TW202035920A - Overfire air port and combustion device equipped with same - Google Patents

Abstract

Provided are an overfire air port that with only partial modification enables the supply of highly straight jets and horizontally spread out jets into a furnace and a combustion device equipped with the overfire air port. An overfire air port (3, 3A) comprises: a straight flow path (31) that is formed concentrically in a multi-tube structure and ejects primary air for two-stage combustion into a furnace (11) in a straight flow (ST); and a swirling flow path (32, 33, 34) that is provided on the outer periphery of the straight flow path (31) and ejects secondary air for two-stage combustion into the furnace (11) in a swirling flow (SW). Provided at the jet outlet (32A, 33A, 34A) of the swirling flow path (32, 33, 34) are: a pair of swirling stop members (41A, 41B) that are arranged so as to sandwich the straight flow path (31) in the vertical direction and block the swirling flow (SW) to change the flow to the straight direction; and a pair of guide vanes (42A, 42B) that are arranged so as to sandwich the straight flow path (31) in the horizontal direction and deflect the swirling flow (SW) to both outer sides in the horizontal direction.

Description

Rear vent hole and combustion device provided with the same

The present invention relates to a rear vent hole and a combustion device provided with the same.

It is known that there is a so-called two-stage combustion method in which fuel is burned in a combustor in a state of insufficient air, and residual air necessary for complete combustion is supplied from a rear vent hole.

In the combustion device of the two-stage combustion method, the flow rate distribution of the combustion gas (including the unburned part) that rises to the installation area of the rear vent will be affected by the arrangement of the burner or the method of supplying fuel and air from the burner. Variety. In order to suppress the remaining combustible parts such as unburned carbon or carbon monoxide (CO) at the outlet of the burner, it is important to appropriately supply the second stage combustion air in accordance with the flow distribution of the combustion gas rising to the installation area of the rear vent of.

For example, the pulverized coal-burning boiler disclosed in Patent Document 1 uses a structure of multiple circular pipes formed on concentric shafts. A straight flow is ejected from the circular pipe at the center, and a swirling flow is ejected from the outer periphery through a baffle. The composite back vent hole promotes the mixing with the combustion gas by the swirling flow, and prevents the combustion gas from the burner side in the central area of the combustion furnace from penetrating by the direct flow.

However, this composite type rear vent may not be able to sufficiently ensure the straightness of the jet flow to the central area of the combustion furnace. In this case, the combustion gas rising from the burner side may be pushed up, causing the combustion gas and air Insufficient mixing. In addition, it is difficult to supply air to the gap between the adjacent rear vent holes, and penetration of the combustion gas rising from the burner side is likely to occur.

Therefore, the rear vents disclosed in Patent Document 2 and Patent Document 3 are configured to divide the ejection port in the horizontal direction, and eject a straight flow from the ejection port formed in the central part that is elongated in the vertical direction, from the left and right outer sides in the horizontal direction. Through the guide vane, the ejection port ejects the horizontal diffusion flow that spreads in the horizontal direction. Thereby, a jet stream with high straightness is ejected, and sufficient air is supplied to the gap between the adjacent rear vent holes. [Prior Technical Literature] [Patent Literature]

[Patent Document 1] International Publication No. 2007/080873 [Patent Document 2] Japanese Patent No. 6025983 [Patent Document 3] International Publication No. 2017/126240

[The problem to be solved by the invention]

However, replacing the composite type rear vent hole installed in the existing boiler with the rear vent hole of the structure disclosed in Patent Document 2 and Patent Document 3 would be a large-scale renovation project and the cost would be high.

Therefore, the object of the present invention is to provide a back vent hole and a combustion device provided with the same, which can supply a highly straight jet stream and a jet stream that spreads in a horizontal direction into a combustion furnace with a partial modification. [Technical means to solve the problem]

In order to achieve the above-mentioned object, the representative invention of the present invention is a rear vent hole formed in a concentric multi-tube structure and provided with a straight flow path for ejecting primary air for two-stage combustion into the combustion furnace in a straight flow , The swirling flow path that is provided on the outer periphery of the straight-in flow path and sprays the secondary air for second-stage combustion into the combustion furnace in a swirling flow, characterized in that the outlet of the swirling flow path is provided with: A pair of anti-rotation members that are arranged to sandwich the straight flow path in the vertical direction and block the swirling flow to change to the straight direction, are arranged to sandwich the straight flow path in the horizontal direction, and the swirling flow is arranged on both outer sides of the horizontal direction A pair of deviated guide vanes. [Effects of Invention]

According to the present invention, it is possible to supply a jet stream with high straightness and a jet stream that spreads in a horizontal direction into the combustion furnace with only partial modification. In addition, the problems, structures, and effects other than the above are clarified from the description of the following embodiments.

