Shaped part for attachment to the upper wall of grate block for a combustion grate

Abstract

The invention relates to a grate block (10) for a combustion grate. The grate block (10) comprises a block body (12) which has an upper wall (14) forming a support surface (16) along which the material to be combusted is conveyed, and a front wall (20) having a lower support edge (23), which support edge (23) is designed to come into contact with the support surface of a grate block adjacent in the thrust direction S, wherein the upper wall (14) has an air supply opening (35) formed by an air supply channel (38). The air supply opening (35) is at least partially surrounded by a thickening (50) projecting from the support surface (16), which forms a protective channel (57) extending the air supply channel (38) and is designed to prevent liquid from flowing into the air supply opening (35).

Description

[0001] The invention relates to a molded part for fastening to an upper wall of a grate block forming a combustion grate.

[0002] Combustion grates for the large-scale incineration of waste have long been known to experts. Such combustion grates can be in the form of pusher combustion grates, for example, which include moving parts capable of performing stoking strokes. The fuel is conveyed from one end of the combustion grate at the inlet to its outlet, where it is burned. To supply the combustion grate with the oxygen required for combustion, appropriate air inlets are provided through the combustion grate, through which the air, also known as primary air, is introduced.

[0003] A frequently used combustion grate is the so-called stepped grate. This consists of adjacent grate blocks, each forming a row of grate blocks. The rows of grate blocks are arranged one above the other in a stepped manner. In so-called pusher grates, the front end of a grate block, viewed in the direction of travel, rests on a support surface of the adjacent grate block in the direction of transport and is moved along this support surface with the corresponding pushing movement.

[0004] In so-called reverse-moving grates, the grate blocks are arranged approximately 180° apart from those of forward-moving grates, as viewed in the direction of transport of the kiln material. Therefore, in reverse-moving grates, the front end of the grate block, viewed in the direction of travel, rests on a support surface of the preceding grate block. In contrast to forward-moving grates, the direction of travel in reverse-moving grates is thus opposite to the transport direction resulting from the inclination of the reverse-moving grate.

[0005] A combustion grate is disclosed in DE 195 02 261 A1, which comprises several rows of grate bars arranged one behind the other in a stepped manner, as viewed in the transport direction of the fuel. Furthermore, the combustion grate comprises support grate bars, which have a shape similar to the grate bars and are shortened according to the length of a nozzle plate. In one embodiment, the nozzle plate can be formed by a hollow nozzle box, in which several rows of air nozzles, in particular swirl nozzles, are integrated in the front side and in the front, upper section, as viewed in the transport direction of the fuel. The design of the swirl nozzles is not discussed in detail. The nozzle plate is provided with a device with which it can be suspended from the support grate bar.A so-called vortex nozzle grate track is formed by several supporting grate bars and nozzle plates suspended from the supporting grate bars, and can extend across the width of the combustion grate. The vortex nozzle grate track can be supplied with compressed air and swirling air independently of the combustion grate's primary air system. Pulsed compressed air is applied to break up and circulate the fuel or slag layer. The resulting circulation loosens the fuel on the grate, enabling improved burnout of incompletely burned fuel particles. Furthermore, the compressed air pulses cause the nozzle plates to self-clean, as fuel or ash particles that have penetrated the air nozzles are blown out again.

[0006] A grate bar for a combustion grate is disclosed in DE 20 2017 006429 U1, wherein the combustion grate comprises several rows of grate bars arranged one behind the other in a stepped manner, viewed in the transport direction of the combustion material. The grate bar comprises a front-side base section and an upper running surface for the front-side base section of a grate bar of a higher-arranged row of grate bars. The running surface has a contour with an elevation and / or depression for deflecting the grate bar of the higher-arranged row during the advance movement of the rows of grate bars of the combustion grate. However, the provision of air supply openings in the grate bars is not addressed in this document.

