Grates and hearths of stoker-type incinerators

Abstract

To provide fire grates and a hearth of a stoker type incinerator capable of suppressing useless supply by enabling sufficient supply of combustion air to objects to be incinerated present on a hearth with fire grates arranged.SOLUTION: In fire grates, a base end side is supported, an undersurface of a tip side is brought into contact with a back surface of a fire grate on the downstream side in the conveyance direction of objects to be incinerated, an undersurface of the tip side of a fire grate on the upstream side in the conveyance direction is arranged to be brought into contact with a back surface, and there is formed a hearth of a stoker type incinerator that accepts on the back surface and conveys the objects to be incinerated by relative movement with the fire grate on the upstream or downstream side in the conveyance direction. In the fire grates, combustion air is configured to be supplied from a gap formed by noncontact between the back surface and the lower part of the tip end side of the fire grate on the upstream side in contact with the back surface during the relative movement, and the area of the gap is configured to be continuously or intermittently smaller due to the relative movement of the fire grate on the upstream side from the base end side to the tip side.SELECTED DRAWING: Figure 4

Description

[[Technical Field]]

[0001] The present invention relates to a grate and a hearth of a stoker-type incinerator. [[Background Art]]

[0002] Patent Document 1 discloses a grate piece structure in which a gas flow path for supplying combustion gas is formed in a space surrounded by an upper wall 1 and left and right side walls 2, a front end wall 3 connected to the upper wall 1 and the left and right side walls 2 is provided, a grate piece main body R having an opening 31 formed in the front end wall 3 for blowing out combustion gas from the gas flow path to the outside is provided, and the lower tip end of the grate piece main body R and the upper wall 1 of an adjacent grate piece main body R relatively reciprocally slide while varying an elevation angle, wherein a swing piece 4 that slides while being in surface contact with the upper wall surface of the adjacent grate piece main body is provided at the lower tip end 32 of the grate piece main body (see FIG. 10(a)).

[0003] Combustion air supplied from below the grate pieces via a wind box is blown out from two openings 31, which are round holes formed in the front end wall 3, so that the combustion air is supplied to the material to be incinerated on the hearth.

[0004] Patent Document 2 discloses a step sliding stoker in which fixed grates and movable grates are alternately arranged in the front-rear direction, each grate includes: a grate body 4 attached to a grate frame 9; an air passage 5 formed from the rear side to the lower front side of the grate body 4; a sliding body 6 detachably provided on the front side of the grate body 4 and slidably abutted against the upper surface of the preceding-stage grate body; a nozzle hole 7 provided on the front side of the air passage 5 and formed between the grate body and an adjacent grate body via a groove provided on a side portion of the grate body 4; and an air outlet 8 formed between the lower front end of the grate body 4 and the upper front end of the sliding body and communicating with the nozzle hole 7 (see FIG. 10(b)). Note that the reference numerals shown in FIGS. 10(a) and 10(b) are the reference numerals used in Patent Documents 1 and 2 as they are, and have no relation to the reference numerals used in the section of the following embodiments of the present invention. [[Prior Art Documents]] [[Patent Documents]]

[0005] [Patent Document 1] Japanese Patent Publication No. 2003-97807 [Patent Document 2] Patent No. 3732670 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] In the grate disclosed in Patent Document 1, combustion air is always blown out from the same position along the width direction of the firebed through a fixed opening consisting of two circular holes formed in the front end wall. This presents a problem in that it is difficult to supply combustion air evenly to the material to be incinerated on the firebed according to its thickness.

[0007] Therefore, there was a problem in that areas where the material to be incinerated was thinly piled up would burn locally, and the resulting radiant heat would raise the grate temperature, causing it to burn out more quickly than other grates.

[0008] The grate disclosed in Patent Document 2 is configured to supply combustion air through wider slits than the grate disclosed in Patent Document 1, but it did not resolve the issues of the thickness of the material to be incinerated and the amount of combustion air supplied, nor the problem of localized abnormal combustion.

[0009] Incidentally, the waste to be incinerated, once placed in the incinerator, undergoes a series of incineration processes—drying, gasification combustion, and solid combustion—as it is transported from the upstream to the downstream side of the hearth, which is composed of a grate. As the incineration process progresses, the volume of the waste gradually decreases, and in the downstream area of ​​the combustion zone where gasification combustion is taking place, the tip of the grate often becomes exposed above the waste layer.

