JP7743157B2 - grate - Google Patents

Description

The present invention relates to a grate that forms the hearth of a stoker-type incinerator.

Patent Document 1 proposes a grate that forms the hearth of a stoker-type incinerator, with the base end supported and the lower part of the tip end abutting 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 abutting 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.

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 tip of the upstream grate that abuts against the back surface, and the position of the gap changes due to the relative movement.

Specifically, an area made up of convex and/or concave surfaces is formed on the back surface across the conveying direction, and the formation positions of the convex and/or concave surfaces in a direction intersecting the conveying direction are formed so as to vary along the conveying direction, and the area includes a first area made up of a reference surface and a convex surface that protrudes above the reference surface, and a second area made up of a concave surface that is recessed below the reference surface, and the first area and the second area are formed so as to switch along the conveying direction.

Patent No. 6550331

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 direction of transport of the incinerated material abutting against the reference surface on its back surface, 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 abutting against a convex surface that is higher than the reference surface, the inclination angle of the tip of the upstream grate relative to the support position on the base end is larger than when it abuts against the reference surface.

As a result, the heat dissipation fins formed on the inside of the grate abut against the convex surface, causing the lower part of the upstream grate's tip to rise above the convex surface, causing combustion air to leak out from the entire width of the upstream grate's tip, resulting in a problem where the intended purpose of dispersing combustion air to the material being incinerated and suppressing the occurrence of localized abnormal combustion could not be achieved.

Furthermore, there was also the problem that contact between the heat dissipation fins and the convex surfaces would leave streaky wear marks on the convex surfaces, shortening the lifespan of the grate.

In view of the above-mentioned problems with the conventional method, the object of the present invention is to provide a grate that allows combustion air to be evenly supplied to the material being incinerated from a fire bed on which the grates are arranged, thereby preventing the occurrence of localized abnormal combustion.

To achieve the above-mentioned 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, with its base end supported and its tip end underside abutting the back surface of the downstream grate in the transport direction of the materials to be incinerated, and is positioned so that the back surface abuts the underside of the tip end of the upstream grate in the transport direction, and that receives and transports the materials to be incinerated on its back surface by relative movement with the upstream or downstream grate in the transport direction. 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 are formed in the reference surface in a continuous direction along the transport direction to form air intakes that supply combustion air between the reference surface and the underside of the upstream grate, and the recesses include a displacement region where the position of the air intakes displaces in the width direction intersecting the transport direction as a result of the relative movement.

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 constantly abutting a reference surface formed on the back of the grates. In this state, combustion air is supplied through an air intake 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 the displacement area as the two grates move relative to each other, the air intake continuously displaces in the width direction, which intersects with the transport direction. As a result, the position of the combustion air intake changes in the width direction, allowing combustion air to be supplied evenly to the material to be incinerated and effectively suppressing the occurrence of localized abnormal combustion.

The second characteristic configuration has the same features as the first characteristic configuration described above, in that 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.

The third characteristic configuration has the same features as the first characteristic configuration described above, in that the recesses are formed in the center in the width direction on the base end side, sandwiching the displacement region, and on both sides in the width direction on the tip end side.

The fourth characteristic feature of the grate is that it forms the hearth of a stoker-type incinerator, with its base end supported and its tip end underside abutting the back surface of the downstream grate in the transport direction of the materials to be incinerated, and the tip end underside of the upstream grate in the transport direction abutting against its back surface. The grate receives and transports materials to be incinerated on its back surface by relative movement with the upstream or downstream grate in the transport direction. A reference surface is formed on the back surface, maintaining a state of abutment with the underside of the upstream grate during the relative movement. Recesses are formed in the reference surface so as to overlap in the direction along the transport direction, forming air intakes for supplying combustion air between the underside of the upstream grate and the reference surface. The recesses include displacement regions in which the positions of the air intakes are discontinuously displaced in the width direction intersecting the transport direction as a result of the relative movement. The underside of the upstream grate is formed 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.

Similar to the first characteristic configuration, 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 constantly abutting a reference surface formed on the back of the grates. In this state, combustion air is supplied through an air intake 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 direction of transport. As the underside of the tip of the upstream grate passes through a displacement region as the two grates move relative to each other, the air intake displaces discontinuously in the width direction, which intersects with the transport direction. As a result, the position of the combustion air intake 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.

Furthermore, if the length of the displacement area of the recess along the transport direction is set longer than a predetermined length when the underside of the upstream grate moves relative to the back of the grate, 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.

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

The position of the air intake can be switched between the upstream and downstream sides, sandwiched between a displacement area formed in the center of the grate's movement width.

