Grate block for a combustion grate

Abstract

The invention relates to a grate block (10) for a combustion grate, in which consecutive grate blocks are arranged one over the other in the manner of a staircase and are designed to rearrange and convey the combustible material during combustion by means of pushing motions performed in relation to each other. The grate block (10) comprises a block body (12) which has an upper wall (14) forming a bearing surface (16), along which wall the combustible material is to be conveyed, and a front wall (20) forming a push surface (22), wherein the front wall (20) has first air supply openings (25), which are formed in each case by a first air supply channel (27) for feeding air to the combustion grate, and a lower bearing edge (23) which is intended to come into contact with the bearing surface of a grate block that is adjacent in the pushing direction S. Further air supply channels (38), which traverse and are directed obliquely with respect to the direction of the first air supply channels, are arranged in the upper wall (14) and in the front wall (20) for cooling the upper and the front wall (20). The most suitable drawing: Fig. 1.

Description

[0001] Grate block for a combustion grate

[0002] The invention relates to a grate block for a combustion grate according to the preamble of claim 1. The invention further relates to a combustion grate comprising at least one such grate block. The invention further relates to the use of said combustion grate for the combustion of waste and to a waste incineration plant comprising such a combustion grate.

[0003] Combustion grates for the large-scale incineration of waste have long been known to experts. Such grates can be in the form of pusher grates, which include moving parts capable of performing stoking strokes. The material to be combusted is conveyed from the inlet end of the grate to its outlet end and is burned during this process. To supply the grate with the oxygen required for combustion, appropriate air inlets are provided through the grate, through which the air, also called primary air, is introduced.

[0004] A commonly used type of combustion grate is the so-called stepped grate. This consists of grate blocks arranged side by side, each forming a row of grate blocks. The rows of grate blocks are arranged one above the other in a step-like fashion, whereby in so-called feed grates, the front end of a grate block (viewed in the direction of feed) rests on a support surface of the adjacent grate block (viewed in the direction of transport) and is moved along this support surface during the corresponding feed motion.

[0005] In so-called retractable grates, the grate blocks are arranged at approximately a 180° angle to the direction of material transport compared to conventional grates. Therefore, in retractable grates, the front end of the grate block, viewed in the direction of movement, rests on a support surface of the preceding grate block. In contrast to conventional grates, the direction of movement in retractable grates is thus opposite to the direction of transport resulting from the inclination of the retractable grate.

[0006] A combustion grate designed as a stepped grate and a grate block for such a combustion grate are described, for example, in WO 2016 / 198119, which refers to an air-cooled grate block. Specifically, the grate block described in WO 2016 / 198119 comprises a cast block body with an upper wall forming a support surface for the waste to be treated and a front wall forming a shear surface. A foot is formed in the lower part of the front wall, designed to rest slidably on the support surface of an adjacent grate block in the shear direction, while air inlet openings for introducing air are arranged in the front wall.

[0007] The fuel conveyed over the grate blocks generally subjects them to relatively high wear. Abrasion is particularly high at the front edge of the support surface, where the fuel is thrown from the support surface of the grate block over a corresponding ejection edge onto the support surface of the next grate block. This can lead to erosion of the air supply openings located below the edge, which can negatively impair the controlled air supply to the combustion bed on the grate. Grate blocks are also subject to very high thermal stress.

[0008] exposed to stress, especially due to the high

[0009] Temperatures during combustion or in the combustion chamber. In normal operation of the combustion grate, this thermal stress is particularly high in the area of ​​the contact surface, even though the material being combusted on the grate block has an insulating effect to a certain extent.

[0010] Very high stresses occur when the fuel is unevenly distributed on the combustion grate and forms only a thin insulating layer, or when this insulating layer is completely absent. The thermal stress promotes erosion through abrasion and chemical reactions occurring at the contact surface, which further damage the contact surface. This ultimately leads to a reduction in the service life of the grate block. The problem to be solved according to the invention is therefore to provide a grate block of the aforementioned type that has a long service life and in which the erosion of the contact surface, in particular the erosion of the front end of the grate block, is minimized.

[0011] This problem is solved by the grate block defined in independent claim 1.