[0007] A grate plate made of cast steel for transporting and cooling, heating, drying or incinerating bulk material is disclosed in DE 298 07 161 U1, which has troughs arranged in a grid on its upper side. Air passages are arranged in the troughs. The design of the air passages in the troughs, i.e. in a plane below the plane of the upper side of the grate plate, takes advantage of the knowledge that larger material particles in the bulk material move over the upper side of the grate plates without hitting the edges of the air passages. In addition, after a certain time a thin layer of fine material settles in the troughs, acting as a cushion, protecting the edges of the air passages. This ensures long-term air passage without the need to inspect the grate plates.

[0008] Grate blocks are subject to very high thermal stress, primarily due to the high temperatures during combustion and in the combustion chamber. During normal operation of the combustion grate, this thermal stress is high, particularly in the area of ​​the upper wall of the grate block, which forms the support surface along which the fuel is conveyed, and the front wall of the grate block, which forms a pushing surface for pushing the fuel.

[0009] Very high loads occur when the fuel is unevenly distributed on the combustion grate, leaving only a thin, heat-insulating layer of fuel in some places or even completely missing. This thermal stress promotes erosion through abrasion and chemical reactions occurring on the support surface, which further damage the support surface. This ultimately leads to a reduction in the service life of the grate block.

[0010] For cooling a grate block and for supplying air to the combustion grate, air supply channels forming air supply openings can be formed in the upper wall and / or in the front wall.

[0011] In particular, the air supply duct formed in the upper wall can become clogged by fuel and / or combustion residue, resulting in inefficient air supply for cooling the grate block and promoting combustion. This ultimately leads to increased maintenance effort and a reduced service life of the grate block.

[0012] Furthermore, the fuel contains materials that can become at least partially liquid during combustion, such as metals, plastics, or tars. In this application, the term "fraction" of the fuel refers to these materials contained in the fuel, and the liquid fraction is referred to as the "liquid fraction."

[0013] The liquid fraction can also flow into the air supply duct and impair the air supply, especially if the air supply duct is formed in the upper wall. In a solidified state, this fraction can even lead to a permanent blockage of the air supply duct.

[0014] EP 0 167 658 A1 describes a grate block for constructing a combustion grate, which comprises a box-shaped block body. The block body has an upper wall forming a support surface for the fuel, wherein the upper wall has air supply openings formed by air supply ducts for introducing gas, in particular air, into the fuel and for cooling the grate block. In one embodiment, the air supply openings are designed as slots and, viewed in cross-section, are curved like a siphon at their gas inlet against the force of gravity in order to form an obstacle to the penetration and fallout of fuel or combustion residues through the air supply openings. Because the upper wall has air supply ducts, it can be cooled. However, the disclosed design of the air supply ducts promotes an accumulation of fuel in a liquid state in the air supply ducts.

[0015] A molded part according to the preamble of claim 1 is disclosed in US 4 102 239.

[0016] The object to be achieved according to the invention is to provide a molded part for the grate block mentioned above, in which, during operation, the risk of impairment of the air supply through the air supply ducts is minimized.

[0017] This object is achieved by the molded part defined in independent claim 1.

[0018] Preferred embodiments of the grate block according to the invention are set out in the dependent claims.

[0019] According to claim 1, the present invention thus relates to a shaped part for fastening to an upper wall of a block body of a grate block around an air supply opening formed in the upper wall, which is formed by an air supply channel running through the upper wall, wherein the grate block is intended for a combustion grate and the block body is designed as a cast part, wherein the upper wall forms a support surface along which the combustion material is to be conveyed, wherein the shaped part, in the fastened state, forms a thickening protruding from the support surface, which surrounds the air supply opening, forms a protective channel extending the air supply channel and is intended to prevent liquid from flowing into the air supply opening, wherein the protective channel is formed by an inner flank of the thickening, ieof the molded part, and the thickening has an outer flank adjoining the inner flank and sloping on the side facing away from the protective channel.

[0020] Furthermore, the protective channel of the molded part comprises an upper protective channel opening which, viewed in the fastened state of the molded part, is arranged on the side of the molded part facing the firing material, ie on the end of the protective channel facing away from the support surface, and a lower protective channel opening arranged on the side facing away from it.