As explained above, the present invention provides a grate that allows combustion air to be evenly supplied to the material being incinerated from a fire bed on which grates are arranged, thereby preventing the occurrence of localized abnormal combustion.

A partially cutaway perspective view showing the combustion chamber of a stoker-type waste incinerator (a) is a perspective view of the back of the grate, and (b) is a perspective view of the bottom of the grate. (a) is a front view of the fire grate, (b) is a plan view of the same, and (c) is a bottom view of the same. (a) is a right side view of the grate, and (b) is a left side view of the same. (a) shows the relative movement of adjacently arranged fire grates in the front and rear, and is an explanatory diagram of the most separated state, (b) is an explanatory diagram of the state moved to an intermediate position, and (c) is an explanatory diagram of the most adjacent state. 1A 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 FIG. 1B is a plan view showing a part of the grates arranged in parallel in the furnace width direction. 1A to 1D are explanatory views showing various modes of recesses formed with respect to a reference surface; FIG. 1A is an explanatory diagram of a mode in which it is difficult to supply combustion air from an air intake port formed between the front end bottom wall of the upstream grate that slides on the back surface of the grate and a recess formed on the back surface; FIG. 1B is an explanatory diagram of a mode in which combustion air can be supplied from an air intake port formed between the front end bottom wall of the upstream grate that slides on the back surface of the grate and a recess formed on the back surface.

Below, an example of a grate according to the present invention that forms the hearth of a stoker-type incinerator is described with reference to the drawings.

Figure 1 shows an example of the 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 on it. Combustion air is supplied from a forced draft fan to a wind box installed below the hearth B, and is supplied to the waste to be incinerated on the hearth B via the fire grates 10.

Each grate 10 is arranged alternately along the waste transport direction, with fixed grate groups 10A having their base ends swingably supported by cylindrical support rods C1 suspended horizontally from a fixed frame C, and movable grate groups 10B having their base ends swingably supported by cylindrical support rods D1 suspended horizontally from a movable frame D that moves back and forth along the waste transport direction 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.

The hydraulic mechanism E reciprocates the movable frame D, causing the movable grate group 10B and the fixed grate group 10A to move relative to each other in the direction of waste transport, stirring up the material to be incinerated on the hearth B and transporting it downstream.

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.

In Figure 1, the central hearth B forms the main combustion zone where gasification combustion is mainly performed, with separate hearths provided on the upstream and downstream sides. The upstream hearth Bu forms the drying zone where materials to be incinerated are mainly dried, and the downstream hearth Bd forms the 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 configured as a single unit.

As shown in Figures 2 to 4, each of the grates 10 that make up each of the hearths Bu, B, and Bd described above is made of casting material in a roughly rectangular parallelepiped shape 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 surface 13"), and a front end wall 14. Three arc-shaped locking claws 15 are formed on the base end opposite the front end wall 14. Three reinforcing ribs 16 that also function as cooling fins are formed on the inside of the back surface 13.

The tip of the back surface 13 bends at a predetermined curvature and connects to the front end wall 14, the lower edge of which is straight. The left and right side walls 11, 12 that connect to the front end wall 14 are formed as inclined walls with a slight inward slope at their lower ends. A front end bottom wall 17 that connects to the lower end of the front end wall 14 is formed at the tip of the bottom (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 material to be incinerated.

Figure 1 shows an example in which the surface enveloping the tip of each grate 10 is horizontal, but the enveloping surface may also 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.

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 of the left and right side walls 11, 12 at the tip and base ends, excluding the longitudinal center of the grate 10. Furthermore, insertion holes H, H for connecting fittings that connect adjacent grates 10 are formed on the left and right side walls 11, 12 at locations approximately one-third of the way from the tip and base ends along the longitudinal direction of the grate 10.

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

In this way, multiple grates 10 are arranged adjacent to each other across the width of the furnace chamber, and the base-end locking claws 15 swingably engage with the support rod C1 of the fixed frame C or the support rod D1 of the movable frame D (see Figure 1), allowing each grate 10 to swing freely around the support rods C1 and 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.

As shown in Figures 5(a) to (c), the front end of the grate 10U located upstream in the direction of transport of the incineration material, i.e., the lower end of the front end wall 14 and the front end bottom wall 17, are positioned so as to abut against the back surface 13 of the grate 10D located downstream 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 top 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.

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 contact with the front end bottom wall 17 of the upstream grate 10 when the grates 10 move relative to each other. A recess 13D is also formed in the direction along the transport direction of the material to be incinerated, forming 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.

