JP2017198372A - Fluidized-bed combustion furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fluidized-bed combustion furnace capable of suppressing generation of clinker in a furnace bottom part.SOLUTION: A fluidized-bed combustion furnace includes: a fluidized-bed part in which a fluidization material and a solid fuel are fluidized; and a free board part positioned upward of the fluidized-bed part. In a second position downward from a first position that is a boundary position between the fluidized-bed part and the free board part, the fluidized-bed part has a second cross sectional area Athat is larger than a first cross sectional area Aof the fluidized-bed part in the first position.SELECTED DRAWING: Figure 2

Description

  The present disclosure relates to fluidized bed combustion furnaces.

2. Description of the Related Art A fluidized bed combustion furnace for fluidizing and burning solid fuel (for example, biomass fuel) is known.
For example, in Patent Document 1, a fluidized bed is formed by jetting fluidizing gas from below into a mixed layer containing a fluidized medium (fluid material) and solid fuel (city waste) provided in a furnace. , A fluidized bed combustion apparatus for burning a combustible object in the fluidized bed is described.

Japanese Unexamined Patent Publication No. 56-42009

By the way, in a fluidized bed combustion furnace, particles of solid fuel coarser than the fluidized material forming the fluidized bed settle at the bottom of the fluidized bed, and the coarse particles are unevenly distributed at the bottom of the furnace. When coarse particles unevenly distributed in the furnace bottom part burn, a hot spot is formed in the furnace bottom part by reaction heat. As a result, the ash produced by the combustion may melt at the bottom of the furnace including the hot spot, and a clinker may be formed.
When the clinker is formed at the bottom of the furnace, the flow of fluidized gas blown from the bottom of the furnace into the fluidized bed is disturbed, the fluidized state of the fluidized bed is deteriorated, uneven distribution of coarse particles is promoted, and hot spots are easily formed. This increases the risk of clinker generation.

  In view of the above circumstances, an object of at least one embodiment of the present invention is to provide a fluidized bed combustion furnace capable of suppressing the generation of clinker at the bottom of the furnace.

(1) A fluidized bed combustion furnace according to at least one embodiment of the present invention includes:
A fluidized bed portion in which fluidized material and solid fuel are fluidized;
A free board portion located above the fluidized bed portion,
The fluidized bed unit is in a second position below the first position the which is a boundary position of the fluidized bed section and said freeboard section, than the first cross-sectional area A ₁ of the fluidized bed portion in the first position a second cross-sectional area _{a 2} larger.

According to the configuration of (1) above, the cross-sectional area (second cross-sectional area A ₂ ) at the second position below the first position is larger than the cross-sectional area (first cross-sectional area A ₁ ) at the first position. Therefore, the flow velocity of the fluidized gas flowing in the vertical direction in the fluidized bed portion is smaller at the second position than at the first position. For this reason, in the 2nd position where the flow velocity of fluidization gas is comparatively small, the state where the bulk density of fluidized material particles is comparatively large is easy to be maintained.
Further, in the fluidized bed portion, as the volatilization of the volatile component by heating and the combustion reaction proceed, pores are formed in the solid fuel particles, and the density of the solid fuel particles considering the pore portions decreases.
For this reason, the density of the solid fuel particles in consideration of the pore portion formed as the combustion reaction progresses during the settling of the solid fuel particles tends to be smaller than the bulk density of the fluid material particles at the second position. Therefore, it becomes difficult for the solid fuel particles to pass through the layer of fluidized material particles near the second position and reach the furnace bottom, and the generation of clinker at the furnace bottom can be suppressed.

(2) In some embodiments, in the configuration of the above (1), the fluidized bed portion satisfies 1.09 ≦ A ₂ / A ₁ ≦ 1.74.

According to the configuration of (2) above, since the fluidized bed portion satisfies A ₂ / A ₁ ≦ 1.74, the flow rate in the vicinity of the second position in the fluidized bed portion is secured to some extent, and the fluidized state is stabilized. Can be maintained. On the other hand, since the fluidized bed portion satisfies 1.09 ≦ A ₂ / A ₁ , it is easy to maintain a state in which the bulk density of the fluidized material particles is relatively large at the second position in the fluidized bed portion. Therefore, according to the structure of said (2), the production | generation of clinker in a furnace bottom part can be suppressed, fully fluidizing a fluidized bed.

(3) In some embodiments, in the configuration of (1) or (2), at least in the fluidized bed portion, at least in the second position, 50% or more of the particle bulk density in a non-fluid state of the fluidizing material. A dense particle layer, which is a region having a bulk density, is formed.

The particle dense layer is a region having a bulk density of 50% or more of the particle bulk density in the non-flowing state of the fluidized material. In the fluidized bed portion, the amount of bubbles is relatively small and the bulk density is relatively large. is there.
According to the configuration of (3) above, in the fluidized bed portion, a particle thick layer having a relatively large bulk density is formed at the second position below the first position, so that solid fuel particles having a relatively low density are formed. It becomes difficult to pass through the particle rich layer formed at least at the second position, and solid fuel particles can be prevented from reaching the bottom of the furnace. Therefore, the production | generation of clinker in a furnace bottom part can be suppressed.

