grate

Abstract

To provide a fire grate capable of suppressing an occurrence of a local abnormal combustion by uniformly supplying combustion air to an object to be combusted from a fire bed where the fire grates are arranged.SOLUTION: A fire grate has a supported basal end side, has a lower surface at a tip side abutting a back surface of the fire grate at a downstream side in a conveying direction of an object to be combusted, is arranged in such a way that the back surface abuts the lower surface at the tip side of the fire grate at an upstream side in the conveying direction, and catches and conveys the object to be combusted by the back surface through relative movement with the fire grate at the upstream side or the downstream side in the conveying direction so as to form a hearth of a stoker type incinerator. A reference surface 13R that maintains an abutting state with a lower surface 17 of the fire grate at the upstream side in the relative movement is formed on a back surface 13. A recess 13D that forms an air inlet G supplying combustion air with the lower surface of the fire grate at the upstream side is formed on the reference surface so as to be continuous in a direction along the conveying direction. The recess includes a displacement region where a formation position of the air inlet is displaced along with the relative movement in a widthwise direction intersecting with the conveying direction.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a grate that forms the hearth of a stoker-type incinerator. [Background technology]

[0002] Patent Document 1 proposes a grate that forms the hearth of a stoker-type incinerator, which is supported at the base end, and is positioned so that the lower part of the tip end abuts against the back surface of the grate on the downstream side in the transport direction of the material to be incinerated, and the lower part of the tip end of the grate on the upstream side in the transport direction abuts against the back surface, and which receives and transports the material to be incinerated on the back surface by relative movement between the grate on the upstream or downstream side in the transport direction.

[0003] The grate is configured so that combustion air is supplied through a gap formed by the lack of contact between the back surface and the lower part of the tip of the upstream grate that abuts against the back surface, and the relative movement changes the position at which the gap is formed.

[0004] Specifically, an area consisting of convex surfaces and / or concave surfaces is formed on the back surface along the conveying direction, and the formation position of the convex surfaces and / or concave surfaces in a direction intersecting the conveying direction is formed so as to displace along the conveying direction, and the area includes a first area consisting of a reference surface and a convex surface protruding above the reference surface, and a second area consisting of a concave surface recessed below the reference surface, and is formed so that the first area and the second area switch along the conveying direction. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6550331 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when the grate disclosed in Patent Document 1 moves back and forth relatively along the transport direction with the lower part of the tip of the upstream grate in the transport direction of the incinerated material abutting against the reference surface on its back, the abutting state between the reference surface and the lower part of the tip of the upstream grate is maintained.However, when the upstream grate moves relatively with the lower part of the tip of the upstream grate abutting against a convex surface that is higher than the reference surface, the inclination angle of the tip side relative to the support position on the base end of the upstream grate becomes larger than when it abuts against the reference surface.

[0007] As a result, the heat dissipation fins formed on the inside of the grate come into contact with the convex surface, causing the lower part of the tip of the upstream grate to rise above the convex surface, and causing combustion air to leak out from the entire width of the tip of the upstream grate, resulting in the problem that the intended purpose of dispersing the supply of combustion air to the material to be incinerated and suppressing the occurrence of localized abnormal combustion cannot be achieved.

[0008] Furthermore, there was also the problem that contact between the heat dissipation fins and the convex surfaces would cause streaky wear marks on the convex surfaces, shortening the life of the fire grate.

[0009] In view of the above-mentioned conventional problems, the object of the present invention is to provide a grate that can supply combustion air evenly to the material to be incinerated from a fire bed on which the grates are arranged, and can suppress the occurrence of localized abnormal combustion. [Means for solving the problem]

[0010] In order to achieve the above-mentioned object, the first characteristic configuration of the grate according to the present invention is a grate that is supported at its base end, and is positioned so that the lower surface of the tip end abuts against the back surface of the grate on the downstream side in the transport direction of the material to be incinerated, and the lower surface of the tip end of the grate on the upstream side in the transport direction abuts against the back surface, and forms the hearth of a stoker-type incinerator that receives and transports the material to be incinerated on its back surface by relative movement with the upstream or downstream grate in the transport direction, and a reference surface is formed on the back surface that maintains a state of abutment with the underside of the upstream grate during the relative movement, and recesses that form air intakes that supply combustion air between the reference surface and the underside of the upstream grate are formed continuously in the direction along the transport direction, and the recesses include a displacement region in which the position of the air intake displaces in the width direction that intersects with the transport direction as the relative movement occurs.