[0010] Figures 8(a) to 8(g) show the behavior of waste being transported as the fixed grate and the movable grate move relative to each other, and the changes in the combustion state of the waste. When the waste layer is thin, as shown in Figure 8(a), as the movable grate moves forward, the tip of the movable grate pushes and transports the waste accumulated on the back of the fixed grate forward. In this process, the waste accumulated on the back of the fixed grate burns due to the air supplied from the nozzle on the tip side of the movable grate (see Figure 8(b)). However, since the waste on the tip side of the fixed grate moves forward with the movable grate on the downstream side, air blow-through occurs (see Figure 8(b)), and then new waste is supplied by the movable grate on the upstream side (see Figure 8(c)).

[0011] Subsequently, as the movable grate moves backward, the debris on the back of the downstream grate is cleared, allowing air to blow through (see Figures 8(d) and (e)). As it moves further backward, it is pressed by the tip of the upstream fixed grate, and new debris is transported to the back of the downstream grate.

[0012] Figure 9 shows the accumulation of the waste layer at the tip of the movable grate during forward and reverse movement. As the movable grate moves forward, the combustible waste (unburned material) near the tip of the grate burns out and turns into ash (burnt residue). After moving backward for a while, the waste (combustible waste and ash) at the tip of the grate disappears, and air blows through. However, if the reverse movement continues, combustible waste is supplied from the upstream side. Note that the accumulation of the waste layer at the tip of a fixed grate is in the opposite phase to that of a movable grate.

[0013] In such a state, the amount of combustion air discharged from the outlets at the tip of the grate that are exposed from the waste layer and have low pressure loss increases, reducing the amount of air supplied to the waste layer and causing uneven combustion. As a result, low air-ratio combustion is impaired, and efficient heat recovery in the waste heat boiler is hindered.

[0014] In view of the above-mentioned conventional problems, the object of the present invention is to provide a grate and a hearth for a stoker-type incinerator that can efficiently supply combustion air to the material to be incinerated present in the hearth where the grates are arranged, and can suppress wasted air supply. [Means for solving the problem]

[0015] To achieve the above objective, the first characteristic configuration of the grate according to the present invention is a grate that forms the hearth of a stoker-type incinerator, in which the base end is supported and the lower surface of the front end is in contact with the back surface of the grate downstream in the direction of transport of the material to be incinerated, and the lower surface of the front end of the grate upstream in the direction of transport is in contact with the back surface, and the material to be incinerated is received and transported at the back surface by relative movement between the grate upstream or downstream in the direction of transport, wherein combustion air is supplied through a gap formed by the absence of contact between the back surface and the lower part of the front end of the upstream grate that is in contact with the back surface during the relative movement, and the area of ​​the gap is continuously and / or intermittently reduced as the upstream grate moves from the base end to the front end.

[0016] As the tip of the upstream grate moves from the base end to the tip end along the back surface of the adjacent downstream grate, combustion air is discharged from the gap formed between the lower surface of the tip end of the upstream grate and the back surface of the adjacent downstream grate. The area of ​​this gap decreases as the lower surface of the tip end of the upstream grate moves from the base end to the tip end of the adjacent downstream grate, so the amount of combustion air supplied decreases from the base end to the tip end of the adjacent downstream grate. In other words, a sufficient supply of combustion air is secured at the base end where the probability of a waste layer being present is high on the back surfaces of the adjacent grates, while the supply of combustion air is limited at the tip end where the probability of a waste layer being present is low. As a result, combustion air can be efficiently supplied to the material to be incinerated, and wasted supply can be suppressed.

[0017] The second characteristic configuration is that, in addition to the first characteristic configuration described above, a reference surface is formed on the back surface that maintains contact with the lower surface of the upstream grate during relative movement, and one or more recesses that form the gap are continuously formed on the reference surface in a direction along the transport direction, and the recesses include a displacement region in which the position of the gap formation is displaced in the width direction intersecting the transport direction as the relative movement occurs.

[0018] A reference surface formed on the back of the grate comes into contact with the lower surface of the upstream grate, and a gap is formed between the recess formed on the reference surface and the lower surface of the upstream grate. The recess is formed such that the position of the gap shifts in the width direction intersecting the transport direction as the grate moves relative to it, thereby ensuring that combustion air is supplied evenly to the material being incinerated, and effectively suppressing the occurrence of localized abnormal combustion.

[0019] The third characteristic configuration is that, in addition to the second characteristic configuration described above, the width and / or depth of the recess changes continuously and / or intermittently from the base end to the tip end.