[0021] On the side of the molded part facing away from the firing material, the molded part has a base penetrated by the protective channel, the outer base surface of which, when the molded part is fastened, is at least approximately flush with the plane of the support surface

[0022] In a preferred embodiment, the molded part is designed to be welded around the air supply opening formed in the upper wall of the grate block body. The method for attaching the molded part is thus carried out by welding it to the upper wall. It should also be noted that the welding can be performed on the side of the upper wall facing the firing material or on the side of the upper wall facing away from the firing material. This ensures an at least approximately airtight connection between the molded part and the block body, so that the air supply to the firing material is controlled.

[0023] In a preferred embodiment, the molded part is mechanically attached to the upper wall of the block body. This design allows for simple attachment without any special welding skills. Furthermore, the mechanical attachment is easily removable, and the molded part can be removed again without any special processing of the block body, e.g., without grinding the weld seam.

[0024] It is also conceivable to design the molded part in such a way that it is first mechanically secured using a fastener in a first step and then, in a second step, by welding. This embodiment has the advantage that welding can be carried out particularly efficiently because the molded part is already held in its operating position by the fastener without the need for any additional tools.

[0025] The grate block is intended for a combustion grate and can be designed as a cast part.

[0026] In a preferred embodiment, the molded part is also designed as a cast part. Such cast parts are particularly advantageous from an economic perspective, as they can be manufactured cost-effectively. Furthermore, a mechanical connection is advantageous in this embodiment because it does not require welding from cast to cast.

[0027] In a preferred embodiment, the molded part is made of a different material than the material of the block body. Thus, the grate block comprises a first material for the block body and a second material for the molded part that differs from the first material. Selecting different materials for the block body and for the molded part can take into account different stresses on the block body and the molded part, for example, different wear, different operating temperatures, or different design features such as geometry or mechanical properties, to name just a few examples. Furthermore, different manufacturing processes can also be considered, allowing for optimization of their production independently of one another.

[0028] Materials such as steel, corrosion-resistant chromium steel, and heat-resistant steel, which can be machined by milling, for example, are particularly suitable for the molded part. These materials, in turn, enable the production of more complex geometries than is possible with a cast part.

[0029] In a preferred embodiment, the molded part is made of a harder material than the material of the block body. This has the advantage that maintenance of the grate block can be performed at longer intervals due to a less wear-resistant molded part.

[0030] According to the invention, the cross-section of the protective channel widens in the direction from the upper protective channel opening to the lower protective channel opening, and is, in particular, continuously widening. As already mentioned above, this design of the protective channel enables easy removal of combustion residues that have entered the protective channel.

[0031] In a preferred embodiment, the molded part has essentially the shape of a hollow truncated cone, preferably with an elliptical base. This embodiment offers an optimal design, which simultaneously reduces the risk of accumulation of liquid fraction in the thickened area. Furthermore, a simple construction is possible, particularly for series production.

[0032] Fasteners that do not belong to the molded part can be used to fasten the molded part, for example a screw.

[0033] In a preferred embodiment, the molded part comprises the fastening means, which is designed such that the mechanical fastening is effected by a positive connection to the upper wall, for example by pressing the molded part into a recess in the upper wall.

[0034] In a preferred embodiment, the molded part comprises the fastening means, which is designed such that the mechanical fastening is effected by a force-locking connection to the upper wall, for example by clamping the molded part into a recess in the upper wall.

[0035] A combination of these fastening methods is possible.

[0036] In a preferred embodiment, the fastening means protrudes from the bottom of the molded part in the form of a projection, away from the side of the molded part facing the firing material, i.e., in the attached state, toward the grate block. The projection is designed to be at least partially received in the recess and held in place by a mechanical connection, for example, by a positive and / or non-positive connection.

[0037] A positive connection can be created, for example, by inserting the projection into the recess, with the recess having a tapered section, i.e., a constriction, and the projection having a widening section. The largest cross-section of the widening section is dimensioned larger than the smallest cross-section of the constriction, such that the widening section of the projection can be pressed through the constriction, thereby clamping the projection.