Hereinafter, the structure of the vent hole and the combustion device equipped with it after each embodiment of the present invention will be described with reference to FIGS. 1 to 8.

<The overall structure of the combustion device 10> First, the overall structure of the combustion device 10 will be described with reference to FIG. 1.

Fig. 1 is a schematic perspective view showing a configuration example of a combustion device 10 (a part of a boiler 100) of each embodiment.

The combustion device 10 is installed in a boiler 100 that burns pulverized coal used in a thermal power plant or the like. The boiler 100 burns pulverized coal produced from coal such as bituminous coal or sub-bituminous coal as a solid fuel, and recovers the heat generated by the combustion.

The combustion furnace 11 of the boiler 100 is installed in a vertical direction with respect to the ground, and has a housing structure surrounded by a water-cooled wall composed of water-cooled pipes. Inside the combustion furnace 11, there is formed a combustion space for fuel, that is, pulverized coal combustion. The combustion gas generated in the combustion space flows from the lower side to the upper side of the combustion furnace 11 in the vertical direction as shown by the thick arrow in FIG. 1.

In the combustion furnace 11, the lower side in the vertical direction is the "upstream side" of the flow of combustion gas, and the upper side in the vertical direction is the "downstream side" of the flow of combustion gas. Therefore, the outlet of the combustion furnace 11 is located on the downstream side of the flow of the combustion gas, that is, on the upper side in the vertical direction.

The upper part (outlet) of the combustion furnace 11 is connected to the flue 12 extending in a staggered (orthogonal) direction to the combustion furnace 11. The heat generated by the combustion in the combustion furnace 11 is mainly the heat transfer caused by the radiation to the water wall to heat and evaporate the water flowing in the water cooling tube. Then, the generated water vapor is superheated by the heat exchange of a heat exchanger (not shown) such as a superheater or a reheater installed inside the flue 12, and is sent to a turbine for power generation. The combustion gas discharged from the boiler 100 passes through a denitration device, an air preheater, etc. (not shown), and then is discharged to the outside as processed exhaust gas.

In addition, in FIG. 1, the direction in which the flue 12 extends is referred to as the "depth direction", the combustion furnace 11 side in the depth direction is referred to as the "front side", and the opposite side is referred to as the "rear side". In addition, the direction intersecting (orthogonal) with the vertical direction and the depth direction is referred to as the "width direction".

The combustion device 10 adopts a two-stage combustion method that divides the combustion air used to burn pulverized coal into two stages and supplies it to the combustion furnace 11, and includes: a plurality of units that burn the pulverized coal with an air volume below the theoretical air volume Burner 2, plural rear vent holes 3 for supplying insufficient air.

In this embodiment, the boiler 100 is a counter-fired boiler, and the plurality of burners 2 and the plurality of rear vent holes 3 are divided into the front wall 110A and the rear wall 110B of the combustion furnace 11 which are arranged facing each other in the depth direction. .

Specifically, 12 burners 2 and 4 rear vent holes 3 are provided on the front wall 110A and the rear wall 110B, respectively. The 12 burners 2 on the side of the front wall 110A and the burners 2 on the side of the rear wall 110B are arranged at positions facing each other, and each has the same structure. Similarly, the four rear vent holes 3 on the side of the front wall 110A and the four rear vent holes 3 on the side of the rear wall 110B are arranged at positions facing each other, and each has the same structure. Here, the structure of 12 burners 2 and 4 rear vent holes 3 on the side of the front wall 110A will be described as an example.

The 12 burners 2 are divided into 3 sections in the vertical direction, and 4 in each section are arranged side by side along the width direction. The four rear vent holes 3 are arranged on the upper side in the vertical direction than the 12 burners 2 and lower than the exit position of the combustion furnace 11 in the width direction. In addition, the arrangement of the plurality of burners 2 and the plurality of rear vent holes 3 on the wall surface of the combustion furnace 11 or the number in the vertical direction and the number in the width direction are not necessarily limited to examples. Hereinafter, the specific structure of the rear vent 3 will be described according to the embodiment.