[0020] By continuously and / or intermittently changing the width and / or depth of the recess from the base end to the tip end, the area of ​​the gap formed between the recess formed on the reference surface and the lower surface of the upstream grate is continuously and / or intermittently reduced.

[0021] The fourth characteristic configuration is that, in addition to the first characteristic configuration described above, the back surface is formed such that a first region with a convex surface protruding above the reference surface and a second region with a concave surface recessed below the reference surface are formed, switching along the transport direction, and during relative movement, the convex surface in the first region maintains contact with the lower surface of the upstream grate, thereby forming the gap between the reference surface and the lower surface of the upstream grate, and the reference surface in the second region maintains contact with the lower surface of the upstream grate, thereby forming the gap between the concave surface and the lower surface of the upstream grate.

[0022] Since the gap formed between the reference surface and the lower surface of the upstream grate in the first region and the gap formed between the concave surface and the lower surface of the upstream grate in the second region are switched along the conveyance direction, the supply position of combustion air changes accordingly, and the occurrence of local abnormal combustion is effectively suppressed.

[0023] In addition to the fourth characteristic configuration described above, the fifth characteristic configuration is characterized in that in the first region, the width and / or height of the convex surface change continuously and / or intermittently from the base end side to the tip end side, and in the second region, the width and / or depth of the concave surface change continuously and / or intermittently from the base end side to the tip end side.

[0024] By changing the width and / or height of the convex surface from the base end side to the tip end side in the first region, the area of the gap decreases continuously and / or intermittently; and by changing the width and / or depth of the concave surface from the base end side to the tip end side continuously and / or intermittently in the second region, the area of the gap decreases continuously and / or intermittently.

[0025] A characteristic configuration of the furnace hearth of a stoker-type incinerator according to the present invention is that grates having any one of the first to fifth characteristic configurations described above are arranged in the conveyance direction and in a direction intersecting the conveyance direction.

[0026] Combustion air can be uniformly supplied to the material to be incinerated that is incinerated on the furnace hearth, and the unnecessary supply of combustion air in regions where the material to be incinerated becomes thinner due to incineration is suppressed.

Effects of the Invention

[0027] As explained above, according to the present invention, it becomes possible to provide a grate and a furnace hearth of a stoker-type incinerator that can efficiently supply combustion air to the material to be incinerated present on the furnace hearth on which grates are arranged, and can suppress unnecessary supply.

Brief Description of the Drawings

[0028] [Figure 1] Partially cutaway perspective view showing the combustion chamber of a stoker-type waste incinerator. [Figure 2] (a) is a plan view showing the back of the grate, (b) is a bottom view of the grate, (c) is a side view of the base end of the grate, and (d) is a side view of the front end of the grate. [Figure 3] (a) is a front view of the grate, and (b) is a cross-sectional view AA of Figure 2(a). [Figure 4] (a) shows the relative movement of fire grates positioned adjacent to each other front and back, illustrating the state of the furthest distance between them; (b) is an illustration illustrating the state of movement to an intermediate position; and (c) is an illustration illustrating the state of movement to the closest proximity between them. [Figure 5] (a) is an explanatory diagram of two different types of grates, and (b) is an explanatory diagram of a hearth formed using the different types of grates. [Figure 6] (a) to (g) are explanatory diagrams of another embodiment of the grate. [Figure 7] Diagram illustrating another embodiment of the fire grate. [Figure 8] (a) to (g) are diagrams illustrating the changes in the combustion state of the incinerated material due to the relative movement of the grate. [Figure 9] Diagram illustrating the changes in the properties of the incinerated material due to the relative movement of the grate. [Figure 10] (a) and (b) are diagrams illustrating a conventional fire grate. [Modes for carrying out the invention]

[0029] Below, an example of a hearth and grate forming the hearth of a stoker-type incinerator will be described with reference to the drawings.

[0030] Figure 1 shows an example of the furnace chamber of a stoker-type incinerator 100. The furnace chamber is covered with a refractory wall W and has a hearth B which is composed of a stoker mechanism with multiple grates 10. Combustion air supplied from a forced-air blower to a wind box installed below the hearth B is supplied to the waste to be incinerated on the hearth B via the grates 10.

[0031] Each grate 10 consists of a fixed grate group 10A, whose base end is pivotably supported by a cylindrical support rod C1 horizontally mounted on a fixed frame C, and a movable grate group 10B, whose base end is pivotably supported by a cylindrical support rod D1 horizontally mounted on a movable frame D that reciprocates along the waste transport direction relative to the fixed frame C. These two groups are arranged alternately along the waste transport direction. Multiple grate groups 10A and 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 these side plates are pressed from the outside toward the center by springs.