[0038] In a preferred embodiment, the projection has a thread and the recess has a threaded receptacle so that the projection can be screwed into the recess.

[0039] Positive and non-positive fastening methods have the advantage that they can be easily implemented and enable a robust fastening of the molded part to the grate block.

[0040] If necessary, the projection can enclose and extend the protective channel.

[0041] The projection is designed such that in the fastened state, in which the projection is received in the recess, the protective channel of the molded part and the air supply channel of the block body are fluidly connected.

[0042] In the attached state, whether in the welded or mechanically attached state, the molded part forms a thickening which offers a solution for reducing the risk of impairment of the air supply through the air supply ducts, as explained above in connection with the thickening according to the invention.

[0043] In this context, this molded part also allows for a flexible design of the grate blocks of a combustion grate, because only individual grate blocks can be equipped, for example, in one area of ​​the combustion grate.

[0044] Furthermore, the molded part can be used to replace a previously formed thickened portion surrounding the air intake opening on the grate block, preferably as disclosed above, when it becomes worn. This contributes to reducing maintenance costs because the entire grate block does not need to be replaced.

[0045] The molded part can also be used if the grate block's air intake opening has been damaged by the operation of the combustion grate, for example, and the edge of the air intake opening has been partially worn away. The molded part can be welded or mechanically attached to cover this damaged area, allowing the grate block to be reinserted.

[0046] In a preferred embodiment, the grate block is intended for a combustion grate in which successive grate blocks are arranged one above the other in a stepped manner and are designed to rearrange and convey the fuel during combustion by means of pushing movements carried out relative to one another. Furthermore, viewed in a pushing direction S oriented substantially parallel to the longitudinal axis L, the foremost end of the support surface forms an edge over which the support surface drops into a pushing surface formed by a front wall. Furthermore, the front wall has a lower supporting edge arranged in a plane E running substantially perpendicular to the longitudinal axis L, which lower supporting edge is intended to come into contact with the supporting surface of an adjacent grate block in the pushing direction S.

[0047] The invention is illustrated by the accompanying figures, which show: Fig. 1 shows a grate block in a perspective view; and Fig. 2 shows a section of the grate block according to Fig. 1 in longitudinal section through the Fig. 1 shown section plane II-II, wherein the thickening is formed integrally with the grate block; Fig. 3 a section of the grate block according to Fig. 1 in longitudinal section through the Fig. 1 shown section plane II-II, wherein the thickening is welded onto the grate block; Fig. 4 a section of another grate block in longitudinal section, wherein a molded part is mechanically attached to an upper wall of the grate block; Fig. 5 a longitudinal section of the molded part according to Fig. 4 without grate block; and Fig. 6 a longitudinal section of the upper wall of the grate block according to Fig. 4 without molded part.

[0048] As from the Fig. 1As can be seen, the grate block 10 comprises a block body 12 designed as a cast part, which is essentially in the form of an elongated cuboid with a longitudinal axis L.

[0049] The block body 12 comprises an upper wall 14 which forms a support surface 16 running parallel to the longitudinal axis L, along which the firing material is to be conveyed and whose foremost end, viewed in the thrust direction S, forms an edge 19 over which the support surface 16 drops into a thrust surface 22 formed by a front wall 20.

[0050] In the embodiments shown, the support surface has a first support surface region 16a and a second support surface region 16b, both of which run parallel to the longitudinal axis L, but the first support surface region 16a is arranged offset upwards relative to the second support surface region 16b and is connected to the latter via a bevelled transition 17.

[0051] 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 support tube. A central web 29 is also arranged on the underside of the grate block 10, facing away from the support surface 16.

[0052] The grate block 10 is closed off at the sides by a side wall 28a, 28b extending in the longitudinal direction L.

[0053] Within the combustion grate, the grate block 10 rests on a grate block following in the thrust direction S. For this purpose, the lowermost region of the front wall 20 is designed in the form of a block 34, which is intended to rest on the support surface of an adjacent grate block in the thrust direction S. The lowermost region, including a front support edge 23 of the thrust surface formed thereby, is arranged in a plane E extending substantially perpendicular to the longitudinal axis L.