(4) In some embodiments, in any one of the above configurations (1) to (3),
The flow velocity V at the second position of the fluidized gas introduced into the lower portion of the fluidized bed portion and upward is V ^*, which is the lowest gas flow velocity at which fluidization in the fluidized bed portion starts, and the fluidized material is not fluidized. 3V ^* ≦ V <, where V _th is a gas flow rate at which the bulk density of the particle dense layer in the fluidized bed portion, which is a region having a bulk density of 50% or more of the particle bulk density in the state, is 500 kg / m ³ or more. _Vth is satisfied.

According to the configuration of (4) above, since the flow velocity V at the second position of the fluidized gas satisfies 3V ^* ≦ V, the fluidized state is ensured to some extent and the fluidized state is stabilized. Can be maintained. On the other hand, since the flow velocity V satisfies V < _Vth , it is easy to maintain a state in which the bulk density of the fluidized material particles is relatively large at the second position in the fluidized bed portion. Therefore, according to the configuration of (4) above, it is possible to suppress the generation of clinker at the furnace bottom while sufficiently fluidizing the fluidized bed.

(5) In some embodiments, the (1) to (4) in any of the configurations of the flow 2 wherein the at lowermost layer portion sectional area A ₂ is the first as the second position greater than the cross-sectional area _{A 1.}

  According to the configuration of (5) above, it is easy to maintain a state in which the bulk density of the fluidized material particles is relatively large at the second position, which is the lowest part (furnace bottom) of the fluidized bed portion. Therefore, the generation of clinker at the bottom of the furnace can be effectively suppressed while ensuring as large a region where the solid fuel particles are burned while descending above the second position of the fluidized bed portion.

(6) In some embodiments, in any one of the configurations (1) to (5), a cross-sectional area of the fluidized bed portion is minimized at the first position, and at a lowermost portion of the fluidized bed portion. Maximum.

In the configuration of (6) above, since the cross-sectional area is the smallest at the first position which is the uppermost part of the fluidized bed part (the boundary position with the free board part), the flow rate of the fluidized gas is increased at the uppermost part of the fluidized bed part. In the vicinity of the uppermost part of the fluidized bed portion, fluidization of the fluidized material and the solid fuel is promoted, the combustion of the solid fuel is facilitated, and the density of the solid fuel is easily reduced. Further, in the configuration of (6), since the cross-sectional area is maximum at the lowermost part of the fluidized bed portion, it is easy to maintain a relatively large bulk density of the fluidized material particles at the lowermost portion of the fluidized bed portion. .
Therefore, according to the configuration of the above (6), the density of the solid fuel can be easily reduced, and the region where the solid fuel particles are burned while descending above the lowermost part of the fluidized bed portion can be ensured as large as possible. Generation of clinker at the bottom of the furnace can be effectively suppressed.

(7) In some embodiments, in any one of the configurations (1) to (6) above,
The fluidized bed portion includes a stepped portion below the first position,
The fluidized bed portion has a larger cross-sectional area in the region below the step portion than the cross-sectional area in the region above the step portion.

According to the configuration of (7) above, by providing the step portion below the first position, in the fluidized bed, the cross-sectional area in the lower region of the step portion is more than the cross-sectional area in the upper region of the step portion. Can be bigger. Therefore, the cross-sectional area (second cross-sectional area A ₂ ) at the second position below the first position is made larger than the cross-sectional area (first cross-sectional area A ₁ ) at the first position by relatively easy construction. This can suppress the generation of clinker at the bottom of the furnace.

(8) In some embodiments, in the configuration of (7) above,
The fluidized bed unit is a constant cross-sectional area at the first cross-sectional area A ₁ in the height range from the first position to the position of the step portion, the bottom of the fluidized bed section from the position of the step portion sectional area at the level range up to a position of constant at the second cross-sectional area a _2.

According to the configuration of (8) above, the cross-sectional area is constant in the height range from the first position to the stepped portion, and the height range from the stepped portion to the lowest position of the fluidized bed portion Since the cross-sectional area is constant, the step portion can be provided by relatively easy construction.
In addition, in the height range below the stepped portion, a relatively large second cross-sectional area A2 of the fluidized bed portion can be secured, so that a region where the bulk density of fluidized material particles is large is actively formed on the furnace bottom side. Can do. Thus, the arrival of coarse particles of solid fuel to the furnace bottom can be effectively inhibited.

(9) In some embodiments, in any one of the configurations (1) to (7), the fluidized bed portion includes a tapered portion whose cross-sectional area gradually increases as it goes downward.

  According to the configuration of (9) above, problems such as turbulence of gas flow and lowering of the fluid state around the cross-sectional area change part of the fluidized bed part, compared with the case where the shape of the combustion furnace with a rapid cross-sectional area change is adopted. Is hard to get up.

(10) In some embodiments, in the configuration of (9) above,
The fluidized bed section, the cross-sectional area in the height range from the first position to the third position lower than the first position is constant in the first cross-sectional area A _1, the flow from the third position The taper portion is provided in a height range up to the lowest position of the layer portion.

