AIR-COOLED GRATE BLOCK

The present invention relates to a grate block as part of a grate for a plant for the thermal treatment of waste.

The heart of a waste material incineration plant is the incineration grate. Here, the waste materials, for example household garbage, is conveyed from one end of the incineration grate to the other end of the incineration grate. The oxygen required for the combustion of the waste materials is present in the air in sufficient quantity. In the process, the air, also called primary air, is forced from below through the incineration grate and is thus fed to the combustion space containing the waste materials to be incinerated.

One type of the various known incineration grate types is the “step grate”. Such a step grate comprises grate blocks which are arranged side by side and are fixedly connected and which form the individual grate block rows. The grate block rows following one another are offset from one another in a step-like manner and rest one on top of the other with the front walls, facing the combustion space, of the grate blocks which form the grate block rows. Some of the grate block rows are arranged to be movable, for example every second grate block row. The waste material is conveyed onto the grate block row following in the transport direction by the lifting movement of these movably arranged grate block rows.

The waste materials which are incinerated in the abovementioned incineration plant vary widely in nature. The range extends from household garbage to industrial waste and actual fuels, e.g. wood in the form of sawdust, biomass and suchlike. Of course, the calorific value of these waste materials varies greatly, depending on the type of waste material. However, there are also considerable variations with regard to the calorific value within one type of waste material. These considerable variations in the calorific value also result in considerable variations in the thermal and mechanical loading of the incineration grate, for example of the individual grate blocks.

At average calorific values (up to about 10 MJ/kg), the incineration grates or the individual grate blocks can be adequately cooled with air (primary air). For waste materials having a higher calorific value, incineration grates having water-cooled grate blocks are known from the prior art. Adequate cooling of the grate blocks is very important, since there is otherwise the risk of melting of the incineration grate.

EP 1 191 282 describes a grate block which has a cooling space for water on its bottom side facing away from the combustion space.

EP 1 219 898 discloses a grate block having a cooling element attached below the bearing surface for the waste. Water is also used here for the cooling.

DE 10 2004 032 291 discloses an air-cooled grate plate having a flow passage formed below the top side of the grate plate.

Although water-cooled grate blocks provide a means which enables efficiently cooled incineration grates to be produced, such incineration grates have the disadvantage that both the production thereof and the subsequent process are much more costly than in the case of incineration grates which are composed of air-cooled grate blocks.

The object of the present invention is to provide a grate block which has at least equally good wear resistance and thus an equally long service life compared with a water-cooled grate block and which at the same time avoids the disadvantages of the latter with regard to the high cost in terms of production and process.

The object is achieved by a grate block having the features of independent claim 1. Preferred embodiments are the subject matter of the dependent claims.

The grate block according to the invention has the features according to claim 1. The grate block has a block body which is designed as a cast part. The block body has a top wall, which forms a bearing surface, and a front wall, on which a foot is integrally formed. The grate block is part of a grate for the thermal treatment of waste. In this case, the grate blocks are arranged one above the other in a step-like manner and the individual grate blocks rest with the foot integrally formed on the front wall on the bearing surface formed by the top wall of the following grate block (step grate). The waste to be thermally treated likewise rests on this bearing surface formed by the top wall. The grate can have an inclination. This inclination is within a range of 0° to 26°, preferably within the range of 10° to 18°, relative to an imaginary horizontal plane. A wall inlet is arranged on the underside of the top wall. This wall inlet lies on that side of the top wall which faces away from the combustion space. Starting from the wall inlet, a first cooling passage section runs through the top wall and the front wall to an outlet opening arranged in the front wall. An inlet opening is arranged adjacent to the front wall and to the foot integrally formed thereon. A cooling passage wall which is at a distance from the front wall and the top wall starts from the inlet opening and forms a second cooling passage section fluidically connected to the first cooling passage section at the wall inlet.

The first cooling passage section and the second cooling passage section together form a cooling passage which has a substantially S-shaped course in longitudinal section. The cross section or the cross-sectional area of the first cooling passage section and of the second cooling passage section—and thus of the substantially S-shaped cooling passage—is constant in the simplest embodiment. However, the cross section may also vary.