[0012] Preferred embodiments of the invention

[0013] Grate blocks are described in the dependent claims. According to claim 1, the present invention thus relates to a grate block for a combustion grate in which successive grate blocks are arranged one above the other in a stepped fashion and are designed to rearrange and convey the fuel during combustion by means of relative thrust movements, i.e., relative movements between the grate blocks. As mentioned above, such combustion grates are also referred to as stepped grates.

[0014] Furthermore, the grate block comprises a block body, preferably designed as a casting. The block body is generally in the form of an elongated cuboid with a longitudinal axis L.

[0015] The block body includes an upper wall that forms a support surface parallel to the longitudinal axis L, along which the fuel is to be conveyed and which defines a fuel side of the upper wall.

[0016] Viewed in a shear direction S, the foremost end of the bearing surface forms an edge, beyond which the bearing surface slopes down into a shear surface formed by a front wall. The edge thus forms a transition between the upper wall and the front wall.

[0017] The side of the upper wall facing away from the contact surface and the side of the front wall facing away from the shear surface define a cooling air side of the block body.

[0018] The thrust direction S describes the direction in which the material being burned is pushed by the thrust surface of the grate block. Generally, the thrust direction S is parallel to the longitudinal axis L.

[0019] The transport direction T describes the direction of movement of the material being combusted from an inlet to an outlet of the combustion grate. The transport direction T is primarily determined by the inclination of the combustion grate.

[0020] The front wall has initial air supply openings, which are formed by first air supply channels running at right angles or obliquely to the shear surface when viewed in longitudinal section, for supplying air to the combustion grate.

[0021] In the following, the term "air" refers to the so-called primary air, which is supplied to the combustion grate or the combustion bed on the combustion grate. The primary air primarily contributes to the combustion of the fuel, but also simultaneously to the cooling of the grate blocks.

[0022] Furthermore, the front wall is designed in its lowest area in the form of a foot, which is intended to rest on the bearing surface of a grate block adjacent in the direction of thrust.

[0023] According to a preferred embodiment, the first air supply channels, viewed in longitudinal section, run at an angle α to the area of ​​the shear surface immediately adjacent to the respective first air supply openings, wherein α lies in a range of 90° to 135°, preferably 95° to 125°, particularly preferably 100° to 120°, and most preferably 105° to 115°. The angle α is measured counterclockwise between the longitudinal axis of the respective first air supply channels and the shear surface. This ensures optimal air supply to the combustion grate or to the combustion bed on the combustion grate, contributing to a very high degree of combustion of the material being combusted. The relevant section of the first air supply channels for determining the angle α is the section immediately before the respective first air supply channel exits the front wall.

[0024] In a preferred embodiment, in which the grate block according to the invention is intended for a feed grate, the foot thus rests on the grate block following in the transport direction T of the material being processed, or on its support surface. However, it is also conceivable that the grate block according to the invention is intended for a return-feed grate; in this case, the foot rests on the grate block preceding in the transport direction T of the material being processed, or on its support surface.

[0025] At least the lower bearing edge of the shear surface is arranged in a plane E that runs substantially perpendicular to the longitudinal axis L. It is conceivable that a surface located in the lowest region of the front wall, whose lower end is formed by the lower bearing edge, is arranged in plane E. However, it is also conceivable that only the line described by the lower bearing edge is arranged in plane E.

[0026] According to the invention, further air supply channels extending through the upper wall and the front wall, oriented obliquely to the direction of the first air supply channels, are formed for cooling the upper wall and the front wall. These further air supply channels form additional air supply openings in the upper wall, i.e., in the bearing surface, and in the front wall, i.e., in the shear surface. This ensures that the distribution of air for cooling the upper wall and the front wall is optimized. Consequently, heat is dissipated more effectively, so that the upper wall and the front wall are subject to reduced erosion. In a preferred embodiment, the upper wall and the front wall are thickened in the area where they meet, as seen in longitudinal section.By thickening the wall in the area of ​​the grate block that is subject to particularly heavy wear, the service life of the grate block can be increased, as significantly greater abrasion can be tolerated.

