JP5215834B2 - Circulating fluidized bed combustion furnace - Google Patents

Description

  In the present invention, a combustion chamber having a square cross section is defined by a furnace wall formed by juxtaposing a plurality of evaporation tubes, a refractory material covering the lower part of the furnace wall is provided, a circulating fluidized material, unburned ash, etc. In a circulating fluidized bed combustion furnace in which the particles of the refractory are lowered along the furnace wall, the shape of the refractory material is adjusted by adjusting the shape of the refractory material such as the collision force between the descending particles and the evaporator tube, thereby reducing the wear and reduction of the evaporator tube. The present invention relates to a circulating fluidized bed combustion furnace that reduces meat.

A conventional circulating fluidized bed combustion furnace will be described with reference to FIG. FIG. 9 is a schematic view of a circulating fluidized bed combustion furnace facility.
As shown in FIG. 9, the circulating fluidized bed combustion facility 2 includes a circulating fluidized bed combustion furnace 4, a cyclone 6 that separates fluidized material circulated from the combustion furnace, an exhaust gas heat exchanger 42, and a bug that removes dust in the exhaust gas. The filter 44 is mainly configured. In FIG. 9, 8 is a combustor, 10 is a furnace bottom, 12 is fuel, 14 is air, 16 is a refractory material, 18 is an evaporating pipe, 19 is a circulating particle, 20 is a seal pot, 26 is an external heat exchanger, 46 is an incentive fan and 48 is a chimney.
Here, a plurality of the evaporation pipes 18 are arranged adjacent to each other at a predetermined interval, and constitute a furnace wall that partitions the combustion chamber.

The refractory material 16 is disposed so as to cover the furnace wall at the lower part of the furnace wall, and in the lower part of the combustion chamber having a strong thermal power, the evaporation pipe 18 constituting the furnace wall is shielded from high temperature, and a fluidized material to be described later. It has a role to protect the evaporation pipe 18 from being worn by particles such as unburned ash.
The distance H1 to the top of the refractory material 16 is about 8000 m when the distance H to the ceiling of the combustor 8 is about 30000 mm.

  In the circulating fluidized bed combustion facility 2 configured as described above, air 14 is blown into the combustor 8 by an air nozzle (not shown) and returned from the vicinity of the fuel 12 such as coal supplied from the outside and the furnace bottom 10. Mixing and fluidizing unburned ash and fluidized material (made of an inert fluid such as silica sand or a desulfurizing agent such as limestone) previously stored in the combustor 8 forms a fluidized bed to promote combustion. .

The high-temperature combustion gas generated at this time is guided to the cyclone 6 together with the fluidized material, and is separated into the combustion gas and the circulating particles 19 by the cyclone 6.
The separated combustion gas is cooled by exchanging heat with an external medium such as air by the exhaust gas heat exchanging means 42, and then the dust in the exhaust gas is removed through the bag filter 44 and is discharged from the chimney 48 to the atmosphere.
On the other hand, the circulating particles 19 separated by the cyclone 6 are divided into high-temperature particles 22 that are directly returned to the combustor 8 by the seal pot 20 and low-temperature particles 24 that are returned to the combustor 8 via the external heat exchanger 26. The route is different but returned to the combustor 8.

  When attention is paid to the behavior of the particles such as the fluidized material and unburned ash in the combustor 8 of the circulating fluidized combustion furnace 4 formed in this way, the particles rise at the center in the combustor 8, but the evaporation pipe 18 and the like. Most of the particles descending along the furnace wall are formed in the vicinity of the furnace wall formed by the above, and the particles such as the fluidized material and unburned ash are circulated in the combustor 8 by the upward flow and the downward flow. .

  Since the upper end of the refractory material 16 is an upper edge of the refractory material formed by a horizontal surface stepped with respect to the furnace wall, sliding of particles descending along the furnace wall causes Local wear will occur.

  As a technique for reducing such local wear that occurs in the evaporator tube 18, for example, in Patent Document 1, a combustion chamber is defined by a furnace wall formed by juxtaposing a plurality of evaporator tubes. In a circulating fluidized bed boiler provided with a refractory material covering the lower part and particles such as circulating fluid material and unburned ash descending along the furnace wall, the refractory material has a horizontal end face at the upper edge thereof. And a circulating fluidized bed furnace provided with a weir extending along the furnace wall in the circumferential direction of the combustion chamber.

