EP0606551B1 - Roller grate for a combustion boiler - Google Patents

Description

The invention relates to a roller grate for operating a combustion boiler, in particular for waste incineration, with a conveyor grate for the combustion material consisting of rotating rollers arranged at a distance, the rollers having gas passage openings for introducing air and / or gas into the combustion chamber or the combustion material and blocking elements are provided between adjacent rollers in order to prevent or minimize combustion material from slipping through the spaces between the rollers. Such a grate is known from document EP-A-0 157 920.

Combustion boilers of this type are used according to the prior art for waste incineration, the combustion material, which mostly consists of organic waste, being conveyed through the rotating rollers of the conveyor grate through the combustion chamber to its end, where the incinerated constituents of the refuse are obtained as coarse ash.

The rollers have air passage openings for introducing combustion air into the combustion material or the combustion chamber. This targeted introduction of air or oxygen is necessary in order to achieve a uniform temperature distribution in the combustion material, a high boiler efficiency and as complete a combustion as possible.

From DE-G 89 10 524.9 a grate roller is known, in which the feed slots for the combustion air are arranged obliquely between the longitudinal sides of adjacent grate bars, so that the air jets also exit obliquely into the fuel layer. In contrast to radially formed slots, this should enable better utilization of the primary air.

EP 0 124 826 A2 shows a roller grate for a waste incineration plant, in which the grate bars can move relative to one another during operation in order to prevent clogging of the air slots.

In addition, systems have become known in which there are locking elements between adjacent rollers which are intended to prevent or minimize the combustion material from slipping downward. The outer edges of these locking elements must be at a certain distance from the roller surfaces, and at the same time they can serve as wipers for combustion material baked on the roller surface. In this way, there are gaps between the locking elements and the rollers, through which a substantial part of the supplied combustion air is pressed due to the lower flow resistance, so that optimal combustion conditions no longer prevail and the boiler efficiency is reduced overall.

The invention is therefore based on the object of providing a roller grate for a waste incineration boiler in which the most uniform possible air supply through the gas passage openings of the rollers and the waste incineration is improved while increasing the boiler efficiency.

This object is achieved in that the space between the locking elements and the roller surfaces sealing towards the combustion chamber, resiliently against the rollers adjacent sealing elements extending in the longitudinal direction of the rollers are provided.

The sealing elements according to the invention provide a seal for the intermediate space between the blocking elements, which can optionally also act as wipers for the roller surfaces, and the roller surfaces to the combustion chamber or to the air supply space. The sealing elements extend in the longitudinal direction of the rollers and rest resiliently on the rollers, so that the spring preload provides a comparatively good sealing effect.

In an advantageous embodiment of the combustion boiler, the blocking elements are designed as strips which are arranged between adjacent rollers at a distance from them and which extend approximately radially to the rollers. The strips attached to brackets prevent combustion material from slipping through in a simple manner and, at the same time, good possibilities for attaching the sealing elements according to the invention are created in this embodiment of the locking elements. The sealing elements can namely be arranged on the one hand below the locking elements on their holders, on the other hand it is also possible to attach them to the strip surfaces which extend approximately radially to the rollers.

In the latter arrangement, the sealing elements can be arranged directly on the locking elements and, if necessary, simultaneously take over the function of wipers, but it is advantageous to arrange the sealing elements in such a way that they seal the space between the locking elements and the roller surfaces at a point which has already been done by stripping elements of caking was cleaned. In this way, a better sealing effect can be achieved.

In order to achieve a sufficient wiping effect while minimizing the slipping of combustion material, the distance between the outer edges of the locking element and the respectively associated circumferential roller surfaces is preferably between approximately 10 and 30 mm. This distance is essentially due to wear and the diameter tolerances of the rollers.

The distance is expediently adjustable, since it can be adapted, for example, to the combustion material to be treated in each case.

In order to ensure the setting of the distance, the outer edges of the locking elements can be formed by locking profiles which can be fastened to them and which are screwed, for example, into corresponding elongated holes and, if necessary, can be moved radially to the rollers. This allows the gap width between the outer edges of the locking elements or wipers and the roller circumferential surface to be set very precisely. This also ensures that the profiles can be replaced quickly.

