Combustion step grate reinforced against breakage, with grate steps made of grate bars or grate blocks clamped together

Abstract

The fracture-reinforced combustion step grate with grate steps consists of grate bars or grate blocks (2) braced together. These have reinforcing ribs (9) or tabs projecting downwards along their underside. Bores lead through these ribs (9), or there are tabs with bores through which the tensioning screws (7) pass, so that the grate bars or grate blocks (2) can be braced together. To provide fracture-reinforcement, reinforcing parts (3) made of sheet metal or cast iron with bores at both ends are attached to at least one inner side of a rib (9) or tab and are braced to the rib (9) or tab of an adjacent grate bar or grate block (2) by means of screw connections. Alternatively, the reinforcing parts (3) made of sheet metal or cast iron can also be welded to the inner sides of the ribs (9) or tabs.

Description

[0001] The invention relates to fracture-reinforced incineration step grates, particularly for waste incineration grates whose steps consist of grate bars or blocks, sometimes also of continuous grate plates. The reinforcements are intended to prevent the cracking or collapse of grate steps and thus the partial or complete subsidence due to fracture of their grate bars or blocks.

[0002] Grate bars, grate blocks, or grate plates are installed in pusher combustion grates, which have stationary and movable grate stages to transport and stoke the fuel. The individual grate stages consist of a row of adjacent grate bars or grate blocks, or of continuous grate plates that rest on one another in a stepped manner, similar to a row of tiles on a tiled roof, although the inclination can also be the opposite of that of a tiled roof. These combustion grates can be installed so that the combustion bed is essentially horizontal, or inclined, with inclines of up to 20 degrees or more being common. The grate bars or grate blocks are made of high-temperature cast iron and, depending on the calorific value of the fuel, are air- or water-cooled. Water-cooled grates are used for higher calorific values.Or the grate stages consist of grate plates made of sheet steel, whereby these grate plates are water-cooled. In the case of grate plates, these can form board-shaped hollow bodies that extend across the entire width of the grate track, i.e., form the entire grate stage between the side walls of a grate. Water can be passed through the cavities of the grate plates as a cooling medium, while the grate bars or grate blocks are used for air-cooled grates and are blown with primary air from below, which also serves to cool them. Every other grate stage is movable and can therefore perform a stoking or transport stroke in the conveying direction of the grate.

[0003] During normal operation, the loads on a grate bar or grate block are low, both in terms of the surface load from the waste and the tensile and compressive forces when moving the grate steps. If the grate bars or grate blocks are correctly dimensioned for the application, they will last until the next scheduled service, even if broken. However, under particularly demanding loads, which are becoming increasingly common, the following problem sometimes arises with a stepped grate with steps made of such grate bars or grate blocks: An increase in explosion incidents has been observed in waste incineration plants, which is usually due to gas cartridges or gas cylinders that are not completely empty and have been carelessly thrown into the garbage. This has been observed in several plants in France, Belgium, the Netherlands, and Germany since around 2020.The additional, unforeseen dynamic load can cause a grate stage to collapse, with the grate bars or blocks breaking in the front area. The fracture occurs in each case on the stage below, as the explosion pressure on the upper grate stage is absorbed over a larger area and dissipated in a concentrated manner via the base with a shock into the grate stage below. As a result, approximately the front third of the grate bar or grate block there sags downwards. This often leads to blockages in the grate mechanism that drives the movable grate stages and to consequential damage that can even lead to an interruption in plant operation. Overloads can also occur during normal operation if deposits on the walls and ceilings become loose and fall onto the grate.The longer a grate stage has been in operation in the system, the greater the likelihood of failure, as the relative movement between the grate stages causes abrasion on the running surface, which weakens the grate stage. The fracture of the grate bars or blocks that make up the grate stage occurs primarily due to the very rapid application of force with a high impact force, which is similar to a notched bar impact test. The material has no opportunity to undergo plastic deformation in such a short time and fractures across the entire cross-section of the grate bar or block.

[0004] As a result of such increasingly frequent incidents, manufacturers tend to build grate bars and blocks more solid and therefore heavier, i.e., with thicker walls, to avoid accidents and, in particular, to prevent the collapse of individual grate bars or blocks. However, a heavier grate also requires a correspondingly stronger substructure and a more powerful drive for the movable grate steps—in other words, significant follow-up costs. Furthermore, a slight material reinforcement usually only leads to increased manufacturing and installation costs, but does not eliminate breakage caused by the effects of the explosion.