The recess 13D has a groove structure with a flat surface recessed several millimeters below the reference surface 13R, and includes a displacement region 13A in which the position of the air intake port G continuously shifts in the width direction, which intersects with the conveying direction, as the grate 10 moves relative to the surface.

As the two grates 10 move relative to each other, the front end bottom wall 17, which is the underside of the tip of the upstream grate, passes through the displacement region 13A, causing the position of the air intake port G to continuously shift in the width direction, which intersects with the conveying direction. As a result, combustion air is supplied evenly from the air intake port G to the material being incinerated overall, effectively suppressing the occurrence of localized abnormal combustion.

As shown in detail in Figure 6(a), the upper left diagram shows the front end bottom wall 17 (indicated by the dashed line with the reference symbol 17) on the underside of the upstream grate 10U positioned near 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 near 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.

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 transport direction (the position shown in Figure 3(b)), and the recesses 13D are formed on both sides of the base end of the grate 10 in the width direction across the displacement region 13A, and also formed in the center of the tip end of the grate 10 in the width direction, and are formed continuously in the direction along the transport direction of the material to be incinerated.

The recess 13D is preferably formed with a cross-sectional shape that ensures that the opening area of the air intake G, which is formed as the grate 10 moves relative to the intake port, is always constant along the width direction, as this ensures a constant supply of combustion air from the air intake port G.

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 long, narrow gap A in the area where no protruding portion 18 is formed. Combustion air is also supplied from this gap A. When the upstream fire grate 10 slides toward the tip and covers the gap A with the upstream fire grate 10, it is cooled by the combustion air from the wind box, thereby reducing the degree of wear caused by the high-temperature combustion heat.

Even if foreign matter such as ash gets in through the gaps between adjacent grates 10 or through gap A during the incineration process as the grates 10 move relative to one another, the lower ends of the left and right side walls 11, 12 are formed as slightly inward-sloping walls, allowing the foreign matter to quickly fall downward. This minimizes the risk of the conveying surface becoming uneven due to the positional fluctuations of the grates 10 caused by foreign matter getting caught in the gaps between adjacent grates 10.

Figures 7(a) to (d) show various shapes that can be used for the reference surface 13R and the recess 13D formed in the reference surface 13R. Figure 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 in the center in the width direction on the tip end side.

Figure 7(a) shows an example in which a reference surface 13R is formed on the back surface 13 of the grate, which maintains contact with the underside of the upstream grate during relative movement, and recesses 13D are formed continuously in the conveying direction on the reference surface 13R, forming air intake ports G that supply combustion air between the underside of the upstream grate. In the following examples, similarly, the displacement region 13A does not need to be formed in the longitudinal center of the grate 10; it may be shaped so 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 other grates, allowing combustion air to be supplied evenly to the material being incinerated overall.

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 inlet G formed between the recess 13D and the front end bottom wall 17, which is the underside of the upstream grate 10U.

As shown in Figure 7(b), recesses 13D may be 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 a recess 13D may also be formed in the widthwise center of the displacement region 13A.

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

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 sandwiching the reference surface 13R.

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

As shown in Figure 8(a), if the recess 13D that forms the air intake port G between the front end bottom wall 17 of the upstream grate 10D is formed intermittently in the conveying direction, and the length L1 of the front end bottom wall 17 of the upstream grate 10 in 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 port G changes along the conveying direction, the recess 13D that serves as the passage for combustion air is closed by the front end bottom wall 17, and there will be times when combustion air cannot be supplied above the stoker.

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 that is longer than the predetermined 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, ensuring that combustion air can always be reliably supplied to the material to be incinerated.

The embodiment described above is merely one example of the present invention, and it is sufficient that a reference surface is formed that maintains contact with the underside of the upstream grate at least during relative movement, and that 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 that the recess is configured to include a displacement region where the position of the air intake port gradually displaces in the width direction intersecting the conveying direction as the relative movement occurs.

It goes without saying that the above-described embodiment is merely one example of the present invention, and the specific structure, shape, materials, size, etc. of each part can be modified as appropriate within the scope of the effects of the present invention.

10: Grate 10A: Fixed grate group 10B: Movable grate group 10U: Upstream grate 10D: Downstream grate 11, 12: Side wall 13: Back side (upper wall)
13D: Recess 13R: Reference flat surface 13A: Displacement region 14: Front end wall 16: Reinforcement rib 17: Front end bottom wall (lower 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 intake port H: Insertion hole

Claims (5)

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. A fire grate as described in 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. A fire grate as described in claim 1, wherein the recesses are formed in the center of the width direction on the base end side, sandwiching the displacement region, and on both sides of the width direction on the tip end side. 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. 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.