 lowering or driven wheel 14 tooth gap 15 lower run 30 pallet car frame 31 roller 32 cross-beam 33 grate bars 34 side wall 41, 41 partition 42, 42 vibration device for side wall 43, 43 vibration device for partition 44, 44 vibration device to be applied or to be introduced 51 chute for hearth layer 52, 52 chute for side layer 53 charging device for green pellets 61 conveyor belt for hearth layer 62, 62 conveyor belt for side layer 63 conveyor belt for green pellets R hearth layer S side layer G green pellet layer