[0005] The object of the present invention is to remedy this situation and to create a fracture-resistant stepped combustion grate that is more resilient and can be operated more safely. Such grates can then effectively prevent the fracture or collapse, and thus the sagging, of its grate bars or grate blocks, either by retrofitting existing combustion grates or by manufacturing new ones with such a fracture protection.

[0006] The task is solved by a combustion step grate reinforced against breakage with grate steps made of grate bars or grate blocks braced together, which have reinforcing ribs or tabs projecting downwards along their sides on their underside and are braced together by means of these ribs or connecting screws and nuts leading through these tabs, characterized by that at least on one inner side of a rib or tab, a reinforcing part made of sheet metal or cast iron with holes at both ends is attached to the rib or tab and is clamped to the rib or tab of an adjacent grate bar or grate block by means of screw connections, or the reinforcing part is welded to the inner side of the rib or tab over the entire length or only spot-welded.

[0007] By separating the functions into multiple components, different materials can be used and combined. Thus, the fracture-prone rod is combined with a rolled and less fracture-prone metal, preferably steel. This allows for disproportionately higher safety against failure at much lower cost, despite the thinner wall thickness of the fracture protection. A high-temperature cast with improved shock fracture properties could also be used. However, this would lead to disproportionately higher costs. Furthermore, a cast structure always has less favorable material properties with regard to fracture compared to a forged / rolled fine-grained metal structure.

[0008] Thanks to these clamped or welded reinforcement parts made of sheet metal or cast iron, the bolted-together grate bars or grate blocks of conventional design can be significantly reinforced, significantly increasing the load-bearing capacity and service life of a newly manufactured or retrofitted step grate. The reinforcement is so effective that the grate bars or grate blocks for newly manufactured step grates can even be made lighter, thus saving costs. A step grate that is ultimately lighter thanks to these clamped steel sheets can bear higher loads than a conventional combustion grate of otherwise identical construction.This combination of lightweight, bolted-together grate bars or blocks, braced with reinforcements made of sheet metal or cast iron, or with welded-on reinforcements made of sheet metal or cast iron, avoids the need for increasingly thick-walled and therefore heavier grate bars or blocks for certain grate types due to the increased loads they are subjected to. Such conventional OEM stepped gratings, whose grate steps are constructed from braced-together grate bars or blocks, can also be easily retrofitted and significantly reinforced with additional reinforcements made of sheet metal or cast iron.

[0009] A significant advantage of this solution is that a row of such grate bars or grate blocks can be made much lighter, and thus less load is transferred to the substructure than with solutions that are made more stable purely by making the cast parts, i.e. the grate bars or grate blocks, stronger.

[0010] This solution also offers maintenance benefits to the operator of a waste incineration plant, which are described in detail below. The fracture-resistant combustion step grate with grate steps made of braced grate bars or grate blocks is described in more detail using the figures, and its special features are discussed.

[0011] It shows: Figure 1: A grate bar with a break at its front end where its nose broke off, and its bulge at the back, with which it rests on a steel pipe and can be hung on it with a precise fit; Figure 2: Three grate levels seen from the front, whereby the lowest grate level has partially broken grate bars and has subsequently sunk over a section A; Figure 3: A screwed connection point between two grate bars or grate blocks seen from below; Figure 4: Two symmetrically arranged reinforcement parts made of sheet metal or cast iron in the installed position seen from above; Figure 5: The two symmetrically arranged reinforcement parts made of sheet metal or cast iron from Figure 4seen from the side; Figure 6: A single reinforcement part made of sheet metal or cast iron with the corresponding screw heads of the inserted tensioning screws, seen from the side; Figure 7: The individual reinforcement parts made of sheet metal or cast iron, seen from above, with inserted tensioning screws; Figure 8: The front part of a grate block seen from below, with tensioning screws inserted on both sides; Figure 9: A grate block seen from below, with a reinforcement part made of sheet metal or cast iron drawn in before being clamped and tensioned, and to the right of the grate block, two loose reinforcement parts made of sheet metal or cast iron; Figure 10: A grate block seen from below, with two reinforcement parts drawn in before being clamped and tensioned; Figure 11: Three grate bars clamped together by means of clamped reinforcement parts, seen from below;Figure 12: A grate bar tilted 90° on its side, i.e. shown in a plan view of its side, in a section along the line CC in ; Figure 11 , with reinforcement part placed on it; Figure 13: A grate step section made of three grate blocks clamped together by means of clamped reinforcement parts; Figure 14: A grate block tilted 90° on its side, i.e. shown in a plan view of its side, in a section along the line BB in Figure 13 , with reinforcement part placed on it; Figure 15: Three grate stages seen from below, each of these grate stages being constructed from a plurality of clamped together grate blocks, and reinforcement parts being clamped to the clamps.

