EP3982044B1 - Method for holding together grate bars lying next to each other and a grate bar assembly - Google Patents

Description

The invention relates to a method for holding together grate bars lying next to one another, which have an upper side designed as a grate, in which the grate bars are pressed together with a holder, the holder being operated through a recess on the upper side of the grate bars and the recess being covered with a cover. In addition, the invention relates to a grate bar arrangement with a grate bar with an upper side designed as a grate and a holder for holding together grate bars lying next to one another.

Grate bars are used for combustion plants, particularly waste incineration plants, and a large number of grate bars form the grate covering on which the fuel is burned. This covering is usually a surface with openings. The openings serve to supply the air required for combustion ("primary air"). The movements required to circulate the fuel ("stirring") take place automatically in larger grate combustion plants by moving the grate.

In particular, the invention relates to a step grate/grate grate. Grates of this type look similar to a flat staircase with a gradient of generally between 0 and 30°, such as 24 or 26°. The fuel is moved over the grate by the grate steps moving and thus transporting the fuel. Depending on the direction of the grate bar movement, the step grate is also called a push-pull grate or a push-pull grate (in both cases, however, the fuel moves forward).

Stair grates are used for coarse and ash-rich fuels that require improved stoking, such as domestic and commercial waste, biomass, waste wood, processed garbage or, less commonly, brown coal.

Staircase grates have a large number of grate bars that can be firmly connected to one another or can be moved relative to one another in order to move the fuel on the grate.

Such grate bars usually have openings for air supply. For this purpose, recesses are provided in the side wall of the grate bar or openings on the top and/or front of the grate bar, which allow air conveyed to the underside of the grate bar to be conveyed between the grate bars or through the grate bars to the combustion bed.

A typical grate bar is from the FR 2 622 278 A1 A similar rust bar is shown in the DE 198 60 552 A1 and a grate bar disclosing the features of the preambles of the independent claims, the US 4 776 287 A .

The invention relates in particular to grate bar arrangements in which several grate bars are arranged next to one another. Grate bars lying next to one another form individual grate steps, which together form the grate covering. A grate step can be arranged slightly offset from another grate step. Grate bars lying next to one another in the transverse direction can be arranged so that they are relatively movable or firmly connected to one another.

When such grate steps move to stoke and transport the fuel, greater forces are generated, which can also affect the position of the individual grate bars relative to one another. This can cause grate bars to be moved sideways, creating gaps between adjacent grate bars.

In order to keep the grate bars parallel and adjacent to each other during operation, the grate bars can be connected to each other using brackets. These are usually screw connections that press grate bars lying next to each other together.

This connection is designed to be detachable so that individual grate bars that have been damaged during operation can be replaced without having to replace the entire grate stage. For this purpose, structures are provided on the underside of the grate bars, i.e. opposite the combustion chamber and the fuel, which make it possible to attach grate bars lying next to each other to one another using a bracket.

The brackets are arranged below the grate bars to protect against harmful temperature and corrosion influences from the combustion of the fuel on the grate surface.

In particular, the fastening of grate bars lying next to each other using screw connections is complex, since in confined spaces below the grate the nut has to be turned against the screw and at the same time the screw has to be prevented from falling out.

The invention is therefore based on the object of further developing a generic method and proposing a grate bar arrangement which makes it easier to hold grate bars lying next to one another together. Preferably, the grate bar arrangement should also make it easier to replace defective grate bars.

This object is achieved by a method having the features of patent claim 1. A grate bar arrangement according to the invention is described in patent claim 10.

Advantageous further training is the subject of the dependent claims.

According to the invention, it is proposed to operate the holder through a recess on the top of the grate bars. This makes it possible to continue to arrange the holder below the top of the grate bars. However, operation is made easier by the fact that the staff can stand on the top of the grate in the combustion chamber while operating the holder, for example to loosen a screw connection or pull off a clamp.

Since grate bars can only be repaired or replaced when the entire combustion plant is at a standstill and has cooled down, the holder no longer has to be operated under the grate, where a funnel and other fittings for moving the grate usually make it difficult to operate the holder.

When operating the bracket, positive or non-positive brackets can be used. It is advantageous if the grate bars are screwed together from the top. A screw or threaded rod running across the grate bars lying next to each other is screwed to at least one nut to hold the grate bars lying next to each other together.

