JPH0127334B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fluidized bed incinerator that incinerates waste using a fluidized bed and recovers the heat of incineration.

[Prior art]

Wastes such as municipal waste and industrial waste have a wide range of constituent substances, their composition ratios are not constant, and their calorific value, moisture content, etc. are also not constant. When incinerating such waste,
Fluidized bed incinerators are used because they have better combustion efficiency than conventional stoker furnaces, produce less incineration residue, and are more adaptable to changes in the characteristics of the materials to be incinerated.

During incineration, high-temperature flames and high-temperature incineration gases are generated.In order to recover and utilize the incineration heat of these flames and incineration gases, heat recovery equipment is installed in the upper part of the incinerator and in the exhaust gas flue. It is being collected by

Fig. 1 shows an example of a conventional furnace, in which 1 is a furnace body, and a dispersion plate 2 is provided at the bottom of the furnace as an air jetting mechanism, and the air supplied to a wind box 3 is distributed and jetted upward. The fluidized medium is fluidized to form a fluidized bed 4. The waste input from the input port 5 is incinerated in the fluidized bed 4, the unburned materials are discharged from the discharge port 6, and the combustion exhaust gas rising in the furnace completely burns the unburned materials in the freeboard 7. After that, the water pipe group 10 passes through the gas cooling chamber 9 of the waste heat boiler 8 provided above the freeboard 7.
It passes through the gap and leads to the next process.

When incineration is performed in such a device, the water-cooled wall of the gas cooling chamber 9, which is a heat recovery section, is heated by the radiant heat from the flames generated in the fluidized bed 4 and the lower part of the freeboard 7. The heat is recovered by the water in the water cooling wall, and the combustion exhaust gas is transferred to the gas cooling chamber 9.
When passing between the water pipe group 10 and the water pipe group 10, heat exchange is performed with the water in the water cooling wall or the water pipes, and combustion heat is recovered.

Although such a fluidized bed incinerator is effective for incinerating waste, conventional fluidized bed incinerators require that the waste be crushed to some extent in advance. In order to improve this point, an incinerator shown in FIG. 2 has been proposed. In this device, a dispersion plate 2 serving as a gas ejection mechanism has side edges 11, 12 and a central portion 1.
The mass velocity of the ejected gas is larger at both side edges 11 and 12 than at the center 13, and furthermore, above both side edges 11 and 12, there is an upward flow path for fluidizing gas. In the fluidized bed 4, side edges 11, 12 are provided.
An active fluidized bed that blows up and then reflects toward the center of the furnace is formed in the upper part, and a moving bed that gradually settles is formed above the central part 13. and circulate in the vertical plane,
Two almost symmetrical circulation flows are formed to actively take in waste, making it possible to incinerate even large-sized waste that cannot be crushed in a short time.

[Problem that the invention seeks to solve]

However, such conventional devices have a problem in that they cannot incinerate municipal waste with a low calorific value in a good manner. Kitchen waste in municipal waste has a high moisture content, especially in the summer, and municipal waste mixed with such kitchen waste has a low calorific value.

On the other hand, when a heat recovery section such as a water-cooled wall is provided above the freeboard 7 as shown in Fig. 2, the freeboard flame temperature decreases due to the radiation cooling effect from the water-cooled wall, and as a result, the fluidized bed temperature decreases. Descend. Even in this case, if the calorific value of the material to be combusted is sufficiently high, the drop in freeboard flame temperature and fluidized bed temperature can be compensated for by the heat generated by combustion, and good combustion can be achieved. In some cases, radiant heat recovery also takes place well.

However, when burning waste with a low calorific value, the calorific value of combustion is small, and the freeboard flame temperature, which drops due to the heat recovery section, cannot be recovered, and the fluidized bed temperature also decreases, making it a good condition. The range where self-combustion operation can be continued, that is, the fluidized bed temperature
If the conditions of being able to maintain the temperature above 600℃ and the freeboard flame temperature drop within the range of 150℃ are not met, combustion will become incomplete and combustion will eventually stop.

As described above, in the conventional heat recovery type fluidized bed combustion furnace, it is not possible to incinerate waste with a low calorific value well in either of the cases shown in Figures 1 and 2. However, in order to compensate for this, it was necessary to use auxiliary fuel, which caused a problem of energy loss.