[0012] First of all, in the Figure 1a grate bar 1 is shown, the front part V of which has been broken away. At the rear, a bulge 11 can be seen, with which it rests on a steel tube that can be moved back and forth transversely to its longitudinal direction and can be precisely suspended on this tube, so that it can execute a stoking movement for a movable grate step.

[0013] The Figure 2 shows a section of three grate steps 4, 4', 4" made of such grate bars 1, with partially collapsed grate bars 1 and subsequently sunk section A. As can be seen here, this damage is considerable. The combustion grate can no longer function properly and must be shut down, and at least the grate bars of this damaged section A must be completely replaced.

[0014] The Figure 3shows a bolted connection point between two grate bars or grate blocks seen from below. Since the grate blocks have drafts or setbacks on the surfaces to be clamped due to their manufacture as cast parts, the surfaces to be clamped are not parallel. This is disadvantageous for a bolted connection, as bolting non-parallel surfaces leads to point loads and bending stresses. In addition, in the present application there is a potentially cyclical temperature load, which can lead to the failure of such a bolted connection. The following section in detail AA with an enlarged view shows how the angle corresponding to the setback in the casting was machined into the safety plate in order to achieve two parallel screw bearing surfaces without the need for remachining of the cast block.You then have grate blocks with screw connections and break protection, with an integrated support bracket and a twist lock for the screw head. As can be seen in . Figure 3As can be seen, the contact surfaces fit snugly against one another and are clamped together with a connecting screw and washers, which also act as fracture protection and angle compensation. There are several approaches to ensuring that the screw connection does not loosen due to load changes and / or temperature fluctuations. The safest type of screw connection is an expansion screw. This means that the screw shaft, at 70% of the maximum tightening torque, creates enough spring deflection to absorb all varying loads. The previous solution, with milled pockets in the cast iron for the screw supports, has a thick and short screw shaft, which is not advantageous.By omitting the pocket milling and the thickening due to the fracture protection plate on both sides, a robust screw connection is created for the operating conditions, which prevents dirt from accumulating between the grate blocks due to loosening of the screw connection.

[0015] The Figure 4 shows two symmetrical reinforcement parts 3 made of sheet metal or cast iron in the installed position seen from above, and in Figure 5 These two symmetrical reinforcement parts 3 are made of Figure 4 Shown from the side. They are lasered, burned, or punched for both sides. Holes 10 are drilled in both end areas of the reinforcement part 3, and adjacent to these holes, a surface is milled on each side with the angle of the cast 5.

[0016] The Figure 6shows a single reinforcement part 3 with corresponding hexagon screw heads 6 of the inserted clamping screws seen from the side, and the Figure 7 shows a single reinforcement part 3 seen from above, with inserted clamping screws 7 with their hexagon screw heads 6.

[0017] The Figure 8shows the front part of a grate block 2 seen from below. On both sides, the grate block 2 forms downwardly projecting ribs 9, and on one side, clamping screws 7 are inserted in the same direction, and on the other side, the nuts are mounted on the shear plate with finishing X. Due to the thickening provided by the shear plate, the screw head is displaced sufficiently away from the rib wall to mill a pocket y without negatively affecting the local surface pressure and thus increasing local abrasion. Due to the direct access to the head, the hidden screws can be tightened ergonomically using normal tools, which was not possible in the old design. and in Figure 9A grate block is shown viewed from below, with a reinforcement part 3 drawn in it before being nestled against the rib 9 and braced with the rib 9, and to the right of the grate block 2, two loose reinforcement parts 3 are shown opposite the rib 9. Instead of ribs 9, individual downward-projecting tabs, each with a hole, can also be used, so that the reinforcement parts can then be placed on the inner sides of these tabs and braced with them.

[0018] In the Figure 10A grate block 2 is shown from below, with two reinforcement parts 3 drawn into it before being nestled and braced with the rib 9. At the bottom right of the reinforcement parts 3, you can see an inserted tensioning screw. This is a screw with a sufficiently long shaft; you could also choose a special expansion screw for even greater security. 7 with screw head 6 and the attached nut 8 for bracing. To the right of the picture, another grate block is to be connected, and the reinforcement part 3 on the far right is then attached to its rib from the right and braced with the grate block 2 shown here.