It is advantageous to provide recesses on both sides of a grate bar through which the screw connections can be inserted and tightened from above. This avoids having to insert the screw or threaded rod into a hole, which makes processing much easier.

For ease of use, it is suggested that the size of the recess be chosen so that one wrench can be placed on the screw head and another on the nut and tightened. Similarly, with a threaded rod, wrenches are placed on two lock nuts.

According to the invention, it is proposed that the recess is covered with a plate. This plate can be part of the holder or can be mounted as a single part above the bracket to cover the recess so that the top of the grate is as flat as possible.

In order to keep the plate securely in the recess even under heavy loads, it is proposed that the plate be anchored in the recess with a positive fit. This makes it possible to remove the plate from the anchorage by moving the plate in order to gain access to a bracket underneath. In order to prevent the plate from moving during operation of the system, it is proposed that the plate be secured with a wedge. This wedge can, for example, be inserted into a recess with a positive fit, which on the one hand creates a flat surface of the grate covering and on the other hand prevents the plate from moving.

Since the wedge falling out could lead to the plate becoming loose, it is suggested that the cover plate or the wedge be welded to the grate bar or the plate to the wedge. Since the cover of the recesses and in particular the plate are preferably made of steel, while the grate bars are usually made of cast steel, welding between the plate and the grate bar is often not possible. The positive connection of the plate to the grate bars in conjunction with welding between the plate and the wedge makes it possible to firmly connect the plate to the grate bars without having to weld the plate to the grate bars.

In terms of the device, the object underlying the invention is achieved in that the top of the grate bar has a recess and the grate bar arrangement has a cover, wherein the recess is covered with a plate and the plate covers the recess in such a way that the top of the grate is as flat as possible. This enables easy operation of the holder, while the cover enables a flat top of the grate.

A first embodiment provides that the bracket has a screw connection. Cumulatively or alternatively, the bracket can have a clamp.

If the bracket is made of a different material to the grate bars, there is a risk that the bracket and the grate bars will expand differently when the furnace heats up and the bracket will either break or become loose. It is therefore suggested that the bracket or an element of the bracket has a smaller coefficient of thermal expansion than the grate bars. The thermal expansion of metals and alloys is given as linear expansion, which is proportional to a linear expansion number that indicates the extension of the unit length for 1 ° increase in temperature between 0 and 100 °C. For example, the linear expansion coefficient for Ni steel, 36Ni, Invar is 1.0 and for cadmium it is 30. The literature gives a linear expansion coefficient of 10.5 for cast iron, for low-alloy steels the linear expansion coefficient is 11.5 and for Ni steel, 30Ni it is 12. However, for Ni steel, 20Ni the linear expansion coefficient is already 19.5. This means that a screw connection or a clamp can expand more in the grate area when heated to 500 ° C, for example, than the grate bar made of cast steel. This can in turn lead to firmly screwed grate bars no longer being firmly screwed during operation of the combustion system because the screw has stretched too much.

If the material of the bracket or an element of the bracket is selected so that it has a smaller coefficient of thermal expansion than the grate bars, the bracket can still be relatively loose when cold, since the greater expansion of the grate bars means that the bracket becomes firm during operation and holds the grate bars together more and more tightly as the temperature increases. For example, the grate bars can then be connected to a form-fitting bracket that exerts a strong holding force on the grate bars when the grate bars expand in order to hold the grate bars together.

Accordingly, it is proposed that the bracket has a connecting element and a clamping element, whereby the connecting element and clamping element have different thermal expansion coefficients. This makes it possible to connect the grate bars easily and, if necessary, loosely when cold by cleverly selecting the material, since the bracket then exerts a special force on the grate bars when the grate bar and bracket are heated in order to hold them together.

Elements with an expansion coefficient that is greater than that of the bracket can also be arranged between the bracket and the grate bars. For example, with a conventional steel screw connection, a washer with a high expansion coefficient can be used that is placed on the screw shaft. Since the steel of the screw connection elongates more than the cast steel of the grate bars, the washer can compensate for this expansion.

To hold the cover securely in the recess, it is proposed that it has an undercut to engage laterally under a top of a grate bar. This allows for a simple, positive connection. In addition, the cover may also have a wedge to secure a plate-shaped cover in the inserted position.

