JPS625242B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a combustion method and a combustion furnace using a fluidized bed.

[Conventional technology]

As this type of combustion furnace, for example, in a combustion furnace for municipal waste, a fluidized bed furnace has recently been used, which has better combustion efficiency than a stoker furnace and produces less combustion residue.

[Problem that the invention seeks to solve]

However, if waste is thrown into the furnace in a state of a certain size or larger, it will inhibit the fluidization of the fluidized medium and prevent combustion.To prevent this, conventional fluidized bed combustion furnaces As a pretreatment of the waste before it is put into the furnace, it is essential to use a crusher to pre-shred the waste to a size small enough not to interfere with the flow of the fluidizing medium.

Such crushing equipment not only has the drawbacks of high equipment costs, operating costs, and maintenance costs, the labor involved in related work, and the need for space for the equipment, but also has the drawbacks that foreign particles may be caught during the crushing process. There have been cases in which the crushing equipment has stopped due to damage to parts due to crushing, etc., and an increase in power, which has led to serious problems such as the need to stop the operation of the furnace.

On the other hand, in terms of combustion capacity, the maximum capacity of the currently operating furnaces is approximately 75t/24h.
Even in the design, the maximum is about 150t/24h,
It was difficult to realize a larger capacity than this.

Several attempts have been made in the past to solve these problems, but all of them still have the following drawbacks.

(1) It is essential to crush garbage and other combustible materials as a pre-treatment before feeding them into the furnace, and not only the cost, labor, and space associated with crushing equipment, but also the problems caused by the crushing process, It may interfere with driving.

(2) Large incombustibles and coarse combustibles get caught in the gap between the lower end of the partition wall that separates the moving bed chamber from the fluidized bed chamber and the distribution plate, preventing smooth circulation of the fluidized medium in the furnace. It reduces combustion efficiency and prevents smooth discharge of non-combustible materials.

(3) The settling velocity of the moving bed is low, the circulation amount of the fluidized medium is small, and the combustion capacity is small.

(4) The control range for the settling speed of the moving layer is small.

(5) The flammable gas generated by thermal decomposition in the moving bed does not diffuse laterally, but escapes upward and burns in the freeboard, so the combustion heat is not useful for heating the fluidized medium. .

(6) Since the tip of the combustible material supply pipe reaches the upper end of the moving bed, it is susceptible to wear, corrosion, and deformation, which may cause problems such as combustible material blockage.

(7) Because the partition plates and supply pipes are inside the furnace, it is difficult to inspect and repair the inside of the furnace.

(8) Clinker is likely to occur, which may impede the flow of the fluidized medium and cause the furnace to stop operating.

(9) Since the horizontal cross-sectional shape of the furnace is circular, it is necessary to increase the radius to increase the capacity, but in order to effectively and smoothly move the fluid medium from the circumference to the center point, it is necessary to increase the radius. has a radius limit, and it is not possible to create a large-capacity combustion furnace with one unit.

In order to eliminate these drawbacks, the inventors conducted numerous experiments and research, confirmed means that could eliminate these drawbacks, and based on the knowledge obtained at that time, the present invention was made. It is something.

The object of the present invention is to eliminate the above-mentioned drawbacks of the conventional methods and provide a useful fluidized bed combustion method and combustion furnace.

[Means for solving problems]

The present invention provides a fluidized bed combustion method in which a combustion material is combusted in a fluidized bed formed by fluidizing a fluidized medium by fluidizing gas ejected upward from the bottom of a combustion furnace, wherein the fluidized bed comprises: The fluidizing gas is held in a fluidized bed chamber having a rectangular horizontal cross section, and the fluidizing gas is ejected from a gas dispersion mechanism that is high in the center and low in both side edges. It is larger at both side edges of the center than near the center of the furnace bottom, and above the both side edge fluidized bed blocks the upward flow path of the fluidizing gas at both side edges, and The fluidized medium is turned toward the center of the furnace, forming a moving layer in the center of the furnace bottom where the fluidized medium settles while maintaining a fluidized state, and the fluidized media on both sides is actively fluidized. forming a bed, the fluidized medium is allowed to settle in the moving bed, migrate to the both side edges at the bottom of the moving bed, rise in the side edge fluidized bed, and rise above the both side edge fluidized bed. The diverted fluidizing gas is diverted toward the top of the moving bed and circulated in the furnace, and there is no partition wall between the moving bed and the side edge fluidized beds, and there is no partition wall between the two layers. A fluidized bed combustion method and a combustion furnace are characterized in that combustion is performed in a state where mass transfer and heat transfer of a fluidized medium, gas, combustible materials, etc. are not hindered.

