PALLET CAR FOR THE TRANSPORT OF BULK MATERIAL FOR A THERMAL TREATMENT

Abstract

Provided is a pallet car for the transport of bulk material for a thermal treatment thereof. The pallet car comprises a frame with at least two opposed cross-beams on which grate bars rest and two end pieces each connecting the cross-beams with each other, which each include at least two rollers and at least one side wall. In the pallet car, the grate bars and/or the side walls and/or the insulating plates are made of a ceramic fiber composite, wherein the fibers are metallic and high-temperature resistant.

Claims

1. A pallet car for the transport of bulk material for a thermal treatment thereof, comprising a frame with at least two opposed cross-beams on which grate bars rest and two end pieces each connecting the cross-beams with each other, which each include at least two rollers and at least one side wall, wherein the grate bars and/or the side walls and/or the insulating plates are made of a ceramic fiber composite, wherein the fibers are metallic and high-temperature resistant.

2. The pallet car according to claim 1, wherein at least one grate bar shows at least one salient such that its supporting surface at which it rests on at least one grate bar is reduced.

3. The pallet car according to claim 1, wherein an insulating plate is provided between at least one part of the pallet car and the grate bar featuring a specific heat capacity of more than 500 J kg.sup.?1 K.sup.?1 and/or featuring a specific heat conductivity of less than 35 W m.sup.?1 K.sup.?1.

4. The pallet car according to claim 1, wherein the cross-beams include at least one upper flange for accommodating at least one grate bar and between upper flange and grate bar an insulating plate is provided.

5. The pallet car according to claim 1, wherein the ceramic composite is a material containing aluminum oxide and/or silicon oxide and/or that the ceramic composite is oxide ceramics.

6. The pallet car according to claim 1, wherein the ceramic composite contains andalusite and/or mullite.

7. The pallet car according to claim 1, wherein the fibers contain iron and/or nickel and/or chromium, silicon, aluminum and/or manganese and/or that the fiber content in the composite material lies between 10 and 90 wt-%.

8. The pallet car according to claim 1, wherein before firing the ceramic composite contains polystyrene, other plastics and/or wood, chopped straw or other biogenic raw materials which largely outgas during firing and leave cavities in the ceramic composite.

9. The pallet car according to claim 1, wherein one side wall is divided into three segments.

10. The pallet car according to claim 1, wherein the side walls are attached to the end pieces of the frame by screws and/or bolts.

11. The pallet car according to claim 1, wherein within the side wall at least one metallic holder is cast in, which protrudes beyond the support surface of the side wall which in operation rests on the end piece or is suitable for accommodating a fastening element and is utilized for attachment to the frame.

12. The apparatus according to claim 1, wherein on the surface facing the frame each side wall contains a metallic carrier plate which at least partly extends between the part of the side wall made of ceramic composite material and the end piece.

13. The pallet car according to claim 12, wherein the metallic carrier plate in at least one direction extends beyond the frame.

14. The pallet car according to claim 1, wherein the side walls are formed such that they get thicker towards the frame.

15. A method for the thermal treatment of bulk material, in which this bulk material is transported through the thermal treatment in a pallet car, wherein the pallet car consists of a frame which on two opposite sides includes rollers and two side walls, wherein the side walls and/or grate bars and/or insulating plates are formed of a ceramic fiber composite with metallic and high-temperature resistant fibers and wherein a bed of bulk material at least partly contacting the side walls and/or grate bars is incorporated for the thermal treatment.

Description

[0058] In the drawings:

[0059] FIG. 1 shows the construction of a traveling grate as seen in y-direction, FIG. 2 shows the configuration of a pallet car according to the invention as section in the x-z plane,

[0060] FIG. 3 shows the configuration of a pallet car according to the invention as section in the y-z plane,

[0061] FIG. 4 shows the configuration of a holding system for the side wall according to the invention, and

[0062] FIG. 5 shows a grate bar according to the invention in combination with the insulating plate according to the invention in three views.

[0063] 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.

[0064] FIG. 2 shows a pallet car 3 by way of example as section in the same perspective as FIG. 1. The pallet car 3 includes a frame 30 which consists of two end pieces 33 which each are equipped with two rollers 31, and which transversely to the direction of movement of the traveling grate chain preferably has five cross-beams 32 which together with the end pieces 33 not shown in FIG. 2 form the frame 30. The two outer cross-beams typically are formed as C-sections, the middle cross-beams as I- or double-T sections. On these cross-beams 32 the grate bars 35 in turn are arranged, which accommodate the hearth layer R not shown in FIG. 2 and the green pellet layer G of the pallet car. In their longitudinal direction, the grate bars 35 extend in direction of movement x of the traveling grate and bridge the gaps between the cross-beams 32.

[0065] FIG. 3 shows the y-z section through the pallet car 3 according to the invention, wherein the sectional plane lies in the middle of the grate bars and the viewer looks from the charging zone of the traveling grate in direction of movement of the traveling grate. The cross-beams 32 form the frame together with the end pieces 33. The wheels 31 are attached to the end pieces. The cross-beams extend almost over the entire height of the frame. On these cross-beams 32 the grate bars 35 are arranged. On these grate bars 35 the so-called heath layer R is applied, which substantially extends as volume over the grate surface of the pallet car 3 formed by the cross-beams 32 and grate bars 35. The number of the actually present grate bars results from the total geometry of the pallet car, wherein the width of a grate bar typically lies between 20 and 50 mm, preferably between 30 and 45 mm, and the length lies between 200 and 450 mm, preferably between 250 and 400 mm. For one tpyical pallet car between 250 and 500, preferably between 300 and 400 grate bars are used, which only are to be indicated by the illustrated grate bars 35.

