JP2021004683A - Boiler furnace and boiler furnace wall panel used in the same and hardening method of boiler furnace wall - Google Patents

Abstract

To provide a boiler furnace wall panel capable of reducing wear of a boiler furnace wall sufficiently and a boiler furnace including the boiler furnace wall panel, and to provide a hardening method of the boiler furnace wall panel.SOLUTION: A boiler furnace (1) includes a furnace hopper (5), narrowed at a furnace bottom side, at a lower part, and is enclosed by a boiler furnace wall (2) including front and rear walls (21, 22) and left and right side walls (23, 24). The boiler furnace wall (2) in the furnace hopper (5) is formed into a spiral shape by alternately joining heat transfer pipes (31) which extend in a direction inclining relative to a vertical direction and in which a fluid flows and plate-like membrane bars (32) extending in a direction in which the heat transfer pipes (31) extend. Further, in scrambled areas (20A to 20D) between the front and rear walls (21, 22) and the left and right side walls (23, 24), padding parts (30, 30A) to which peening treatment is performed are provided at the side facing an interior of the furnace.SELECTED DRAWING: Figure 4

Description

The present invention relates to a boiler furnace for a coal-fired boiler, a boiler furnace wall panel used therein, and a method for hardening the boiler furnace wall.

In a boiler furnace of a coal-fired boiler, a heat transfer tube extending in a direction inclined with respect to the vertical direction and flowing a fluid inside and a plate-shaped membrane bar extending in a direction extending in the direction in which the heat transfer tube extends are alternately joined. As a result, it is surrounded by a spirally formed boiler furnace wall. The lower part of the boiler furnace is equipped with a substantially triangular columnar fireplace hopper that narrows the bottom side, and after the combustion ash and clinker adhering to the furnace wall and the suspended heat transfer tube fall on the fireplace hopper, the bottom of the fireplace It is discharged to the outside of the furnace through the opening formed in.

At this time, since the heat transfer tubes are arranged in a spiral shape, the combustion ash particles and clinker, and the debris generated by the collision of these particles with the front and rear walls of the fireplace hopper, are the front and rear walls and the left and right side walls of the fireplace hopper. It is easy to concentrate on the connection part with and fall. Therefore, the surface of the boiler furnace wall is worn at the joint portion.

Therefore, for example, in the boiler furnace disclosed in Patent Document 1, a plurality of protrusions such as a build-up portion, a semicircular ring, and a stud are transmitted at a joint corner portion between the front and rear walls of the hopper-shaped furnace bottom portion and the side wall. It is attached to the heat pipe along the direction of the tube axis to slow down the falling speed of the combustion ash and clinker collected at the joint corners and reduce the amount of wear on the heat transfer tube.

Japanese Unexamined Patent Publication No. 2005-265309

However, since combustion ash, clinker, etc. fall particularly concentrated in a narrow area near the boundary between the front and rear walls and the left and right side walls, in the case of the boiler furnace described in Patent Document 1, combustion ash and clinker due to a plurality of protrusions It is difficult to obtain the dispersion effect such as, etc., and a sufficient effect may not be obtained as a measure for reducing the wear of the boiler furnace wall in the furnace hopper.

Therefore, an object of the present invention is to provide a boiler furnace capable of sufficiently reducing wear of the boiler furnace wall, a boiler furnace wall panel used therefor, and a method for hardening the boiler furnace wall.

In order to achieve the above object, a typical invention is a boiler furnace provided with a furnace hopper whose bottom side is narrowed down and surrounded by a boiler furnace wall including front and rear walls and left and right side walls. The boiler furnace wall in the hopper is alternately joined with a heat transfer tube extending in a direction inclined with respect to the vertical direction and flowing through the inside, and a plate-shaped membrane bar extending in the direction in which the heat transfer tube extends. As a result, it is formed in a spiral shape, and a built-up welded portion that has been subjected to a peening treatment is provided on the side facing the inside of the furnace in the connection region between the front and rear walls and the left and right side walls. It is characterized by.