〔Example〕

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the drawings in an embodiment in which a dispersion plate is used as a dispersion mechanism for fluidizing air in a municipal waste combustion furnace.

Fig. 1 shows an example of municipal waste combustion equipment using a fluidized bed combustion furnace 6, in which waste stored in a pit 1 is dumped into a hopper 4 by a bucket 3 of a crane 2, and a dust supply which is a combustion material supply device is used. The device 5 is adapted to supply a combustion furnace 6 . In the combustion furnace 6, the fluidizing gas supplied by the blower 7 is ejected upward from the distribution plate 8 into the furnace, hits the inclined wall 9 and becomes a swirling flow 10 in a vertical plane, dispersing the fluidized medium such as sand. A swirling fluidized bed is formed by flowing along this line. Furthermore, as will be described later, a descending moving bed is formed in the center of the furnace, and the swirling fluidized bed and descending moving bed allow the waste to be burnt well in a short period of time, inhibiting fluidization even if crushing is not performed in advance. high combustion efficiency can be obtained without

11 is a combustion exhaust gas duct, 12 is a non-combustible material discharge device, 13 is a vibrating sieve, 14 is a conveyor for discharging lump non-combustible materials, and 15 is an elevator for collecting a fluid medium such as sand.

In the dust supply device 5, 16 is a garbage inlet;
Reference numeral 7 indicates an outlet for the crushed waste, 18 indicates an outlet for large incombustible materials that are not allowed to enter the combustion furnace 6, and 19 indicates a return chute. 53 is a damper that temporarily receives large incombustible materials in order to remove them.

Details of the structure of the dust supply device 5 can be found in Japanese Patent Application No. 55-164223.
However, as shown in FIG.
Screws having opposite torsion blades are arranged parallel to the screw driven by the screw 7, and are rotated in opposite directions by gears. When the blades of both screws rotate toward each other at the top (forward rotation), the waste moves to the right and is thrown into the combustion furnace 6 through the outlet 17. Uncombustible lumps that are not allowed to be introduced into the combustion furnace 6 are thrown back into the chute 19 through the discharge port 18 by reversing both screws and moving them to the left.

The pitch of the screw near the exit 17 is wider than the pitch near the entrance 16.

The combustion furnace 6 will be explained.

As shown in FIGS. 2, 3, and 4, the combustion furnace 6
An air distribution plate 42 for fluidization is provided at the bottom of the furnace. The distribution plate 42 has both side edges lower than the center, and is formed into a chevron-shaped cross section (roof-like shape) that is substantially symmetrical with respect to the center line 57 of the furnace. The inclination may be different between the center portion and both side edge portions. Incombustible material discharge ports 48 are connected to both side edges. Nonflammable material discharge port 4
8 does not necessarily have to have exactly the same shape on both the left and right sides; for example, one side may have a shape as shown in FIG. 4, and the other may have a shape as shown in FIG. 5. It is sufficient if they are placed on both sides so that the flow direction is approximately equal.

The fluidized air sent from the blower 7 is sent to the air chamber 4.
3, 44, and 45, and is ejected upward from the dispersion plate 42. Air chambers 43, 45 on both side edges
Mass velocity of fluidized air ejected from (Kg/ ^m2・
sec) has a sufficient size to form a fluidized bed, but the mass velocity of the fluidized air ejected from the central air chamber 44 is selected to be smaller than the former.

For example, the mass velocity of the fluidized air ejected from the air chambers 43 and 45 is 4 to 20 Gmf, preferably 6 to 20 Gmf.
12 Gmf, whereas the mass velocity of the fluidized air ejected from the air chamber 44 is selected to be 0.5 to 3 Gmf, preferably 1 to 2.5 Gmf. Here, 1 Gmf is the fluidization starting mass velocity.

The number of air chambers is selected from three or more. In many cases, the mass velocity of the fluidizing air is small near the center and large near the side edges.