According to the above configuration (10), a relatively narrow first cross-sectional area A ₁ of the region is formed in a height range from the first position to the third position, a relatively large gas flow rate in this region, the The combustion reaction of the solid fuel fluidized in the region can be promoted. Thus, the combustion space that mainly contributes to the combustion reaction is positively formed in the upper region of the fluidized bed portion (region in the height range of the first position to the third position), so that coarse particles of solid fuel are formed in this region. It is possible to make it difficult to settle downward. In addition, because it is easy to ensure a relatively large combustion space with a relatively high gas flow rate, even if the density variation due to individual differences in solid fuel particles is large, sedimentation of coarse particles of solid fuel to the bottom of the furnace It becomes easy to disturb.

(11) In some embodiments, in the configuration of (9) above,
The fluidized bed unit, wherein the tapered portion sectional area in the height range from the first position to the fourth position below the first position is gradually increased from the first cross-sectional area A ₁ toward the lower The cross-sectional area is constant in the height range from the fourth position to the lowest position of the fluidized bed portion.

According to the configuration of (11) above, in the height range below the fourth position, a relatively large cross-sectional area of the fluidized bed portion can be ensured, and therefore, a region where the bulk density of fluidized material particles is large on the furnace bottom side. Can be actively formed. Thus, the arrival of coarse particles of solid fuel to the furnace bottom can be effectively inhibited.
Further, according to the configuration of (11), the construction is relatively easy because the cross-sectional area is constant in the height range from the fourth position below the first position to the lowest position of the fluidized bed portion. It is.

(12) In some embodiments, in any one of the configurations (9) to (11), the taper portion has an inclination angle θ [°] with respect to a horizontal direction that satisfies 40 ≦ θ ≦ 80.

  According to the configuration of (12) above, by setting the inclination angle θ of the tapered portion with respect to the horizontal direction to 40 degrees or more, the ratio of the second cross-sectional area A2 to the first cross-sectional area A1 is prevented from becoming excessive. It is easy to ensure the likelihood of the gas flow rate at the second position with respect to the fluidization start speed. Further, by setting the inclination angle θ to 80 degrees or less, the ratio of the second cross-sectional area A2 to the first cross-sectional area A1 is increased to some extent, the gas flow velocity at the second position is made relatively small, and the coarse particles of the solid fuel Can be effectively inhibited from reaching the bottom of the furnace.

(13) In some embodiments, in any one of the configurations (1) to (12), the fluidized bed portion has a fluidized bed height of 1 m or more.

  According to the configuration of (13), since the fluidized bed height of the fluidized bed portion is 1 m or more, the solid fuel particles supplied from the upper portion of the fluidized bed portion are solidified in the process of settling in the fluidized bed portion. Combustion proceeds sufficiently in the fuel particles, and the density of solid fuel particles (density considering the pores) decreases. For this reason, it becomes difficult for the solid fuel particles to pass through the layer of fluidized material particles in the vicinity of the second position having a relatively large bulk density, and the coarse particles of the solid fuel can be prevented from reaching the bottom of the furnace. Therefore, the production | generation of clinker in a furnace bottom part can be suppressed.

(14) In some embodiments, in any one of the configurations (1) to (13), the solid fuel includes biomass.

  According to the configuration of (14), in the fluidized bed combustion furnace that burns the solid fuel containing biomass, it is possible to suppress the generation of clinker at the furnace bottom. Moreover, since the particle density of biomass is relatively small, a significant density difference can be realized between the bulk density of the fluidized material particles on the furnace bottom side, and the arrival of biomass particles at the furnace bottom (1) It can be effectively inhibited by the configuration described in.

  According to at least one embodiment of the present invention, a fluidized bed combustion furnace capable of suppressing the generation of clinker at the furnace bottom is provided.

It is a schematic structure figure of combustion equipment to which a fluidized bed combustion furnace concerning one embodiment was applied. It is a schematic structure figure of a fluidized bed combustion furnace concerning one embodiment. It is a schematic structure figure of a fluidized bed combustion furnace concerning one embodiment. It is a schematic structure figure of a fluidized bed combustion furnace concerning one embodiment. It is a schematic structure figure of a fluidized bed combustion furnace concerning one embodiment. It is a graph which shows typically the correlation of the flow velocity of fluidization gas, and a fluidized material bulk density. It is a figure which shows an example of a structure of a general fluidized bed combustion furnace.

  Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments or shown in the drawings are not intended to limit the scope of the present invention, but are merely illustrative examples. Absent.

  First, with reference to FIG. 1, the combustion equipment to which the fluidized-bed combustion furnace which concerns on some embodiment is applied is demonstrated. FIG. 1 is a schematic configuration diagram of a combustion facility to which a fluidized bed combustion furnace according to an embodiment is applied. As shown in FIG. 1, a combustion facility 100 includes a fluidized bed combustion furnace 1 for burning particulate solid fuel. The fluidized bed combustion furnace 1 includes a combustion part 5, a wind box 4 provided below the combustion part 5, and a porous plate 3 provided between the combustion part 5 and the wind box 4.

  Combustion air (fluidized gas) 8 is supplied to the wind box 4 from a blower. The combustion air 8 that has flowed into the wind box 4 is supplied to the combustion section 5 located above the porous plate 3 through the pores 2 of the porous plate 3 provided above the wind box 4.