According to the present invention, it is possible to improve the durability against wear or impact caused by ash particles of dropped combustion ash, clinker, etc., and to sufficiently reduce the wear thinning of the boiler furnace wall due to the above characteristics. .. Issues, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

It is a schematic schematic diagram which shows one structural example of the boiler fireplace which concerns on embodiment of this invention. It is a plan view when the fireplace hopper is seen from above. It is a top view of the fireplace hopper. It is a partial sectional view of the boiler furnace wall in a fireplace hopper. It is an enlarged perspective view of the boiler furnace wall around the 1st connection area in a fireplace hopper. It is a perspective view which shows the boiler furnace wall panel which comprises the boiler furnace wall including the 1st connection area. A configuration example of an air hammer used for the peening process of the overlay weld layer is shown, (a) is a side view, and (b) is a front view. It is an enlarged perspective view around the 1st connection area of the boiler furnace wall in the furnace hopper of the boiler furnace which concerns on the modification.

Hereinafter, the boiler fireplace according to the embodiment of the present invention will be described with reference to FIGS. 1 to 6.

(Structure of boiler fireplace 1)
First, the configuration of the boiler furnace 1 will be described with reference to FIGS. 1 to 5.

FIG. 1 is a schematic schematic view showing a configuration example of a boiler furnace 1 according to an embodiment of the present invention. FIG. 2A is a schematic plan view of the fireplace hopper 5 viewed from above, and FIG. 2B is a plan view of the fireplace hopper 5 viewed from above. FIG. 3 is a partial cross-sectional view of the boiler furnace wall 2 in the furnace hopper 5. FIG. 4 is an enlarged perspective view of the boiler furnace wall 2 around the first connection region 20A in the furnace hopper 5. FIG. 5 is a perspective view showing a boiler furnace wall panel 2A constituting the boiler furnace wall 2 including the first connection region 20A.

The boiler furnace 1 is mounted on a coal-fired boiler used in a thermal power plant or the like. A coal-fired boiler burns pulverized coal generated from coal such as bituminous coal or sub-bituminous coal as solid fuel, and recovers the heat generated by the combustion.

The boiler furnace 1 is installed along the vertical direction with respect to the ground, and has a housing structure surrounded by a boiler furnace wall 2. A combustion space for burning pulverized coal is formed inside the boiler furnace 1. The combustion gas generated in the combustion space flows from the lower side to the upper side in the vertical direction of the boiler furnace 1. That is, in the boiler furnace 1, 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.

The boiler furnace wall 2 is a panel-shaped water cooling wall in which a heat transfer tube 31 through which cooling water as a fluid flows and a plate-shaped membrane bar 32 extending in the extending direction of the heat transfer tube 31 are alternately joined. Yes (see Figures 3-5).

A flue 11 extending in a direction intersecting with the boiler furnace 1 is connected to the upper outlet of the boiler furnace 1. The heat generated by combustion in the boiler furnace 1 is mainly transferred by radiation to the boiler furnace wall 2 to heat and evaporate the cooling water flowing in the heat transfer tube 31. The generated steam is superheated by a heat exchanger (not shown) such as a superheater or a reheater mounted inside the flue 11 and sent to a steam turbine for power generation. Further, the combustion gas discharged from the boiler furnace 1 passes through a denitration device, an air preheater, etc. (not shown), and then is discharged to the outside as treated exhaust gas.

In FIG. 1, the direction in which the flue 11 extends is referred to as the “depth direction”, the boiler furnace 1 side in the depth direction is referred to as the “front side”, and the opposite side is referred to as the “rear side”. Further, the direction in which the vertical direction and the depth direction intersect is defined as the "width direction", the left side with respect to the rear direction is defined as the "left side", and the opposite side is defined as the "right side".