The sealing elements for sealing the combustion chamber from the air supply space below the rollers are expediently carried out via sealing elements which are resiliently tangential to the roller peripheral surfaces. As already mentioned, the contact zone between the sealing elements and the roller circumferential surfaces should be at a point at which combustion material that has caked on the outside of the roller has already been removed by the action of the locking profiles or wipers. Since the rollers are driven with the same direction of rotation in the working direction, this results in an arrangement of the sealing elements, in which the left sealing element lies tangentially downward on the left roller and the right sealing element lies tangentially upward on the right roller if the direction of rotation of the rollers corresponds to the clockwise direction.

The sealing elements preferably have a skid-shaped curved end part, each pointing in the direction of rotation of the rollers. Because of the skid-shaped curved end part, it is in fact easily possible to let the rollers run back against their usual working direction if this should be necessary for certain reasons. Due to the skid-like protruding shape of the end part, the sealing element cannot get caught and is raised accordingly when the rollers return.

As already mentioned, the sealing elements are under spring prestress, it being advantageous to increase the spring action by means of an auxiliary spring which presses the contact zone of the sealing element and the roller peripheral surface against the roller peripheral surface. This prevents a decrease in the spring force of the sealing elements, which are heated to relatively high operating temperatures, and the overall spring effect is increased. To increase the bending stiffness or the spring action, the sealing elements preferably consist of a plurality of spring-metal strips placed one above the other. A suitable steel material is, for example, the steel grade NiCr 22 Mo 9 Nb. This steel is temperature resistant and resilient even at high temperatures.

A wear-resistant and abrasion-resistant strip layer made of a suitable stainless steel is preferably provided on the side of the sealing elements facing the rollers.

In particular, the strip layer forming the skid profile is expediently made from this material.

The spring sheet metal strips or the wear-resistant strip layer can be connected to one another by rivets or welding spots, so that the sealing elements are produced by known methods. The end of the spring elements is clamped, for example, in screw or clamp connections which are fastened to the holder of the locking elements or to them themselves with the aid of angles or the like.

In order to be able to use the effect of gravity in the combustion boiler according to the invention to convey the combustion material, the rollers forming the conveying grate are preferably arranged in an inclined plane which is inclined in the direction of the combustion material conveying direction. As a result, the coarse ash produced is adequately conveyed towards the end of the combustion section, while the proportion of fine ash which can pass downward through the relatively narrow gas passage openings in the rollers remains comparatively low. The rollers are preferably designed as hollow rollers, the jacket of which has the gas passage openings already mentioned several times. Since the amount of gas passing through the gap between the rollers in the combustion boiler according to the invention is practically zero, there is a greater exposure of the roller material to fresh air, so that it is better cooled and thus the service life of the rollers or the combustion boiler is increased.

Figur 1

eine schematische Schnittansicht durch einen erfindungsgemäßen Verbrennungskessel,

Figur 2

ein Sperrelement zwischen zwei benachbarten Rollen sowie zwei Dichtelemente gemäß Figur 1 in vergrößerter Darstellung,

Figur 3

das obere Dichtelement aus Figur 2,

Figur 4

das untere Dichtelement aus Figur 2,

Figur 5

eine vergrößerte Ansicht des unteren Nietbereiches aus Figur 4,

Figur 6

eine vergrößerte Ansicht des oberen Nietbereiches aus Figur 4,

Figur 7

eine Verbindung gemäß Figur 5 mit punktgeschweißten Blechlagen,

Figur 8

eine alternative Verbindung gemäß Figur 6 mit punktgeschweißten Blechlagen, und

Figur 9

den Übergangsbereich eines kufenförmig gekrümmten Dichtelementes gemäß Figur 3 bzw. 4.