[0054] As from the Fig. 2 As can be seen, the upper wall 14 further has an air supply opening 35, which is formed by an air supply duct 38 extending through the upper wall 14. Primary air is supplied to the combustion grate or the combustion bed on the combustion grate through the air supply duct 38.

[0055] In the embodiment shown, the air supply channel 38 forms a slot-shaped air supply opening 35 in the upper wall 16, which is aligned in the longitudinal direction of the grate block 10, and the air supply channel 38 defines a longitudinal plane of symmetry P. In the Fig. 2 the section plane II-II runs in the longitudinal symmetry plane P.

[0056] The air supply duct 38 extends concentrically to an axis R running at right angles to the support surface 16 and in the longitudinal plane of symmetry P, wherein the clear opening of the air supply duct 38 is essentially elliptical and continuously widens in the shape of a cone in the direction away from the support surface 16. The air supply duct 38 comprises a first air supply duct section 38a facing the support surface 16 and a second air supply duct section 38b adjoining the first air supply duct section 38a on the side thereof facing away from the support surface, wherein the widening of the second air supply duct section 38b is greater than the widening of the first air supply duct section 38a. With respect to the axis R, the generatrix of the cone forms a first angle of 10 degrees in the first air supply duct section 38a and a second angle of 15 degrees in the second air supply duct section 38b.

[0057] Furthermore, the air supply opening 35 is completely surrounded by a thickened portion 50 protruding from the support surface 16. The thickened portion 50 forms a protective channel 57 extending the air supply channel 38 and is intended to prevent liquid from flowing into the air supply opening 35.

[0058] The protective channel 57 comprises a lower protective channel opening 57a on the end of the protective channel 57 facing the support surface 16 and an upper protective channel opening 57b on the end of the protective channel 57 facing away from the support surface 16, ie on the side of the thickening facing the firing material.

[0059] Furthermore, the protective channel 38 is enclosed by an inner flank 54 of the thickened portion 50, wherein the inner flank 54 is formed directly adjacent to an edge of the air supply opening 58 running in the support surface. In addition, the thickened portion 50 has an outer flank 55 adjoining the inner flank 54 and running sloping and straight on the side facing away from the protective channel 38. Furthermore, a flattened transition region 60 of the thickened portion 50 extends between the inner flank 54 and the outer flank 55. In the embodiment shown, the height h of the thickened portion, measured from the support surface, is approximately 20 mm. In addition, the inner flank, viewed in cross-section, runs at least approximately in the extension of the lateral surface of the first air supply channel section 38a.

[0060] In the Fig. 2 the thickening 50 is formed integrally with the grate block 10 in a casting process.

[0061] In the Fig. 3the grate block is according to Fig. 1 , wherein the thickening is formed by a shaped part 50' and welded onto the grate block 10. Accordingly, the grate block 10 has a weld seam 70 at the interface between the shaped part 50' and the support surface 16. The shaped part 50' essentially has the shape of a truncated cone with an elliptical base, which extends concentrically to the axis R. Furthermore, the shaped part 50' comprises a protective channel 57 extending concentrically to the axis R, which is intended to extend the air supply channel 38. The protective channel 57 is designed such that its inner flank 54 runs in the extension of the lateral surface of the air supply channel 38.

[0062] The other features of the Fig. 3 The sections of the grate block 10 shown are similar to those in the Fig. 2 and can be found in the corresponding description.

[0063] During operation, the grate blocks 10 are moved relative to each other by means of the block support tubes. Depending on whether the block support tubes are assigned to a stationary or a movable grate block, the block support tubes are either attached to stationary brackets or to brackets arranged in a movable grate carriage.

[0064] The drive is provided by hydraulic cylinders, which move the grate trolleys back and forth via rollers on corresponding running surfaces.