Slanted walls 9 are provided directly above the air chambers 43 and 45 on both side edges as reflective walls that block the upward flow path of the fluidized air and reflect the fluidized air toward the center of the furnace.

The upper side of the inclined wall 9 is provided with an inclined surface 58 having an opposite slope to the inclined wall 9, so as to prevent the flow medium from accumulating.

The inclination of the dispersion plate 42 is preferably about 5 to 15 degrees, and the inclination of the inclined wall 9 is preferably about 10 to 60 degrees with respect to the horizontal. The surface of the inclined wall 9 may be a flat surface, a convex surface, or a concave surface.

The outlet 17 of the dust supply device 5 is provided in the furnace ceiling 59.
A combustion material inlet 60 connected to the central air chamber 4
It is set up to correspond to 4.

Therefore, in the furnace space surrounded by the furnace wall 61 (including the inclined wall 9 and the inclined surface 58), the distribution plate 42, and the ceiling part 59, there is a partition wall (for example, a partition) that partitions the space near the upper part of the distribution plate 42. board) is not provided at all.

The inclined wall 9 may be a wall body made of a metal pipe, and preheating may be performed by passing fluidized air into the pipe.

To explain the operation of the combustion furnace 6, the blower 7 sends fluidized air to the air chambers 43, 45.
Air is ejected from the air chamber 44 at a large mass velocity, and from the air chamber 44 at a small mass velocity.

In a normal fluidized bed, the fluidized medium moves violently up and down like boiling water to form a fluidized state, but the fluidized medium above the air chamber 44 does not move violently up and down. Forms a moving bed in a weakly fluid state. The width of this moving layer is narrow at the top, but it becomes slightly wider at the bottom due to the effect of the slope of the dispersion plate 42, and a part of the bottom is expanded to the air chambers 4 at both side edges.
Since it reaches above 3,45, it receives a jet of air with a large mass velocity and is blown up. Since some of the fluid medium at the skirt is removed, the layer directly above the air chamber 44 will fall under its own weight. Above that bed, a fluidized medium from a fluidized bed with a swirling flow 10 is replenished as described below. By repeating this process, the fluidized medium above the air chamber 44 is almost brought together in a certain region while remaining in a weak fluidized state, forming a descending moving layer 46 that gradually descends.

The fluidized medium that has moved onto the air chambers 43 and 45 is blown upward, but it hits the inclined wall 9 and is reflected and turned upward while facing the center of the furnace, moves to the top of the above-mentioned descending moving layer 46, and gradually It descends, reaches the hem, and is blown up again to circulate. A portion of the fluidized medium circulates in the fluidized bed as a swirling flow 10.

In the combustion furnace 6 in such a state, the garbage input from the combustion material inlet 60 descends to the top of the descending moving layer 46. Near the top, the flow of the fluid medium flows in a concentrated direction from the outside toward the center, so that the debris is caught up in this flow and sucked into the top of the descending moving bed 46. Therefore, even light materials such as paper can be reliably taken into the descending moving bed 46, so that the paper can be burned on the sand without greatly contributing to the heating of the fluidized medium, as in conventional fluidized beds. It is possible to prevent this from happening and to reliably perform combustion in the descending moving bed 46 and the fluidized bed 10 to heat the fluidized medium.

In the descending moving layer 46, thermal decomposition occurs partially and combustible gas is generated. In this embodiment, since there is no partition wall, the generated combustible gas diffuses horizontally, enters the fluidized bed, and burns, so that the heat effectively serves to heat the fluidized medium.

When heavy and large objects such as bottles and irons are dropped onto the surface of the downward movement layer 46 and supplied, these objects do not fall instantly to the top of the air chamber 44 but are supported by the downward movement layer 46. Then, it gradually descends with the flow of the fluid medium.

Furthermore, since there is no partition wall in this embodiment, even large combustible objects will not cause problems due to getting caught on the partition wall.
It can be made to descend smoothly and gradually through the moving bed, and there is no risk of clogging or impeding the flow of the fluid medium.

Therefore, even if the combustible material is quite large, it will be dried, gasified, and burned as it gradually descends in the descending moving layer 46, and by the time it reaches the bottom, most of it will have been burned and broken into small pieces. , so the formation of a fluidized bed is not inhibited.