The invention is illustrated in the drawing, for example, and is explained in detail below with reference to the drawing. Show it:

Figure 1

2 shows a schematic sectional view through a combustion boiler according to the invention,

Figure 2

a locking element between two adjacent rollers and two sealing elements according to Figure 1 in an enlarged view,

Figure 3

the upper sealing element from Figure 2,

Figure 4

the lower sealing element from Figure 2,

Figure 5

3 shows an enlarged view of the lower rivet area from FIG. 4,

Figure 6

3 shows an enlarged view of the upper rivet area from FIG. 4,

Figure 7

5 a connection with spot-welded sheet metal layers,

Figure 8

an alternative connection according to Figure 6 with spot-welded sheet metal layers, and

Figure 9

the transition area of a skid-shaped curved sealing element according to Figure 3 or 4.

In Figure 1, a combustion boiler for refuse incineration is shown schematically in a section, which essentially consists of a combustion chamber 1, in the lower region of which a conveyor grate 3 consisting of rotating rollers 2 is arranged, which has the task of not having the one located in the combustion chamber 1 promote the combustion material shown to the right.

The direction of rotation of the rollers 2 is indicated by the arrows 4.

Below the actual combustion chamber 1 there is an air supply chamber 5, into which air is blown in through air supply channels 6. In order to distribute the supplied air as finely and evenly as possible in the combustion material or combustion chamber 1, the jacket 7 of the rollers 2 designed as hollow rollers has a multiplicity of gas passage openings 8 through which, in addition to the required combustion air, gas mixtures or combustion gases, for example, are also blown into the combustion chamber 1 can be. (see Fig. 2)

In order to prevent combustion material from sliding out of the combustion space 1 between the rollers 2 into the area of the air supply space 5, strip-shaped locking elements 9 are provided between the rollers 2 and are fastened to vertical brackets 10. The strip-shaped locking elements 9 extend in the longitudinal direction of the rollers 2 and run approximately radially to them.

In addition to the function as a locking element to minimize slippage of combustion material, the locking elements 9, due to the locking profiles 11 attached to them, also serve as wipers for the rollers 2 Rotation of the rollers 2 constantly removed.

In order to prevent combustion air from entering the combustion chamber 1 through the gap 13 formed by the locking elements 9 or locking profiles 11 and the roller outer sides 12 flows, which would lead to uneven combustion with deteriorated efficiency, 10 sealing elements 14 are screwed to the brackets, which also run in the longitudinal direction of the rollers 2 and resiliently abut against the roller outer sides 12 with a contact zone 15.

The sealing elements shown in FIGS. 1 to 4 lie approximately tangentially on the roller outer sides 12 and are curved in a skid shape at their free end 16, so that the rollers 2 can also return without the sealing elements 14 becoming caught.

To increase the spring force, the sealing elements 14 have internal auxiliary springs 17 which press the contact zone 15 against the outside of the roller 12 or resiliently support the sealing element 14.

The sealing elements 14 are arranged so that the free end 16 points in the running direction or circumferential direction of the rollers 2.

The combustion elements 1 are almost completely separated from the air supply space 5 by the described sealing elements 14. A positive connection exists only through the gas passage openings 8 in the jacket 7 of the rollers 2. Of course, a small proportion of fine ash can also pass through these openings 8, which falls into discharge channels 18 located below the rollers. (Fig. 1)

In FIGS. 3 and 4, the sealing elements 14 from FIG. 2 are each shown in an enlarged view. In these figures it can be seen that the sealing elements 14 and the auxiliary springs 17 consist of three superimposed spring sheet strips 19 which are connected by means of a clamp connection 20 and an angle 21 are attached to the bracket 10.

The free end 22 of the auxiliary spring 17 bears freely against the inside of the inner spring plate strip 23.

On the outside of the outer spring sheet metal strip 24 there is a wear and abrasion-resistant strip layer 26 which forms the runner profile 25 and forms the contact zone 15. The strip layer 26 consists of temperature-resistant, abrasion-resistant stainless steel.

Two rivets 27 serve to connect the individual strips of the sealing element 14, as is shown enlarged in section in FIGS. 5 and 6.

As an alternative to a rivet connection, the individual spring metal strips 19 can also be connected to one another, for example by spot welding (28). (Figures 7 and 8)

In Figure 9, the free end 22 of the auxiliary spring 17 is shown in an enlarged view, which rests against the inner spring plate strip 23 under spring preload.