[0065] Due to the relative movement thus obtained, the foot 34 of a first grate block 10 is pushed forwards and backwards over the support surface 16 of the respective subsequent grate block 10, wherein the firing material is conveyed over the support surface 16 before it is thrown over the edge 19 onto the support surface 16 of the subsequent grate block 10.

[0066] In the Fig. 4a section of a grate block 10 is shown, wherein the thickening is formed by a molded part 50' and is mechanically attached to the grate block 10. The grate block 10 comprises a block body 12, which has the same design features as the grate block of the Fig. 1 In the following, only the differences are described in more detail and the same parts are designated by the same reference numerals.

[0067] The block body 12 has a recess 72 extending around the air supply opening 35. In the present case, the air supply opening 35 and the recess 72 are rotationally symmetrical about an axis Q extending perpendicular to the support surface 16 and defined by the air supply opening 35. The recess 72 has a tapered section, ie, a constriction, in the form of a lip 74, which adjoins the support surface 16.

[0068] The molded part 50' has essentially the shape of a hollow truncated cone with an elliptical base, as shown in Fig. 4 and Fig. 5 can be seen. On the side of the molded part facing away from the firing material, the molded part has a bottom 80 penetrated by the air supply channel, the outer bottom surface 82 of which corresponds to the base surface of the truncated cone. Fig. 4 In the embodiment shown, in the fastened state of the molded part, the outer bottom surface 82 is at least flush with the plane of the support surface 16.

[0069] Furthermore, the molded part 50' comprises a fastening means in the form of a projection 84, which protrudes from the bottom 80 of the molded part in a direction away from the side of the molded part facing the firing material. The projection 84 is frustoconical and rotationally symmetrical to the axis Q. The projection 84 is designed to be received in the recess 72 and held by a mechanical connection.

[0070] For this purpose, the largest cross-section of the widening portion of the projection 84 is dimensioned larger than the smallest cross-section of the constriction 74, such that the projection 84 can be pressed and inserted into the recess 72. As a result, the projection 84 remains clamped in the recess 72. List of reference symbols

[0071] Grate block 10 Block body 12 Upper wall 14 Support surface 16 Support surface area 16a, 16b Transition 17 Edge 19 Front wall 20 Rear wall 24 Hook 26 Side wall 28a, 28b Central web 29 Block 34 Air supply opening 35 Air supply duct 38 First or second air supply duct section 38a, 38b Thickening or molded part 50, 50' Inner flank 54 Outer flank 55 Protective duct 57 Lower and upper protective duct opening 57a or 57b Edge of the air supply opening 58 Transition area 60 Weld seam 70 Plane of the front wall E Longitudinal axis L Direction of thrust S Longitudinal symmetry plane P Axis R Height of the thickening h Recess 72 Lip 74 Base 80 Base surface 82 Projection 84 Axis Q

Claims

1. A molded part for fastening to an upper wall (14) of a block body (12) of a grate block about an air supply opening (35) which is configured in the upper wall and formed by an air supply duct (38) extending through the upper wall (14), wherein the grate block is specified for a combustion grate and the block body (12) is configured as a casting, wherein the upper wall (14) forms a bearing face (16) along which the incinerator charge is to be conveyed, wherein the molded part, in the fastened state, forms a thickening (50) that projects from the bearing face (16), surrounds the air supply opening (35), forms a protection duct (57), which extends the length of the air supply duct (38), and is specified for preventing liquid flowing into the air supply opening (35), wherein the protection duct (57) is enclosed by an inner flank (54) of the thickening (50) and the thickening (50) has an outer flank (55) that adjoins the inner flank (54) and runs in a descending manner on the side that faces away from the protection duct (57), characterized in that the cross section of the protection duct (57) widens, and in particular is configured so as to widen continuously, in the direction from the end of the protection duct (57) that faces away from the bearing face (16) to the bearing face (16).

2. The molded part as claimed in claim 1, characterized by substantially the shape of a hollow truncated cone, preferably having an elliptical base area.

3. The molded part as claimed in one of claims 1 or 2, characterized by a fastening means for mechanical fastening to the upper wall (14).

Images