RU2810175C1 - Grate element with rising protrusion - Google Patents

Abstract

FIELD: power engineering.

SUBSTANCE: grate element (1) as part of a grate in an installation for thermal waste treatment, in which the grate elements are staggered one above the other and are designed in such a way that, by means of translational movements relative to each other during combustion, they shift the burned material and move it in feed direction F. The grate element contains element body (3), made in the form of a cast part and having the following components: rear end (5) and front end (7), in feed direction F located opposite to rear end (5), upper wall (4) extending substantially parallel to longitudinal axis L of element body (3) and forming rear support surface (11) for the waste being processed, rear support surface (11) defining a substantially horizontal plane (23), and protrusion (13) located in the region of front end (7) and raised relative to horizontal plane (23), and raised protrusion (13) contains front supporting surface (15) rising in feed direction F to culmination point (17), as well as lowering end section (19) adjacent to front support surface (15) after culmination point (17). The descending end portion (19) includes release surface (21) that is substantially arcuately descending in feed direction F. In longitudinal section, as viewed in feed direction F, front support surface (15) is S-shaped.

EFFECT: ability to ensure a very uniform transfer of waste to be burned and at the same time creation of a uniform layer of waste on the underlying grate elements.

14 cl, 3 dwg

Description

The present invention generally relates to a grate provided for use in an incineration plant. Grate grates for industrial waste incineration have long been known to specialists. They usually consist of many individual grates, which, when connected to each other, form a corresponding grate. This design allows individual grates to be easily replaced if individual areas of the grate are damaged.

In such incinerators, the combustible material is usually fed from the inlet end of the grate to its outlet end (ie in the feed direction) and is simultaneously burned. To supply the combustion material with combustion air, also called primary air, the grates or grates are supplied with an air flow from the bottom and have outlet openings through which the incoming combustion air can enter the combustion material. Such grates or grates are known, for example, from DE 20111804 U1.

A frequently used grate is the so-called stepped grate. It contains grate elements located next to each other, forming a row of grate elements. In this case, the rows of grate elements are arranged stepwise above each other, and when viewed in the feed direction (or in the direction of supply of the burned material) in the so-called pushing grate grids, the front end of the first grate element lies on the supporting surface of the second grate element located under the first grate element with displacement in the feed direction, and with a corresponding translational movement moves along the specified supporting surface.

Due to the combustion material fed through the grate elements, the grate elements are generally subject to relatively high abrasive wear. In the front region (also called the protrusion) of each grate element, the burned material from the supporting surface along the corresponding discharge edge is dumped onto the supporting surface of the subsequent grate element. Therefore, abrasion or wear is particularly high precisely in said front end portion of the supporting surface, also called the feed portion.

Due to the high temperature during combustion or in the combustion chamber, the grate elements are also subjected to a very high thermal load. In normal grate operation, said thermal load is high, particularly in the area of the supporting surface, although the combustion material on the grate element acts as insulation to a certain extent. However, peak loads occur in particular when the combustion material is unevenly distributed over the grate and in some places only a thin insulating layer is formed, or when said insulating layer is completely absent. Thermal stress promotes erosion due to abrasion and chemical reactions occurring on the supporting surface, further damaging the supporting surface. These processes ultimately lead to a reduction in the service life of the grate element.

To reduce the thermal load, the grate elements are usually cooled using a cooling medium from below, i.e. on the side of the grate located opposite to the combustion. The cooling medium is usually air or water. However, as stated above, the heat load can also be reduced by evenly distributing the combustion material on the grate.

In order to crush and/or mix the waste more or less vigorously during transport from one grate element to the next (underlying) grate element, grate elements with special projection shapes have been proposed in the prior art.

German patent application No. 568,164 discloses a push grate with movable and fixed grate elements (movable pushers and fixed plates). The stationary grate elements have a thickening at the front end, and the inner edge of the thickening, depending on the composition of the waste to be burned, is designed in such a way that it is rather flat or rather steep. Rather, a shallow inner edge is selected to move the waste to a greater extent, while a steep inner edge is selected to agitate the waste to a greater extent.

The disadvantage of this grate design is that it is not suitable for highly variable waste compositions, since the inclination of the inner edge of the thickening cannot be changed during operation. Also, two different types of grate elements are used (pushers and plates), which complicates the design of the grate and the replacement of grate elements.