The present invention solves the above-mentioned problems of the conventional methods, and enables good combustion without the need for auxiliary fuel and without interfering with self-combustion, even for waste with a low calorific value of about 600 to 2000 Kcal/Kg. It is an object of the present invention to provide a fluidized bed incinerator that can perform effective heat recovery while performing the following.

[Means for solving problems]

The inventors conducted many experiments in order to solve this problem, and based on the knowledge they obtained,
The present invention was developed based on the idea of making the center of the heat recovery section horizontally eccentric from the center of the fluidized bed.

The present invention includes a gas ejection mechanism for forming a fluidized bed at the bottom of the furnace, and a heat recovery section for recovering incineration heat above the freeboard section at the top of the furnace, and the gas ejection mechanism ejected from the gas ejection mechanism The mass velocity of the fluidizing gas is set higher at both side edges than at the center, and the upward flow path of the fluidizing gas is blocked above both side edges of the gas ejection mechanism to direct the fluidizing gas into the furnace. Equipped with a reflective wall that deflects reflection toward the center,
The furnace space surrounded by the furnace wall, the gas ejection mechanism, and the reflecting wall is not provided with any obstacles that partition the furnace space and impede the horizontal flow of materials and heat within the furnace. In a fluidized bed thermal reactor in which a thermal reaction is carried out by circulating a fluidized medium in a vertical plane within the furnace space, the center of the fluidized bed formed by the gas ejection mechanism is The fluidized bed incinerator is characterized in that the center of the heat recovery section is eccentric in the horizontal direction.

〔Example〕

Embodiments of the present invention will be described with reference to the drawings.

As shown in FIGS. 3, 4, and 5, an air dispersion plate 2 is provided at the bottom of the incinerator body 1 as a gas ejection mechanism for forming a fluidized bed. The distribution plate 2 has both side edges lower than the center, and is formed into a shaped cross-sectional shape (roof-like shape) that is substantially symmetrical with respect to the center line 15 of the furnace. The inclination may be different between the center portion and both side edge portions. Incombustible material discharge ports 6 are connected to both side edges. The incombustible material discharge port 6 does not necessarily have to have exactly the same shape on both sides; for example, one side may have a shape as shown in FIG. 5, and the other side may have a shape as shown in FIG. It suffices if they are placed on both sides so that the discharge amount and flow direction are approximately equal.

Fluidized air sent from the blower 16 passes through air chambers 17, 18, and 19 and is blown upward from the distribution plate 2. Air chambers 17, 19 on both side edges
Mass velocity of fluidized air ejected from (Kg/ ^m2・
sec) is large enough to form a fluidized bed, but the mass velocity of the fluidized air jetting out from the central air chamber 18 is chosen to be smaller than the former.

For example, the mass velocity of the fluidized air ejected from the air chambers 17 and 19 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 18 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.

Reflection walls 14 are provided above the air chambers 17, 19 on both side edges to block the upward flow path of the fluidized air and reflect the fluidized air toward the center of the furnace.

The upper side of one of the reflecting walls 14 is provided with an inclined surface 20 having a reflective slope with respect to the reflecting wall 14 to prevent the flowing medium from accumulating.

The inclination of the dispersion plate 2 is preferably about 5 to 15 degrees. The slope of the reflective wall 14 is preferably about 10 to 60 degrees with respect to the horizontal. The surface of the reflective wall 14 may be a flat surface, a convex surface, or a concave surface.

A raw material inlet 5 connected to the outlet of the dust supply device 22 is provided in the furnace ceiling 21 .

The fluidized bed 4 is mainly formed in the range from above the dispersion plate 2 to the height near the constriction part 23, which is the narrowest part in the furnace at the upper end of the reflecting wall 14. , a dispersion plate 2, a reflection wall 1
4. If a vertical wall is provided below the reflective wall 14, the space surrounded by that furnace wall and the furnace wall in the direction perpendicular to the reflective wall 14 contains material and heat inside the furnace in the horizontal direction. No obstacles are provided to impede the flow, that is, the flow toward the opposing wall surface, so that the fluidized bed 24 and moving bed 25 in the fluidized bed 4 can freely come into contact as described below. .

The reflective wall 14 may be constructed by arranging metal pipes, and preheating may be performed by passing fluidized air through the pipes.

A gas cooling chamber 9 is provided above the freeboard 7. The gas cooling chamber 9 is surrounded by a water cooling wall 26 made up of a large number of water pipes. This water-cooled wall is connected to an upper drum 27 and a lower drum 28 which are connected by a large number of water pipe groups 10, and constitutes a part of the waste heat boiler 8.