Therefore, garbage does not need to be crushed with a crusher in advance.
There is no problem with just breaking the bag of the dust supply device 5, and not only can the crusher and crushing process be omitted to make the device more compact, but also the problem in the crushing process can be prevented from seriously hindering the operation of the furnace. can be prevented.

In addition, since the waste thrown into the descending moving bed 46 is quickly diffused into the fluidized medium, the combustion efficiency is increased.

The medium-sized noncombustibles supplied through the dust supply device 5 first move downward in the descending movement layer 46, but at this time, they may not adhere to the noncombustibles or combustibles that are integrated with them (for example, (e.g. the covering of electric wires) will burn. The incombustible materials that have reached the hem reach the incombustible material discharge port 48 due to the lateral movement of the fluid medium and the inclination of the distribution plate 42, and are discharged into the vertical path 49.

A screw conveyor is used as the incombustible material discharge device 12. Screw 50 feather 51
Since the conveyor casing 52 has a flow passage cross section that allows medium-sized solid noncombustibles introduced into the furnace to pass through, the noncombustibles can be quickly discharged.

54 is a screw conveyor, which is used in the position of the vibrating screen 13 in FIG. The conveyor casing 52 and the screw conveyor 54 are almost filled with incombustible materials and a fluid medium for sealing purposes, but the level indicator controller 5 checks whether they are filled to the required level.
5, and if the level has not been reached, the screw conveyor 54 is stopped, etc. to recover the level. 56 is connected to the casing 52 and the freeboard 47 to ensure the sealing effect.
This is a pressure equalizing pipe that communicates with the

Reference numeral 53 denotes an opening/closing damper provided in the return chute 19, which is normally closed to receive and store foreign matter from the discharge port 18. After removing the foreign matter manually or mechanically, the damper 53 is opened manually or by power,
Return the fine dust that has accumulated on it to pit 1.

The air volume of the distribution plate 42 will be explained.

If the flow velocity of the fluidized air ejected from the air chamber 44 is too small, fluidity will be lost and accumulation will occur, and if it is too large, the fluidized air will become a fluidized bed and the descending moving bed 46 will not be formed.

According to the research conducted by the inventors, as shown by the solid line in FIG. 6, for example, as the descending moving bed air volume increases, the descending moving bed 46 becomes more fluid and its settling speed increases.
A high sedimentation rate means that the descending moving layer 4
This means that the combustible materials taken into the fuel cell 6 reach the fluidized bed quickly and begin to burn, and the amount of fluidized medium circulated increases, both of which are associated with an increase in combustion capacity. Moreover, when the air volume is at a certain value (in Figure 6,
3Gmf), the downwardly moving layer 46 is no longer formed. According to the research of the inventors, the downward moving layer 4
The air volume for 6 is preferably 0.5 to 3Gmf, and 1 to 3Gmf.
It was found that 2.5Gmf is more preferable.

The dotted line in FIG. 6 shows the case where a partition plate is provided to partition the descending moving bed and the fluidized bed, as in the conventional case. Since the partition plate helps to hold the downwardly moving layer, it is possible to form a downwardly moving layer even at a large air flow of up to 4 Gmf, but since there is little lateral movement, the settling speed is small. That is, the sedimentation rate is higher when there is no partition plate as in this example.
Furthermore, this means that a large change in sedimentation speed can be obtained with a small air volume or a small change in air volume, and the control range of the sedimentation speed can be widened.

The solid line in FIG. 7 shows the relationship between the air volume for the fluidized bed and the sedimentation speed of the descending moving bed; as the fluidized bed air volume increases, the sedimentation speed of the descending moving bed also increases. The one-dot chain line shows the conventional one with a partition plate.

As is clear from the figure, the sedimentation velocity is higher and the combustion capacity is greater when there is no partition plate as in this example.

Moreover, since there is no partition plate in this embodiment, not only does the flow of the fluid medium not be obstructed, but also large non-combustible foreign objects can be smoothly moved without being obstructed from the non-combustible material discharge port 48. You can definitely take it out.

Furthermore, in this embodiment, since the combustible material supply pipe that reaches the descending moving layer 46 from the combustible material inlet 60 of the ceiling part 59 is omitted, the combustible material due to wear, corrosion, deformation, etc. at the lower end of the supply pipe is omitted. Problems such as blockage can be avoided.