[0027] In a particularly preferred embodiment, the wall thickening, viewed in longitudinal section, is configured such that the edge, viewed in the shear direction S, is offset forward with respect to the plane E. In other words, the region of the shear surface in which the first air supply openings and, optionally, further air supply openings are arranged is located in a plane that is offset along the longitudinal axis L and, viewed in the shear direction S, backward with respect to the edge. Since the edge is offset forward with respect to the plane E along the longitudinal axis L and in the shear direction S, the first air supply openings and, optionally, the further air supply openings, which are formed below the edge, are at least partially protected. This arrangement has the additional advantage that the air can escape more easily through the first and further air supply openings. Thus, improved cooling of the front wall is achieved.

[0028] In a preferred embodiment, the wall thickening is curved in longitudinal section, e.g., in the form of a bulge. The curved shape of the wall thickening ensures that the material being fired can be transported unhindered over the grate block, i.e., without being blocked by angular irregularities.

[0029] The term thickening of the upper or front wall is to be understood as meaning that the upper or front wall, in the area where it is thickened, has a greater wall thickness than in the area directly surrounding the thickening.

[0030] The wall thickening, due to the additional material it forms, allows the grate block to absorb extra heat during operation. On the one hand, this wall thickening extends the service life of the grate block because the thickened upper or front wall resists erosion for a longer period. On the other hand, however, the erosion of the wall thickening can increase due to the high thermal stress. Therefore, further optimization of the grate block involves improving the cooling of the wall thickening.

[0031] In a preferred embodiment, the additional air supply channels are arranged within the wall thickening, i.e., they extend through the wall thickening. This arrangement of the additional air supply channels and the corresponding additional air supply openings ensures better cooling of the wall thickening by air and thus reduces its erosion.

[0032] However, it is also possible to arrange the additional air supply channels only in the upper wall, i.e., above the edge of the upper wall. Since erosion by abrasion occurs primarily at the contact surface, it is advantageous for the wall thickening to be predominantly located on the upper wall in the area where the upper wall and the front wall meet. Thus, this arrangement of the additional air supply channels allows for optimized cooling of the wall thickening.

[0033] In a preferred embodiment, the additional air supply channels, viewed in longitudinal section, run at an angle β to the longitudinal axis L of the block body, with the angle β ranging from 10° to 60°. The angle β is measured counterclockwise with respect to the longitudinal axis L. Because the additional air supply channels run obliquely to the longitudinal axis L of the block body, they are longer than if they were running parallel to the longitudinal axis L. Consequently, the air flowing through the additional air supply channels can provide efficient cooling.

[0034] Preferably, the angle β is between 15° and 50°. The angle β is chosen such that the slag resulting from the combustion of the fuel falls as little as possible through the further air supply channels and causes blockages. This ensures reliable cooling of the grate block.

[0035] In a preferred embodiment, a first group of additional air supply channels is formed in a first plane extending at a first angle β1 to the support surface of the block body. Furthermore, a second group of additional air supply channels is formed in a second plane extending at a second angle β2 to the support surface of the block body. The first angle β1 is from 10° to 35°, preferably from 10° to 20°, and the second angle β2 is from 35° to 60°, preferably from 40° to 50°. Dividing the additional air supply channels into groups and distributing them in planes ensures that the air flowing through the additional air supply channels provides efficient, distributed cooling around these planes. This extends the service life of the grate block.

[0036] In a preferred embodiment, the additional air supply channels of the first group and the additional air supply channels of the second group are arranged parallel to each other. Preferably, the additional air supply channels of the first group and the additional air supply channels of the second group are arranged parallel to a longitudinal section plane P that is perpendicular to the support surface and includes the longitudinal axis L. This arrangement has the additional advantage that the manufacture of the additional air supply channels is simplified.

[0037] In a preferred embodiment, the additional air supply channels in the first and / or second level are evenly spaced across the width of the grate block. This ensures that the air flowing through these additional air supply channels provides homogeneous cooling around these levels. Consequently, the distribution of stresses caused by heat distribution during operation of the grate block is also homogeneous in the first and second levels, minimizing the formation of cracks across the grate block's width. This leads to an extension of the grate block's service life.

[0038] In a preferred embodiment, a further air supply channel, optionally a further air supply channel of the first group and a further air supply channel of the second group, and a first air supply channel are arranged in the same plane, which runs parallel to the longitudinal section plane P. This arrangement of the first and the further air supply channels ensures that the stresses during operation of the grate block, viewed in longitudinal section, are also homogeneously distributed. Thus, the formation of cracks can be minimized.