The cover can be arranged as a single part above the bracket. A special design variant provides that the cover is connected to the bracket or part of the bracket. The bracket or part of the bracket thus simultaneously forms the cover.

Several brackets can be provided between two grate bars to ensure that the grate bars are held close together over their entire length. However, it is advantageous if only one bracket is provided to hold grate bars lying next to each other together.

Figur 1

den Kopf eines Roststabes,

Figur 2

einen Schnitt durch zwei nebeneinander liegende Roststäbe,

Figur 3

eine Draufsicht auf zwei nebeneinander liegende Roststäbe,

Figur 4

schematisch die Verbindung von Roststäben mittels einer U-förmigen Klammer,

Figur 5

schematisch die Verbindung zweier Roststäbe mittels einer C-förmigen Klammer und

Figur 6

schematisch die Verbindung zweier Roststäbe mittels eines Bolzen.

Advantageous embodiments are shown in the drawing and are described in more detail below. It shows

Figure 1

the head of a rust bar,

Figure 2

a section through two adjacent grate bars,

Figure 3

a top view of two grate bars lying next to each other,

Figure 4

schematically the connection of grate bars by means of a U-shaped clamp,

Figure 5

schematically the connection of two grate bars by means of a C-shaped clamp and

Figure 6

schematically the connection of two grate bars by means of a bolt.

The Figure 1 The head 1 of a grate bar 2 shown has an upper side 3 which is essentially flat and has a raised portion 5 towards the front end 4. Between this raised portion 5 and the flat area 6 of the surface, a recess 7, 8 is provided on both sides of the grate bar 2, into which a holder 9 can be inserted.

The Figure 2 now shows two grate bars 2 and 12 lying next to each other with a bracket 9 in between, which holds the grate bars 2 and 12 together via a screw connection 10. Above the screw connection 10 serving as a bracket 9, the recesses 8 and 13 are covered with a cover 15, which has a plate 16 and a wedge 17 with which the plate 16 is secured.

In order to produce a grate covering 18 with several grate bars 2, 12, the grate bars 2, 12 each have recesses 7, 8 and 13, 14 on both long sides 19, 20.

In the Figure 2 The screw connection 10 shown consists of a screw 21 with screw head 22 and nut 23.

The plate 16 of the cover 15 has undercuts 27 and 25, which allow the plate 16 to be inserted into the recess 7, 8 and held by the undercuts 24 and 25. The plate 16 is prevented from falling out of the recess 7, 8 by an inserted wedge 17, which was welded to the plate 16 after it was inserted.

As a simple alternative to screwing, Figure 4 a clamp 30 is shown to hold two grate bars 2 and 12 together. This clamp 30 is made of a material with a smaller coefficient of thermal expansion than the grate bars 2, 12, which are made of cast steel. The clamp 30 can therefore simply be slipped over the webs 31, 32 that are adjacent to one another at the sides. When the grate bar arrangement is in use, the grate bars expand due to the high heat and the clamp, which expands only a little, holds the grate bars in place.

At the Figure 5 In the C-shaped clamp 40 shown, which also holds two side parts 31 and 32 of grate bars 2 and 12 together, the clamp is made of steel, which expands more than the grate bars. However, this is compensated for by insert plates 43, 44, which have a particularly high thermal expansion and thus press the webs 41 and 42 together.

The Figure 6 shows a bolt connection in which a bolt 50 is inserted between two grate bars 2 and 12 to hold the grate bars 2 and 12 together. Washers 53 and 54 are arranged between the bolt 50 and the webs 51 and 52 of the grate bars 2 and 12, which compensate for the different thermal expansion coefficients between the grate bars 2 and 12 and the bolt 50 so that an elongation of the bolt 50 does not lead to a loosening of the connection between the grate bars 2 and 12.

The Figures 4 to 6 show that the brackets 30 and 40 serving as holder 9 and the bolt 50 can have disks 43, 44 or washers 53, 54 as elements in order to compensate for the different thermal expansion coefficients.

If the bolt 50 has a threaded rod 56 as a connecting element and two nuts 57, 58 as a clamping element, the thermal expansion coefficient can also be determined by the selection of materials and adjusted so that the grate bars are held securely together even in the event of strong temperature fluctuations.