  Particulate solid fuel 6 is supplied from a fuel supply facility (not shown) to the combustion unit 5 through a fluid fuel supply pipe 17, and the particulate fluid 7 is supplied from a fluid material supply facility (not shown). It comes to be supplied. The solid fuel 6 and the fluidized material 7 are mixed while being transported by the transporting air 19 and supplied as the fluidized fuel 20 above the porous plate 3.

In some embodiments, the solid fuel 6 may be a solid fuel having a density lower than that of the fluidized material 7. In some embodiments, the solid fuel 6 may include biomass or lignite.
In some embodiments, the flow material 7 may include sand or limestone.

The fluidized fuel 20 (fluidized material 7 and solid fuel 6) supplied to the combustion unit 5 is fluidized by the combustion air (fluidized gas) 8 blown into the combustion unit 5 from below to above and flows. The layer portion 9 is formed. In the combustion part 5, a free board part 21 not filled with the fluidizing material 7 is formed above the fluidized bed part 9.
That is, the fluidized bed combustion furnace 1 includes a fluidized bed portion 9 in which the fluidized material 7 and the solid fuel 6 are fluidized, and a free board portion 21 positioned above the fluidized bed portion 9.

  In the fluidized bed portion 9, the solid fuel 6 and the combustion air 8 are agitated and mixed, and the solid fuel 6 burns.

  Next, the fluidized bed combustion furnace 1 according to some embodiments will be described in more detail with reference to FIGS. 2 to 5 are schematic configuration diagrams of a fluidized bed combustion furnace 1 according to an embodiment, respectively. 2-5, illustration of the extraction pipe | tube 10 (refer FIG. 1) provided in the perforated panel 3 is abbreviate | omitted.

In some embodiments, in the fluidized bed combustion furnace 1, the fluidized bed unit 9 has a second position 24 below the first position 22 that is a boundary position between the fluidized bed unit 9 and the freeboard unit 21. 1 having a second cross-sectional area _{a 2} greater than the first cross-sectional area _{a 1} of the fluidized layer 9 at position 22. That is, A ₁ and A ₂ satisfy A ₁ <A ₂ . The first position 22 and the second position 24 are positions in the vertical direction (vertical direction).

In the embodiment shown in FIGS. 2 to 4, the second position 24 is the same position as the lowermost portion (furnace bottom portion 26) of the fluidized bed portion 9. Further, in the embodiment shown in FIG. 5, a predetermined range in which the diameter of the fluidized bed portion 9 is expanded (up and down) between the first position 22 that is the uppermost portion of the fluidized bed portion 9 and the lowermost portion (furnace bottom portion 26). The range in the direction) is the second position 24.
In the case where the second position 24 is present over a range in the vertical direction, second cross-sectional area A ₂ of the second position 24, may be constant in the vertical direction of the range, be adapted to change Also good.

Here, FIG. 7 is a diagram illustrating an example of a configuration of a general fluidized bed combustion furnace. In the fluidized bed combustion furnace 101 shown in FIG. 7, the fluidized bed unit 9 has a first position 22 at a second position 24 below the first position 22 that is a boundary position between the fluidized bed unit 9 and the freeboard unit 21. Fluidized bed section 9
Has a smaller second cross-sectional area _{A 2} than the first cross-sectional area _{A 1} in. That is, A ₁ and A ₂ satisfy A ₁ > A ₂ . Further, the cross-sectional area of the fluidized bed portion 9 decreases from the first position 22 toward the lower furnace bottom portion 26 and is minimum at the furnace bottom portion 26 (the lowest portion of the fluidized bed portion 9).

  Conventionally, the flow rate of the fluidized gas in the lower region of the fluidized bed is increased by making the shape of the fluidized bed portion tapered, for example, as shown in FIG. Thus, by improving the flow state of the furnace bottom, the formation of clinker at the furnace bottom was suppressed.

  On the other hand, in some embodiments of the present invention, a bulk density of fluidized material particles is provided by providing a diameter-enlarged portion around the furnace bottom portion 26 and relatively reducing the flow velocity of the fluidizing gas in the vicinity of the furnace bottom portion 26. Is relatively easy to maintain. In such a state, the solid fuel particles having a relatively small density through combustion in the fluidized bed are unlikely to enter the layer of fluidized material particles having a relatively large bulk density, and do not settle to the vicinity of the furnace bottom portion 26.

That is, according to the embodiment shown in FIGS. 2 to 5, the cross-sectional area (second cross-sectional area A ₂ ) at the second position 24 below the first position 22 is the cross-sectional area at the first position 22 (the first cross-sectional area A ₁ ). Since it is larger than the cross-sectional area A ₁ ), the flow rate of the fluidized gas flowing from the lower side to the upper side in the fluidized bed portion 9 is smaller than the first position 22 at the second position 24. For this reason, in the 2nd position 24 where the flow velocity of fluidization gas is comparatively small, the state where the bulk density of fluid material particles is comparatively large is easy to be maintained.
Further, in the fluidized bed portion 9, as the volatilization of the volatile component by heating and the combustion reaction proceed, pores are formed in the solid fuel particles, and the density of the solid fuel particles considering the pore portions decreases.
For this reason, the density of the solid fuel particles in consideration of the pores formed with the progress of the combustion reaction during the settling of the solid fuel particles tends to be smaller than the bulk density of the fluid material particles at the second position 24. . Therefore, it becomes difficult for solid fuel particles to pass through the layer of fluidized material particles in the vicinity of the second position 24 and reach the furnace bottom portion 26, and generation of clinker in the furnace bottom portion 26 can be suppressed.

