The invention relates to a device for thermal treatment of bulk material, compris- ing a travelling grate chain being capable of revolving in direction of movement consisting of an endless travelling grate with moveable grate carriages each consisting of a frame with crossbars and end pieces and grate rods being arranged on crossbars and at least two wind boxes which are arranged such that gas flows through the grate being formed of the grate rods from the or into the at least two wind boxes. The invention also relates to a method for thermal treatment of bulk material in this facility.

In pellet burning or sintering machines the bulk material to be treated, such as for example iron ore, iron oxides or also zinc ore, is loaded onto grate carriages. These grate carriages consist of a frame being provided with wheels and consisting of end pieces and crossbars, and grate rods being arranged between the crossbars. A plurality of such grate carriages forms an endless grate carriage chain which is also referred to as travelling grate. In figure 1 , for example, a pellet burning machine 1 for burning pellets of iron ore is shown, wherein here the present invention has been employed. At a feeder station before a hood 2 the bulk material is loaded onto grate carriages 3 forming an endless grate carriage chain which is referred to as travelling grate 4. Under the hood 2 the bulk material being transported on the grate carriages 3 passes through a number of thermal treatment stations. In detail, these stations are

1 . the charging zone,

2. the first drying zone,

3. the second drying zone, 4. the preburning zone,

5. the burning zone,

6. the afterburning zone,

7. the cooling zone and

8. the exit zone.

In these zones the grate carriages are charged with the material, the bulk material is dried, preheated, fired and subsequently cooled again. At the treatment stations under the hood 2 the travelling grate is guided on a carrying run 5 of a continuous conveyer 6, wherein the rollers 7 of the grate carriages 3 are guided between an inner rail guide 8 and an outer rail guide 9. The drive of the travelling grate 4 is effected via a driving or elevating wheel 10 being designed as a gear wheel and engaging with its tooth spaces (recesses 1 1 ) at the rollers 7 of the grate carriages 3.

After passing through the hood 2 the grate carriages 3 of the travelling grate 4 reach a discharge station which is assigned to a descending or output wheel 13 of the continuous conveyer 6. Like in the case of the elevating wheel 10 at the descending wheel 13 tooth spaces 14 of the output gear wheel engage with the rollers 7 of the grate carriages 3. The grate carriages 3 are tilted so that their load is discharged by gravitational force. Since the grate carriages 3 are guided by the outer rail guide 9, they itself do not fall down, but will be returned back to the elevating wheel 10 upside down in a lower run 15 of the continuous conveyer 6. Below the hood 2 wind boxes 16 are arranged which allow a controlled gas flow. In the region of the carrying run 5 the grate carriages 3 travel along between the above lying hood 2 and the below lying wind boxes 16 without colliding with the components of the hood 2 or the wind boxes 16.

During normal operation the travelling grate 4 revolves on the continuous con- veyer 6 in an endless manner and transports the bulk material to be treated through the treatment stations under the hood 2, before it is discharged at the discharge station and is processed further in a manner which is not described in detail here. As already mentioned, in the two drying zones, the preburning zone, the burning zone, the afterburning zone and the cooling zone the bulk material contained in the grate carriages is thermally treated by the fact that hot or cold gas flows either from the wind box through the bulk bed in the grate carriage into the hood or from the hood through the bulk bed in the grate carriage into the wind box. In the charging zone and the exit zone no flow prevails. Therefore, between the charging zone and the first drying zone with a flow which is oriented upwards a change of the vectorially oriented flow takes place, since here a change between no flow and a flow from the wind box through the bulk bed into the hood takes place. For this purpose the wind box being assigned to the first drying zone is characterized by excess pressure. The second change of the direction of the flow takes place between the first and second drying zones, since in the second drying zone gas is drawn from the hood through the bulk bed into the wind box, because the wind box in this zone is characterized by a low pressure. Finally, between the afterburning zone and the cooling zone a change of the direction of the flow takes place again, once the preburning zone, the burning zone and the afterburning zone were all still characterized by a flow oriented from the hood into the wind boxes caused by low pressure in the respective wind boxes. The cooling in turn is characterized by a flow which is oriented from the wind box into the hood caused by excess pressure in the wind boxes which are assigned to the cooling. A further difference of the flow can be found between the cooling zone and the exit zone, because in the latter no flow occurs at all.