[0019] In Figure 11Three grate bars 1 are shown braced or screwed together, seen from below, and clamped together by means of clamped reinforcement pieces 3. This significantly strengthens a grate level in every respect, absorbing any torque and torsional forces that occur. A further advantage and cost reduction can be achieved with these reinforcing steel sheets 3 because the washers can be omitted. The reinforcement piece 3 has the same function as a washer. It distributes the compressive force of the screw head 6 or the nut 8 over a larger area and protects the weaker cast iron substrate from friction damage during tightening. Due to its greater thickness, the reinforcement piece 3 made of sheet metal or cast iron distributes the compressive force even better, which is more advantageous and can withstand larger torques.These occur when the front part breaks due to the twisting of the front part when pulling back and forth. It also protects the cast iron from the rotation of the nut 8 during tightening.

[0020] Reinforcement part 3 offers potential for ergonomic improvements during assembly and disassembly of the grate. Access to the screw connection is particularly limited at the front of the grate block, necessitating the use of special tools. This can be remedied by a welded-on anti-rotation device that prevents screw head 6 from rotating, so that only lock nut 8 needs to be tightened using a special tool. One option is to weld a block onto reinforcement part 3 in such a way that there is space for screw head 6 but it can no longer rotate. This eliminates the need for locking when screwing on, and you can concentrate entirely on tightening one side, i.e., nut 8. Only a single offset hand tool is then required. The only disadvantage is the additional cost of manufacturing the block and the precise welding.A better solution is therefore to mill the angled cut slightly deeper on one side only to ensure parallelism of the screw support. This creates an edge against which the screw head 6 can rest, as shown in . Figure 6 As shown. In this variant, a slightly thicker reinforcement part 3 will be used. There is no anti-rotation edge on the nut side to allow unhindered tightening of the nut. If the reinforcement parts 3 are defined as disposable parts, the screws can also be spot-welded directly onto the reinforcement part 3, creating an even easier-to-install assembly.

[0021] For higher volumes, the part could be manufactured using a repeatable manufacturing process. Casting would generally be the material of choice for this. The reinforcement parts 3 are manufactured either using sand or special sand casting, or using the lost-wax casting process. With the lost-wax casting process, all necessary tolerances in the final part are achieved without any post-processing, and as an added benefit, it results in a finer microstructure. Due to the size of these parts, special fracture-resistant and rust-resistant steels can also be used, keeping costs within economically viable limits given the relatively small casting weights involved. When manufacturing from sheet metal for prototypes, one is dependent on either structural steel or simple stainless steel. Structural steel will likely require surface treatment to protect against corrosion, while stainless steel as a base material is much more expensive and more complex to manufacture.

[0022] Reinforcement part 3 enables a further improvement due to its thickness. Due to the thickness and the omission of the milling for the screw in the casting, the screw head is shifted by 5-25 mm on each side. This shift makes it possible to mill a milling into the base of the grate block at the support to the next grate block, as the force is sufficiently distributed across the side wall to the support surface. This allows a pocket to be cast or milled into which simple open-end wrenches can be inserted to tighten the nuts. This eliminates the need for special offset tools. These pockets can also prove advantageous in terms of wear, as particles that get between the supports slide into the pocket due to the lifting movement and are thus evacuated from the support area more quickly.

[0023] For the plant operator, the downtime of a grate is a very important parameter. With improvements and a reduction in the number of parts, a time saving of several minutes can be achieved per grate block, which adds up for a large grate. Plants have between 1,000 and 4,000 grate bars. By reducing the number of components, eliminating locking, and improving access to the nuts 8, installation time reductions of several hours to several days can be achieved. These justifiable improvements may be reflected in the bid price, but for the operator, the reduction in downtime costs is of far greater importance.

[0024] The Figure 12 shows a rust bar made of Figure 11in a section along the line CC and tilted by 90° to the side, i.e. shown in a top view of its side, with the reinforcing part 3 attached to it. You can see the millings 5 ​​for the screw heads 6, so that they cannot rotate.

[0025] The Figure 13 shows a grate step section made up of three grate blocks 2 clamped together by means of clamped reinforcement parts 3. Just like the bracing of narrower grate bars 1, the outer ribs 9 of the grate blocks 2 are clamped between two reinforcement parts 3 each.

[0026] The Figure 14 shows such a grate block in a section along the line BB in Figure 13 and tilted by 90° on its side, i.e. shown in a top view of its side, with reinforcement part 3 made of sheet metal or cast iron placed on it.