  In some embodiments, a particle dense layer that is a region having a bulk density of 50% or more of the particle bulk density in the non-flowing state of the fluidizing material 7 is formed at least at the second position 24 in the fluidized bed portion 9. .

Here, the particle dense layer is a region having a bulk density of 50% or more of the particle bulk density in the non-flowing state of the fluidizing material 7, and in the fluidized bed portion 9, the amount of bubbles is relatively small and the bulk density is low. This is a relatively large area.
In the fluidized bed portion 9, a particle thick layer having a relatively large bulk density is formed at the second position 24 below the first position 22, so that solid fuel particles having a relatively low density are at least at the second position 24. Therefore, it is difficult to pass through the particle thick layer formed in the first layer, and the arrival of the solid fuel particles to the furnace bottom 26 can be inhibited. Therefore, the production | generation of the clinker in the furnace bottom part 26 can be suppressed.

  The particle bulk density in the fluidized bed in the fluidized state can be determined, for example, by measuring the intensity of laser diffracted light and reflected light with a sensor when the laser is irradiated into the fluidized bed. In other words, from the waveform data obtained by this measurement, the presence of the bubble phase is detected by using the difference in signal intensity between the particle dense layer and the bubble layer, and the space ratio of the bubble phase in the fluidized bed is determined. It is calculated as the ratio of the detection time to the measurement time. The volume occupied by the bubble phase and the volume of the particle dense layer can be calculated from the space ratio of the bubble phase. The particle weight of the particle rich layer can be calculated by the product of the pressure loss of the fluidized bed and the cross-sectional area of the fluidized bed. This pressure loss in the fluidized bed corresponds to the differential pressure between the lowermost part of the fluidized bed and the uppermost part of the fluidized bed. Furthermore, the bulk density of the particle rich layer can be calculated from the volume of the particle rich layer and the particle weight of the particle rich layer. The bulk density in the fluidized bed in the fluidized state can be measured not only by laser measurement but also by imaging the fluidized state and performing image processing. Also in the image processing, since a difference in strength occurs between the particle dense layer and the bubble layer, the particle bulk density in the fluidized bed in the fluidized state can be obtained based on this difference in strength.

  Since there is a correlation between the particle bulk density and the flow rate of the fluidized gas, a predetermined particle bulk density (for example, a bulk of 50% or more of the particle bulk density in the non-flowing state of the fluidized material 7 in the fluidized bed portion 9). In order to obtain (density), the fluidizing gas may be flowed at a predetermined gas flow rate corresponding to the correlation.

In this regard, in some embodiments, the flow velocity V at the second position 24 of the fluidized gas introduced into the lower portion of the fluidized bed portion 9 and traveling upward satisfies 3V ^* ≦ V < _Vth . Here, V ^* is the lowest gas flow velocity at which fluidization in the fluidized bed portion 9 starts, and _Vth is the particle dense layer in the fluidized bed portion 9 (that is, the particle bulk density in the non-fluid state of the fluidized material 7). The gas flow rate at which the bulk density of the region having a bulk density of 50% or more is 500 kg / m ³ or more.
Here, the flow velocity V of the fluidizing gas at the second position 24 is a value obtained by dividing the flow rate of the fluidizing gas at the second position 24 by the cross-sectional area of the fluidized bed portion 9 at the second position, that is, at the second position 24. It is the average flow rate of fluidized gas.

If the flow velocity V of the fluidized gas at the second position 24 satisfies 3V ^* ≦ V, a fluid velocity in the vicinity of the second position 24 in the fluidized bed portion 9 can be secured to some extent, and the fluidized state can be stably maintained. Moreover, if the flow velocity V satisfies V < _Vth , it is easy to maintain a state in which the bulk density of the fluid material particles is relatively large at the second position 24 in the fluidized bed portion 9.
Therefore, by setting the flow velocity V of the fluidized gas at the second position 24 within the above range, it is possible to suppress the generation of clinker at the furnace bottom portion 26 while sufficiently fluidizing the fluidized bed.

Here, the reason why the gas flow rate at which the bulk density of the particle dense layer is 500 kg / m ³ or more is adopted as the flow rate value that defines the upper limit value of the gas flow rate V will be described with reference to FIG. FIG. 6 is a graph schematically showing the correlation between the flow rate of the fluidizing gas and the bulk density of the fluidized material.
As shown in the graph of FIG. 6, there is a correlation between the flow rate of the fluidizing gas and the fluidized material bulk density, and the fluidized material bulk density tends to decrease as the gas flow rate increases. Therefore, when it is desired to obtain a fluidized material bulk density of a predetermined value or more, for example, as in the above-described particle concentrated layer, the gas corresponding to the fluidized material bulk density is based on the correlation shown in the graph of FIG. The fluidizing gas is circulated at a gas flow rate below the flow rate.
Further, as a result of intensive studies by the present inventors, in a typical combustion apparatus, the fluidized material bulk density suitable for achieving both the sedimentation speed and the combustion speed of the solid fuel particles in the fluidized bed portion 9 is approximately 500 kg. / M ³ was found.
Therefore, the gas flow velocity V _th (see FIG. 6) when the fluidized material bulk density is 500 kg / m ³ is adopted as the flow velocity value that defines the upper limit of the flow velocity V of the fluidizing gas.