[0032] 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 along the waste transport direction, and the material to be incinerated on the hearth B is agitated and transported downstream.

[0033] A combustion burner is installed in the ceiling of the furnace chamber, and is used to raise the temperature inside the furnace when starting up the furnace. If the calorific value of the waste is low, the heat from the combustion burner stirs and transports the material to be incinerated on the hearth B while it burns.

[0034] In Figure 1, the central hearth B constitutes the main combustion zone where gasification combustion primarily takes place, with separate hearths provided on the upstream and downstream sides. The upstream hearth Bu constitutes the drying zone where the materials to be incinerated are primarily dried, and the downstream hearth Bd constitutes the post-combustion zone where the solid materials after gasification combustion are reduced to ashes. In some cases, the upstream hearth Bu and the central hearth B are integrated into a single unit.

[0035] Figures 2 to 4 show the individual grates 10 that make up each of the hearths Bu, B, and Bd described above. Each grate 10 is made of a roughly rectangular casting with an open bottom, and has left and right side walls 11 and 12, a top wall 13 (in the following description, the top surface of the top wall will also be referred to as the "back surface 13"), and a front end wall 14. Three arc-shaped locking claws 15 are formed on the base end side opposite to the front end wall 14. Three reinforcing ribs 16, which also function as cooling fins, are formed on the inside of the back surface 13.

[0036] The leading edge of the back surface 13 is bent with a predetermined curvature and connects to the front end wall 14, and the lower edge of the front end wall 14 is formed in a straight line. The left and right side walls 11 and 12 that connect to the front end wall 14 are formed as inclined walls, with the lower end of the outer surface slightly inclined inward. A front bottom wall 17 is formed at the leading edge of the bottom, connecting to the lower end of the front end wall 14. The front bottom wall 17 becomes the lower surface that abuts against the back surface 13 of the grate 10 on the downstream side in the direction of transporting the material to be incinerated.

[0037] Figure 1 shows an example in which the surface enclosing the tip of each grate 10 is in a horizontal position. However, the enclosing surface may be configured to be inclined along the direction of transport of the material to be incinerated, for example, it may be configured to be inclined downward along the direction of transport of the material to be incinerated.

[0038] Furthermore, an overhang 18 is formed on the upper edge of the grate 10 of the left and right side walls 11 and 12, with a flat surface of a predetermined width projecting outward in the width direction. In addition, insertion holes H, H for connecting fittings that connect adjacent grates 10 are formed on the left and right side walls 11 and 12, approximately one-third of the way from the front end and base end along the longitudinal direction of the grate 10.

[0039] Bolts and nuts are preferably used as connecting fittings. After inserting the bolts through the insertion holes H of each adjacent grate 10 and tightening them with nuts, the bolts and nuts are welded together while slightly loosened, thereby creating a slight gap between adjacent grates 10. In addition, a predetermined number of adjacent grates in the width direction (3 to 4 in this embodiment) are connected to each other as a unit with bolts and nuts.

[0040] In this way, multiple grates 10 are arranged adjacent to each other in the width direction of the furnace chamber, and each grate 10 is pivotably supported around the support rods C1 and D1 by the locking claws 15 at the base end engaging with the support rod C1 of the fixed frame C or the support rod D1 of the movable frame D (see Figure 1). The grate 10 supported by the support rod C1 becomes the fixed grate, and the grate 10 supported by the support rod D1 becomes the movable grate.

[0041] Figure 4 shows a configuration in which the front end of the grate 10U located on the upstream side of the incinerator, specifically the lower end of the front end wall 14 and the front end bottom wall 17 (shown as a translucent rectangular area enclosed by a dashed line in the figure), are in contact with the back surface 13 of the grate 10D located downstream in the direction of transport of the incinerator. As the grates 10U and 10D move relative to each other, the front end bottom wall 17 of the upstream grate 10U reciprocates along the upper part of the back surface 13 of the downstream grate 10D in the direction of transport of the incinerator.

[0042] As shown in Figures 2(a), 3(a), (b), and 4, a reference surface 13R is formed on the back surface 13 of each grate 10 to maintain contact with the front bottom wall 17 of the upstream grate 10 when the grates 10 move relative to each other. Additionally, a recess 13D is continuously formed in the direction along the transport direction of the material to be incinerated, forming an air intake G which is a gap for supplying combustion air between the front bottom wall 17 of the upstream grate 10 and the reference surface 13R that maintains contact with the front bottom wall 17 of the upstream grate 10.