The grate block according to the invention permits the use of gaseous cooling media, in particular air, even during the thermal treatment of waste materials having a higher calorific value (>10 MJ/kg). Water cooling, which is often required in the case of waste materials having a higher calorific value, is dispensed with. The grate block according to the invention permits excellent and differentiated cooling of those points of the grate block which are subjected to the greatest thermal loading. This is therefore very advantageous since—in the case of air cooling—the primary air available for the cooling is limited. Furthermore, the primary air used for the cooling is heated by about 120° to 150°, for which reason preheating (hitherto necessary) of the primary air can be dispensed with. In addition to the omission of the preheating of the primary air, even cooler air than was hitherto possible can be used for the cooling. The cooling is thus additionally improved overall. The grate block according to the invention achieves outstanding, i.e. long, service life comparable with the service life of water-cooled grate blocks.

In a preferred embodiment, the first cooling passage section and the second cooling passage section run with a varying cross section. The term “cross section” designates the cross-sectional area of the first and the second cooling passage sections. The shape of the cross-sectional area may vary. Possible cross-sectional shapes are rectangular, quadrilateral, polygonal, e.g. a truncated hexagon, circular or oval.

The heat removal by the gaseous cooling medium, preferably the primary air, designates the quantity of heat dissipated by the cooling medium per unit time. The heat removal depends, inter alia, on the flow velocity of the cooling medium relative to its surroundings, in the present case the first and the second cooling passage sections. It is all the greater, the higher the flow velocity of the cooling medium is.

If the cross section of the two cooling passage sections varies, this means that the cross-sectional area changes. The cross-sectional area can become smaller or larger. If the cross-sectional area becomes smaller for example, the flow velocity of a gaseous cooling medium, preferably of the cooling air, increases, which leads to greater cooling as a result of the increased heat removal by the gaseous cooling medium. Increased heat removal means that the gaseous cooling medium absorbs a greater heat quantity from its surroundings and dissipates said heat quantity due to the increased flow velocity on account of the reduced cross-sectional area. With a corresponding variation of the cross section of the first and the second cooling passage sections, highly differentiated cooling of individual regions of the grate block is achieved. As a result, the cooling can be adapted to the specific thermal loading of the individual grate block region. Thus, for example, the front wall of the grate block can be cooled to a deliberately increased extent.

Widening the cross section of the first cooling passage section or of the second cooling passage section in regions which are thermally loaded to a less pronounced extent reduces the flow velocity of the gaseous cooling medium, e.g. of the primary air, and thus also reduces the heat removal achieved. It thus becomes possible, with a limited quantity of cooling medium, e.g. primary air, to also cool regions of the grate block that are thermally loaded to a less pronounced extent, whereby the cooling overall is improved.

In another embodiment, the grate block has a rib extending in the longitudinal direction of the block body. The rib is integrally formed on the top wall and the front wall and is arranged substantially perpendicularly thereto. The stability of the grate block is increased by means of the rib.

In a preferred embodiment, the rib is a central rib, i.e. it is arranged centrally in the transverse direction of the block body. The arrangement of the rib in the center additionally simplifies the production of the grate blocks according to the invention by casting, since identical half shells can be used.

In a preferred embodiment, the first cooling passage section and the second cooling passage section fluidically connected thereto extend over the entire length of the top wall of the grate block according to the invention. Cooling of the grate block over the entire length of the top wall is thus achieved.

However, it is also possible according to a further embodiment for the first cooling passage section and the second cooling passage section to extend only over part of the length of the top wall. The first cooling passage section and the second cooling passage section preferably extend over 10%-90%, in particular preferably over 30%-70%, of the length of the top wall of the grate block.

In a further embodiment of the grate block according to the invention, the cross section of the second cooling passage section increases from the inlet opening toward the wall inlet. The cross section of the first cooling passage section, on the other hand, decreases from the wall inlet toward the outlet opening. The cross-sectional change can be effected both continuously and in discrete steps. A continuous cross-sectional change is obtained, for example, if the first and/or the second cooling passage section has a conical section. Due to the change in the cross section of the first cooling passage section and of the second cooling passage section, zones cooled to a different extent are obtained in the first cooling passage section and in the second cooling passage section. In this case, the cooling is weaker in zones having a greater cross section and stronger in zones having a smaller cross section.