In some embodiments, the fluidized bed portion 9 has a ratio A ₂ / A ₁ of the second cross-sectional area A ₂ at the second position to the first cross-sectional area A _{1 at} the first position is 1.09 ≦ A _2. / A ₁ ≦ 1.74 is satisfied.

If the fluidized bed portion 9 satisfies A ₂ / A ₁ ≦ 1.74, the gas flow rate in the vicinity of the second position 24 in the fluidized bed portion 9 can be secured to some extent, and the fluidized state can be stably maintained. On the other hand, if the fluidized bed portion 9 satisfies 1.09 ≦ A ₂ / A ₁ , it is easy to maintain a state in which the bulk density of the fluidized material particles is relatively large at the second position 24 in the fluidized bed portion 9. Thereby, the production | generation of the clinker in the furnace bottom part 26 can be suppressed, fully fluidizing the fluidized bed part 9. FIG.
For example, in a fluidized bed combustion furnace 1 having a height of the fluidized layer 9 within a predetermined range (height of the first position 22 relative to the furnace bottom 26), for the first cross-sectional area A ₁ of the second cross-sectional area A ₂ By adjusting the ratio A ₂ / A ₁ within the above-mentioned range, the above-described effects can be obtained.

In some embodiments, as shown in FIGS. 2 to 4, the lowermost portion (furnace bottom portion 26) of the fluidized bed portion 9 is the second position 24, and the lowermost portion (furnace bottom portion 26) of the fluidized bed portion 9. The second cross-sectional area A ₂ is larger than the first cross-sectional area A _{1 at} the first position 22.

  In this case, the bulk density of the fluidized material particles is easily maintained at the second position 24, which is the lowest part (furnace bottom portion 26) of the fluidized bed portion 9, and is more than the second position 24 of the fluidized bed portion 9. On the upper side, it is possible to effectively suppress the generation of clinker at the furnace bottom portion 26 while ensuring as large a region where the solid fuel particles are burned while descending.

  In some embodiments, as shown in FIGS. 2 to 4, the cross-sectional area of the fluidized bed portion 9 is minimized at the first position 22 and maximized at the lowermost portion (furnace bottom portion 26) of the fluidized bed portion 9. ing.

Thus, since the cross-sectional area is the smallest at the first position 22 which is the uppermost part of the fluidized bed part 9 (the boundary position with the free board part), the flow velocity of the fluidized gas is increased at the uppermost part of the fluidized bed part 9. In the vicinity of the uppermost part of the fluidized bed portion 9, fluidization of the fluidized material 7 and the solid fuel 6 is promoted, so that the combustion of the solid fuel 6 is facilitated, and the density of the solid fuel 6 is easily reduced. Further, since the cross-sectional area is maximum at the lowermost portion (furnace bottom portion 26) of the fluidized bed portion 9, a state in which the bulk density of the fluidized material particles is relatively large is maintained at the lowermost portion (furnace bottom portion 26) of the fluidized bed portion 9. It has become easier.
Therefore, the density of the solid fuel 6 is likely to decrease, and the area where the solid fuel particles burn while descending above the lowermost part (furnace bottom part 26) of the fluidized bed part 9 can be secured as large as possible. The production of clinker in can be effectively suppressed.

  In the exemplary embodiment shown in FIG. 1, the fluidized bed portion 9 includes a stepped portion 32 below the first position 22. In the fluidized bed portion 9, the cross-sectional area in the lower region 38 of the step portion 32 is larger than the cross-sectional area in the upper region 23 of the step portion 32.

  Thus, by providing the step portion 32 below the first position 22, the fluidized bed portion 9 has a cross-sectional area in the lower region 38 of the step portion 32 rather than a cross-sectional area in the upper region 23 of the step portion 32. Can be bigger. Therefore, the cross-sectional area (second cross-sectional area A2) at the second position 24 below the first position 22 is larger than the cross-sectional area (first cross-sectional area A1) at the first position 22 by relatively easy construction. Thus, the generation of clinker at the furnace bottom portion 26 can be suppressed.

Further, in the exemplary embodiment shown in FIG. 1, the fluidized bed portion 9 has a cross-sectional area of the first cross-sectional area A _{1 in} the height range (upper region 23) from the first position 22 to the position of the stepped portion 32. there in a constant, a constant at the bottom (furnace bottom 26) height range position to the (lower region 38) the cross-sectional area at the second cross-sectional area a ₂ of the fluidized bed portion 9 from the position of the step portion 32 .