German patent publications Nos. 1,301,421 and 969,643 disclose grate bars that are equipped with sharp-edged, pyramidal projections in the corresponding feed section. These areas are used to crush incinerated waste through mixing movements.

US 2013/0167762 A1 also discloses a grate element with pyramidal projections in the projection area. In particular, a grate with a replaceable head equipped with a transport ledge opens. The transport lip has a triangular cross-section and is mounted on the inclined surface of the replacement head. In addition, the replaceable head contains a mixing protrusion mounted on the horizontal surface of the head and also having a pyramidal shape. The conveying lip supports the return movement and circulation of waste on the grate, while the stirring lip supports the forward and downward movement of waste on the grate.

Already known grate elements in pushing grate grates have the disadvantage that the processed waste, during normal translational movements, falls onto the underlying grate element in portions or, accordingly, periodically. In this case, the transfer of waste from the first grate element to the underlying second grate element can be carried out in two ways. On the one hand, the transfer of waste can be accomplished by causing the first grate element to move in the feed direction and thus transfer the waste to a second grate element located below the first grate element. On the other hand, waste may also fall onto the second grate element located below the first grate element as a result of the rearward movement of the first grate element. When the grate element moves backward (against the direction of transportation or, accordingly, feed), the waste lying on it, due to its inertia, is set in motion only with a delay. Since the waste lies in a layer on the grate element, its backward movement is further hindered, resulting in the grate element moving more backwards than the waste layer located on it. This results in the fact that each time the grate element moves backward, the front of the waste layer (as seen in the direction of transport) falls onto the grate element located below.

As described above, the waste layer has an insulating effect and protects the grate element from excessive thermal load. In this regard, an even distribution of waste is desirable. However, the above-described "falling" of waste - in portions or periodically - on the "receiving" grate element often results in a waste layer of uneven thickness, which contributes to the occurrence of temperature peaks. In addition, due to the “falling” of waste in the waste layer formed on the lower grate element, ventilation holes appear, which also leads to local increased flame formation and the associated increased thermal load on the grate element.

Although grate elements with pyramidal projections, such as those described in DE 1 301 421 and DE 969 643, cause waste to move together when the grate element moves, the waste is still transferred to the underlying grate element in portions or, accordingly, periodically, which consequently leads to uneven distribution or, accordingly, uneven thickness of the waste layer.

Due to the different positions of the grate elements in the grate, their wear is also different. In general, the higher the thermal load, the greater the wear on the bearing surface. When measured in a longitudinal section, the wear of the grate element per year averages 5 mm. In an area with a higher thermal load, wear per year is up to 10 mm, which corresponds to a service life of the grate element of 2-3 years.

It is therefore an object of the invention to overcome the shortcomings of the prior art and to provide a grate that allows the combustion material fed over the grate elements to be evenly distributed on the supporting surface of the grate elements in order to prevent temperature peaks and the resulting peak loads.

According to the invention, this problem is solved thanks to the grate element according to paragraph 1 and the grate according to paragraph 10 of the claims. Preferred embodiments of the invention are shown in the dependent claims.

The grate element according to the invention is part of a grate grid consisting of a plurality of such grate elements, the grate elements of which are staggered one above the other. The grate is intended for use in a waste heat treatment plant. In this case, the grate elements are designed in such a way that, through translational movements relative to each other during combustion, they transfer the burned material and move it in the feed direction.

The grate element according to the invention comprises an element body made in the form of a cast part and having a rear end and a front end located opposite the rear end in the feed direction. In addition, the element body contains an upper wall forming an outer, rear supporting surface for the processed waste, at least partially extending parallel to the longitudinal axis L of the element body. In this case, the rear supporting surface defines a substantially horizontal plane.

In addition, the grate element according to the invention contains a protrusion located in the region of the front end and raised relative to the horizontal plane. In this case, the raised protrusion contains a front support surface that rises in the direction of delivery up to the culmination point, as well as a descending end section adjacent to the front support surface after the culmination point. The descending end portion comprises a discharge surface that is substantially arcuately descending in the direction of delivery.

In the context of the present invention, grate elements arranged in steps on top of each other are defined as grate elements on a grate arranged in the form of steps of an ascending or descending staircase.