In another embodiment, the grate block has deflecting webs integrally formed on the rib, preferably a central rib, and projecting substantially perpendicularly from the latter. These deflecting webs are arranged offset from one another.

In a further embodiment, the deflecting webs form a meandering passage which is fluidically connected to the second cooling passage section at the inlet opening. In this case, a passage inlet opening is in a position which is dependent on a position of the grate block relative to a grate block following in a direction L.

The direction L corresponds to the conveying direction of the waste in the longitudinal direction of the grate. In the process, the waste passes through various zones, starting with the drying zone at an end of the grate right through the combustion zone to the burnout zone at the other end, opposite the drying zone, of the grate.

In a preferred embodiment, the top wall of the grate has trough-shaped recesses on its side facing the combustion space.

The trough-shaped recesses are located in a region of the top wall which adjoins the front wall of the grate block. Waste or slack rests continuously in this region during the operation of the grate, which means pronounced thermal loading.

Incinerated waste or slag collects in these trough-shaped recesses during operation of the incineration grate. The incinerated waste or the slag form an insulating layer between the top wall and the combustion space and thus reduce the input of heat from the combustion space into the grate block.

The grate blocks according to the invention can be used in a grate. Such a grate preferably comprises only grate blocks according to the invention.

A grate has, as a rule, a plurality of fixed grate block rows and a plurality of movable grate block rows. These grate block rows are formed by a plurality of grate blocks arranged side by side and attached to a block-retaining tube, the grate blocks arranged next to one another being fixedly connected to one another. The fixed and the movable grate block rows are arranged alternately and in a step-like manner. In this case, both the fixed and the movable grate block rows are formed by grate blocks according to the invention.

Whereas the block-retaining tubes of fixed grate block rows are attached to fixed brackets, block-retaining tubes of movable grate block rows are assigned to movable grate carriages. These grate carriages are driven, for example, by means of hydraulic cylinders and in the process are moved forward and backward via rollers. As a result, the movable grate block rows are likewise moved and thus exert a pushing and shearing effect on the waste resting on the grate. The waste is thus firstly circulated, wherein new waste portions are constantly subjected to the thermal treatment in the combustion space. Secondly, constant forward conveyance of the waste in the direction of a grate end is thus achieved.

The grate block according to the invention is explained in more detail below with reference to exemplary embodiments shown in the drawings, in which, purely schematically:

FIG. 1 shows a first embodiment of the grate block in longitudinal section;

FIG. 2 shows a further embodiment of the grate block in longitudinal section;

FIG. 3 shows a further embodiment of the grate block in longitudinal section, having an extended top wall;

FIG. 4 shows a further embodiment of the grate block in longitudinal section, having a substantially S-shaped cooling passage of mean length with respect to the distance from the front to the rear wall;

FIG. 5 shows a further embodiment of the grate block in longitudinal section, having a short, substantially S-shaped cooling passage;

FIG. 6 shows a further embodiment of the grate block in longitudinal section, having a short, substantially S-shaped cooling passage and additional deflecting webs arranged offset;

FIG. 7 shows an embodiment of the grate block in cross section;

FIG. 8 shows a further embodiment of the grate block in cross section;

FIG. 9 shows a further embodiment of the grate block in cross section, having a trough-shaped recess on that side of the top wall which faces the combustion space;

FIG. 10 shows three grate blocks arranged side by side according to FIG. 7, in cross section;

FIG. 11 shows three grate blocks arranged side by side according to FIG. 8, in cross section;

FIG. 12 shows three grate blocks arranged side by side according to FIG. 9, in cross section;

FIG. 13
a shows four grate blocks, arranged one above the other in a step-like manner, according to the embodiment shown in FIG. 6, the movably arranged grate blocks being fully extended;

FIG. 13
b shows four grate blocks, arranged one above the other in a step-like manner, according to the embodiment shown in FIG. 6, the movably arranged grate blocks being arranged in a central position;

FIG. 13
c shows four grate blocks, arranged one above the other in a step-like manner, according to the embodiment shown in FIG. 6, the movably arranged grate blocks being fully retracted;

FIG. 14
a shows four grate blocks, arranged side by side, in a perspective view according to the embodiment shown in FIG. 9, having trough-shaped recesses;

FIG. 14
b shows in an enlarged detail one of the trough-shaped recesses according to FIG. 14a; and

FIG. 15 shows a detail of a step grate having fixed and movably arranged grate blocks.