[0043] The recess 13D is a groove structure formed on a flat surface that is recessed from the reference surface 13R, and on an inclined surface where the depth of the recess gradually decreases from the base end to the tip end, and includes a displacement region 13A in which the formation position of the air intake port G is continuously displaced in the width direction intersecting the transport direction as the grate 10 moves relative to it.

[0044] This will be explained in detail based on Figure 4. The left side of Figure 4(a) shows that the front bottom wall 17 (indicated by the dashed line labeled 17), which is the lower surface of the upstream grate 10U, is located at the base end of the downstream grate 10D. The left side of Figure 4(b) shows that the front bottom wall 17 is located in the central part of the downstream grate 10D. The left side of Figure 4(c) shows that the front bottom wall 17 is located at the tip end of the downstream grate 10D. The positions of the corresponding air intakes G are shown in the right side of the diagram.

[0045] In this embodiment, the displacement region 13A is formed in the longitudinal center of the grate 10, and the recess 13D is formed on both sides in the width direction on the base end side of the grate 10, flanking the displacement region 13A, and is also formed in the width direction in the center on the front end side of the grate 10, and is continuously formed in a direction along the conveying direction of the material to be incinerated.

[0046] In the right-hand diagram of Figure 4(a), the air intake G formed on the base side of the displacement region 13A of the grate 10U is shown by a thick line. In the right-hand diagram of Figure 4(b), the air intake G formed in the displacement region 13A of the grate 10U is shown by a thick line. In the right-hand diagram of Figure 4(c), the air intake G formed on the tip side of the displacement region 13A of the grate 10U is shown by a thick line. The total length in the width direction of each thick line is constant, but the length in the height direction is longer at the base side and shorter at the tip side. In other words, the recess 13D is formed such that the opening area of ​​the air intake G formed as the grate 10 moves decreases from the base side to the tip side.

[0047] As the two grates 10 move relative to each other, the front bottom wall 17, which is the lower surface of the leading edge of the upstream grate, passes through the displacement region 13A, causing the formation position of the air intake G to continuously displace in the width direction intersecting the transport direction. Consequently, combustion air is supplied evenly from the air intake G to the material to be incinerated as a whole, effectively suppressing the occurrence of localized abnormal combustion.

[0048] Furthermore, as the upstream grate 10U moves from the base end to the tip end, the area of ​​the gap that becomes the air intake G continuously decreases, so the amount of combustion air supplied decreases from the base end to the tip end of the adjacent downstream grate 10D.

[0049] In other words, downstream of the combustion zone, where the thickness of the waste layer tends to decrease, the supply of combustion air can be secured at the base end where the probability of the waste layer being present is relatively high, behind the adjacent grates 10U and 10D, while the supply of combustion air is limited at the tip end where the probability of the waste layer being present is relatively low. As a result, combustion air can be efficiently supplied to the material to be incinerated, and wasted supply can be suppressed.

[0050] Furthermore, the area of ​​the gap that forms the air intake G may be configured to decrease intermittently as the upstream grate moves from the base end to the tip end, and for this purpose, the width and / or depth of the recess 13D may be configured to change continuously and / or intermittently from the base end to the tip end.

[0051] In other words, the grate 10 is configured such that combustion air is supplied through a gap formed when the back surface does not come into contact with the lower part of the tip of the upstream grate that abuts the back surface during relative movement, and the area of ​​the gap is continuously and / or intermittently reduced as the upstream grate moves from the base end to the tip end.

[0052] Figure 5(a) shows a pair of grates 10 in which the shapes of the reference surface 13R and recess 13D formed on the back surface 13 of the grate 10 are inverted and symmetrical. As shown in Figure 5(b), the pair of grates 10 may be arranged alternately along the direction of transport of the material to be incinerated so that combustion air can be supplied uniformly to the material to be incinerated as a whole hearth.

[0053] Figures 6(a) to 6(g) show the plan view patterns of the recesses 13D formed in the grate described above. Each of these comprises one or more recesses 13D formed such that the depth of the recesses 13D becomes continuously or gradually shallower from the base end to the tip end of the grate, or the width of the recesses 13D becomes continuously or gradually narrower from the base end to the tip end of the grate.

[0054] Each of the grates in Figures 6(b) to 6(g) may be configured as a pair of grates 10 with the shapes of the reference surface 13R and recess 13D reversed and symmetrical, similar to the embodiment described in Figures 5(a) and (b). By arranging the pair of grates 10 alternately along the direction of transport of the material to be incinerated, combustion air can be supplied uniformly to the material to be incinerated as a whole hearth.