The term "translational movements performed relative to each other" means translational movements performed in the direction of supply or, respectively, against the direction of supply of the burnt material. Thus, in a stepped grate, the feed direction runs parallel to the negative inclination or, respectively, the positive inclination of the grate.

In this case, the longitudinal axis of the element body or, respectively, the grate element means an axis running parallel to the general inclination of the stepped grate and thus parallel to the direction of supply of the processed waste.

In the context of the present application, a supporting surface is understood to mean a surface which is located on the outer upper side of the grate element and on which the waste to be cooked lies. As already stated at the outset, it is known that said support surface in combustion plants is subject to increased mechanical and thermal stress and is susceptible to the formation of lumps of combustion products.

In general, the protrusion is the front (in the feed direction) part of the element body. As used herein, "raised protrusion" means a protrusion whose highest point in the vertical direction is above the rear support surface.

The culmination point is generally defined as the highest point, and in this application, the highest point of the raised protrusion. In this case, the culmination point can be made in the form of a single point, for example, in the form of the top of a pyramid, or in the form of the top point of a curve or arc. However, the culmination point can also be made in the form of a horizontal plane. In this case, the entire plane is defined as the culmination point in the sense of the culmination plane.

The descending end section is the surface that, in the feed direction, is located at the front end of the element body and descends starting from the culmination point. According to the invention, the lowering end section is lowered in the vertical direction. This means that the descending end portion has a negative slope.

The term "substantially arced" means that the downgoing fault surface has an arcuate shape, or preferably a circular arc shape. Such an arcuate surface can also be formed by arranging a plurality of short straight surface segments in a row, which, however, as a whole have an arcuate shape.

Compared to the prior art, the grate element according to the invention has the advantage that, thanks to the raised projection, waste is transferred from the first grate element to the underlying second grate element sequentially and evenly, so to speak smoothly, and thus the discharge of waste in batches or periodically is prevented. In this case, the raised lip acts as an obstacle to prevent periodic falls when moving waste backwards. Similarly, waste transferred from the first grate element to the second grate element is moved from the second grate element to the third grate element during the feed movement of the first grate element. This controlled feed movement prevents periodic waste "falling" and allows waste to be moved in a continuous stream, which ultimately results in a more uniform layer of waste on the supporting surface of the grate elements. This uniform waste layer has a uniform insulating effect and thus prevents thermal load peaks on the grate element.

In a preferred embodiment of the grate element, the culmination point relative to the horizontal plane in the vertical direction is at a distance of 10-35 mm, preferably 15-30 mm, particularly preferably 18-25 mm and most preferably 20-21 mm.

It has been found that a grate element with the above horizontal distance values (also referred to as clear width or clear distance) is particularly well suited for creating an even layer of waste on the underlying grate element.

The rising front support surface is preferably in the form of a ramp and in the middle part has an average positive slope of 10-35%, preferably 15-32%, particularly preferably 20-30% and most preferably 26-28%.

In the context of the present invention, the term "ramp" or "ramp-like" refers to a surface adjacent to a horizontal plane and having a positive slope, i.e. going to a point elevated relative to the horizontal plane. In this case, the ramp can have any shape (for example, convex or S-shaped).

It has been found that a support surface shaped like a ramp with a medium slope according to the values stated above is particularly well suited for creating a uniform layer of waste on the underlying grate element.

In a preferred embodiment of the grate element in longitudinal section, when viewed along the feed direction, the front supporting surface has an S-shape.

In the context of the present invention, an S-shaped front support surface (as viewed in longitudinal section) means that the support surface in the first region adjacent to the horizontal plane has a constantly increasing positive slope, and in the second region, in the feed direction directly or indirectly adjacent to the first region, has a constantly decreasing positive slope. Preferably, in the third region located between the first region and the second region, the positive slope may be constant. The S-curve has other names: sigmoid function, S-shaped function, or Fermi function. Equation for an example S-curve:

It turned out that the grate element, which in longitudinal section has an S-shaped front supporting surface, provides a very uniform transfer of waste to be burned and at the same time creates a uniform layer of waste on the underlying grate elements.

Preferably, the arcuately descending release surface at a point in the forward supply direction comprises preferably a rounded release edge.