FIG. 1 shows a grate block according to the invention having a block body 5 which is designed as a cast part. The block body 5 has a top wall 10, which forms a bearing surface 15, and a front wall 20. A foot 25 is integrally formed on the front wall 20. The foot 25 is intended to rest on the bearing surface 15 of a following grate block 1 in a relatively displaceable manner. Arranged on the underside 30 of the top wall 10, that is to say on the side facing away from the combustion space 2, is a wall inlet 35, from which a first cooling passage section 40 runs through the top wall 10 and the front wall 20 to an outlet opening 45 arranged in the front wall 20. In the embodiment shown, the outlet opening 45 is directed obliquely downward, i.e. in the direction of the bearing surface 15 of the following grate block 1. Arranged adjacent to the foot 25 and to the front wall 20 is an inlet opening 50, starting from which a cooling passage wall 55 which is at a distance from the front wall 20 and the top wall 10 forms a second cooling passage section 60 fluidically connected to the first cooling passage section 40 at the wall inlet 35. In the embodiment shown, the first and the second cooling passage sections 40, 60 do not extend over the entire length of the top wall 10. The cross section or the cross-sectional area of the first cooling passage section 40 and of the second cooling passage section 60 shown in FIG. 1 varies in the course of the two cooling passage sections. However, the cross section can also be kept constant.

The grate block according to the invention has, for example, the following dimensions: a length of 500 mm to 700 mm, a height of approximately 150 mm and a width of approximately 100 mm.

FIG. 2 shows a further embodiment of the grate block according to the invention. In this embodiment, the grate block has a rib 65 and a rear wall 75. The rib 65 is integrally formed on the front wall 20, the top wall 10, the cooling passage wall and the rear wall 75 and is arranged substantially perpendicularly thereto. The rib 65 extends from the front wall 20 up to the rear wall 75. The rear wall 75 is provided with a hook 80. The grate block 1 is attached to a block-retaining tube (not shown here) by means of this hook 80. The circumference of the grate block 1 is not exactly rectangular. On the contrary, said grate block 1 is sloped where the top wall 10 meets the front wall 20.

FIG. 3 shows a further, modified embodiment of the grate block 1 according to the invention. At the circumference, the top wall 10 and the front wall 20 again have a slope, which is extended by a lug 85 beyond the outer side 21, facing the combustion space 2, of the front wall 20. The lug 85 therefore projects beyond the outer side 21 of the front wall 20. The outlet opening 45 thus points substantially perpendicular downward in the direction of the bearing surface 15 of a following grate block 1.

FIG. 4 shows another embodiment of a grate block 1 having a block body 5. The block body 5 has a front wall 20, a top wall 10 and a rear wall 75. A foot 25 is integrally formed on the front wall 20 and a hook 80 is integrally formed on the rear wall 75. A first cooling passage section 40 runs from a wall inlet 35 through the top wall 10 and the front wall 20 to an outlet opening 45. Extending from an inlet opening 50, which is arranged adjacent to the foot 25 and to the front wall 20, is a cooling passage wall 55 which is at a distance from the front wall 20 and the top wall 10 and which forms a second cooling passage section 60 fluidically connected to the first cooling passage section 40 at the wall inlet 35. The first and the second cooling passage sections 40, 60 extend only over part of the length of the top wall 10. In the embodiment shown, they extend approximately over half the length of the top wall 10 and thus over a region subjected to greater thermal loading.

FIG. 5 shows an embodiment of a grate block according to the invention similar to the embodiment shown in FIG. 4. In this case, the first cooling passage section 40 and the second cooling passage section 60 extend only over a region of approximately one third of the length of the top wall 10, said region adjoining the front wall 20.