In this case, the cross-sectional area is constant in the height range from the first position 22 to the position of the stepped portion 32 (upper region 23), and from the position of the stepped portion 32 to the bottom of the fluidized bed portion 9 (furnace bottom portion 26). Since the cross-sectional area is constant in the height range up to the position (lower region 38), the step portion can be provided by relatively easy construction.
Further, in the height range (lower region 38) below the stepped portion 32, it is possible to secure a second cross-sectional area A ₂ of a relatively large fluidized bed unit 9, the bulk density of the fluidized material particles in the furnace bottom portion 26 side Large areas can be actively formed. Thus, the arrival of coarse particles of the solid fuel 6 to the furnace bottom portion 26 can be effectively inhibited.

  In the exemplary embodiment shown in FIGS. 3 and 4, the fluidized bed portion 9 includes a tapered portion 34 whose cross-sectional area gradually increases as it goes downward.

  In this case, as compared with the case of adopting the shape of the combustion furnace with a rapid change in the cross-sectional area, problems such as gas flow disturbance and a decrease in the flow state around the cross-sectional area change part of the fluidized bed part 9 are less likely to occur.

In the exemplary embodiment shown in FIG. 3, the fluidized bed portion 9 has a first sectional area A having a sectional area in a height range 27 from the first position 22 to the third position 25 below the first position 22. ₁ and has a tapered portion 34 in a height range 28 from the third position 25 to the position of the lowermost portion (furnace bottom portion 26) of the fluidized bed portion 9.

In this case, relatively narrow first cross-sectional area A ₁ of a region is formed in the height range 27 from the first position 22 to the third position 25, and relatively large gas flow rate in this region, fluidization in this region The combustion reaction of the solid fuel 6 thus made can be promoted. In this way, the combustion space that mainly contributes to the combustion reaction is actively formed in the upper region of the fluidized bed portion 9 (the region in the height range 27 from the first position 22 to the third position 25). Coarse particles can be less likely to settle below this region. In addition, since it is easy to ensure a relatively wide combustion space with a relatively high gas flow rate, even if the density variation due to individual differences in solid fuel particles is large, coarse particles of solid fuel 6 to the bottom of the furnace It becomes easy to prevent sedimentation.

In the exemplary embodiment shown in FIG. 4, the fluidized bed portion 9 is configured so that the cross-sectional area decreases in the height range from the first position 22 to the fourth position 29 below the first position 22. has a tapered portion 34 gradually increases from 1 cross-sectional area a _1, the cross-sectional area in the high range 33 to the position of the bottom (furnace bottom 26) of the fluidized bed portion 9 from the fourth position 29 is constant.

In this case, in the height range 33 below the fourth position 29, a relatively large cross-sectional area of the fluidized bed portion 9 can be secured, and therefore, an area where the bulk density of fluidized material particles is large is positively provided on the furnace bottom portion 26 side. Can be formed. Thus, the arrival of coarse particles of the solid fuel 6 to the furnace bottom portion 26 can be effectively inhibited.
Further, in this case, since the cross-sectional area is constant in the height range 33 from the fourth position 29 below the first position 22 to the position of the lowermost portion (furnace bottom portion 26) of the fluidized bed portion 9, the construction is relatively performed. Is easy.

  In some embodiments, the inclination angle θ [°] may be θ that satisfies 40 ≦ θ ≦ 80. Here, the inclination angle θ [°] of the tapered portion 34 is the inclination angle θ [°] of the tapered portion 34 with respect to the horizontal direction, as shown in FIGS. 3 and 4.

In this case, by setting the inclination angle θ of the taper portion 34 with respect to the horizontal direction to 40 degrees or more, the ratio of the second cross-sectional area A ₂ to the first cross-sectional area A ₁ is prevented from becoming excessive, and the second position It is easy to ensure the likelihood of the gas flow rate at 24 for the fluidization start speed. Further, by setting the inclination angle θ to 80 degrees or less, the ratio of the second cross-sectional area A ₂ to the first cross-sectional area A ₁ is increased to some extent, the gas flow velocity at the second position 24 is made relatively small, and the solid fuel 6 coarse particles can be effectively prevented from reaching the furnace bottom 26.

  In some embodiments, the fluidized bed portion 9 has a fluidized bed height H of 1 m or more. In addition, the fluidized bed height H is the height from the lowest part (furnace bottom part 26) of the fluidized bed part 9 to the uppermost part (1st position 22), as shown in FIGS.

  In this case, since the fluidized bed height H of the fluidized bed portion 9 is 1 m or more, the solid fuel 6 particles supplied from the upper part of the fluidized bed portion 9 burn in the solid fuel particles in the process of settling in the fluidized bed portion. Is sufficiently advanced, and the density of the solid fuel particles (the density considering the pores) decreases. For this reason, it becomes difficult for the solid fuel particles to pass through the layer of fluidized material particles near the second position 24 having a relatively large bulk density, and the coarse particles of the solid fuel 6 can be prevented from reaching the bottom of the furnace. . Therefore, the production | generation of the clinker in the furnace bottom part 26 can be suppressed.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to embodiment mentioned above, The form which added the deformation | transformation to embodiment mentioned above and the form which combined these forms suitably are included.