Since these changes of the direction of the flow each are caused by different pressures in the assigned wind boxes and these wind boxes directly lay side by side, it is important to seal up the passage between the adjacent wind boxes for avoiding that here unintentional gas flows directly from the wind box with the higher pressure into the wind box with the lower pressure occur. At best, such unintentional gas flows only result in an increased consumption of electricity of the connected fans, because an additional volumetric flow rate has to be provided. But in a lot of cases the unintentional gas flow in addition results in a partial pressure equalization between the adjacent wind boxes so that the pressure in the wind box with the higher pressure decreases, whereas the pressure in the wind box with the lower pressure increases. This in turn results in the fact that the rate of the flow through the bulk bed on the grate carriages decreases which has the consequence that the thermal treatment in the respective zone does not reach the desired degree. So in each form the efficiency of the thermal treatment is compromised. The problem of sealing up is complicated by the condition that it should be possible to move the grate carriages from one zone to the next zone in an unimpeded manner.

Normally, therefore, sealing dampers are used which are provided between both wind boxes with different pressures and which are pressed onto the lower side of the passing grate carriages by means of a set of levers and weights. The design of the extents of such sealing dampers is such that they seal up both wind boxes from each other with respect to their length and also with respect to their width, when they abut upon the grate carriage. Such sealing dampers are particularly problematic in two aspects. On the one hand, in the case of events of fault it is necessary that the grate carriages can also be moved contrary to the normal direction of movement. In such a case the edge of a grate carriage can hit onto the edge of the sealing damper and they can become wedged together such that the sealing damper and/or the grate carriage may permanently be damaged. On the other hand, the grate carriages are characterized by the property that they are plastically deformed during operation. This means that the crossbars are deformed into the direction of the wind boxes resulting in U- shaped crossbars due to the weight load resulting from the bulk bed of the bulk material in connection with the increased temperatures of these crossbars. In the case of such a deformation only the lowest point of the curve which is described by the crossbar rests on the sealing damper, whereas in the remaining region of the grate frame there is no contact with the sealing damper, and thus no sealing up can be reached any longer. In addition, normally, after a certain operating time the crossbars of the grate carriages are turned upside down so that then the crossbars with their curved form vault the sealing damper, and therefore also no sealing effect can be reached any longer.

Furthermore, in a case in which the at first passed wind box is characterized by excess pressure and the subsequent wind box is characterized by low pressure, it has to be considered that these pressure ratios may result in the problem that the movably mounted sealing damper at the lever, despite the weight, does not completely close any longer.

In total this results in the fact that no reliable sealing performance is provided and rather, in the case of movement contrary to the normal direction of movement during operation, the grate carriage chain and the sealing dampers may seriously be damaged.

Therefore, it is also an object of the present invention to provide a sealing arrangement for the wind boxes in a facility for thermal treatment of bulk materials which guarantees a good sealing performance in both of the following cases, namely, on the one hand, when there are pressure differences between both wind boxes, and on the other hand, when the crossbars of the grate carriages are deformed. Furthermore, this sealing should be designed such that also a movement of the grate carriage chain contrary to the normal direction of movement is possible without damaging the grate carriage chain or other compo- nents. This object is solved by a facility with the feature of patent claim 1 .

The device according to the present invention comprises a travelling grate chain being capable of revolving in the direction of movement consisting of an endless travelling grate with movable links. Furthermore, it comprises the grate carriages each consisting of a frame with wheels and grate rods being arranged on crossbars. Furthermore, the facility comprises at least two wind boxes which are arranged one after the other in the direction of movement and which are also arranged such that gas can flow through the grate carriages from or into at least one of the wind boxes.