[0039] In a preferred embodiment, the additional air supply channels are distributed symmetrically with respect to a longitudinal plane of symmetry of the grate block that runs perpendicular to the support surface. This arrangement has the further advantage that the manufacture of the additional air supply channels is simplified.

[0040] The number of air supply channels and additional air supply channels is calculated proportionally to the width of the grate block and the size of the wall thickening in order to achieve optimized cooling of the grate block.

[0041] In a preferred embodiment, the additional air supply channels have a substantially constant cross-sectional area along their length, which is particularly between 40 mm² and 100 mm². The diameter is selected such that as little slag as possible, resulting from the combustion of the fuel, falls through the additional air supply channels and causes blockages. This ensures reliable cooling of the grate block. Preferably, the cross-sectional area is 80 mm² to achieve optimal results.

[0042] In a preferred embodiment, the additional air supply channels are continuously widened along their length from the combustion side to the cooling air side, with the cross-sectional area of ​​the additional air supply channels on the combustion side and the cross-sectional area of ​​the additional air supply channels on the cooling air side being in a ratio of 1:1.2 to 1:2.5, preferably 1:2.25. The cross-sectional area of ​​the additional air supply channels on the combustion side is measured at the contact surface or shear surface and corresponds to the cross-sectional area of ​​the additional air supply openings defined above. The cross-sectional area of ​​the additional air supply channels is measured at their end located on the cooling air side. This design of the additional air supply channels facilitates the easy removal of combustion residues that have entered the additional air supply channels.The combustion residues are pushed further towards the cooling air side into the additional air supply channels by the fuel on the grate block and released due to the widening of these channels. This prevents a blockage of the air supply.

[0043] According to another aspect, the present invention also relates to a combustion grate comprising at least one of the grate blocks described above.

[0044] Furthermore, the present invention relates to the use of a combustion grate described above for the combustion of waste, as well as a

[0045] A waste incineration plant comprising such a combustion grate. The invention is illustrated with reference to the accompanying figures. Of these, the following are shown:

[0046] Fig. 1 shows a grate block according to the invention in a perspective view; and

[0047] Fig. 2 shows a section of the grate block according to Fig. 1.

[0048] Longitudinal section through the section plane II-II shown in Fig. 1; and

[0049] Fig. 3 shows a section of the grate block according to Fig. 1.

[0050] Cross-section through the section plane III-III shown in Fig. 2. As can be seen from Fig. 1, the grate block 10 comprises a block body 12 designed as a casting, which is essentially in the form of an elongated cuboid with a longitudinal axis L.

[0051] The block body 12 comprises an upper wall 14, which forms a support surface 16 parallel to the longitudinal axis L. The material to be combusted is conveyed along this surface, and this surface defines a material-bearing side of the upper wall 14. The foremost end of the support surface 16, viewed in the thrust direction S, forms an edge 19, over which the support surface 16 slopes down into a thrust surface 22 formed by a front wall 20. The side of the upper wall 14 facing away from the support surface and the side of the front wall 20 facing away from the thrust surface 22 define a cooling air side of the block body 12.

[0052] In the embodiment shown, the bearing surface has a first bearing surface area 16a and a second bearing surface area 16b, wherein the first bearing surface area 16a is arranged offset upwards relative to the second bearing surface area 16b and is connected to it via a chamfered transition 17.

[0053] On the side opposite the front wall 20, the block body 12 has a rear wall 24, which is equipped with at least one hook 26 with which the grate block 10 can be suspended in a block holding tube. A central web 29 is also arranged on the underside of the grate block 10 facing away from the support surface 16.

[0054] The grate block 10 is bounded laterally by a side wall 28a, 28b extending in the longitudinal direction L.

[0055] Within the combustion grate, the grate block 10 rests on a subsequent grate block in the thrust direction S. For this purpose, the lowest region of the front wall 20 is formed in the form of a block 34, which is designed to rest on the bearing surface of a grate block adjacent in the thrust direction S. The lowest region, including a lower bearing edge 23 of the thrust surface formed by this block, is arranged in a plane E extending substantially perpendicular to the longitudinal axis L.