The boiler furnace wall 2 includes a front wall 21 arranged on the front side and serving as a front surface of the boiler furnace 1, a rear wall 22 arranged facing the front wall 21 and serving as a rear surface of the boiler furnace 1, and a front wall 21 and a rear surface. The left side wall 23 which is arranged between the wall 22 and becomes the left side surface of the boiler furnace 1, the right side wall 24 which is arranged opposite to the left side wall 23 and becomes the right side surface of the boiler furnace 1, and the front wall 21 and the rear Includes a wall 22, a left wall 23, and a ceiling wall 25 that is located above the right wall 24 and serves as the ceiling of the boiler furnace 1.

In the following, the front wall 21 and the rear wall 22 may be collectively referred to as “front and rear walls 21 and 22,” and the left wall 23 and the right wall 24 may be collectively referred to as “left and right side walls 23, 24”.

A plurality of burners 4 for supplying pulverized coal and air into the boiler furnace 1 are provided on the lower side of the front wall 21 and the rear wall 22, respectively. In FIG. 1, eight burners 4 are arranged in two stages in the vertical direction on each of the front wall 21 and the rear wall 22.

Further, the boiler fireplace 1 is provided with a funnel-shaped fireplace hopper 5 whose bottom side is narrowed down below the position where a plurality of burners 4 are provided. An opening 10 that opens downward is formed in the bottom of the boiler furnace 1, and the furnace hopper 5 has an inclined portion 51 that inclines toward the opening 10 and a hanging portion that hangs down from the lower end of the inclined portion 51. It has a part 52 and. The combustion ash generated by combustion in the boiler furnace 1 and the clinker or the like obtained by sintering and solidifying the combustion ash fall into the furnace hopper 5 and are discharged to the outside of the furnace through the opening 10. In the inclined portion 51, the front and rear walls 21 and 22 are inclined toward the inside of the furnace, respectively. In FIG. 2B, the left and right side walls 23 and 24 of the inclined portion 51 are also shown in an inclined state inside the furnace for convenience of explanation, but in reality, as shown in FIG. 1, a horizontal plane (ground). It is provided perpendicular to, that is, along the vertical direction.

As shown in FIGS. 2A and 2B, in the furnace hopper 5, the boiler furnace wall 2 is formed in a spiral shape in which a plurality of heat transfer tubes 31 and a plurality of membrane bars 32 extend in a direction inclined with respect to the vertical direction. There is. As a result, the first connection area 20A, which is the connection area between the front wall 21 and the left side wall 23, the second connection area 20B, which is the connection area between the left side wall 23 and the rear wall 22, and the rear wall 22 and the right side. In the third connection area 20C, which is the connection area with the wall 24, and the fourth connection area 20D, which is the connection area between the right side wall 24 and the front wall 21, the angles of the plurality of heat transfer tubes 31 and the plurality of heat transfer tubes 31, respectively. The angle of the membrane bar 32 has changed significantly.

In the first connection area 20A and the third connection area 20C, the second connection area 20B and the fourth connection area 20B and the fourth connection area 20B are joined in order to join a plurality of heat transfer tubes 31 drawn out from the lowermost part of the furnace hopper 5 to the pipes. The inclination angles of the plurality of heat transfer tubes 31 and the inclination angles of the plurality of membrane bars 32 are larger in the peripheral portions of the left and right side walls 23 and 24 than in the combined region 20D.

Therefore, the particles of combustion ash, clinker, etc. generated in the left and right side walls 23 and 24 in the boiler furnace 1 are likely to fall in the vicinity of the first to fourth connection regions 20A to 20D. In particular, as shown in FIG. 2B, in the first connection region 20A and the third connection region 20C, the flow of combustion ash particles and clinker collected at the corners (indicated by arrows in FIG. 2B) is in the vertical direction. Since it is blocked by the left and right side walls 23 and 24 arranged along the line and becomes concentrated, the wear in the first connection region 20A and the third connection region 20C becomes remarkable.