[0055] Figures 7(a) and 7(b) show yet another embodiment. The back surface 13 of the grate 10 is formed such that it switches along the transport direction between a first region in which a convex surface 13H protruding above the reference surface 13R is formed and a second region in which a concave surface 13L recessed below the reference surface 13R is formed.

[0056] During the relative movement of the grate 10, in the first region, the convex surface 13H maintains contact with the front bottom wall 17, which is the lower surface of the upstream grate 10U, thereby forming an air intake opening that forms a gap between the reference surface 13R and the front bottom wall 17, which is the lower front of the upstream grate 10U. In the second region, the reference surface 13R maintains contact with the front bottom wall 17, which is the lower surface of the upstream grate 10U, thereby forming an air intake opening that forms a gap between the concave surface 13L and the front bottom wall 17, which is the lower surface of the upstream grate 10U.

[0057] In the first region, the gap formed between the reference surface and the lower surface of the upstream grate, and in the second region, the gap formed between the concave surface and the lower surface of the upstream grate, switch along the transport direction. Consequently, the supply point of combustion air changes, and the occurrence of localized abnormal combustion is effectively suppressed.

[0058] Furthermore, the width and / or height of the convex surface 13H in the first region changes continuously and / or intermittently from the base end to the tip end, and the width and / or depth of the concave surface 13L in the second region changes continuously and / or intermittently from the base end to the tip end, thereby causing the area of ​​the gap to decrease continuously and / or intermittently.

[0059] The grates described above are all air-cooled grates that use heat dissipation fins for cooling, but it goes without saying that the present invention can also be applied to water-cooled grates that have cooling water passages formed inside.

[0060] It should be noted that the embodiments described above are merely examples of the present invention, and it goes without saying that the specific structure, shape, material, size, etc. of each part can be appropriately modified and designed within the scope of achieving the effects of the present invention. [Explanation of symbols]

[0061] 10: Fire grates 10A: Fixed grate group 10B: Movable grate group 10U: Upstream grate 10D: Downstream grate 11,12: Side wall 13: Rear (upper wall) 13D: Recessed 13R: Reference surface 13A: Displacement region 14: Front end wall 16: Reinforcement Ribs 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 (gap) H: Insertion hole

Claims

1. A grate that forms the hearth of a stoker-type incinerator, wherein the base end is supported, the lower surface of the tip end abuts against the back surface of the grate downstream in the direction of transport of the material to be incinerated, and the lower surface of the tip end of the grate upstream in the direction of transport abuts against the back surface, and the material to be incinerated is received and transported at the back surface by relative movement between the grate upstream or downstream in the direction of transport, The system is configured such that combustion air is supplied through a gap formed when the rear surface and the lower part of the tip of the upstream grate that abuts the rear surface do not come into contact during the relative movement. A grate configured such that the area of ​​the gap decreases continuously and / or intermittently as the upstream grate moves relative to the upstream grate from the base end to the tip end.

2. A reference surface is formed on the back surface to maintain contact with the lower surface of the upstream grate during relative movement, and one or more recesses forming the gap are continuously formed on the reference surface in a direction along the transport direction. The grate according to claim 1, wherein the recess includes a displacement region in which the position of the gap formation is displaced in the width direction intersecting the transport direction as a result of the relative movement.

3. The grate according to claim 2, wherein the width and / or depth of the recess changes continuously and / or intermittently from the base end to the tip end.

4. On the back surface, a first region is formed in which a convex surface protruding above the reference surface, and a second region is formed in which a concave surface recessed below the reference surface, and these regions are formed so as to switch along the transport direction. The grate according to claim 1, wherein, during the relative movement, the convex surface maintains contact with the lower surface of the upstream grate in the first region, thereby forming the gap between the reference surface and the lower surface of the upstream grate, and the reference surface maintains contact with the lower surface of the upstream grate in the second region, thereby forming the gap between the concave surface and the lower surface of the upstream grate.

5. The grate according to claim 4, wherein in the first region, the width and / or height of the convex surface changes from the base end to the tip end, and in the second region, the width and / or depth of the concave surface changes continuously and / or intermittently from the base end to the tip end.

6. A hearth for a stoker-type incinerator, wherein the grates according to any one of claims 1 to 5 are arranged in the conveying direction and in a direction intersecting the conveying direction.

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