[0011] The two grates move relative to each other in the direction of transport of the material to be incinerated, with at least a portion of the underside of the tip of the upstream grate always abutting against a reference surface formed on the back of the grates. In this state, combustion air is supplied from an air inlet formed between the underside of the tip of the upstream grate and a recess formed in the reference surface along the transport direction. As the underside of the tip of the upstream grate passes through a displacement region due to the relative movement of the two grates, the air inlet is continuously displaced in the width direction, which intersects with the transport direction. As a result, the position of the combustion air inlet changes in the width direction, allowing combustion air to be supplied evenly to the material to be incinerated, effectively suppressing the occurrence of localized abnormal combustion.

[0012] The second characteristic configuration is that, in addition to the first characteristic configuration described above, the recesses are formed on both sides of the displacement region on the base end side in the width direction, and are formed in the center of the width direction on the tip end side.

[0013] The third characteristic configuration is that, in addition to the first characteristic configuration described above, the recess is formed in the center of the width direction on the base end side, sandwiching the displacement region, and is formed on both sides of the width direction on the tip end side.

[0014] The fourth characteristic configuration is a grate that forms the hearth of a stoker-type incinerator, which is supported at its base end and has its lower surface at the tip end abutting against the back surface of the grate downstream in the transport direction of the material to be incinerated, and is positioned so that the lower surface at the tip end of the grate upstream in the transport direction abuts against its back surface, and which receives and transports the material to be incinerated on its back surface by relative movement with the upstream or downstream grate in the transport direction, and a reference surface is formed on the back surface to maintain a state of abutment with the underside of the upstream grate during the relative movement, and recesses that form air intakes for supplying combustion air between the underside of the upstream grate and the reference surface are formed intermittently so as to overlap in the direction along the transport direction, and the recesses include a displacement region in which the position of the air intake port displaces discontinuously in the width direction intersecting the transport direction as the relative movement occurs, and the underside of the upstream grate is formed to a predetermined length in the direction along the transport direction, and the length of the displacement region along the transport direction is set longer than the predetermined length.

[0015] Similarly to the first characteristic configuration, the two grates move relative to each other along the transport direction of the material to be incinerated, with at least a portion of the underside of the tip of the upstream grate always abutting against a reference surface formed on the back surface of the grates. In this state, combustion air is supplied through an air inlet formed between the underside of the tip of the upstream grate and recesses formed intermittently on the reference surface so as to overlap in the transport direction. As the underside of the tip of the upstream grate passes through a displacement region due to the relative movement of the two grates, the air inlet is displaced discontinuously in the width direction, which intersects with the transport direction. As a result, the position of the combustion air inlet changes in the width direction, allowing combustion air to be supplied evenly to the material to be incinerated, effectively suppressing the occurrence of localized abnormal combustion.

[0016] Furthermore, when the underside of the upstream grate moves relatively along the back surface of the grate, if the length of the displacement area of ​​the recess along the conveying direction is set to be longer than a predetermined length, even if the recess is formed intermittently, the air intake will not be blocked by the underside when the underside of the upstream grate passes through the displacement area, and combustion air can be reliably supplied to the material to be incinerated.

[0017] The fifth characteristic feature of the present invention is that, in addition to the fourth characteristic feature described above, the displacement area is formed in the center of the relative movement width of the fire grate on the upstream side in the conveying direction.

[0018] The position of the air intake port can be switched between the upstream side and the downstream side across a displacement region formed in the center of the movement width of the grate. [Effects of the Invention]

[0019] As described above, according to the present invention, it is possible to provide a grate that can supply combustion air evenly to the material to be incinerated from a fire bed on which grates are arranged, thereby suppressing the occurrence of localized abnormal combustion. [Brief explanation of the drawings]