<The first embodiment> The structure of the rear vent hole 3 of the first embodiment of the present invention will be described with reference to FIGS. 2 to 5.

FIG. 2 is a front view of the vent hole 3 after the first embodiment viewed from the combustion furnace 11 side. Fig. 3 is a cross-sectional view taken along line A-A in Fig. 2. Fig. 4 is a cross-sectional view taken along the line B-B in Fig. 2. Fig. 5 is a schematic view of the rotation stop member 41A viewed from the vertical direction.

The rear vent hole 3 is formed in a concentric multi-tube structure with a circular cross-section and is provided with a straight flow path 31 for ejecting primary air for the second stage combustion into the combustion furnace 11 in a straight flow ST, and is provided in the straight flow path The secondary air for the second stage combustion is ejected to the swirling flow path 32 in the combustion furnace 11 in the swirling flow SW on the outer periphery of 31. In addition, in FIGS. 3 and 4, the central axis C of the rear vent hole 3 is represented by a dotted chain line.

In the present embodiment, the rear vent hole 3 has a double pipe structure formed by two pipes of the first pipe 301 and the second pipe 302. The first pipe 301 is arranged inside the second pipe 302 (that is, the second pipe 302 is arranged outside the first pipe 301), so the first pipe 301 corresponds to the inner pipe, and the second pipe 302 corresponds to the outer pipe.

Then, a straight flow path 31 is formed inside the first pipe 301, and a swirling flow path 32 is formed between the first pipe 301 and the second pipe 302. In addition, the discharge port 32A of the swirling flow path 32 is provided with a pair of rotation stop members 41A, 41B, which block the swirling flow SW adjusted by the stopper 40 and change it to a straight direction; and a pair of guides The blades 42A and 42B deflect the swirling flow SW toward both outer sides in the horizontal direction (the width direction of the combustion furnace 11).

As shown in FIGS. 2 and 3, the pair of rotation stop members 41A and 41B are arranged to sandwich the first pipe 301, that is, the straight flow path 31, in the vertical direction. The swirling flow SW swirling in the swirling flow path 32 with the center axis C as the center will collide with the pair of rotation stop members 41A and 41B at two positions in the vertical direction of the nozzle 32A, respectively, and be ejected straight to the combustion furnace 11 Inside. Therefore, in addition to the straight flow ST flowing in the straight flow path 31, the jet flowing straight in the combustion furnace 11 will also be added with the jet flow jetted from the vertical direction of the straight flow path 31 up and down, that is, the swirling flow SW. The swirling jet is blocked by a pair of rotation stopping members 41A, 41B (indicated by hollow arrows in FIG. 3). Thereby, it is possible to improve the straightness of the air (jet flow) ejected from the rear vent hole 3 into the central area of the combustion furnace 11.

The pair of rotation stop members 41A, 41B each include: a pair of vertical plates 411A, 411B erected at a predetermined interval along the outer peripheral surface of the first pipe 301; and a pair of vertical plates 411A, 411B to connect between的横板412. The pair of vertical plates 411A, 411B and the horizontal plate 412 are all formed of rectangular plate-shaped members having long sides in the axial direction of the first pipe 301 (the direction along the central axis C) as shown in FIG. 5. In addition, since the pair of rotation stop members 41A and 41B have the same structure, FIG. 5 shows an example of the rotation stop member 41A arranged on the upper side in the vertical direction among the pair of rotation stop members 41A and 41B.

As mentioned above, the pair of vertical plates 411A and 411B are erected with their long sides along the central axis C. Therefore, the collision area of the swirling flow SW is large, and the swirling flow SW caused by the pair of rotation stop members 41A and 41B is blocked. Strength will increase.

In the present embodiment, as shown in FIG. 2, the pair of rotation stop members 41A, 41B are fixed to the first pipe 301 by welding a pair of vertical plates 411A, 411B to the outer peripheral surface of the first pipe 301, respectively. In addition, a gap is formed between the second pipe 302 and the second pipe 302. The second pipe 302 is relatively close to the cold water pipe compared to the first pipe 301 and is prone to thermal expansion. Therefore, the pair of rotation stop members 41A and 41B should not be fixed to both the first pipe 301 and the second pipe 302.