This water cooling wall 26 is a heat exchanger that recovers the incineration heat generated when incinerating waste through heat exchange between the radiant heat from the flame at the bottom of the freeboard 7 and the combustion exhaust gas passing through the gas cooling chamber 9. Acts as a recovery section.

However, the centerline 29 of the heat recovery section is horizontally eccentric from the centerline 15 of the fluidized bed 4 by a distance l.

The operation of such a fluidized bed incineration facility will be explained.

The blower 16 feeds fluidized air and blows it out from the air chambers 17 and 19 at a high mass velocity and from the air chamber 18 at a small mass velocity.

In a normal fluidized bed, the fluidized medium violently moves up and down like boiling water to form a fluidized state, but the fluidized medium above the air chamber 18 does not move violently up and down, but has a weak flow. form a moving layer in the state. The width of this moving layer is narrow at the top, but it widens slightly at the bottom due to the effect of the slope of the dispersion plate 2, and a part of the bottom is formed by air chambers 17 on both side edges,
19, it receives a jet of air with a large mass velocity and is blown up. Since part of the fluidizing medium at the skirt is removed, the layer directly above the air chamber 18 will fall under its own weight. Above this layer, a fluidized medium from a fluidized bed accompanied by a circulating flow 30 is replenished and deposited as will be described later. By repeating this process, the fluidized medium above the air chamber 18 almost comes together in a certain region, forming a descending moving layer 25 that gradually descends.

Note that each air chamber 17, 18, 19 may be further divided into several chambers. Even in this case, the fluidized air must be distributed as described above so that a moving bed is formed in the center of the fluidized bed and a fluidized bed is formed in the left and right parts.

The fluidized medium that has moved onto the air chambers 17 and 19 is blown upward, but it hits the reflective wall 14 and is reflected and turned upwards while facing the center of the furnace, loses its upward speed as the cross-section inside the furnace rapidly increases, and the above-mentioned downward movement occurs. Mobile phase 2
It falls to the top of 5, gradually descends, reaches the hem, and is blown up again to circulate. A portion of the fluidized medium is circulated in the fluidized bed as a recycled flow 30.

In the incinerator in such a state, the garbage input from the raw material input port 5 descends to the top of the descending moving layer 25. Near the top, the flow of the fluid medium is concentrated from the outside toward the center, so
The garbage is caught up in this flow and moves down to the downward moving layer 25.
It is crawled into the top of the. Therefore, even light materials such as paper can be reliably taken into the descending moving bed 25, 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 reliably perform combustion in the descending moving bed 25 and the fluidized bed 24 to heat the fluidized medium.

In the descending moving layer 25, 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 descending layer 25, these objects do not fall instantly to the top of the air chamber 18, but are supported by the descending layer 25. Then, it gradually descends with 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 25, and by the time it reaches the bottom, most of it will be burned and fragmented. Therefore, the formation of a fluidized bed is not inhibited.

Therefore, even if the garbage is not crushed in advance using a crusher, it is sufficient to break the bags using the dust supply device 22, and the crusher and crushing process can be omitted, resulting in a compact device.

In addition, since the waste thrown into the descending moving bed 25 is quickly diffused into the fluidized medium, the combustion efficiency is increased.

The medium-sized noncombustibles supplied through the dust supply device 22 first move downward and laterally in the descending moving layer 25, but the noncombustibles attached to the falling noncombustibles or the combustibles ( For example, the coating on electric wires) will burn. The incombustibles that have reached the hem reach the incombustibles discharge port 6 by the lateral movement of the fluid medium and the inclination of the distribution plate 2, and are discharged into the vertical path 31.

Screw conveyor 32 as a non-combustible material discharge device
is used. Feather 34 of screw 33
Since the conveyor casing 35 has a flow passage cross section that allows the passage of medium-sized solid noncombustibles thrown into the furnace, the noncombustibles can be quickly discharged.

The above explanation has been made regarding an incinerator using the dispersion plate 2 as a gas ejection mechanism, but the specific shape of the ejection port may be as shown in FIGS. 7 to 9, for example, and the fluidized medium can be supported as a whole. It is sufficient if a plate surface is formed. Furthermore, a similar effect can be achieved in the case of a pipe grid.