FIG. 6 shows another embodiment of a grate block 1 according to the invention. The grate block 5, designed as a cast part, has a top wall 10, which forms a bearing surface 15, and a front wall 20, wherein a foot 25 is integrally formed on the front wall 20. The foot 25 is intended to rest on the bearing surface 15 of a following grate block 1 in a relatively displaceable manner. Arranged on the underside 30 of the top wall 10, on the side facing away from the combustion space 2, is a wall inlet 35, from which a first cooling passage section 40 runs through the top wall 10 and the front wall 20 to an outlet opening 45 arranged in the front wall 20. In the embodiment shown, the outlet opening 45 is directed obliquely downward, i.e. in the direction of the bearing surface 15 of the following grate block 1. Arranged adjacent to the foot 25 and to the front wall 20 is an inlet opening 50, starting from which a cooling passage wall 55 at a distance from the front wall 20 and the top wall 10 forms a second cooling passage section 60 fluidically connected to the first cooling passage section 40 at the wall inlet 35. In the embodiment shown, the first and the second cooling passage sections 40, 60 extend only over approximately the front third of the length of the top wall 10. The cross section or the cross-sectional area of the first cooling passage section 40 and of the second cooling passage section 60 shown in FIG. 6 varies in the course of the two cooling passage sections. Starting from the inlet opening 50, the second cooling passage 60 has a narrow cross section along the front wall 20, said cross section then widening considerably toward the wall inlet 35. In the first cooling passage section 40, the widened cross section narrows again toward the outlet opening 45 to approximately the same narrow cross section as runs in the second cooling passage 60 along the front wall. In addition, the block body 5 has a rib 65 which is integrally formed on the front side 20, the top side 10 and a rear side 75 and is arranged substantially perpendicularly thereto. In this embodiment, too, the rear wall 75 is provided with a hook 80. Integrally formed on the rib 65 is a deflecting web 70 which is arranged substantially perpendicularly to the rib 65.

In the embodiment shown, there are a total of 5 deflecting ribs 70, which run obliquely downward from the top in a direction L. The direction L also corresponds to the conveying direction of the waste (not shown) resting on the bearing surface 15. The deflecting webs 70 are alternately arranged offset. That is to say, the deflecting webs 70 are either integrally formed with their top end on the underside 30 of the top wall 10 or are spaced apart with their top end from the bottom side 30 of the top wall 10 in such a way that the bottom end 72 of the deflecting webs 70 is located in a plane with the bottom surface 26 of the foot 25.

FIG. 7 shows a cross section through a grate block 1 according to the invention. The block body 5 has a top wall 10 having a bearing surface 15 and an underside 30 and a rib 65. A first cooling passage section 40 runs through the top wall 10. The cooling passage wall 55 at a distance from the top wall 10 forms together with the latter a second cooling passage section 60. The rib 65 is arranged centrally in the embodiment shown.

FIG. 8 shows a further cross section through a grate block 1. Here, of the block body 5, only the top wall 10 having the cooling passage section 40, which runs through the top wall 10 and which, as can be seen here in cross section, is divided into 4 smaller cooling passage sections, and the cooling passage wall 55, at a distance from the top wall 10, and the second cooling passage section 60 can be seen. Likewise shown is the rib 65, which again is arranged in the center of the block body 5 and substantially perpendicularly thereto.

FIG. 9 shows another embodiment of a grate block 1 according to the present invention. The block body 5 again has a top wall 10, forming a bearing surface 15 and having an underside 30, a cooling passage wall 55 at a distance from the top wall 10, and a centrally arranged rib 65. The first cooling passage section 40 running through the top wall 10 and the second cooling passage section 60 formed by the cooling passage wall 55 and the top wall 10 can likewise be seen. In addition, the top wall has a trough-shaped recess 90. As can be seen from FIG. 14a, this recess 90 extends only over approximately the front third of the grate block 1. Slag collects in this trough-shaped recess, which results in screening of the grate block relative to the combustion space 2. The thermal loading of the grate block 1 is lower in this region of the screening due to a reduced input of heat.

FIG. 10, with three grate blocks 1 according to FIG. 7 which are arranged side by side, shows a detail of a grate block row in cross section. In this case, the first cooling passage section 40 and the second cooling passage section 60 are jointly formed by in each case two adjacently arranged grate blocks 1. Whereas the first cooling passage section 40 runs through the top wall 10, the second cooling passage section 60 is formed by the cooling passage wall 55, which is arranged at a distance from the top wall 10, together with this top wall 10. The lateral boundary of both the first cooling passage section 40 and the second cooling passage section 60 is formed by the ribs 65 of two adjacently arranged grate blocks 1, said ribs 65 being arranged substantially centrally with respect to the individual grate block.