Furthermore, in order to fix the pair of rotation stop members 41A, 41B more firmly, it is better to fix the pair of rotation stop members 41A, 41B to the first pipe 301 than the second pipe 302, but it is only necessary to fix it to at least the first pipe. Either one of 301 and second pipe 302 may be used.

Also, as described above, each of the pair of rotation stop members 41A, 41B has only one end in the short side direction of the pair of vertical plates 411A, 411B in a fixed state. Therefore, in order to ensure a stable fixed state, the pair of vertical plates The 411A and 411B are connected by a horizontal plate 412 for reinforcement.

As shown in FIGS. 2 and 4, the pair of guide vanes 42A and 42B are arranged in the horizontal direction with the first pipe 301, that is, the straight flow path 31 interposed therebetween. As shown in FIG. 4, a pair of guide vanes 42A and 42B are each provided with two vanes 421 and 422. The two vanes 421 and 422 are each inclined at the front end on the side of the burner 11 with respect to the central axis C so as to face the outside in the horizontal direction.

As a result, the swirling flow SW flowing in the swirling flow path 32 is deflected to the outside of the horizontal direction by the two vanes 421, 422 at the left and right positions of the discharge port 32A in the horizontal direction, and is ejected into the combustion furnace 11 ( It is indicated by a hollow arrow in Figure 4). As a result, the air ejected from the predetermined rear vent hole 3 also diffuses to the side of the adjacent rear vent hole 3, so the air is supplied to the gap between the adjacent rear vent holes 3, and the rise from the burner 2 side can be suppressed The penetration of combustion gases.

In addition, the inclination angles of the two vanes 421 and 422 with respect to the central axis C can be set appropriately, and can be freely adjusted according to the combustion condition of the fuel in the combustion furnace 11 or the specifications of the combustion device 10.

As described above, even for the multi-tube structure formed in a circular cross-section on a concentric axis, and the straight flow ST and the swirling flow SW are ejected into the combustion furnace 11, only a pair of anti-rotation members The modification of the part where 41A, 41B and a pair of guide vanes 42A, 42B are provided at the nozzle 32A of the swirling flow path 32 can supply the jet stream with high straightness and the jet stream that spreads in the horizontal direction into the combustion furnace 11.

(Modification) Next, a modification of the pair of rotation stop members 41A, 41B will be described with reference to FIGS. 6A to 6C.

6A to C show the structure of the rotation stop member 41A of each modification of the present invention. FIG. 6A is a front view of the rotation stop member 41A of Modification 1 viewed from the combustion furnace 11 side, and FIG. 6B is viewed from the combustion furnace 11 side The front view of the rotation stop member 41A of the modification 2, and FIG. 6C is a schematic view of the rotation stop member 41A of the modification 3 viewed from a vertical direction.

As shown in FIG. 6A, the rotation stop member 41A of Modification 1 includes three first to third vertical plates 411A, 411B, and 411C that are erected along the outer peripheral surface of the first pipe 301 at predetermined intervals; A pair of upper and lower horizontal plates 412A, 412B connecting the adjacent first vertical plate 411A and the second vertical plate 411B; and connecting the adjacent second vertical plate 411B and the third vertical plate 411C A pair of upper and lower horizontal plates 412C, 412D.

As described above, with regard to the structure of the rotation stopping member 41A of the first embodiment, the number of vertical and horizontal plates is increased, thereby increasing the force to block the rotation of the swirling flow SW and improving the stability of the rotation stopping member 41A.

As shown in FIG. 6B, in the rotation stop member 41A of Modification 2, a pair of vertical plates 411A and 411B are each erected in the normal direction of the outer peripheral surface of the first pipe 301. That is, the rotation stop member 41A is fixed to the first pipe in a state that the upper end portion of each of the pair of vertical plates 411A, 411B is slanted in the vertical direction so that the lower end portion (welded portion) is further out of the horizontal direction. The outer peripheral surface of 301.

As a result, the swirling flow SW is likely to collide vertically with each of the pair of vertical plates 411A and 411B, so the force of the rotation stop member 41A to block the swirling of the swirling flow SW is increased.