JP 2004-28430 A

  However, even the technique disclosed in Patent Document 1 is not sufficient as a measure for reducing local abrasion of the evaporation tube, and particularly when biomass fuel or high Cl fuel is used as the fuel, thinning becomes remarkable. Therefore, measures with high durability are desired.

  Accordingly, in view of the problems of the prior art, the present invention provides a circulating fluidized bed combustion furnace that suppresses wear and thinning generated in the evaporation pipe by particles such as fluidized material and unburned ash on the upper edge side of the refractory material. With the goal.

In order to solve the above problems, in the present invention, a combustion chamber having a square cross section is defined by a furnace wall formed by juxtaposing a plurality of evaporator tubes, and a refractory material covering the lower part of the furnace wall is provided and circulated. In a circulating fluidized bed combustion furnace in which particles such as fluidized material and unburned ash descend along the furnace wall,
While projecting the upper edge of the refractory material so that the distance from the inner wall surface of the evaporation tube to the end of the refractory material is 50 mm or more,
At the corner of the combustion chamber, the refractory material is provided with a recess having a square cross section,
The concave portion is an evaporation tube in which the steam pipe on the side side is relatively thinner than the evaporation pipe in other portions, and the steam pipe on the side side of the concave portion having the rectangular cross section is It is characterized by being covered with a heat insulating wall to the vicinity of the ceiling .

According to the invention, the upper edge of the refractory material is projected so that the distance from the inner wall surface of the evaporation tube to the end portion of the refractory material is 50 mm or more,
At the corner of the combustion chamber, the refractory material is provided with a recess having a square cross section,
The concave portion is an evaporation tube in which the steam pipe on the side side is relatively thinner than the evaporation pipe in other portions, and the steam pipe on the side side of the concave portion having the rectangular cross section is Since it is covered with a heat insulating wall up to the vicinity of the ceiling, the wear width in which particles such as fluidized material and unburned ash descending along the furnace wall (hereinafter sometimes referred to as descending particles) scrape the inner wall surface in the vertical axis direction. As a result, local wear and thinning are alleviated.
Further, when the upper edge of the refractory material is projected over 50 mm over the entire furnace wall surface, in the corner of the combustion chamber, that is, in the vicinity of the corner, an evaporating tube in the vicinity of the corner due to the flow of the descending particles from the corner. However, by providing a refractory material at the corner of the combustion chamber with a recess having a square cross section, the inflow can be prevented, and the evaporation pipe in the vicinity of the corner is also substantially the same as the other evaporation pipes. The amount of thinning can be suppressed to the same level.

In addition, since the steam pipe on the side of the concave portion having the rectangular cross section is covered with a heat insulating wall up to the vicinity of the ceiling, the flow of the fluidized material is particularly intense at the corners of the combustion chamber, that is, the corners. It is necessary to prevent damage caused by. Then, the damage by the said flow can be prevented by covering the vapor | steam pipe | tube in the side part side of the said recessed part of a square cross section with a heat insulation wall to ceiling vicinity.

The rectangular recess has a tapered portion, and the number of steam pipes on the side of the recess is determined by the taper angle of the tapered portion.
This facilitates the design of dimensions and the like when providing the recess.

  As described above, according to the present invention, it is possible to provide a circulating fluidized bed combustion furnace in which wear and thinning generated in the evaporation pipe due to particles such as fluidized material and unburned ash are suppressed on the upper edge side of the refractory material.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, but are merely illustrative examples. Not too much.

First, prior to the examples, an intermediate form in which the upper edge of the refractory material is projected so that the distance from the inner wall surface of the evaporation tube to the end portion of the refractory material is 50 mm or more will be described.
FIG. 4 is a schematic view showing a part of a refractory material installation site of a circulating fluidized bed combustion furnace according to an intermediate configuration. Since the configuration of the circulating fluidized bed combustion facility is the same as that shown in FIG. 9 of the prior art, the description thereof will be omitted, and the same reference numerals as those in FIG.
As shown in FIG. 4, the combustion chamber is defined by a furnace wall (fin) 19 formed by juxtaposing a plurality of evaporator tubes 18 (only one is shown in FIG. 4), and the lower part of the furnace wall 19 is covered. In a circulating fluidized bed furnace provided with a refractory material 16 and particles such as circulating fluid material and unburned ash descend along the furnace wall 19, from the inner wall surface 18a of the evaporation pipe 18 to the end surface 16a of the refractory material. The projecting distance X is set to 50 mm or more.