According to the present invention, a component, normally a profile, but it may also be a plate, is provided which is arranged such that during normal operation in at least one position of the travelling grate it is pre-stressed, wherein for that it is in contact with two crossbars. Thus, the profile may for example be a leaf spring which establishes the contact. Here, at the same time, the profile is the pre-stressed component and also the component which seals up. But it is also possible that these objects are solved by different components so that one profile is the pre-stressed component, while the sealing up is effected via a second sealing component such as for example a plate.

Contact in the sense of the invention means that the component directly touches the grate carriage, preferably the crossbar(s) of the grate carriage. This contact between the profile and the grate carriage results in the fact that the undesired gas flow from the wind box with the higher pressure to the wind box with the lower pressure is considerably reduced.

It is an advantage of the design according to the present invention, also in the case of a deformation of the grate carriage which cannot be avoided due to the high temperatures and mechanical strains during operation, that the profile is readjusted by itself due to its pre-stress, and thus the sealing effect is retained. In addition, the sealing plate can be moved freely so that the risk of becoming wedged with the grate carriage during a movement contrary to the normal direc- tion of movement of the travelling grate is strongly reduced.

It is particularly preferable, when the profile in contact with a not deformed grate carriage crossbar is pre-stressed with a maximum bending stress which is between 50 and 70 % of the yield point of the material used for the profile. This allows a sufficiently large range of elastic deformations of the profile for guaranteeing a sufficient sealing effect also in the case of differently deformed grate carriage crossbars and reliably avoiding in such a case a plastic deformation of the profile. It was shown to be particularly advantageous, when the geometry of the profile is selected such that the maximum bending stress in the profile is between 60 and 80 % of the yield point, when the grate carriage crossbar is maximally bent downwards, and is between 40 and 60 % of the yield point, when the grate carriage crossbar is maximally bent upwards.

Furthermore, it was shown to be advantageous, when the profile in the stress- relieved or not pre-stressed state, thus without contact with at least one grate carriage, is a horizontal or curved plate which in at least one position of the travelling grate is in direct contact with the two grate carriages. Thus, in the simplest case, the profile is designed as a spring leave, for example as a parabolic spring, sinuous spring, elliptic spring (three-quarter elliptic spring, semi- elliptic spring, quarter elliptic spring). The dimensioning is such that the profile itself in at least one position of the travelling grate during operation is in direct contact with two grate carriages, and thus a sealing is realized. By the pre- stress of the profile and its simultaneous effect as a sealing element further points of intersection which are additional weak points in the system due to the high thermal load can be avoided. In the case of a curved design of the profile in the stress-relieved state the curvature extends into the direction of movement of the travelling grate. The concave form is a result of the fact that either it is curved with respect to a center part or it has permanently taken on this form by a previous pre-stress. This design has the advantage that a snagging of the grate carriages during passing the profile without previous contact of the grate carriages with the plate occurs less likely than in the case of a plate extending horizontally in the stress-relieved state.

As another alternative a design of the profile having a center part preferably extending horizontally in the stress-relieved state is possible which is preferably oriented in a parallel direction to the direction of movement of the travelling grate and on which at least one region which is branching off in the direction of movement is provided. This region has an angle of between 1 and 179 °.

In this variant it is particularly advantageous, when the form in the stress- relieved state is a trapezoid form based on a cross-section parallel to the direction of movement of the travelling grate. The trapezoid form has the advantage that with the parallel arrangement of the center part also in the case of a movement contrary to the direction of movement of the travelling grate the sealing plate is not shifted, since by the sloped regions on both opposite sides the grate carriages can be moved in both directions under the same conditions, namely into the normal direction of movement and into the opposite direction thereto. The angles of both opposite regions may be the same or may be different, but in any case they are between 1 and 179 °.