As shown in FIG. 6C, the rotation stop member 41A of Modification 3 is fixed so that the longitudinal directions of the pair of vertical plates 411A, 411B, and the horizontal plate 412 are along the turning direction opposite to the turning direction of the turning flow SW.

Thereby, the swirling flow SW easily collides with each of the pair of vertical plates 411A and 411B, so the force of the rotation stop member 41A to block the swirling of the swirling flow SW is increased.

In addition, among the pair of rotation stop members 41A and 41B, the rotation stop member 41A arranged on the upper side in the vertical direction is used as an example to describe each modification, but the rotation stop member 41B arranged on the lower side in the vertical direction is also same.

<The second embodiment> Next, the structure of the vent hole 3A after the second embodiment of the present invention will be described with reference to FIGS. 7 and 8. In FIGS. 7 and 8, with regard to constituent elements common to those described in the vent hole 3 after the first embodiment, the same reference numerals are attached and the description thereof is omitted.

Fig. 7 is a cross-sectional view along the vertical direction of the vent hole 3A after the second embodiment. Fig. 8 is a cross-sectional view taken along the horizontal direction of the vent hole 3A after the second embodiment.

The rear vent hole 3A of this embodiment is different from the rear vent hole 3 of the first embodiment in that the three pipes of the first pipe 301, the second pipe 302, and the third pipe 303 form a triple pipe structure. Two first swirling flow paths 33 and two second swirling flow paths 34 are provided on the outer circumference of the first pipe 301.

Specifically, the first pipe 301 is arranged at the innermost side, the second pipe 302 is arranged outside the first pipe 301, and the third pipe 303 is arranged outside the second pipe 302. Therefore, the first pipe 301 corresponds to the innermost pipe, and the third pipe 303 corresponds to the outermost pipe.

The first swirling flow path 33 is formed between the first pipe 301 and the second pipe 302, and the second swirling flow path 34 is formed between the second pipe 302 and the third pipe 303. As shown in FIG. 7, the pair of rotation stop members 41A and 41B are provided from the discharge port 33A of the first swirling flow path 33 to the discharge port 34A of the second swirling flow path 34, respectively.

Also in this embodiment, similarly to the first embodiment, a pair of vertical plates 411A and 411B are welded to the outer peripheral surface of the first pipe 301 to fix the first pipe 301 of the innermost pipe to the outermost pipe. A gap is formed between the third pipes 303 of the pipe. In addition, the horizontal plate 412 is provided at a position on the extension of the second pipe 302.

In addition, each of the pair of vertical plates 411A and 411B does not necessarily have to be fixed to the first pipe 301 only. For example, it may be fixed to both the first pipe 301 and the third pipe 303 so as to be separated from the second pipe 302. It may be fixed only to the second pipe 302 to be separated from each of the first pipe 301 and the third pipe 303.

As shown in FIG. 8, the pair of guide vanes 42A and 42B of the present embodiment each include three vanes 421 to 423. Two of the vanes 421 and 422 among the three vanes 421 to 423 are provided in the ejection port 33A of the first swirling flow path 33, and the remaining one vane 423 is provided in the ejection port 34A of the second swirling flow path 34. As in the first embodiment, the three vanes 421 to 423 each incline the front end on the side of the combustion furnace 11 to the outer side in the horizontal direction with respect to the central axis C.

As described above, even for the rear vent hole 3A provided with two first swirling flow passages 33 and second swirling flow passage 34, that is, the rear vent hole 3A with three flow passages, a pair of anti-rotation members 41A, 41B may be provided The pair of guide vanes 42A and 42B can also exhibit the same functions and effects as those of the first embodiment in this embodiment.

In addition, the present invention is not limited to the above-mentioned embodiment, and includes other various modifications. For example, the above-mentioned embodiments have been described in detail in order to facilitate the description and understanding of the present invention, and are not limited to those having all the structures described.

For example, in the above-mentioned embodiment, although the two-channel rear vent 3 and the third-channel rear vent 3A are provided with a pair of rotation stop members 41A, 41B and a pair of guide vanes 42A, 42B, the structure has been described, but as long as it is The number of flow paths is not particularly limited if the composite type rear vent hole of the straight flow ST and the swirling flow SW is ejected.