Contaminants in municipal waste are indeterminate and include noncombustibles of considerable size, so unlike sludge combustion furnaces, noncombustibles must be discharged. When discharging noncombustibles, a fluid medium that is about 20 to 30 times as much as the noncombustibles itself is also discharged, and this discharging is almost continuous. Therefore, if the incombustible materials and the fluidized medium are not discharged evenly and smoothly, the flow of the fluidized medium in the furnace will not be even and smooth, and the formation of the downwardly moving layer will also become unstable. A board is required, which brings about the disadvantages mentioned above.

In this embodiment, the incombustible material discharge ports 48 are provided at both side edges so that the flow and amount of discharge of the fluidized medium are almost equal on the left and right sides, and each part of the furnace is also approximately parallel to the center line 57. Since it is symmetrically formed, it is easy to maintain a symmetrical flow of the fluid medium inside the furnace, and in order to obtain a stable downward moving layer, there is no need for partition plates, and the furnace space is free from obstructions. It can be made into an integrated space, and the various effects described above can be achieved.

Since there are no obstructions such as partitions that partition the space inside the furnace, inspection and repair of the inside of the furnace becomes extremely easy.

The horizontal cross-section of the fluidized bed chamber, which holds the fluidized bed in the reactor, is rectangular, so to design one with different capabilities, you only need to change the width of the same cross-section. A rectangular shape is advantageous and facilitates design. It is also easy to manufacture.

According to the inventors' research, in the example, the swirling efficiency of the fluidized medium (the amount of swirling of the fluidized medium per 1 m ³ /h [NTP] of fluidizing air) did not change much even if the furnace width was changed significantly. , it does not decrease even when the size is increased.
In addition, since the flow of the fluidized medium is extremely smooth and the settling speed of the descending moving bed is high, it is easy to increase the size of the furnace.

Although the above description has been made regarding the combustion furnace 6 using the dispersion plate 42, similar effects can be achieved even when the dispersion mechanism for fluidized air is a pipe grid.

In the case of pipe grids, when forming widely spaced sections of pipes in order to pass large-sized noncombustible materials, it is preferable to avoid forming them under the descending moving layer in the center.

Incombustible materials are discharged from the outlet in the center of the bottom of the furnace below the pipe grid.

According to the present invention, there is no partition wall between the moving bed in the center and the fluidized beds on both sides, and the mass transfer and heat transfer of the fluidized medium, gas, combustion materials, etc. between the two layers is not hindered. It is possible to provide a fluidized bed combustion method and a combustion furnace in which combustion is carried out under the following conditions, and which has the following practical effects.

(1) It is no longer necessary to crush the combustible material in advance, eliminating the need for crushing equipment, which not only provides advantages in terms of cost, labor, and space, but also improves the operation of the furnace, such as when the furnace stops due to problems in the crushing process. It is possible to prevent serious problems from occurring.

(2) There is no problem of non-combustibles or combustibles getting caught in the gap at the lower edge of the partition wall, which occurs with conventional products, and the flow of the fluidized medium is not obstructed, increasing the amount of circulation in the furnace and improving combustion efficiency. can be improved.

(3) It is possible to increase the settling velocity of the fluidized medium in the descending moving bed, increase the amount of circulation in the furnace, and increase the combustion capacity.

(4) The control range of the sedimentation speed of the descending moving layer can be increased.

(5) The combustible gas generated by thermal decomposition in the descending moving bed diffuses laterally, so it is combusted in the fluidized bed and can be effectively used to heat the fluidized medium.

(6) Since the combustible materials are quickly diffused into the moving bed, heating can be carried out quickly and sufficiently, increasing combustion efficiency.

(7) Since there is no combustible material supply pipe, troubles such as combustible material clogging due to wear, corrosion, and deformation can be avoided.

(8) The inside of the furnace is an integrated space without partition plates or supply pipes, making inspection and repair inside the furnace extremely easy.

(9) Preventing the generation of clinker and preventing the flow of the fluidized medium from being obstructed, resulting in shutdown of the furnace due to blockage near the bottom of the partition wall, or insufficient supply of fluidized medium to the side fluidized bed due to the same blockage. This can prevent problems such as blowouts.