In the Figures 1 to 3 In the embodiment shown, assembly is carried out by placing the grate bars on the grate. The grate carriage is usually in the middle position. Using a wrench on the screw head and another on the nut, the screw connection inserted into the opening between two grate bars is tightened. The locking plate 16 is then inserted and pushed to the side. Finally, the wedge 17 is inserted for locking and welded to the plate.

When dismantling, the weld seam is first opened and then the wedge is levered out. The plate can then be removed so that the screw connection can finally be loosened and removed.

This method has the advantage that the entire covering can be screwed on from above, regardless of the position of the grate carriages. Climbing into the grate hoppers is no longer necessary. It is also no longer necessary to move the carriages during assembly. Although welding the wedges 17 to the plates 16 means an additional assembly step, the overall assembly time is significantly reduced compared to previously known methods.

Further improvements can be achieved by designing according to the Figures 4 to 6 be achieved.

Claims (16)

1. Method for holding adjacent grate bars (2, 12) together, which have an upper side (3) designed as a grate covering (18), in which the grate bars (2, 12) are pressed against one another using a holder (9), wherein the holder (9) is operated through a recess (7, 8, 13, 14) on the upper side (3) of the grate bars (2, 12), and the recess (7, 8, 13, 14) is covered by a cover (15), wherein the cover (15) has a plate (16), characterized in that the plate (16) covers the recess (7, 8, 13, 14) such that an upper side of the grate is a flat as possible.
2. Method according to claim 1, characterized in that the grate bars (2, 12) are screwed from the upper side (3).
3. Method according to claim 2, characterized in that recesses (7, 8, 13, 14), through which the screw connections (10) can be inserted and tightened from above, are provided on both longitudinal sides (19, 20) of a grate bar (2, 12).
4. Method according to claim 3, characterized in that the size of the recess (7, 8, 13, 14) is selected such that a screw wrench can be applied to the screw head (22) and another can be applied to the nut (23) and can be tightened.
5. Method according to one of the preceding claims, characterized in that the plate (16) is a part of the holder (9) or is arranged above the holder as an individual part.
6. Method according to one of the preceding claims, characterized in that the cover (15) has the plate (16) and a spline (17) with which the plate (16) is secured.
7. Method according to claim 6, characterized in that the plate (16) is welded to the spline (17).
8. Grate bar assembly comprising a grate bar (2, 12) with an upper side (3) designed as a grate covering (18) and a holder (9) in order to hold adjacent grate bars (2, 12) together, wherein the upper side (3) of the grate bar (2, 12) has a recess (7, 8, 13, 14) and the grate bar arrangement has a cover (15), wherein the cover (15) has a plate (16), characterized in that the plate (16) covers the recess (7, 8, 13, 14) such that an upper side of the grate is a flat as possible.
9. Grate bar assembly according to claim 8, characterized in that the holder (9) has a screw connection (10).
10. Grate bar assembly according to claim 8 or 9, characterized in that the holder (9) has a bracket (30, 40).
11. Grate bar assembly according to one of claims 8 to 10, characterized in that the holder (9) or an element (43, 44, 53, 54) of the holder (9) has a lower coefficient of thermal expansion than the grate bars (2, 12).
12. Grate bar assembly according to one of claims 8 to 11, characterized in that the holder (9) has a connecting element (56) and a clamping element (57, 58), wherein the connecting element (56) and the clamping element (57, 58) have different coefficients of thermal expansion.
13. Grate bar assembly according to one of claims 8 to 12, characterized in that elements (43, 44, 53, 54), with a coefficient of thermal expansion which is higher than that of the holder (9), are arranged between the holder (9) and the grate bars (2, 12).
14. Grate bar assembly according to one of claims 8 to 13, characterized in that the cover (15) has an undercut (24, 25) in order to engage laterally under an upper side (3) of a grate bar (2, 12).
15. Grate bar assembly according to one of claims 8 or 14, characterized in that the cover is connected to the holder (9) or to a part of the holder (9).
16. Grate bar assembly according to one of claims 8 to 15, characterized in that only one holder (9) is arranged between two grate bars (2, 12) in order to hold adjacent grate bars (2, 12) together.

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