Furthermore, in the above embodiment, the pair of rotation stop members 41A and 41B are fixed to the first pipe 301 in consideration of the thermal expansion of the second pipe 302, but as long as the rotation of the swirling flow SW can be blocked, the pair of rotation stop members 41A and 41B The fixing method of each of the rotating members 41A and 41B is not particularly limited.

In addition, in the above-mentioned embodiment, although the pair of rotation stopping members 41A and 41B each have a vertical plate and a horizontal plate, it is not limited to this, and the structure is not particularly limited as long as it is a shape that can block the rotation of the swirling flow SW.

Furthermore, in the above embodiment, although pulverized coal is used as the fuel supplied from the plurality of burners 2 into the combustion furnace 11, the type of fuel is not particularly limited. In addition to pulverized coal, liquids such as biomass energy or oil, and gases And so on.

2: burner 3,3A: Rear vent 10: Combustion device 11: Burning furnace 31: Straight flow path 32, 33, 34: swirling flow path 32A, 33A, 34A: nozzle 41A, 41B: A pair of anti-rotation members 42A, 42B: a pair of guide vanes 110A: front wall 110B: back wall 301: 1st piping (inner tube) 302: The second piping (inner pipe, outer pipe) 303: 3rd piping (outer pipe) 411A, 411B, 411C: vertical plate 412, 412A, 412B, 412C, 412D: horizontal board C: Central axis ST: Straight flow SW: Swirl flow

[Fig. 1] is a schematic perspective view showing a structural example of a combustion device (a part of a boiler) of each embodiment of the present invention. Fig. 2 is a front view of the vent hole after the first embodiment of the present invention viewed from the side of the combustion furnace. [Fig. 3] is a cross-sectional view taken along line A-A in Fig. 2. [Fig. 4] is a sectional view taken along the line B-B in Fig. 2. [Fig. [Fig. 5] is a schematic view of the rotation stop member viewed from the vertical direction. [Fig. 6A] is a front view of the rotation stop member of Modification 1 of the present invention viewed from the side of the combustion furnace. [Fig. 6B] is a front view of the rotation stop member of Modification 2 of the present invention viewed from the side of the combustion furnace. [FIG. 6C] is a schematic view of the rotation stop member of Modification 3 of the present invention viewed from a vertical direction. Fig. 7 is a cross-sectional view taken along the vertical direction of the vent hole after the second embodiment of the present invention. [Fig. 8] is a cross-sectional view along the horizontal direction of the vent hole after the second embodiment.

3: Rear vent

31: Straight flow path

32: Swirling flow path

41A, 41B: A pair of anti-rotation members

42A, 42B: a pair of guide vanes

301: 1st piping (inner tube)

302: The second piping (inner pipe, outer pipe)

411A, 411B: vertical plate

412: Horizontal Board

421,422: Two vanes

Claims (5)

A rear vent hole formed as a multiple tube structure on a concentric shaft, including: a straight flow path for injecting primary air for two-stage combustion into the combustion furnace in a straight flow, and a straight flow path provided on the outer periphery of the straight flow path and the two The secondary air for stage combustion is sprayed into the swirling flow path in the aforementioned combustion furnace in a swirling flow, which is characterized by: At the outlet of the aforementioned swirling flow path, there are: A pair of anti-rotation members that are arranged in the vertical direction sandwiching the straight flow path and block the swirling flow to change into the straight direction, A pair of guide vanes that are arranged to sandwich the straight flow path in the horizontal direction and deflect the swirling flow to both outer sides in the horizontal direction. After the vent as described in claim 1, wherein, The pair of rotation stop members are each fixed to any one of an inner tube and an outer tube that forms the swirling flow path in the middle. After the vent as described in claim 2, wherein, The aforementioned pair of anti-rotation members each have: A plurality of vertical plates erected at predetermined intervals along the outer peripheral surface of the inner tube, A horizontal plate that connects adjacent vertical plates, The plurality of vertical plates and the horizontal plates all have long sides in the axial direction of the inner tube. The rear vent as described in claim 3, wherein, The aforementioned plural longitudinal plates, Each is erected in the normal direction of the outer peripheral surface of the inner tube. A combustion device characterized by: The burner is installed on the wall of the combustion furnace arranged in the vertical direction, and burns the fuel with an air volume below the theoretical air volume; and The rear vent hole according to any one of claims 1 to 4 is provided in the wall of the burner on the upper side in the vertical direction than the burner.

Images