(10) The planar shape of the fluidized bed is rectangular, and by extending the furnace in the width direction (direction perpendicular to the plane of the paper in Figure 2), a single unit can be used without changing the operating conditions of the fluidized bed or moving bed. The capacity of the furnace can be increased significantly.

(11) Since the gas dispersion mechanism is formed so that the central part is high and the side edges are low, the lateral movement of the fluid medium at the bottom of the moving bed is smooth and the circulation of the fluid medium is promoted.

[Brief explanation of the drawing]

The drawings relate to embodiments of the present invention, and FIG. 1 is a cross-sectional front view of a waste combustion field, FIG. 2 is a longitudinal cross-sectional view of a combustion furnace, FIG. Fig. 5 is a partial view of another embodiment corresponding to Fig. 4, Fig. 6 is a diagram showing the relationship between descending moving bed air volume and sedimentation velocity, and Fig. 7 is a diagram showing the relationship between fluidized bed air volume and sedimentation velocity. It is a diagram of the relationship with the descending moving bed sedimentation velocity. 1... pit, 2... crane, 3... bucket, 4... hopper, 5... dust supply device, 6... combustion furnace, 7... blower, 8... distribution plate, 9... inclined wall, 10...Swirling flow, 11...Exhaust gas duct, 1
2... Incombustible material discharge device, 13... Vibrating sieve, 14...
...Conveyor, 15...Elevator, 16...Inlet, 17...Exit, 18...Discharge port, 19...Return chute, 27...Motor, 42...Dispersion plate,
43, 44, 45... Air chamber, 46... Descending moving layer, 47... Free board, 48... Incombustible material discharge port, 49... Vertical path, 50... Screw, 51
... Vane, 52 ... Casing, 53 ... Damper, 54 ... Screw conveyor, 55 ... Level indicator controller, 56 ... Pressure equalization pipe, 57 ... Center line, 58 ... Inclined surface, 59 ... Ceiling part, 60...
Combustible material inlet, 61...furnace wall.

Claims (1)

[Scope of Claims] 1. A fluidized bed combustion method in which a combustion material is combusted in a fluidized bed formed by fluidizing a fluidized medium with fluidized gas injected upward from the bottom of a combustion furnace, comprising: The layer is held in a fluidized bed chamber having a rectangular horizontal cross section, and the fluidizing gas is ejected from a gas dispersion mechanism that is high in the center and low in both side edges, and the mass velocity of the fluidizing gas is is larger at both side edges of the center than near the center of the furnace bottom, and above the both side edge fluidized bed, an upward flow path of the fluidizing gas at both side edges is formed. It is blocked and diverted towards the center of the path, forming a moving layer in the center of the hearth bottom where the fluidized medium settles while maintaining its fluidized state, and the fluidized media is actively fluidized at both side edges. forming a fluidized bed on both sides, and allowing the fluidized medium to settle within the moving bed;
Transferring to the both side edges at the lower part of the moving bed, rising in the both side edge fluidized bed, and turning toward the top of the moving bed by the turning fluidizing gas at the upper part of the both side edge fluidized bed, circulating in the furnace, without using a partition wall between the moving bed and the fluidized bed on both sides, and not impeding mass transfer and heat transfer of the fluidized medium, gas, combustion materials, etc. between the two layers. A fluidized bed combustion method characterized by carrying out combustion in a state of 2. The fluidized bed combustion method according to claim 1, wherein the fluidizing gas mass velocity at both side edges is 4 to 20 Gmf. 3. A fluidized bed chamber with a rectangular horizontal cross section is provided at the bottom of the furnace, and a fluidizing gas dispersion mechanism is provided at the bottom of the furnace, and the gas distribution mechanism is high at the center and low at both side edges. , the fluidizing gas mass velocity at both side edges of the gas dispersion mechanism is made higher than the fluidizing gas mass velocity at the central portion, and the upward flow path of the fluidizing gas is blocked directly above the both side edges; A furnace space surrounded by the furnace wall, the dispersion mechanism, and the slope wall is provided with an inclined wall that reflects and diverts the fluidizing gas toward the center of the furnace, and a combustion material inlet is provided at the upper part of the furnace. A fluidized bed combustion furnace characterized in that it is formed as an integral space without a partition wall that partitions the space. 4. The fluidized bed combustion furnace according to claim 3, wherein a discharge port is connected to the both side edges of the gas dispersion mechanism.