[0056] Furthermore, the grate block 10 is thickened in the area where the upper wall 14 and the front wall 20 meet. Specifically, the wall thickening 40, viewed in longitudinal section, is curved on the side of the upper wall 14 facing the fuel.

[0057] In the embodiment shown, the edge 19 formed by the wall thickening 40 is offset forward along the longitudinal axis L and in the thrust direction S with respect to the plane E, with the distance D between the edge 19 and the plane E being approximately 25 mm.

[0058] Thus, in the embodiment shown, the second bearing surface area 16b first runs essentially in a plane and then slopes downwards in a curved area extending to the foremost end of the bearing surface 16 when viewed in the thrust direction S.

[0059] The edge 19 formed by the foremost end of the support surface 16 is located below the plane of the second support surface area 16b. The shear surface 22 begins above the edge 19, initially extending backwards with respect to the edge 19 and then extending into the plane E.

[0060] As can be seen in Figures 2 and 3, the front wall 20 has two first air supply openings 25, each formed by a first air supply channel 27 extending through the front wall 20. In this case, the first air supply channels 27 open into an undercut in the front wall 20 formed by the wall thickening 40 and the plane E. The first air supply openings 25 are located below the wall thickening 40 in Figure 1 and are not visible. Primary air is supplied to the combustion grate or the combustion bed on the combustion grate through the first air supply channels 27.

[0061] Furthermore, the first air supply openings 25 are set back along the longitudinal axis L and in the thrust direction S with respect to the edge 19, in the embodiment shown by a distance d of approximately 12 mm.

[0062] In the grate block shown in Fig. 2, the first air supply channels 27 run in longitudinal section at an angle of approximately 110° to the shear surface 22 in their area immediately adjacent to the respective air supply opening.

[0063] Furthermore, the grate block 12 includes further air supply channels 38 extending into the upper wall 14 and arranged in the wall thickening 40, inclined to the direction of the first air supply channels 27, for cooling the upper wall 14, wherein the further air supply channels 38 form further air supply openings 35 in the wall thickening 40.

[0064] In the illustrated embodiment, a first group of two further air supply channels 38 is formed in a first plane G1 extending at a first angle β1 to the support surface 16. Furthermore, a second group of two further air supply channels 38 is formed in a second plane G2 extending at a second angle β2 to the support surface 16. The first angle β1 is 15° and the second angle β2 is 45°. For clarity, the angles β1 and β2 are shown in Fig. 2 with respect to the longitudinal axis L, which runs parallel to the support surface 16.

[0065] As shown in Fig. 3, the two first air supply channels 27 and the two groups of two further air supply channels 38 are each distributed symmetrically in pairs to a longitudinal plane of symmetry P of the grate block 12 which runs perpendicular to the support surface.

[0066] Furthermore, the first two air supply channels 27 and the two groups of two further air supply channels 38, viewed towards the interior of the grate block 12, are designed to widen continuously, so that combustion residues entering the first or the further air supply channels 27 or 38 can be more easily removed, thus preventing a blockage of the air supply. The diameter of the first and the further air supply channels 27 and 38 is 15 mm at their end facing the interior of the grate block 10 and 10 mm at their other end.

[0067] During operation, the grate blocks 10 are moved relative to each other by means of the block holding tubes. Depending on whether the block holding tubes are assigned to a stationary or a moving grate block, the block holding tubes are either attached to fixed brackets or to brackets arranged in a moving grate carriage. The drive is provided by hydraulic cylinders, which move the grate carriages back and forth on rollers along corresponding running surfaces.

[0068] The resulting relative movement pushes the foot 34 of a first grate block 10 forward and backward over the support surface 16 of the subsequent grate block 10, conveying the fuel over the support surface 16 before it is dropped over the edge 19 onto the support surface 16 of the subsequent grate block 10.