That is, in the intermediate form, a large number of evaporation pipes 18 are connected by spacing pieces (not shown) to form a furnace wall, and the lower part thereof is covered with a refractory material 16 and vortex of particles such as fluidized material and unburned ash. It is prepared for wear and thinning due to etc.
Further, the refractory material 16 is formed with a horizontal end surface at the upper end edge, and the protruding distance X from the inner wall surface 18a of the evaporation pipe 18 to the end surface 16a of the refractory material is 50 mm or more.
As shown in the relationship diagram between the thickness of the refractory material (protrusion distance X) and the wear depth ratio, the protrusion distance X increases as the protrusion distance X increases.
As shown in FIG. 5, it can be confirmed that the wear amount is reduced to 1/10 or less by setting the protrusion distance X of the refractory material from 50 mm to 130 mm or more. In addition, the longer the projection distance of the refractory material is 50 mm or more, and more preferably 130 m or more, it is preferable that the projecting distance is 1000 mm or less.
Here, the wear depth ratio is obtained by converting the wear amount at each refractory material thickness into a ratio with the wear amount when the protrusion distance X of the refractory material is 50 mm as 1.

Here, the reason why the wear depth ratio is reduced when the protrusion distance is extended will be described with reference to FIG. 6 showing the relationship between the protrusion distance of the refractory material and the wear area of the evaporation pipe.
As shown in FIG. 6, particles descending along the evaporation pipe 18 near the wall surface accumulate on the stage on the upper surface of the refractory material 16 to form an inclined surface based on the angle of repose α. This angle of repose α is constant as long as the particle size, operating conditions, etc. of the fluidizing material do not change.
When the protruding distance is short (Y), the wear area (width) b for cutting the inner wall surface 18a of the evaporation pipe 18 is small, but when the protruding distance is long (50 mm or more) as in this intermediate form. In (X), the wear region (width) a increases in the vertical axis direction.
As a result, local wear on the inner wall surface of the evaporator tube is alleviated, and local wear and thinning of the evaporator tube are suppressed.

  FIG. 7 is a perspective view of the vicinity of the corner portion in the combustor in the intermediate configuration, and FIG. 8 is an upper plan view of the vicinity of the corner portion in the combustor in the intermediate configuration. As shown in FIGS. 7 and 8, the evaporation pipe 18A existing in the immediate vicinity of the corner portion is covered with a heat insulating wall 28 up to the vicinity of the ceiling to protect the evaporation pipe 18A. This is because the fluidized material has a particularly strong flow at the corner in the combustor to prevent damage.

  Further, the refractory material 16 and the heat insulating wall 28 are formed by spraying a wear-resistant film on the surface thereof, and are prepared for wear caused by the flow of particles.

  In such a combustor, the particles 32 descending along the evaporation pipe 18 in the vicinity of the wall surface are deposited on the stage on the upper surface of the refractory material 16 to form a deposition portion 30, and then a flow F1 inward toward the combustor is formed. And fall into the combustor.

At this time, the evaporation pipe 18A covered with the heat insulating wall 28 is prevented from being worn and thinned by the heat insulating wall 28, and the evaporation pipe 18C disposed at a position away from the corner portion causes the heat insulating material 16 to protrude. Although the wear and thinning were suppressed and reduced, wear and thinning were observed in the evaporation pipe 18B that was not covered with the heat insulating wall 28 and was disposed near the corner.
This is because, in the vicinity of the corner portion, the particles falling on the stage on the upper surface of the heat insulating material 16 generate not only the flow F1 directed inward of the combustor but also the flow F2 in the direction substantially along the furnace wall, and therefore the flow F2 This is because the particles concentrate in the vicinity of the evaporation pipe 18B and wear and thin.

Therefore, in this embodiment, in addition to the structure of the heat insulating material 16 shown in FIGS. 7 and 8 in the intermediate form, a concave portion 17 having a square cross section is provided at a position corresponding to the corner portion of the heat insulating material 16. FIG. 1 is a perspective view of the vicinity of a corner portion in the combustor in the embodiment, and FIG. 2 is a top plan view of the vicinity of the corner portion in the combustor in the embodiment.
As a result, a flow F3 in the direction of the concave portion 17 is generated around the corner portion, and a flow F2 in a direction substantially along the furnace wall is hardly generated.
The concave portion 17 is provided so that the vapor pipe on the side of the concave portion 17 becomes an evaporation pipe that is thinner than the evaporation pipes in other portions, that is, the evaporation pipe 18B. If the concave portion is too small, the effect of reducing the flow F2 is small. If the concave portion is too large, the protrusion of the heat insulating material immediately adjacent to the evaporation pipe 18C that can suppress wear and thinning becomes short, and the evaporation pipe 18C. This is because there is a possibility that the suppression of wear and thinning of the steel becomes insufficient.
The size and position of the concave portion 17 is, for example, a tapered portion 17a provided in the concave portion 17, and the tapered portion 17a so that the position of the side of the tapered portion end position 17b is near the intermediate position between the evaporation pipe 18B and the evaporation pipe 18C. Adjustment is possible by determining the taper angle.