Reference list

• 1 combustion chamber
• 2 roll
• 3 conveyor grate
• 4 direction of rotation
• 5 air supply space
• 6 air supply duct
• 7 coat
• 8 gas passage opening
• 9 locking element
• 10 bracket
• 11 locking profile
• 12 roll outside, roll circumferential surface
• 13 gap
• 14 sealing element
• 15 contact zone
• 16 free end
• 17 auxiliary spring
• 18 discharge channel
• 19 spring strips
• 20 clamp connection
• 21 angles
• 22 free end
• 23 inner spring steel strips
• 24 outer spring steel strips
• 25 skid profile
• 26 wear-resistant strip layer
• 27 rivet
• 28 spot welds

Claims (14)

1. Combustion vessel, particularly for refuse incineration, with a feed grate (3) consisting of rotating, spaced-apart rollers (2) for the material to be incinerated, in which the rollers (2) have openings (8) for the passage of gas for the introduction of air and/or gas into the combustion chamber or into the material to be incinerated, and retaining elements (9) are provided between adjacent rollers for preventing or minimizing slippage of material to be incinerated through the spaces between the rollers, characterized in that sealing elements (14) are provided sealing the space between the retaining elements (9) and the roller surfaces (12) from the combustion chamber (1) with respect to combustion air, resiliently abutting the rollers (2) and extending longitudinally relative to the rollers (2).
2. Combustion vessel according to Claim 1, characterized in that the retaining elements (9) are formed as heat-resistant strips which are fixed to mountings (10) and extend between adjacent rollers (2), spaced therefrom, parallel to the roller axis, and which extend approximately radially relative to the rollers (2).
3. Combustion vessel according to Claim 1 or Claim 2, characterized in that the sealing elements (14) are disposed beneath the retaining elements (9) on the mountings (10) thereof.
4. Combustion vessel according to Claim 1 or Claim 2, characterized in that the sealing elements (14) are disposed on the strips which extend approximately radially relative to the rollers (2).
5. Combustion vessel according to any one of Claims 1 to 4, characterized in that the distance between the outer edges of the retaining element (9) and the respective associated peripheral roller surfaces is between 10 and 30 mm.
6. Combustion vessel according to any one of Claims 1 to 5, characterized in that the distance between the outer edges of the retaining element (9) and the respective associated peripheral roller surfaces is adjustable.
7. Combustion vessel according to any one of Claims 1 to 6, characterized in that the outer edges of the retaining element (9) are formed by retaining profiles (11) attachable thereto.
8. Combustion vessel according to any one of Claims 1 to 7, characterized in that the sealing elements (14) are formed as skid profiles (25) which abut the peripheral roller surfaces (12) tangentially and the skid-shaped curved free end (16) of which points in the direction in which the rollers (2) rotate.
9. Combustion vessel according to any one of Claims 1 to 8, characterized in that the spring action of the sealing elements (14) is reinforced by an auxiliary spring (17) pressing the contact region (15) of sealing element (14) and peripheral roller surface (12) towards the peripheral roller surface or bracing the sealing element (14) outwardly.
10. Combustion vessel according to any one of Claims 1 to 9, characterized in that the sealing elements (14) or the auxiliary spring (17) consist of a plurality of superposed spring steel strips (19), preferably three strips.
11. Combustion vessel according to any one of Claims 1 to 10, characterized in that the sealing elements (14) have a wear- and abrasion-resistant strip layer (26) on the side facing the rollers (2).
12. Combustion vessel according to either of Claims 10 and 11, characterized in that the spring steel strips (19) and/or the wear-resistant strip layer (26) are connected to one another by rivets (27) or spot welds (28).
13. Combustion vessel according to any one of Claims 1 to 12, characterized in that the plane contacting all of the peripheral roller surfaces (12) is an inclined plane sloping in the direction of supply of the material to be incinerated.
14. Combustion vessel according to any one of Claims 1 to 13, characterized in that the rollers (2) are formed as hollow rollers with through-holes in their walls.

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