[0069] Reference character list

[0070] Grate block 10

[0071] Block body 12

[0072] upper wall 14

[0073] Contact surface 16

[0074] Support surface area 16a, 16b Transition 17

[0075] Margin 19

[0076] front wall 20

[0077] Shear surface 22

[0078] lower support edge 23 rear wall 24

[0079] first air intake opening 25 hooks 26

[0080] first air supply duct 27 side wall 28a, 28b

[0081] Middle walkway 29

[0082] Block 34

[0083] Additional air supply opening 35 Additional air supply duct 38

[0084] Wall thickening 40 Longitudinal axis L

[0085] Thrust direction S plane E

[0086] Longitudinal section plane P

[0087] Distance d by which the air supply openings are set back along the longitudinal axis L and in the thrust direction S with respect to the edge

[0088] Distance D by which the edge is offset along the longitudinal axis L and in the thrust direction S with respect to the plane E

[0089] angle

[0090] Angle β1, β2

Claims

Patent claims 1. Grate block (10) for a combustion grate, in which successive grate blocks are arranged one above the other in a stepped fashion and are designed to rearrange and convey the fuel during combustion by means of relative thrust movements, wherein the grate block (10) comprises a block body (12) having an upper wall (14) and defining a longitudinal axis L, wherein the upper wall (14) forms a support surface (16) along which the fuel is to be conveyed and whose foremost end, viewed in a thrust direction S oriented substantially parallel to the longitudinal axis L, forms an edge (19) over which the support surface (16) slopes into a thrust surface (22) formed by a front wall (20), the front wall (20) having first air supply openings (25) which each extend perpendicular or obliquely to the thrust surface (22) when viewed in longitudinal section,first air supply channel (27) for supplying air to the combustion grate, and has a lower support edge (23) arranged in a plane E extending substantially perpendicular to the longitudinal axis L, which is designed to come into contact with the support surface of a grate block adjacent in the thrust direction S, characterized by further air supply channels (38) extending through the upper wall (14) and the front wall (20) and oriented obliquely to the direction of the first air supply channels for cooling the upper wall (14) and the front wall (20).

2. Grating block according to claim 1, characterized in that the upper wall (14) and the front wall (20) are thickened in the area where they meet, viewed in longitudinal section as a wall thickening (40) and that the edge (19), viewed in the shear direction S, is offset forward with respect to the plane E.

3. Grate block according to claim 2, characterized in that the further air supply channels (38) are arranged in the wall thickening (40).

4. Grate block according to one of claims 1 to 3, characterized in that the further air supply channels (38), viewed in longitudinal section, extend at an angle β to the longitudinal axis L of the block body, wherein β is from 10° to 60°, preferably from 15° to 50°.

5. Grate block according to one of claims 1 to 4, characterized in that a first group of the further air supply channels (38) in a first plane extending at a first angle λl to the support surface of the block body and a second group of further air supply channels (38) in one in a second Angles β2 to the bearing surface of the block body are formed in the second plane, wherein β1 is from 10° to 35°, preferably from 10° to 20°, and β2 is from 35° to 60°, preferably from 40° to 50°.

6. Grate block according to claim 5, characterized in that the further air supply channels (38) of the first group are parallel to each other, preferably parallel to a surface perpendicular to the support surface (16) Longitudinal section plane P, and the further Air supply channels (38) of the second group in parallel to each other, preferably parallel to the Longitudinal section plane P is formed.

7. Grate block according to claim 5 or 6, characterized in that the further air supply channels (38) are located in the first level and / or in the second level The planes are distributed at least approximately evenly spaced from each other across the width of the grate block.

8. Grate block according to one of claims 1 to 7, characterized in that the further air supply channels (38) are distributed symmetrically to a longitudinal plane of symmetry of the grate block (10) which extends perpendicularly to the support surface (16).

9. Grate block according to one of claims 1 to 8, characterized in that the further air supply channels (38) have a substantially constant cross-sectional area over their length, which is 40 mm2 to 100 mm2, preferably 80 mm2.

10. Grate block according to one of claims 1 to 8, characterized in that the further air supply channels (38) along its length from the side of the fuel to the The cooling air side is designed to be continuously widening, wherein the cross-sectional area of ​​the further air supply channels (38) on the combustion side and the cross-sectional area of ​​the further air supply channels on the cooling air side is in a ratio of 1 : 1.2 to 1 : 2.5, preferably 1 : 2.

25.

11. Combustion grate comprising at least one grate block (10) according to any one of claims 1 to 10.

12. Use of a combustion grate according to claim 11 for the combustion of waste.

13. Waste incineration plant comprising a Combustion grate according to claim 11.