[0020] [Figure 1] A partially cutaway perspective view showing the combustion chamber of a stoker-type waste incinerator [Figure 2] (a) is a perspective view of the back of the grate, and (b) is a perspective view of the bottom of the grate. [Figure 3] (a) is a front view of the grate, (b) is a plan view of the same, and (c) is a bottom view of the same. [Figure 4] (a) is a right side view of the grate, and (b) is a left side view of the same. [Figure 5] (a) shows the relative movement of adjacently arranged fire grates, with the most distant state shown, (b) shows the state when they have moved to an intermediate position, and (c) shows the state when they are closest to each other. [Figure 6](a) is an explanatory diagram of the change in position of the air inlet formed between the front end bottom wall of the upstream grate sliding on the back surface of the grate and a recess formed on the back surface, and (b) is a plan view showing part of the grates arranged in parallel in the furnace width direction. [Figure 7] 1(a) to 1(d) are explanatory views showing various modes of recesses formed with respect to a reference surface. [Figure 8] 1(a) is an explanatory diagram of a mode in which it is difficult to supply combustion air from the air intake port formed between the front end bottom wall of the upstream grate sliding on the back surface of the grate and a recess formed on the back surface, and FIG. 1(b) is an explanatory diagram of a mode in which combustion air can be supplied from the air intake port formed between the front end bottom wall of the upstream grate sliding on the back surface of the grate and a recess formed on the back surface. DETAILED DESCRIPTION OF THE INVENTION

[0021] An example of a grate according to the present invention that forms the hearth of a stoker-type incinerator will be described below with reference to the drawings.

[0022] Figure 1 shows an example of a furnace chamber of a stoker-type incinerator 100. The furnace chamber is covered with a fire-resistant wall W and has a hearth B consisting of a stoker mechanism with multiple fire grates 10 arranged in it. Combustion air supplied from a forced draft fan to a wind box installed below the hearth B is supplied via the fire grates 10 to the waste to be incinerated on the hearth B.

[0023] Each grate 10 is made up of a fixed grate group 10A whose base end is swingably supported by a cylindrical support rod C1 hung horizontally on a fixed frame C, and a movable grate group 10B whose base end is swingably supported by a cylindrical support rod D1 hung horizontally on a movable frame D that moves back and forth in the direction of waste transport relative to the fixed frame C. The multiple grate groups 10A, 10B arranged side by side in the width direction are sandwiched between a pair of side plates located on both sides of the furnace chamber, and the side plates are pressed from the outside toward the center by springs.

[0024] The movable frame D is driven back and forth by the hydraulic mechanism E, causing the movable grate group 10B and the fixed grate group 10A to move relative to each other in the direction of waste transport, and the material to be incinerated on the hearth B is stirred and transported downstream.

[0025] A combustion burner is installed on the ceiling of the furnace chamber and is used to raise the temperature inside the furnace when starting up the furnace.When the calorific value of the waste is low, the heat from the combustion burner stirs and transports the material to be incinerated on hearth B while it is being burned.

[0026] In Figure 1, the central hearth B forms the main combustion zone where gasification combustion mainly takes place, with separate hearths provided on the upstream and downstream sides. The upstream hearth Bu forms a drying zone where materials to be incinerated are mainly dried, and the downstream hearth Bd forms a post-combustion zone where solid materials after gasification combustion are incinerated. Note that the upstream hearth Bu and the central hearth B may sometimes be integrated into one unit.

[0027] As shown in Figures 2 to 4, each of the fire grates 10 constituting each of the hearths Bu, B, and Bd described above is made of casting material in the shape of a roughly rectangular parallelepiped with an open bottom, and includes left and right side walls 11 and 12, a top wall 13 (in the following description, the upper surface of the top wall will also be referred to as the "back wall 13"), and a front end wall 14. Three arc-shaped locking claws 15 are formed on the base end side opposite the front end wall 14. Three reinforcing ribs 16 that also function as cooling fins are formed on the inside of the back wall 13.

[0028] The tip of the back surface 13 is bent at a predetermined curvature and connected to the front end wall 14, the lower edge of which is formed straight. The left and right side walls 11, 12 connected to the front end wall 14 are formed as inclined walls with their lower ends slightly inward. A front end bottom wall 17 is formed at the tip of the bottom and connected to the lower end of the front end wall 14 (see Figure 4(b)). The front end bottom wall 17 forms the underside that abuts against the back surface 13 of the grate 10 on the downstream side in the transport direction of the incineration material.

[0029] Figure 1 shows an example in which the surface enveloping the tip of each grate 10 is in a horizontal position, but the enveloping surface may be configured to be inclined along the transport direction of the material to be incinerated, for example, to be inclined downward along the transport direction of the material to be incinerated.