The advantage of a rounded reset edge is that material wear is reduced in this area of the projection. In addition, it is possible to smoothly transfer the waste to the grate element located next to and below, resulting in an even layer of waste and preventing local cutter effect.

In a preferred embodiment of the grate element, the descending end portion in the region between the culmination point and the forward point (as viewed in the feed direction) comprises a first arcuate segment.

Said arcuate segment may be part of an arcuate fault surface or form a connecting portion between the culmination point and the arcuate fault surface. The arcuate contour of the first arcuate segment allows a uniform flow of waste to be burned on the front support surface, thereby reducing friction and thus wear on the grate element and creating a uniform layer of waste on the underlying grate elements.

The first arcuate segment preferably has a first radius of curvature R1 having a length of 60-120 mm, preferably 70-110 mm, particularly preferably 80-100 mm and most preferably 90 mm.

The average radius of the first arcuate segment is determined as the first radius of curvature R1. It is quite possible that the first arcuate segment is composed of smaller straight segments, which as a whole form an arcuate segment. Preferably, the outer surface of the arcuate segment in longitudinal section forms a curved line of a circular sector. Thus, in a longitudinal section, the surface of the first arcuate sector is limited by an arc of a circle and two radii of the circle. With regard to uniform feeding of waste along the first arcuate segment, a radius of curvature having the above values has proven to be particularly advantageous.

In a preferred embodiment of the grate element, the first arcuate segment in longitudinal section defines a sector surface with a central angle α of 60° to 72°, preferably approximately 66°.

Preferably, the descending end portion comprises a second arcuate segment, particularly preferably in the feed direction adjacent and most preferably directly adjacent to the first arcuate segment.

The first arcuate segment and the second arcuate segment may be connected to each other directly or through an intermediate element. In this case, the intermediate element can be made in the form of a flat surface or also in the form of an arcuate segment.

In a preferred embodiment of the grate element, the second arcuate segment in longitudinal section has a second radius of curvature R2, preferably 10-30 mm, preferably 15-25 mm, particularly preferably 18-22 mm and most preferably 20 mm.

In this case, the average radius of the second arcuate segment is determined as the second radius R2 of curvature (when observed in a longitudinal section). It is quite possible that the second arcuate segment is composed of smaller straight segments, which as a whole form an arcuate segment.

Preferably, the first radius of curvature and the second radius of curvature have different lengths. This also means that the first arcuate segment and the second arcuate segment preferably have different arcuate curvatures. Various arc curvatures, particularly those with the preferred curvature radii R1, R2 indicated above, have proven to be particularly effective in consistently discharging debris through the discharge edge.

The second arcuate segment, when viewed in longitudinal section, preferably defines a sector surface with a central angle β of 70° to 120°, preferably approximately 90°.

In a preferred embodiment of the grate element, the element body has a front wall offset rearward against the feed direction relative to the front point (as viewed in the feed direction) of the descending end portion, so that an undercut is formed. Thus, in this preferred embodiment, the grate element has a protruding projection. Particularly preferably, the grate element has ventilation openings in the front wall in the area of the undercut. This has the advantage that the primary or secondary air vents can be located below the discharge lip and are thus not blocked or clogged by falling waste. Preferably, an arcuate transition from the discharge edge to the undercut is advantageous from the point of view of uniform movement of the waste discharge.

In a preferred embodiment, the distance between the culmination point (23) and the discharge edge, measured in longitudinal section, is 60-100 mm, preferably 70-90 mm and particularly preferably 80-82 mm.

Preferably, the length of the protrusion, measured along the longitudinal axis, is 170 mm. In this case, the length of the protrusion is defined as the clear distance between the starting point of the rising front supporting surface, which has the shape of a ramp, and the discharge edge.

The above preferred dimensions with respect to the distance between the culmination point and the discharge edge and the length of the protrusion are advantageous in particular from the point of view of the use of the grate element in an incineration plant.

In a preferred embodiment, the grate element has a depression in the rear support surface, preferably adjacent to the front support surface. Ventilation openings are preferably located in the area of said recess. Said ventilation openings preferably define the outlet of an air channel passing through an elevation having an outer contour in the form of a volcano. The air channel preferably continuously expands, starting from the ventilation opening, towards the inside of the grate element. This effectively prevents waste particles from clogging the air openings.