[0066] From the grate surface of the pallet car 3 two opposite side walls 34 rise at an angle ? with values between 90 and 120?, whose course is arranged parallel to the grate bars 35. The side walls 34 are bolted to the end pieces 33. The end pieces with their typical length of 1.5 m are just as long as the side walls and in their longitudinal orientation hence lie in the direction of movement of the traveling grate, which in this representation is defined as x-coordinate.

[0067] Enclosed by the side walls 34 and the hearth layer R the green pellet layer G also is located within the pallet car, which contains the material to be fired or to be sintered, which preferably is present as pellets.

[0068] FIG. 4 shows an inner steel skeleton of a non-illustrated side wall 34 according to the invention to improve the stability.

[0069] It was found to be advantageous to provide the side wall with an internal metallic carrier structure. This carrier structure positively connects the part of the side wall made of ceramic fiber composite with the carrier plate, so that the part of the side wall made of composite material especially in the region of the lower run does not drop off the carrier plate due to gravity. In the case of cracks in the composite material the inner structure also ensures that possibly existing broken pieces are held at their place and do not break out of the side wall. When the side wall is provided with threaded sleeves for lifting eyes, these threaded sleeves also are connected with the inner structure. To compensate the different thermal expansions between composite material and metallic structure and to better produce the positive connection, the inner structure preferably is formed by undulated round bars, which permanently are connected with the carrier plate, e.g. by welding.

[0070] The individual holders 41 can be formed straight and/or twisted and/or alsoas shownundulated. Furthermore, it is possible to connect the individual holders 41 among each other with horizontally aligned transverse struts 42 and thus even further increase the stability. The transverse struts also can be straight, undulated or twisted.

[0071] The holders 41 are mounted on a carrier plate 43 which serves for attachment on the pallet car 3. The carrier plate 43 is made of steel, preferably cast steel. It is connected with the end pieces 33 of the pallet car in a technically usual way, e.g. by bolts and nuts or by bolts only. For this purpose the carrier plate 43 can include through bores or threaded bores. It also is possible to weld at least one threaded bolt or a bolt with transverse hole for a splint or locking pin to the bottom side of the carrier plate.

[0072] FIG. 5 shows a grate bar 35 according to the invention in two views and a section (FIG. 5a in x-z-coordinates, FIG. 5b in z-y-coordinates and FIG. 5c in x-y-coordinates).

[0073] Each grate bar typically is mounted between two cross-beams 32 such that the cutouts 51 enclose the edge of the upper flange of the cross-beam. This produces a positive connection, so that the grate bars are securely held in every position of the pallet car without having to be fastened by means of bolts, pins or rivets. It was found to be advantageous when each grate bar has a certain mobility with respect to the cross-beams and with respect to the neighboring grate bar, so that thermal expansions are possible in all directions free of mechanical strain and that possibly stuck pellets or other solid particles can again free themselves due to the relative movements. Each grate bar in addition has surfaces 52 which rest against the neighboring grate bar. Between the surfaces 52 a half slot 53 extends in longitudinal direction of the grate bar, which together with the half slot of the neighboring grate bar forms the slot 54 for the passage of the gas flow through the grate. The insulating plate 55 protects the upper flange 56 of the cross-beam 32 against inadmissibly high temperatures. It can simply be placed on the cross-beam 32, preferably extends along the entire length of the cross-beam from one side wall 34 to the other side wall and is prevented from falling down by the grate bars 35. The insulating plate 55 also can be divided into 2 to 8 parts in longitudinal direction, in order to facilitate the transport, for example.

EXAMPLE

[0074] A typical pallet car with a length in direction of movement of the traveling grate (x-coordinate in the representations) of 1500 mm, a mean width in y-direction of 4000 mm and a side wall height in z-direction of 450 mm has a filling volume of 2.586 m.sup.3, of which the hearth layer totals 0.606 m.sup.3 with a hearth layer thickness of 100 mm, and with a side layer thickness of 80 mm the side layer totals 0.084 m.sup.3. When as a consequence of the side walls according to the invention, the side layer can be omitted, this corresponds to an increase of the volume for green pellets of 4.4%. When the hearth layer is omitted completely, but the side layer is maintained, this corresponds to an increase in volume of about 32%. When hearth and side layer are omitted partly or completely, the volume of the pallet car for green pellets can be increased by values in the range between 20 and almost 36%, compared with the operation with side layer and hearth layer.

LIST OF REFERENCE NUMERALS

[0075] 1 pellet induration furnace [0076] 2 hood [0077] 3 pallet car [0078] 4 traveling grate, pallet car chain [0079] 5 upper run [0080] 6 continuous conveyor [0081] 7 track roller of the pallet car [0082] 8 inner rail guide [0083] 9 outer rail guide [0084] 10 lifting or drive wheel [0085] 11 tooth gap [0086] 13 lowering or driven wheel [0087] 14 tooth gap [0088] 15 lower run [0089] 30 frame [0090] 31 track roller [0091] 32 cross-beam [0092] 33 end piece [0093] 34 side wall [0094] 35 grate bar [0095] ? angle of the side wall inner surface to the grate [0096] 41 holder [0097] 42 transverse struts [0098] 43 carrier plate [0099] 51 cutout on the end face of the grate bar [0100] 52 surface for contacting the neighboring grate bar [0101] 53 half slot [0102] 54 slot [0103] 55 insulating plate [0104] 56 upper flange of the cross-beam 32 [0105] R hearth layer [0106] G green pellet layer