[0030] In addition, protrusions 18, which are flat surfaces of a predetermined width that protrude outward in the width direction, are formed on the upper edge portions of the tip and base ends of the left and right side walls 11, 12, excluding the longitudinal center of the grate 10. Furthermore, insertion holes H, H for connecting fittings that connect adjacent grates 10 are formed in the left and right side walls 11, 12 at positions approximately one-third of the length from the tip and base ends along the longitudinal direction of the grate 10.

[0031] Bolts and nuts are preferably used as the connecting fittings. A bolt is inserted into each insertion hole H of adjacent fire grates 10, and then tightened with a nut. The bolt and nut are then welded and fixed in a slightly loosened state, allowing a slight amount of play between adjacent fire grates 10. A predetermined number of adjacent fire grates in the width direction (three to four in this embodiment) are connected to each other with bolts and nuts as a unit.

[0032] In this way, multiple grates 10 are arranged adjacent to each other in the width direction of the furnace chamber, and the base end locking claws 15 are swingably engaged with the support rod C1 of the fixed frame C or the support rod D1 of the movable frame D (see Figure 1), so that each grate 10 is swingably supported around the support rods C1, D1. The grate 10 supported by the support rod C1 is the fixed grate, and the grate 10 supported by the support rod D1 is the movable grate.

[0033] As shown in Figures 5(a) to 5(c), the grate 10U located upstream in the direction of incineration material transport is arranged so that the lower end of the front end wall 14 and the front end bottom wall 17 of the upstream grate 10U abut against the back surface 13 of the downstream grate 10D in the direction of transport of the incineration material. As the grates 10U and 10D move relative to each other, the front end bottom wall 17 of the upstream grate 10U moves back and forth over the upper part of the back surface 13 of the downstream grate 10D in the direction of transport of the incineration material. Figure 5(a) shows the state in which the upstream grate 10U is most retracted to the rear, Figure 5(c) shows the state in which the upstream grate 10U is most advanced forward, and Figure 5(b) shows an intermediate position.

[0034] As shown in Figures 2(a), 3(b), and 6(a), the back surface 13 of each grate 10 has a reference surface 13R that maintains a state of abutment with the front end bottom wall 17 of the upstream grate 10 when each grate 10 moves relative to another, and a recess 13D that forms an air intake port G that supplies combustion air between the front end bottom wall 17 of the upstream grate 10 and the reference surface 13R is formed continuously in the direction along the transport direction of the material to be incinerated.

[0035] The recess 13D has a groove structure with a flat surface recessed by several millimeters from the reference surface 13R, and includes a displacement region 13A in which the formation position of the air intake port G continuously displaces in the width direction intersecting the conveying direction as the grate 10 moves relative to the surface.

[0036] As the front end bottom wall 17, which is the underside of the tip of the upstream grate, passes through the displacement area 13A in accordance with the relative movement of the two grates 10, the formation position of the air inlet G is continuously displaced in the width direction, which intersects with the conveying direction. As a result, combustion air is supplied evenly from the air inlet G to the materials to be incinerated as a whole, and the occurrence of localized abnormal combustion is effectively suppressed.

[0037] As shown in detail in Figure 6(a), the upper left diagram shows the front end bottom wall 17 (indicated by the dashed line indicated by the symbol 17) on the underside of the upstream grate 10U positioned at the base end of the downstream grate 10D, the middle left diagram shows the front end bottom wall 17 positioned in the center of the downstream grate 10D, and the lower left diagram shows the front end bottom wall 17 positioned at the tip end of the downstream grate 10D. The positions of the air intake ports G formed corresponding to each are shown in the right diagram.

[0038] In this embodiment, the displacement region 13A is formed in the center of the movement width of the grate 10 on the upstream side of the conveying direction (the position shown in Figure 3(b)), and the recess 13D is formed on both sides in the width direction at the base end side of the grate 10, sandwiching the displacement region 13A, and is formed in the center in the width direction at the tip end side of the grate 10, and is formed continuously in the direction along the conveying direction of the material to be incinerated.

[0039] The recess 13D is preferably formed in a cross-sectional shape that keeps the opening area of ​​the air intake port G, which is formed in conjunction with the relative movement of the fire grate 10, constant along the width direction, in order to keep the amount of combustion air supplied from the air intake port G constant.