FIG. 3 is a schematic cross-sectional view showing how the evaporation pipe 18 is covered with a heat insulating wall. FIG. 3A shows the state of the heat insulating wall in the example shown in FIGS. 1 and 2, and FIG. 3B shows the state of the heat insulating wall in another example.
In FIG. 3 (A), only the evaporation pipe 18A in the immediate vicinity of the corner portion is covered with the heat insulating wall 28, but in FIG. 3 (B), in addition to the evaporation pipe 18A, relative to the evaporation pipes in other parts. The evaporation pipe in which the thinning occurs, that is, the evaporation pipe 18B was also covered with the heat insulating wall 28. By covering the steam pipe 18B, which is located on the side of the concave section 17 having a rectangular cross section and is susceptible to thinning, with a heat insulating wall up to the vicinity of the ceiling, damage due to the flow of particles in the evaporation pipe B can be more efficiently prevented. .

  On the upper edge side of the refractory material, it can be used as a circulating fluidized bed combustion furnace in which wear and thinning generated in the evaporation pipe due to particles such as fluidized material and unburned ash are suppressed.

It is a perspective view of the corner part vicinity in the combustor in an Example. It is a top plan view near a corner part in a combustor in an example. It is a schematic sectional drawing which shows a mode that an evaporation pipe is covered with a heat insulation wall. It is the schematic which shows a part of refractory material installation site | part of the circulating fluidized bed combustion furnace which concerns on an intermediate form. It is a related figure of refractory material thickness (protrusion distance X) and wear depth ratio. It is a figure which shows the relationship between the protrusion distance of a refractory material, and the abrasion area | region of an evaporation pipe. It is a perspective view of the corner part vicinity in the combustor in intermediate technology. It is a top plan view near a corner part in a combustor in intermediate technology. It is the schematic of a circulating fluidized bed combustion furnace installation.

Explanation of symbols

4 Circulating Fluidized Bed Combustion Furnace 16 Heat Insulating Material 17 Recessed portion 18 Evaporating Pipe 28 Heat Insulating Wall

Claims (3)

A furnace wall formed by juxtaposing a plurality of evaporation tubes defines a combustion chamber having a square cross-sectional shape, and a refractory material covering the lower part of the furnace wall is provided, and circulating fluid particles and unburned ash particles are In a circulating fluidized bed combustion furnace adapted to descend along the furnace wall,
While projecting the upper edge of the refractory material so that the distance from the inner wall surface of the evaporation tube to the end of the refractory material is 50 mm or more,
At the corner of the combustion chamber, the refractory material is provided with a recess having a square cross section,
The concave portion is an evaporation tube in which the steam pipe on the side side is relatively thinner than the evaporation pipe in other portions, and the steam pipe on the side side of the concave portion having the rectangular cross section is A circulating fluidized bed combustion furnace characterized by being covered with a heat insulating wall to the vicinity of the ceiling . The rectangular recess has a tapered portion,
The taper angle of the tapered portion, the circulating fluidized bed combustion furnace according to claim 1, wherein the determining the number of steam pipes on the side edge side of the recess. A furnace wall formed by juxtaposing a plurality of evaporation tubes defines a combustion chamber having a square cross-sectional shape, and a refractory material covering the lower part of the furnace wall is provided, and circulating fluid particles and unburned ash particles are In a circulating fluidized bed combustion furnace adapted to descend along the furnace wall,
While projecting the upper edge of the refractory material so that the distance from the inner wall surface of the evaporation tube to the end of the refractory material is 50 mm or more,
At the corner of the combustion chamber, the refractory material is provided with a recess having a square cross section,
The recess is an evaporation tube in which the steam pipe on the side side is relatively thinner than the evaporation tube in other parts , and the rectangular recess has a tapered portion,
The taper angle of the tapered portion, circulating fluidized bed combustion furnace you and determining a number of steam pipes on the side edge side of the recess.

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