Therefore, in the boiler furnace wall 2 of the furnace hopper 5, the overlay welded portion 30 formed of a nickel-based alloy such as Alloy 22 or Alloy 625 is formed in the boiler furnace 1 in the first connection region 20A and the third connection region 20B. It is provided on the surface facing the surface.

As shown in FIG. 3, the build-up welded portion 30 is provided as a layer over the outer peripheral surfaces of the plurality of heat transfer tubes 31 and the surfaces of the plurality of membrane bars 32 on the side facing the inside of the boiler furnace 1. There is. Then, by applying the peening treatment described later to the surface of the overlay layer, the surface of the overlay welded portion 30 is harder than the other regions of the boiler furnace wall 2.

As a result, even when particles of combustion ash, clinker, etc. fall in a narrow area near the joint between the front and rear walls 21 and 22 and the left and right side walls 23 and 24, the first to fourth takers are taken. Since the joint regions 20A to 20D are covered with the overlay welded portion 30 that has been subjected to the peening treatment, it is possible to sufficiently reduce the wear caused by the fallen combustion ash particles, clinker, and the like.

In addition, in FIG. 4 and FIG. 5, the configuration of the boiler furnace wall 2 around the first connection region 20A in the furnace hopper 5 is shown as an example, and the overlay welded portion 30 subjected to the peening treatment is shown by a thick line. Shown. Further, the “overlay welded portion 30” indicates a state in which the surface of the overlaid weld layer is subjected to a peening treatment.

In the first connection area 20A and the third connection area 20C, as described above, due to the structure of the fireplace hopper 5, combustion ash particles, clinker, etc. are gathered more than the second connection area 20B and the fourth connection area 20D. It is easy and the surface is easily worn. Therefore, in the first connection region 20A and the third connection region 20C, it is particularly desirable to provide the overlay welded portion 30 subjected to the peening treatment on the surface on the side facing the inside of the boiler furnace 1.

Further, the boiler furnace wall 2 is configured by connecting a plurality of small boiler furnace wall panels 2A by welding, for example, and as shown in FIG. 5, constitutes the boiler furnace wall 2 including the first connection region 20A. In the boiler furnace wall panel 2A, a build-up welded portion 30 that has been subjected to a peening process is formed in advance in a region located in the first connection region 20A. Therefore, even if the boiler furnace wall 2 around the first connection area 20A in the furnace hopper 5 needs to be repaired due to long-term use of the boiler furnace 1, the entire boiler furnace 1 or the entire furnace hopper 5 should be replaced. Instead, only the boiler furnace wall panel 2A needs to be replaced.

(Hardening method for boiler wall 2)
Next, a method for hardening the boiler furnace wall 2 in the furnace hopper 5, specifically, a peening treatment for the overlay weld layer will be described with reference to FIG.

6 (a) and 6 (b) show a configuration example of the air hammer 6 used for the peening process of the overlay weld layer, FIG. 6 (a) is a side view, and FIG. 6 (b) is a front view. Is.

In the present embodiment, first, of the boiler furnace wall 2, the surface facing the inside of the boiler furnace 1 has a thickness of about 2.0 mm with respect to the first welding area 20A and the third welding area 20C in the furnace hopper 5. Form an overlay welded layer. Then, the surface of the formed overlay weld layer is repeatedly hit with the air hammer 6 shown in FIGS. 6 (a) and 6 (b) to perform a peening process.

The air hammer 6 is a tapered rod-shaped tool made of steel as shown in FIG. 6 (a), and has a spherical tip as shown in FIG. 6 (b). The air hammer 6 is vibrated by the force of air and a spring, and the tip is repeatedly collided with the surface of the overlay weld layer to form a dent.