In the case of a pipe grid, incombustible materials are dropped from between the pipes, so a slope like a dispersion plate is not necessarily required. When forming pipes with wide spacing in order to pass large-sized incombustibles, it is preferable to avoid forming the pipes under the descending moving layer in the center.

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

Since this embodiment is configured and operates as described above,
It has the following effects.

(1) Effect of making the center of the heat recovery section above the freeboard eccentric in the horizontal direction with respect to the center of the fluidized bed.

(i) The distance of the heat recovery section from the fluidized bed increases,
Furthermore, since the radiation direction is oblique, the radiant cooling effect from the heat recovery section is reduced, increasing the freeboard flame temperature, and the cooling effect on the fluid medium that has flown into the freeboard is also reduced, resulting in low heat generation. Even with a large amount of waste, the fluidized bed temperature and freeboard flame temperature can be maintained at high values without using auxiliary fuel, and good combustion can be performed without disturbing nature.

(ii) As the freeboard flame temperature increases, the amount of radiant heat recovered in the heat recovery section also increases significantly.
Since the temperature of the combustion exhaust gas also increases, the amount of heat recovered in the water tube group 10 in addition to the heat recovery section (water cooling wall 26) also increases, making it possible to improve the heat recovery rate.

(iii) The chances of the fluid medium flying out from the fluidized bed surface onto the freeboard colliding with the water pipes of the water cooling wall are significantly reduced, thereby preventing wear on the water pipes.

(2) The effect of the fact that there are no obstacles such as partition walls in the space in which the fluidized bed is formed that prevents the horizontal movement of substances or heat.

As a result of conducting a comparative experiment with one with a partition wall, the following effects were found.

(i) The temperature of the fluidized bed becomes stable.

(ii) No clinker is generated, and accidents such as passage blockage and unstable flow conditions due to clinker can be prevented.

(iii) No blow-through phenomenon occurs in the fluidized bed.

(iv) Since there are no partition walls, there is no risk of passage blockage.

(v) No drivable accidents will occur due to non-combustible materials.

〔Effect of the invention〕

The present invention makes it possible to provide a fluidized bed incinerator that can perform good combustion without using auxiliary fuel even for waste with a low calorific value, and can effectively recover heat. , which has an extremely large practical effect.

[Brief explanation of drawings]

Figures 1 and 2 are cross-sectional explanatory diagrams of the conventional example;
The figure is a cross-sectional front view of an embodiment of the present invention, and FIG.
Fig. 5 is a cross-sectional plan view taken along the - line in Fig. 4, Fig. 6 is a plan view of the discharge port of another embodiment, and Figs. 7 to 9 are cross-sections of the embodiment of the gas ejection port. It is a diagram. 1...furnace body, 2...dispersion plate, 3...wind box, 4...fluidized bed, 5...inlet, 6...outlet, 7...free board, 8...waste heat boiler,
9... Gas cooling room, 10... Water tube group, 11, 12
...Side edge part, 13...Central part, 14...Reflection wall,
15... Center line, 16... Blower, 17, 18,
19... Air chamber, 20... Inclined surface, 21... Ceiling part, 22... Dust supply device, 23... Throttle part, 24
...fluidized bed, 25 ... moving bed, 26 ... water-cooled wall,
27... Upper drum, 28... Lower drum, 29
... Center line, 30 ... Circulation flow, 31 ... Vertical path,
32...screw conveyor, 33...screw, 34...blade, 35...conveyor casing.

Claims (1)

[Claims] 1. A gas ejection mechanism for forming a fluidized bed at the bottom of the furnace;
A heat recovery section for incineration heat recovery is provided above the freeboard section in the upper part of the furnace, and the mass velocity of the fluidizing gas ejected from the gas ejection mechanism is controlled to be higher at both side edges than at the center. and a reflecting wall is provided above both side edges of the gas ejection mechanism to block the upward flow path of the fluidizing gas and reflect the fluidizing gas toward the center of the furnace, and the furnace wall and the gas The furnace space surrounded by the ejection mechanism and the reflecting wall is not provided with any obstructions that would partition the furnace space and obstruct the horizontal flow of materials and heat within the furnace. In a fluidized bed thermal reactor in which a thermal reaction is carried out by circulating a fluidized medium in a vertical plane, the center of the heat recovery section is located relative to the center of the fluidized bed formed by the gas ejection mechanism. A fluidized bed incinerator characterized by being eccentric in the horizontal direction.