In addition, the invention relates to a grate containing a plurality of grate elements according to the invention.

Preferably, the individual grate elements move in the grate at a speed of 0-5 mm/s over a feed distance of 150-250 mm, particularly preferably approximately 200 mm. In comparable known systems, feed distances of up to 350-450 mm are common. Due to the fact that, according to the invention, the feed distance is preferably comparatively quite short, the grates are moved up to 45 times per hour from the starting position to the final position and back to the starting position. Shorter feed distances have proven beneficial in terms of uniform transfer of the burned material.

In the main combustion zone of the grate, the grate elements move preferably at a speed of 2-3 mm/s, and in the afterburning zone of the grate - preferably at a speed of 1 mm/s. The speed of individual grate elements is usually adjusted based on the composition of the waste to be burned.

Below, the invention is explained in more detail with the help of exemplary embodiments shown in the drawings. If alternative embodiments differ only in certain features, the same reference designations are used for the unchanged features. The drawings show purely schematically the following:

fig. 1 is a perspective view of an embodiment of a grate element according to the invention;

fig. 2 is a longitudinal section along the longitudinal axis L through the body of the element according to FIG. 1; And

fig. 3 is an enlarged view of a longitudinal section along the longitudinal axis L through the front region of the element body of FIG. 1.

The grate element 1 shown in FIG. 1 and fig. 2, contains an element body 3 made in the form of a cast part with an upper wall 4 extending in the feed direction F from the rear end 5 to the front end 7. In the area of the rear end 7 the element body has a fastening device 9, by means of which the element body 3 is connected to the drive system (not shown) in the grate, and which initiates its movements in the direction or against the feed direction F. In addition, the housing 3 in the region of the rear end 5 contains an outer rear surface 11 for heat treatment of waste to be burned. In the region of the front end 7, the element body 3 includes a raised protrusion 13. Said protrusion, when viewed in the feed direction F, has an outer front support surface 15 rising to a culmination point 17, and adjacent to the culmination point 17 a descending end portion 19 with a release surface 21 , descending essentially in an arc. The rear support surface 11 defines a substantially horizontal plane 23 having a recess 25. In the feed direction F, the horizontal plane 23 is adjacent to an outer front support surface 15. The rising outer front support surface 15 is designed as a ramp and, when viewed in longitudinal section, has a substantially S -shape. In this regard, in the illustrated embodiment, the inclination of the front support surface 15 after the horizontal plane 23 increases continuously until it remains constant in the middle part 27, and then towards the culmination point 17 decreases, so that the inclination towards the culmination point 17 tends to zero. Here, the culmination point 17 is designed as a single point between the front support surface 15 and the descending end portion 19, but alternatively it can be configured as a culmination plane. The descending end portion 19 of the raised protrusion 13 has a rounded release edge 31 at the forward (as viewed in the feed direction F) point 29.

In addition, the element body 3 contains a front wall 33, shifted rearward in the direction opposite the feed direction F from the front point 29 of the lowering end section 19 and forming an undercut 35 with the lowering end section 19. On the lower side, a surface 37 is adjacent to the front wall 33 of the element body 3 sliding, by which the element body 3 slides along the outer rear supporting surface 11 of the underlying second grate element (not shown). In the front wall 33 there are ventilation openings 39, which, due to their position in the area of the undercut 35, are protected from falling waste, so that blockage of the ventilation openings 39 can be prevented. In addition, in the upper wall 4 in the area of the horizontal plane 23 there is another ventilation opening 41, which is the outlet of an air channel passing through an elevation made in the form of a pyramid or volcano. The diameter of the air channel, starting from the ventilation hole 41, increases concentrically towards the inside of the element body so that waste entering the air channel through the ventilation hole 41, due to the increasing diameter, falls down without clogging the ventilation hole 41. Ventilation holes 39 and 41 are used for feeding primary or secondary air to ensure efficient combustion.