In the case of a trapezoid design the pre-stressed profile and/or the sealing plate comprise a horizontal base area and at least one lateral face branching off of the base area in an angle a in the direction of movement of the travelling grate, preferably two oppositely arranged lateral faces. Favorably, the angle a between a lateral face and the base area is between 130 and 170 °. So it is guaranteed that during movement of the travelling grate no snagging occurs. Particularly preferable is a design of two oppositely arranged lateral faces, wherein their angles a may be the same or may be different, but in any case are in the range of 130 to 170 °, because so also in the case of a movement contrary to the normal direction of movement a snagging of the grate carriages with the sealing plate can be avoided.

It is particularly advantageous, when the profile being a trapezoid one in the stress-relieved state is concavely deformed in the pre-stressed state during the operation of the travelling grate. Furthermore, it is advantageous, when at least two profiles are arranged on top of each other and are kept together by a center bolt and/or a spring clip. So the permanent elasticity of the device can be increased.

In this connection it was shown to be particularly advantageous, when between at least two profiles a lubrication and/or plastic, for example in the form of a foil or plastic plates, is provided. So abrasion between both profiles and thus an increased wear of material can be avoided or reduced.

Furthermore, it was shown to be advantageous, when the at least one profile is pre-stressed by at least one further elastic L- or C-shaped profile or also by two further elastic C-shaped profiles. For that these further profiles are arranged oppositely to the travelling grate chain and they press the first profile from below preferably in an orthogonal direction to the direction of movement of the travelling grate chain against the grate carriages. The further profiles described are particularly simple and thus low-maintenance components. In addition, it is advantageous, when the thickness of the first profile in the direction of the opposite sides being arranged in the direction of movement of the travelling grate decreases. So the profile at the site of the increased material strain by the pre-stress is strengthened.

Preferably, the dimensioning of the pre-stressed profile itself and/or of the sealing plate is such that during normal operation of the travelling grate always two grate carriage crossbars are in contact with the sealing plate. For that the extent of the part being in contact, thus of the pre-stressed profile itself or of an applied plate, in x-direction is selected such that it corresponds to at least the largest distance between one and the next but one crossbar occurring in the whole travelling grate chain. According to the present invention, at the few sites at which a pressure difference between two adjacent wind boxes exists a device according to the present invention is arranged each and is designed such that during operation there is always contact between at least two crossbars and the pre-stressed profile or a plate being present between the pre-stressed profile and the grate carriage.

In practice this is the case between the charging zone and the first drying zone, between the first and the second drying zones, between the afterburning zone and the cooling zone and between the cooling zone and the exit zone. In addition, between the first and second drying zones there is a change of the direction of the flow which means that in the first drying zone gas flows from the wind box through the grate carriage into the direction of the hood, while in the second drying zone the gas flows from the hood through the grate carriage into the wind box. Normally, the pressure difference between the adjacent wind boxes is about 100 mbar. The same also applies to the situation between the afterburning zone and the cooling zone, because in the afterburning zone gas starting from the hood flows through the grate carriage into the wind box, while in the cooling zone cold air starting from the wind box flows through the grate carriage into the hood. Also between the last wind box of the afterburning zone and the first wind box of the cooling zone a pressure difference in the order of 100 mbar is common. These changes of the direction of the flow require the maximum pressure difference between the respectively adjacent wind boxes, so that here, in particularly, it is important that always two grate carriage crossbars are in direct or indirect contact with the pre-stressed profile so that also these high pressure differences do not result in partial opening of the sealing element. It makes sense that at those sites where adjacent wind boxes are characterized by the same pressure no sealing plate is provided, because so a better penetration of the bulk bed of pellets on the grate carriages can be achieved. Preferably, the installation of the profile should be implemented by a flange or a screw connection so that in the case of wear of the sealing plate it can be replaced in a relatively easy manner.

Preferably, the profile between the at least two wind boxes is formed of a metal- lie material. When the profile is in direct contact with the grate carriage, that is the profile touches the grate carriage during operation, then it was shown to be advantageous, when the metallic material has a mean thickness of between 1 and 50 mm. So it is guaranteed that the sealing despite the high temperatures of 500 to 800 °C remains stable over a very long period of time.