In the present embodiment, the tip of the air hammer 6 has an outer diameter φ of 3.0 mm. When the outer diameter φ of the tip of the air hammer 6 is smaller than 1.5 mm, the grinding force becomes stronger and the surface of the overlay weld layer is easily scratched, and the pressure on the overlay weld layer is increased. It becomes excessive and the air hammer 6 is easily worn, and the overlay weld layer is scraped off. On the other hand, when the outer diameter φ of the tip portion of the air hammer 6 is larger than 5.0 mm, the pressure required for the curing process cannot be obtained, and the tip portion is formed in the gap between the weld beads in the overlay welding layer. The entire surface of the overlay weld layer cannot be peened without entering. Therefore, it is desirable that the outer diameter φ of the tip portion of the air hammer 6 is 1.5 mm or more and 5.0 mm or less (1.5 ≦ φ ≦ 5.0).

Further, in the present embodiment, the peening treatment is performed until the surface hardness of the overlay weld layer becomes 400 HV (Vickers hardness at a test load of 10 kg) or more. The boiler furnace wall 2 is cooled by cooling water flowing inside each of the plurality of heat transfer tubes 31, and the surface temperature thereof is maintained at, for example, about 450 ° C. On the other hand, the particles of combustion ash and clinker falling on the furnace hopper 5 are heated to about 1000 ° C. by the combustion gas. Taking silicon dioxide (SiO ₂ ) as an example of particles of combustion ash, clinker, etc., the hardness is about 400 HV under such a temperature environment in the boiler furnace 1. Therefore, it is desirable that the surface of the overlay welded portion 30 subjected to the peening treatment be hardened to a hardness equal to or higher than 400 HV of combustion ash particles, clinker, or the like.

In the peening process, metallic luster appears when the surface hardness of the overlay weld layer reaches the target value of 400 HV or more. This is because the outermost surface of the boiler furnace wall 2 is covered with a thin oxide film immediately after overlay welding to the boiler furnace wall 2 or after stress relief annealing, but the oxide film is formed by applying a peening treatment. This is because the surface irregularities are smoothed by curing by peening. Therefore, the peening process can be performed using the metallic luster appearing on the surface of the overlay weld layer as a simple index.

In the present embodiment, nickel-based alloys Alloy22 and Alloy625 are used to form the overlay weld layer, thereby reducing the risk of damage due to peeling of the overlay layer and thermal fatigue. Further, since the nickel-based alloy has ductility even after being subjected to the peening treatment, cracks are unlikely to occur due to bending in the first to fourth joint regions 20A to 20D.

Further, when a nickel-based alloy is used for the overlay weld layer, the dent (depth of dent) formed on the surface by performing the peening treatment until it reaches the target value of 400 HV or more becomes 0.05 mm or less. While the thickness of the overlay weld layer is approximately 2.0 mm or more, the range that contributes to hardening is narrow. Therefore, even if the peening processed portion is repeatedly deformed due to plant operation, fatigue damage starting from surface irregularities is unlikely to occur.

In the present embodiment, as a method for hardening the boiler furnace wall 2, a peening treatment using an air hammer 6 for the overlay weld layer has been described. However, if the surface of the overlay weld layer can be cured, For example, a hardening process such as shot peening in which high-pressure gas is injected onto the surface of the overlay weld layer to cause hard particles to collide at high speed, or scraping with a wire cup brush formed by twisting hard wires. It may be a method. When these methods are used, the surface irregularities of the overlay weld layer can be formed more finely than when the air hammer 6 is used, so that stress concentration due to the excessive uneven shape can be reduced and the overlay can be built up. Damage to the weld layer can be prevented.

(Modification example)
Next, a modified example of the boiler furnace 1 according to the embodiment of the present invention will be described with reference to FIG. 7. In FIG. 7, the components common to those described for the boiler furnace 1 according to the embodiment are designated by the same reference numerals and the description thereof will be omitted.

FIG. 7 is an enlarged perspective view of the vicinity of the first connection region 20A of the boiler furnace wall 2 in the furnace hopper 5 of the boiler furnace 1 according to the modified example.