[0040] Figure 6(b) shows three fire grates 10 arranged side by side in the width direction. Between adjacent fire grates 10, the protruding portions 18 described in Figures 2 and 3 abut against each other, forming a narrow gap A in the area where the protruding portions 18 are not formed. Combustion air is also supplied from this gap A. When the upstream fire grate 10 slides toward the tip and the gap A is covered by the upstream fire grate 10, it is cooled by the combustion air from the wind box, and the degree of wear caused by the high-temperature combustion heat is suppressed.

[0041] Even if foreign matter such as ash gets in through the gaps between adjacent grates 10 or through gap A during the incineration process of the materials to be incinerated as each grate 10 moves relative to another, it will quickly fall downward because the lower ends of the left and right side walls 11, 12 are formed as inclined walls that slope slightly inward. Therefore, uneven bending of the conveying surface due to fluctuations in the position of the grates 10 caused by foreign matter getting caught in the gaps between adjacent grates 10 is avoided as much as possible.

[0042] 7(a) to 7(d) show various shapes that can be adopted as the reference surface 13R and the recess 13D formed in the reference surface 13R. Fig. 7(a) shows the embodiment already described, in which the recess 13D is formed on both sides in the width direction on the base end side that sandwich the displacement region 13A, and is formed in the center in the width direction on the tip end side.

[0043] 7(a) shows an example in which a reference surface 13R is formed on the back surface 13 of the grate, which maintains a state of abutment with the underside of the upstream grate during relative movement, and recesses 13D are formed in the reference surface 13R continuously in the conveying direction, forming air intake ports G that supply combustion air between the reference surface 13R and the underside of the upstream grate. The following examples are similar, but the displacement region 13A does not need to be formed in the longitudinal center of the grate 10, and it is sufficient that the position where the air intake ports G are formed changes across the width of the grate 10 as the grate 10 moves relative to the material, so that combustion air is supplied evenly to the material as a whole.

[0044] In this example, combustion air supplied from the wind box toward the underside of the upstream grate 10U flows into a recess 13D formed in the downstream grate 10D, and is blown into the furnace through an air intake G formed between the recess 13D and the front end bottom wall 17, which is the underside of the upstream grate 10U.

[0045] As shown in Figure 7(b), recesses 13D are formed on both widthwise ends of the base end and tip end of the grate 10, sandwiching an approximately X-shaped displacement region 13A formed in the longitudinal center of the grate 10, and recesses 13D may also be formed in the widthwise center of the displacement region 13A.

[0046] As shown in Fig. 7(c), recesses 13D may be formed in the center in the width direction on the base end side sandwiching the displacement region 13A, and may be formed independently and intermittently on both sides in the width direction on the tip side.Alternatively, as shown in Fig. 7(d), multiple linear recesses 13D inclined in the width direction of the grate 10 may be formed independently and intermittently in parallel in the longitudinal direction of the grate 10.

[0047] Figures 7(c) and (d) show an example in which a reference surface 13R is formed on the back surface 13 of the grate, which maintains a state of abutment with the underside of the upstream grate (front end bottom wall 17) during relative movement, and recesses 13D are formed in the reference surface 13R to form air intakes that supply combustion air between the underside of the upstream grate and the reference surface 13R, overlapping when viewed in the width direction in the direction along the conveying direction and intermittently on either side of the reference surface 13R.

[0048] In Fig. 7(c), as in the above, recess 13D has displacement region 13A formed in the longitudinal center of grate 10, where the position of the air intake port is discontinuously displaced in the width direction intersecting the conveying direction as a result of relative movement. In Fig. 7(d), displacement region 13A is formed so as to be repeated along the longitudinal direction of grate 10, where the position of the air intake port is discontinuously displaced in the width direction intersecting the conveying direction as a result of relative movement.

[0049] As shown in Figure 8(a), when the recess 13D that forms the air intake G between the front end bottom wall 17 of the upstream grate 10D is formed intermittently in the direction along the conveying direction, if the length L1 of the front end bottom wall 17 of the upstream grate 10 in the direction along the conveying direction is longer than the length L2 of the displacement region 13A in the conveying direction, when the position of the air intake G changes along the conveying direction, the recess 13D that serves as a passage for combustion air is closed by the front end bottom wall 17, and there will be a time when combustion air cannot be supplied onto the stoker.