Furthermore, it was shown to be advantageous, when the profile is manufactured of steel. Spring steel was shown to be particularly advantageous. So a long lifetime at the prevailing process conditions is guaranteed. In addition, the profile can be pre-stressed with common methods. In addition, it is advantageous to manufacture the sealing plate of a softer material than the grate carriage crossbars so that wear preferably occurs on the side of the sealing plate. Namely, it is more cost-effective to replace the sealing plates, because the number of the crossbars is much higher than the number of the sealing plates.

In one embodiment of the invention the profile is lowerable so that a collision with the grate carriages in the case of a movement contrary to the normal direction of movement can be avoided. So also the insertion of the grate carriages during the installation can be facilitated. Preferably, the sealing plate after the movement contrary to the normal direction of movement and/or after the positioning of the grate carriages is lifted very slowly, while the grate carriage is moved into the normal direction. But in the sense of the invention, lowerable may also mean that the further profile is lowered or that the further profiles are lowered and that so the pre-stress of the first profile is removed.

Finally, the invention also comprises a method for thermal treatment of bulk material with the features of patent claim 16. Here, a travelling grate chain revolves in direction of movement, wherein the travelling grate chain comprises a plurality of grate carriages each consisting of two end pieces with wheels and grate rods being arranged on at least two crossbars. In addition, the travelling grate chain comprises at least two wind boxes which are arranged one after the other such that in at least one wind box gas flows downwards or upwards through the grate carriages. The different pressure between the two adjacent wind boxes is sealed up by guiding the grate carriages over a pre-stressed profile. This pre-stressed profile at least at one position of the travelling grate during normal operation directly or indirectly is in contact with both grate carriages. Further features, advantages and possible applications of the invention follow from the description of the figures below. Here, all described and/or depicted features form on its own or in arbitrary combination the subject matter of the invention, independently from their summary in the patent claims or their back references.

Shown are: in fig. 1 the construction of a travelling grate, in fig. 2 the design of the sealing according to the present invention as a section of a travelling grate chain in the region of two wind boxes, in fig. 3 the design of the sealing according to the present invention in the perspective of the direction of movement of the travelling grate chain, and in fig. 4a-f different variants of the device according to the present invention.

Fig. 1 has already been explained in detail and shows in principle the arrangement of a travelling grate as is also the basis of the present invention.

The fig. 2a and 2b show the section of a travelling grate chain 1 which is depicted by way of example with two adjacent wind boxes 41 and 43 and three grate carriages 3i, 32 and 33. The three grate carriages 3i , 32 and 33 each comprise a frame 30 which consists of two end pieces 33 extending in their largest extent in x-direction and which contains preferably five crossbars 32 being arranged across thereto and being fixed at the end pieces 33 and extending in their largest extent in y-direction. On these crossbars 32 in turn the grate rods 35 are arranged which gather the filling B of the grate carriage. The three grate carriages 3< _\ , >2 and 33 pass the wind box 41 and the wind box 43. Between both wind boxes 41 and 43 a profile 50 is arranged . The profile 50 can be connected with the lateral walls of the wind boxes 41 and 43.

When the grate carriages are moved in the normal direction of movement, then they pass the profile 50 between both adjacent wind boxes 41 and 43. During that the crossbars 32 lightly touch the profile 50 which is elastically deflected during that so that a sealing effect between both wind boxes 41 and 43 results. This profile 50 is pre-stressed so that always a contact force between the profile 50 and the grate carriage crossbars 32 exists. In the fig . 2a and 2b with dashed lines it is shown, how the profile 50 is deformed and/or shifted, when a grate carriage crossbar 32 is sagged downwards. During that the contact force between the profile 50 and the crossbar 32 increases. As shown in fig . 2a, the pre- stress can also be generated by a further profile 51 . In this case a pre-stress of the profile 50 is possible, but not necessarily required.