In fig. 3 shows an enlarged view of the raised projection 13 and the front area 7 of the grate element of FIG. 1. A vertical axis V, indicated by a dotted line, passes through the culmination point 17. Starting from the culmination point 17, the outer contour of the descending end portion 19 in the feed direction F is lowered and thereby forms a first arcuate segment 43. The first arcuate segment 43 has an average radius of curvature R1 and defines angle α between the vertical axis V and the first axis A1 of the segment. Adjacent to the first arcuate segment 43 is a second arcuate segment 45. The second arcuate segment 45 has an average radius of curvature R2 and defines an angle β between the first segment axis A1 and the second segment axis A2. The first arcuate segment 43 and the second arcuate segment 45 may be connected to each other directly or through an intermediate element (not shown). In this case, the intermediate element can be made in the form of a flat surface or also in the form of an arcuate segment. Depending on the magnitude of the angles α and β, the front point 29 with the rounded relief edge 31 can be located in the first arcuate segment 43 or the second arcuate segment 45.

Claims (20)

1. A grate element (1) as part of a grate in an installation for thermal waste treatment, in which the grate elements are arranged in steps one above the other and are designed in such a way that, by means of translational movements relative to each other during combustion, they transfer the burned material and move it into feed direction F, wherein the grate element contains a body (3) of the element, made in the form of a cast part and having the following components: rear end (5) and front end (7), in the feed direction F located opposite to the rear end (5), an upper wall (4) extending substantially parallel to the longitudinal axis L of the element body (3) and forming a rear supporting surface (11) for the waste being processed, the rear supporting surface (11) defining a substantially horizontal plane (23), and a protrusion (13) located in the region of the front end (7) and raised relative to the horizontal plane (23), wherein the raised protrusion (13) includes a front support surface (15) rising in the feed direction F up to the culmination point (17), as well as a descending end portion (19) adjacent to the front support surface (15) after the culmination point (17), wherein the descending end portion (19) comprises a release surface (21) that is substantially arcuately descending in the feed direction F, characterized in that in longitudinal section, as seen in the feed direction F, the front supporting surface (15) has an S-shape. 2. The grate element according to claim 1, characterized in that the culmination point (17) relative to the horizontal plane (23) in the vertical direction is at a distance of 10-35 mm, preferably 15-30 mm, especially preferably 18-25 mm and most preferably 20-21 mm. 3. Grate element according to one of paragraphs. 1-2, characterized in that the rising front support surface (15) is made in the form of a ramp and in the middle part (27) has an average slope of 10-35%, preferably 15-32%, especially preferably 20-30% and most preferably 26 -28%. 4. Grate element according to one of paragraphs. 1-3, characterized in that the arc-shaped lowering surface (21) of the discharge at the point (29), in the feed direction F located in front, preferably contains a rounded discharge edge (31). 5. Grate element according to one of paragraphs. 1-3, characterized in that the descending end portion (19) contains a first arcuate segment (43) in the region between the culmination point (17) and the point (29) in the forward feed direction F. 6. The grate element according to claim 5, characterized in that the first arcuate segment (43) has a first radius of curvature R1 having a length of 60-120 mm, preferably 70-110 mm, particularly preferably 80-100 mm and most preferably 90 mm. 7. The grate element according to claim 5 or 6, characterized in that the first arcuate segment (43), when observed in longitudinal section, defines a sector surface with a central angle α of 60° to 72°, preferably approximately 66°. 8. Grate element according to one of paragraphs. 5-7, characterized in that the lowering end portion (19) contains a second arcuate segment (45), preferably in the feed direction F adjacent and especially preferably directly adjacent to the first arcuate segment (43). 9. The grate element according to claim 8, characterized in that the second arcuate segment (45) has a second radius of curvature R2, preferably having a length of 10-30 mm, preferably 15-25 mm, especially preferably 18-22 mm and most preferably 20 mm . 10. The grate element according to claim 9, characterized in that the second arcuate segment (45), when observed in longitudinal section, defines a sector surface with a central angle β from 70° to 120°, preferably approximately 90°. 11. Grate element according to one of paragraphs. 4-10, characterized in that the body (3) of the element contains a front wall (33) shifted back in the direction opposite the feed direction F relative to the front point (29) of the lowering end section (19) so that an undercut (35) is formed. 12. The grate element according to claim 11, characterized in that in the area of the front wall (33) of the undercut (35) there are ventilation holes (41). 13. Grate element according to one of paragraphs. 1-12, characterized in that a depression (25) is made in the rear support surface (11), preferably adjacent to the front support surface (15). 14. A grate containing a plurality of grate elements (1) according to one of paragraphs. 1-13.