In the boiler furnace 1 according to this modification, the overlay welded portion 30A is also provided in the connecting region 50 between the inclined portion 51 and the hanging portion 52 of the furnace hopper 5. For example, as shown in FIG. 7, the overlay welded portion 30A has the front wall 21 and the left side wall 23 of the connection area 50 from the first connection area 20A, which is the connection area between the front wall 21 and the left side wall 23. It is continuously provided over a part of the area corresponding to.

In the connection region 50, since the plurality of heat transfer tubes 31 and the plurality of membrane bars 32 are bent toward the inside of the fireplace hopper 5, combustion ash particles and clinker falling from above are likely to collide with each other. Therefore, the boiler furnace wall 2 is provided with a build-up welded portion 30A also in the connection region 50 to harden the side facing the inside of the furnace to improve durability and reduce wear.

In addition, in FIG. 7, the boiler furnace wall 2 is provided with the overlay welded portion 30A only in the region around the first connection region 20A in the connection region 50, but is not limited to this, and the entire connection region 50 is not limited to this. It may be provided over.

The present invention is not limited to the above-described embodiments and modifications, and includes various other modifications. For example, the above-described embodiments and modifications have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations.

For example, in the above embodiment, the first connection area 20A and the third connection area 20C have been described as examples, but the present invention is not limited to this, and at least in any one of the first to fourth connection areas 20A to 20D. , The overlay welded portions 30, 30A that have been subjected to the peening treatment may be provided on the side facing the inside of the furnace.

1 Boiler fireplace 2 Boiler fireplace wall 2A Boiler fireplace wall panel 5 Fireplace hopper 10 Opening 20A 1st connection area 20B 2nd connection area 20C 3rd connection area 20D 4th connection area 21 Front wall 22 Rear wall 23 Left side Wall 24 Right side wall 30, 30A Overlay welding part 31 Heat transfer tube 32 Membrane bar 50 Connection area 51 Inclined part 52 Hanging

Claims (4)

A boiler fireplace that has a fireplace hopper with a narrowed bottom side and is surrounded by a boiler furnace wall that includes the front and rear walls and the left and right side walls.
The boiler furnace wall in the furnace hopper is
A heat transfer tube extending in a direction inclined with respect to the vertical direction and flowing through the inside and a plate-shaped membrane bar extending in the direction in which the heat transfer tube extends are alternately joined to form a spiral shape. As well as being done
A boiler fireplace characterized in that a overlay welded portion subjected to a peening treatment is provided on a side facing the inside of the furnace in a connecting region between the front and rear walls and the left and right side walls. The boiler fireplace according to claim 1.
The fireplace hopper
An inclined portion inclined toward the opening formed in the furnace bottom, and an inclined portion
It has a hanging portion that hangs down from the lower end of the inclined portion.
A boiler fireplace characterized in that the overlay welded portion is also provided in a connecting region between the inclined portion and the hanging portion. Used in the boiler fireplace according to claim 1 or 2.
A boiler furnace wall panel comprising the boiler furnace wall including the connection region in the furnace hopper. In a furnace hopper that includes the front and rear walls and left and right side walls of a boiler furnace and is provided in the lower part of the boiler furnace and whose bottom side is narrowed, a heat transfer tube that extends in a direction inclined with respect to the vertical direction and allows fluid to flow inside. A method for hardening a boiler furnace wall formed in a spiral shape by alternately joining plate-shaped membrane bars extending in a direction in which the heat transfer tube extends.
A build-up welded layer is formed on the surface of the boiler furnace wall facing the inside of the boiler furnace with respect to the connection region between the front and rear walls and the left and right side walls of the furnace hopper, and the build-up welded layer is formed. A method for curing a boiler furnace wall, which comprises curing the surface by repeatedly striking or rubbing it until it becomes glossy.

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