In this specification, an expression representing a relative or absolute arrangement such as “in a certain direction”, “along a certain direction”, “parallel”, “orthogonal”, “center”, “concentric” or “coaxial”. Represents not only such an arrangement strictly but also a state of relative displacement with tolerance or an angle or a distance to obtain the same function.
For example, an expression indicating that things such as “identical”, “equal”, and “homogeneous” are in an equal state not only represents an exactly equal state, but also has a tolerance or a difference that can provide the same function. It also represents the existing state.
In this specification, expressions representing shapes such as quadrangular shapes and cylindrical shapes not only represent shapes such as quadrangular shapes and cylindrical shapes in a strict geometric sense, but also within a range where the same effects can be obtained. In addition, a shape including an uneven portion or a chamfered portion is also expressed.
In this specification, the expression “comprising”, “including”, or “having” one constituent element is not an exclusive expression for excluding the existence of another constituent element.

DESCRIPTION OF SYMBOLS 1 Fluidized bed combustion furnace 2 Porous 3 Porous plate 4 Wind box 5 Combustion part 6 Solid fuel 7 Fluid 8 Fluid air 9 Fluidized bed part 10 Extraction pipe 11a Valve 11b Valve 12 Hopper 17 Fluid fuel supply pipe 19 Carrying air 20 Fluidized fuel 21 Free board portion 22 First position 23 Upper region 24 Second position 25 Third position 26 Furnace bottom portion 27 Height range 28 Height range 29 Fourth position 32 Stepped portion 33 Height range 34 Tapered portion 38 Lower region 100 Combustion equipment 101 Fluidized bed combustion furnace A ₁ First sectional area A ₂ Second sectional area H Fluidized bed height θ Inclination angle

Claims (14)

A fluidized bed portion in which fluidized material and solid fuel are fluidized;
A free board portion located above the fluidized bed portion,
The fluidized bed unit is in a second position below the first position the which is a boundary position of the fluidized bed section and said freeboard section, than the first cross-sectional area A ₁ of the fluidized bed portion in the first position fluidized bed combustion furnace, characterized in that it comprises a second cross-sectional area a ₂ larger. The fluidized bed combustion furnace according to claim 1, wherein the fluidized bed portion satisfies 1.09 ≦ A ₂ / A ₁ ≦ 1.74.   The particle dense layer, which is a region having a bulk density of 50% or more of a particle bulk density in a non-flowing state of the fluidizing material, is formed at least in the second position in the fluidized bed portion. 3. A fluidized bed combustion furnace according to 1 or 2. The flow velocity V at the second position of the fluidized gas introduced into the lower portion of the fluidized bed portion and upward is V ^*, which is the lowest gas flow velocity at which fluidization in the fluidized bed portion starts, and the fluidized material is not fluidized. 3V ^* ≦ V <, where V _th is a gas flow rate at which the bulk density of the particle dense layer in the fluidized bed portion, which is a region having a bulk density of 50% or more of the particle bulk density in the state, is 500 kg / m ³ or more. The fluidized bed combustion furnace according to any one of claims 1 to 3, wherein _Vth is satisfied. According to the any one of claims 1 to 4 fluidized bed unit and the second cross-sectional area A ₂ in the bottom of being greater than the first cross-sectional area A ₁ as the second position Fluidized bed combustion furnace.   6. The fluidized bed combustion furnace according to claim 1, wherein a cross-sectional area of the fluidized bed portion is minimized at the first position and is maximized at a lowermost portion of the fluidized bed portion. . The fluidized bed portion includes a stepped portion below the first position,
The fluidized bed according to any one of claims 1 to 6, wherein the fluidized bed portion has a larger cross-sectional area in a lower region of the step portion than a cross-sectional area in an upper region of the step portion. Layer combustion furnace. The fluidized bed unit is a constant cross-sectional area at the first cross-sectional area A ₁ in the height range from the first position to the position of the step portion, the bottom of the fluidized bed section from the position of the step portion 8. The fluidized bed combustion furnace according to claim 7, wherein a cross-sectional area is constant at the second cross-sectional area A ₂ in a height range up to the position of 8.   The fluidized-bed combustion furnace according to any one of claims 1 to 7, wherein the fluidized-bed portion includes a tapered portion whose cross-sectional area gradually increases as it goes downward. The fluidized bed section, the cross-sectional area in the height range from the first position to the third position lower than the first position is constant in the first cross-sectional area A _1, the flow from the third position The fluidized bed combustion furnace according to claim 9, wherein the tapered portion is provided in a height range up to a position of a lowermost portion of the layer portion. The fluidized bed unit, wherein the tapered portion sectional area in the height range from the first position to the fourth position below the first position is gradually increased from the first cross-sectional area A ₁ toward the lower 10. The fluidized bed combustion furnace according to claim 9, wherein a cross-sectional area is constant in a height range from the fourth position to a lowermost position of the fluidized bed portion.   The fluidized bed combustion furnace according to any one of claims 9 to 11, wherein the tapered portion has an inclination angle θ [°] with respect to a horizontal direction satisfying 40 ≦ θ ≦ 80.   The fluidized bed combustion furnace according to any one of claims 1 to 12, wherein the fluidized bed section has a fluidized bed height of 1 m or more.   The fluidized bed combustion furnace according to any one of claims 1 to 13, wherein the solid fuel contains biomass.

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