As shown in fig . 2a, the profile 50 may be a concave form which is curved . But it is also possible that the profile 50, as shown in fig . 2b, consists of a stiff, plane base plate 50G comprising two lateral faces 50 ¹ s and 50 ² s being arranged opposite to each other in the direction of movement and being rounded in relation to the base area 50G or comprising an angle a so that these lateral faces 50 ¹ s and 50 ² s with respect to the base area 50G protrude away from the grate carriage crossbars 32. The reason for that is that so no edge is formed on which the grate carriages can get snagged or caught. It is possible to provide such a lateral face 50 ¹ s only at the position which is passed first during normal operation, but preferably opposite to this lateral face 50 ¹ s a second lateral face 50 ² s is arranged so that in the case of moving the travelling grate 1 contrary to the normal direction of movement also a snagging or canting can definitely be avoided. The base plate 50G is pressed upwards against the crossbars 32 of the grate carriage 3 via an elastic, pre-stressed further profile 51 . This pre-stressed profile 51 is directly or indirectly, for example via a plate 55, mounted on supports 53, but also a direct mounting on the side walls of the wind boxes 41 and 43 is possible.

Preferably, the design of the mounting is such that the profile 50 can be replaced in the context of maintenance work. According to the present invention, it is also possible to design the supports 53 such that the profile 50 and the further profile 51 together with the plate 55 can be lowered downwards so far that the grate carriage crossbars 32 and the profile 50 are no longer in contact with each other. Such a lowering can also be realized by a suitable mechanical means which pulls the profile 50 downwards by further elastic pre-stress of the further profile 51 . This kind of lowering is advantageous in cases of operation in which a sealing between the adjacent wind boxes 41 , 43 is not necessary and thus also the contact between the grate carriage crossbars 32 and the profile 50 is not required. In such cases of operation the lowering of the profile 50 reduces the risk that the components are damaged, and thus also reduces their wear. Fig. 3 shows the cross-section through the system according to the present invention in the y-z plane at the position of a profile 50. Also here the grate carriage 3 comprises a frame 30 from which in this cross-section two end pieces 33 and one crossbar 32 can be seen. At the end pieces 33 the carrying wheels 31 are mounted. Above the crossbars 32 the grate rods 35 lying on them and extending in their largest extent in x-direction can be found. Onto these grate rods 35 the filling B is applied. Here the filling B is confined by the side wall 34.

During passing the profile 50 the grate carriage crossbar 32 is at least partially in contact with the pre-stressed profile 50, as shown in figure 2. The pre- stressed profile 50 is mounted on supports 53 which may be designed such that the height of the profile 50 can be adjusted.

Here, the profile 50 itself is characterized either by a concave or a trapezoid profile.

The figures 4a to 4f show different embodiments of the further profile 51 or the further profiles 51 . Here, fig. 4a shows the placement of a sealing plate 50 on a C-shaped profile 51 1 which is preferably designed such that its half-rounded side extents into the direction of movement of the travelling grate 1 . Fig. 4b shows two C-shaped profiles being arranged on top of each other 512. Fig. 4c shows an L-shaped profile 513, while fig. 4d shows two L-shaped profiles 513 being arranged one after the other. The fig. 4e and 4f show two C-shaped profiles 51 1 being arranged one after the other with different orientation of their curvatures.

List of reference signs:

1 pellet burning machine

2 hood

3 grate carriage

4 travelling grate, grate carriage chain

5 carrying run

6 continuous conveyer

7 roller of the grate carriage

8 inner rail guide

9 outer rain guide

1 0 elevating or driving wheel

1 1 tooth space

1 3 descending or output wheel

14 tooth space

1 5 lower run

30 grate carriage frame

31 roller

32 crossbar

33 end piece

34 side wall

35 grate rod

41 first wind box

43 second wind box

50 pre-stressed profile

50 _G plane surface of the profile

50 ¹ s, 50 ² s lateral faces of the profile

51 further profile

51 i C-shaped profile

C-shaped profiles being arranged on top of each other 513 L-shaped profile

52 longitudinal wall of the wind box

53 support

55 plate

56 running rail

57 running rail carrier

a angle of the lateral face of the profile