FIG. 11, with three grate blocks 1 according to FIG. 8 which are arranged side by side, shows a detail of a grate block row in cross section. Of the block body 5 of each of the three grate blocks 1 shown, the top wall 10, the cooling passage wall 55 at a distance therefrom and the rib 65, again arranged substantially centrally, can be seen. The first cooling passage section 40 runs through the top wall 10. The division of the first cooling passage section into 4 smaller cooling passage sections can likewise again be seen, said cooling passage sections running through the top wall 10 and through the front wall 20 and opening into the outlet openings arranged in this front wall 20. The second cooling passage 60 is jointly formed by two adjacent grate blocks 1.

FIG. 12, with three grate blocks 1 according to FIG. 9 which are arranged side by side, shows a detail of a grate block row in cross section. The first cooling passage section 40 and the second cooling passage section 60 are jointly formed by in each case two adjacently arranged block bodies 5 of the grate blocks 1. Whereas the first cooling passage section 40 runs through the top wall 10, the second cooling passage section 60 is formed by the cooling passage wall 55, which is arranged at a distance from the top wall 10, and this top wall 10. The lateral boundary of both the first cooling passage section 40 and the second cooling passage section 60 is formed by the ribs 65 of two adjacently arranged grate blocks 1, said ribs 65 being arranged substantially centrally with respect to the individual grate block. The trough-shaped recess 90 in the top wall 10 of the block bodies 5 can likewise be seen.

FIGS. 13
a,
13
b,
13
c each show, in cross section, four grate block rows 100, 101, 102 and 103 which are arranged one behind the other in a step-like manner and which each comprise a plurality of grate blocks 1 arranged side by side. The embodiment of the grate blocks 1 shown corresponds to that of FIG. 6. The grate block rows 100 and 102 are fixed grate block rows, whereas the grate block rows 101 and 103 are arranged to be movable. The grate blocks 1 of the movable grate block rows 101 and 103 can be seen in different positions in FIGS. 13a, 13b and 13c. In FIG. 13a, the grate blocks 1 of the movable grate block rows 101 and 103 are fully extended in direction L, which corresponds to the conveying direction of the waste. In this case, a meandering passage 110 having a passage inlet opening 115 is formed by the deflecting webs 70 of the grate blocks 1 of the movable grate block rows 101 and 103, and the gaseous cooling medium, e.g. the primary air, flows through said meandering passage 110. In FIG. 13b, the grate blocks 1 of the movable grate block rows 101 and 103 are shown, in direction L, in a central position, which is located between the fully extended position shown in FIG. 13a and the fully retracted position, in the opposite direction to direction L, shown in FIG. 13c. As a result, both the length of the meandering passage 110 and the position of the passage inlet opening 115 change. The result of this is that the grate blocks 1 of the movable grate block row 101 and 103 are always cooled in that region which is exposed to the waste in the combustion space 2.

FIG. 14
a shows a perspective view of a grate block row consisting of four grate blocks 1 arranged side by side. The top wall 10, forming a bearing surface 15, the front wall 20 and the foot 25 integrally formed thereon can be seen here. The rear wall 75 provided with a hook 80 and the rib 65 arranged centrally with respect to the individual grate block 1 are likewise shown. Only partly visible is the cooling passage wall 55, which, starting from an inlet opening 50, runs at a distance from the front wall 20 and the top wall 10 toward a wall inlet 35 and forms a second cooling passage section 60 which is fluidically connected to the first cooling passage section 40 at the wall inlet 35. The first cooling passage section 40 runs from the wall inlet 10 through the top wall 10 and the front wall 20 toward outlet openings 45. In the embodiment shown, the block body 5 has trough-shaped recesses 90 in the top wall 10. These trough-shaped recesses 90 are arranged in the top wall 10 in that region of the grate block 1 which adjoins the front wall 20. This region is continuously exposed to the waste during operation.

FIG. 14
b shows, in an enlarged detail of FIG. 14a, the trough-shaped recesses 90 arranged in the top wall 10.

FIG. 15 shows a longitudinal section of an incineration grate having grate blocks 1 arranged one behind the other in a step-like manner, as known from the prior art. The grate blocks 1 are not arranged horizontally but rather rise obliquely upward in direction L.

AIR-COOLED GRATE BLOCK

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