[0027] Finally, in Figure 15three grate stages are shown as seen from below, whereby these grate stages are each constructed from a plurality of clamped together grate blocks 2, and reinforcement parts 3 made of sheet metal or cast iron are clamped to the bracing. Index

[0028] 1 Grate bar 2 Grate block 3 Reinforcement part made of sheet metal or cast iron 4 Grate level 4, 4', 4" 5 Millings on the reinforcing steel sheet, tightening angle 6 Screw head of the screw 7 Screw for bracing the reinforcement part 8 Nut for screw 7 9 Side rib on the grate bar or grate block 10 Holes in the reinforcement part 11 Bulge on the grate bar

Claims

1. A combustion step grate reinforced against breakage with grate steps made of grate bars (1) or grate blocks (2) braced together, which have reinforcing ribs (9) or tabs projecting downwards along their sides on their underside and are braced together by means of holes (10) leading through the ribs (9) or tensioning screws (7) and nuts (8) leading through these tabs, characterized by that at least on one inner side of a rib (9) or tab, a reinforcing part (3) made of sheet metal or cast iron with bores (10) at both ends is applied to the rib (9) or tab and is clamped to the rib (9) or tab of an adjacent grate bar or grate block by means of screw connections, or the reinforcing steel sheet is welded to the inner side of the rib or tab over the entire length or only spot-welded.

2. A combustion grate reinforced against breakage according to claim 1 , characterized, thaton both inner sides of the outer ribs (9) of the grate bars (1) or grate blocks (2), a reinforcing part (3) with bores (10) at both ends is attached to the rib (9) and is clamped to the adjacent ribs (9) of an adjacent grate bar (1) or grate block (2) by means of screw connections, or these reinforcing parts (3) are welded to the inner side of the ribs (9) or tabs.

3. A combustion grate reinforced against breakage according to any one of the preceding claims, characterized by that each reinforcing part (3) projects downwards beyond the rib (9) to which it is clamped or welded.

4. A combustion grate reinforced against breakage according to one of claims 1 to 2, characterized by that each reinforcing part (3) has a congruent contour (K) to the rib (9) to which it is clamped or welded.

5. A combustion grate reinforced against breakage according to any one of the preceding claims, characterized by that the screws (7) and nuts (8) used for bracing the reinforcing parts (3) are clamped between the screw connections to the reinforcing part (3) without the use of any washers that would otherwise be present.

6. A combustion grate reinforced against breakage according to any one of the preceding claims, characterized by that the support surfaces for the screw head and nut on which a reinforcement part (3) is reworked in such a way that the rework compensates for the casting tightening and thus the screw support surfaces can be screwed parallel to each other.

7. A combustion grate reinforced against breakage according to any one of the preceding claims, characterized by thatfor the tensioning of the reinforcing parts (3), more than two tensioning screws (7) and nuts (8) per reinforcing part (3) are used, which cross the ribs (9), for the increased absorption of the torques and torsional forces acting on the grate step, and that the screw connections of the reinforcing parts (3) are realized by means of screws (7) and nuts (8), wherein this screw connection is equipped with an anti-twist device for the screw head.

8. A combustion grate reinforced against breakage according to any one of the preceding claims, characterized by that the anti-twist protection of the screw heads of the screws (7) is realized by reworking the reinforcing part (3), whereby an edge is created in the reinforcing part (3) which prevents the screw head from twisting.

9. A combustion grate reinforced against breakage according to any one of the preceding claims, characterized by thatthe anti-rotation lock of the screw head is realized by means of an attached block which is fixed at a distance so that the screw head cannot rotate.

10. A combustion grate reinforced against breakage according to any one of the preceding claims, characterized by that in the case of a reinforcing part (3) made of sheet metal, the screws are welded to the sheet metal so that the screw head is secured against rotation, and that the reinforcing parts (3) are at least 2 mm thick and are made of steel.

11. A combustion grate reinforced against breakage according to any one of the preceding claims, characterized by that instead of two screw connections, the reinforcement part (3) is welded at least 2 points.

12. A combustion grate reinforced against breakage according to any one of the preceding claims, characterized by thatthe material of the reinforcing part (3), in the case of sheet metal, is increased in its strength by forming by rolling and / or forging.

13. A combustion grate reinforced against breakage according to any one of claims 1 to 9, characterized by that the reinforcement parts (3) are designed as ready-to-assemble cast parts and are designed in such a way that a fine-grained structure > 60 µm is created, and the combustion step grate can withstand shock-like impacts despite this cast structure.

14. A combustion grate reinforced against breakage according to any one of the preceding claims, characterized by that it is made of rust-resistant material and therefore no surface rust protection treatment is necessary.

15. A combustion grate reinforced against breakage according to any one of the preceding claims, characterized by thatThe screws and nut support are dimensioned in such a way that the screws are considered to be an expansion screw connection, but the web is designed to be less strong depending on the load.

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