[0050] As shown in Figure 8(b), in preparation for such a case, when the front end bottom wall 17 of the upstream grate 10U moves relatively along the back surface 13 of the grate 10D, the length of the displacement region 13A of the recess 13D along the conveying direction is set to a length L2 longer than the specified width L1.This prevents the air intake G from being blocked by the front end bottom wall 17 when the front end bottom wall 17 of the upstream grate 10U passes through the displacement region 13A, and ensures that combustion air can always be supplied to the material to be incinerated.

[0051] The embodiment described above is merely one example of the present invention, and it is sufficient that a reference surface is formed that maintains a state of abutment with the underside of the upstream grate at least during relative movement, and a recess is formed along the conveying direction to form an air intake port that supplies combustion air between the underside of the upstream grate, and the recess is configured to include a displacement region in which the position of the air intake port gradually displaces in the width direction that intersects with the conveying direction as the relative movement occurs.

[0052] It goes without saying that the above-described embodiment is merely one example of the present invention, and the specific structure, shape, material, size, etc. of each part can be appropriately modified and designed within the scope of the effects of the present invention. [Explanation of symbols]

[0053] 10: Fire grate 10A: Fixed grate group 10B: Movable grate group 10U: Upstream grate 10D: Downstream grate 11,12: Side wall 13: Back (top wall) 13D: Recess 13R: Reference flat surface 13A: Displacement area 14: Front end wall 16: Reinforcement rib 17: Front end bottom wall (bottom surface) 100: Stoker-type incinerator B: Hearth (combustion zone) Bu: Hearth (drying zone) Bd: Hearth (post-combustion zone) C: Fixed Frame C C1: Support rod D: Movable frame D1: Support rod G:Air supply port H: Through hole

Claims

1. A grate that forms the hearth of a stoker-type incinerator, the base end side of which is supported, and the lower surface of the tip side of which is in contact with the back surface of the grate on the downstream side in the transport direction of the material to be incinerated, and the lower surface of the tip side of the grate on the upstream side in the transport direction is in contact with the back surface, and the grate forms the hearth of a stoker-type incinerator, the grate receives and transports the material to be incinerated on the back surface by relative movement with the grate on the upstream side or the grate on the transport direction, A reference surface is formed on the rear surface, which maintains a state of abutment with the lower surface of the upstream grate during the relative movement, and a recess is formed on the reference surface in a direction along the transport direction, which recess forms an air intake port for supplying combustion air between the lower surface of the upstream grate and the reference surface, The recessed portion is a grate including a displacement region in which the formation position of the air inlet is displaced in a width direction intersecting the conveying direction as the relative movement occurs.

2. The fire grate according to claim 1 , wherein the recesses are formed on both sides in the width direction at the base end side, sandwiching the displacement region, and are formed in the center in the width direction at the tip end side.

3. The fire grate according to claim 1 , wherein the recess is formed in the center in the width direction on the base end side, and on both sides in the width direction on the tip end side, sandwiching the displacement region.

4. A grate that forms the hearth of a stoker-type incinerator, the base end side of which is supported, and the lower surface of the tip side of which is in contact with the back surface of the grate on the downstream side in the transport direction of the material to be incinerated, and the lower surface of the tip side of the grate on the upstream side in the transport direction is in contact with the back surface, and the grate forms the hearth of a stoker-type incinerator, the grate receives and transports the material to be incinerated on the back surface by relative movement with the grate on the upstream side or the grate on the transport direction, A reference surface is formed on the rear surface, which maintains a state of abutment with the lower surface of the upstream grate during the relative movement, and recesses that form air intake ports for supplying combustion air between the reference surface and the lower surface of the upstream grate are intermittently formed on the reference surface so as to overlap in a direction along the transport direction, the recess includes a displacement region in which a formation position of the air supply port is discontinuously displaced in a width direction intersecting the transport direction as a result of the relative movement, The lower surface of the upstream grate is formed to a predetermined length along the conveying direction, and the length of the displacement region along the conveying direction is set to be longer than the predetermined length.

5. 5. The grate according to claim 4, wherein the displacement region is formed at the center of the relative movement width of the grate on the upstream side in the conveying direction.

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