JP2664655B2 - Method and apparatus for supplying fluidized gas in fluidized bed heat recovery apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluidized bed heat recovery apparatus for incinerating industrial waste, municipal solid waste, coal and the like in a fluidized bed made of sand particles and the like and recovering heat generated thereby. And a method and apparatus for supplying a fluidized gas for fluidizing the fluidized bed.

[0002]

2. Description of the Related Art Conventionally, as a device for recovering heat due to incineration of industrial wastes and the like, a fluidized bed made of sand particles is formed on an air dispersion plate, and the fluidized bed is used to incinerate waste. 2. Description of the Related Art Fluidized bed heat recovery apparatuses that recover heat generated by incineration through heat transfer tubes are widely known. This device has the advantages that the mixing of the particles in the fluidized bed is extremely good and the temperature in the bed can be kept uniform, and that the particle layer has a large heat retention capability, so that restarting is easy. I have.

In this apparatus, heat can be recovered even if the heat transfer tube is provided above the fluidized bed. However, it is preferable to embed the heat transfer tube in the fluidized bed for the following reasons. ing. The heat transfer coefficient in the fluidized bed is 7 to 10 times higher than the heat transfer coefficient in the exhaust gas above the fluidized bed, so that the heat transfer area can be reduced and the boiler can be made compact. Hydrogen chloride is generated by incineration in the fluidized bed, and the concentration of hydrogen chloride in the fluidized bed is about 1/10 of the concentration of hydrogen chloride in the exhaust gas above the fluidized bed. The heat transfer tube is less likely to be corroded by hydrogen chloride when buried. Since the corrosion hardly occurs, the steam flowing in the heat transfer tube can be heated to high temperature and high pressure. The amount of heat recovery can be adjusted by changing the amount of fluidizing gas supplied into the heat recovery section, and therefore, it can be widely used from low calorific value fuels to high calorific value fuels.

Therefore, as a device in which a heat transfer tube is provided in a fluidized bed, for example, JP-A-5-23321 discloses that the fluidized bed is divided into a main combustion section and a heat recovery section by a partition wall. In addition, the heat transfer tube is provided at the same time, and the fluidized gas is injected from the bottom of the main combustion section, so that the fluidized particles of the main combustion section pass above the baffle, enter the heat recovery section, and further pass below the baffle. There is disclosed an apparatus in which a return flow is formed in the main combustion section. In such a device, when the waste is put into the main combustion section, the waste is mainly incinerated in the main combustion section, and the heat generated thereby is transferred to the heat transfer tube in the heat recovery section using fluidized particles as a medium. become.

[0005]

In the above apparatus, in order to fluidize the fluidized bed in the heat recovery section, a sufficient flow rate to the heat recovery section (generally, one to two times the required minimum fluidization speed) is required. A means for supplying a fluidizing gas at a flow rate at which a velocity can be obtained is effective. As the fluidizing gas, it is generally considered that primary air for combustion is diverted at room temperature.

However, when the fluidizing air is supplied to the heat recovery section, the following inconvenience occurs.

A) In the above-mentioned apparatus, when the calorie of the injected fuel is high, such as when the in-bed combustion rate is low, it is difficult to recover all the necessary heat unless the heat recovery rate from the sand layer is increased. There is a possibility that. However, if the in-layer heat recovery rate is excessively increased, the temperature in the sand layer decreases and stable combustion cannot be maintained, so there is a limit to increasing the in-layer heat recovery rate.

As a means for improving the heat recovery efficiency, a method of preheating the fluidizing air supplied into the heat recovery section using the heat energy of the combustion exhaust gas can be considered. The combustion in the heat recovery unit is promoted by the temperature rise of the forming air. When the combustion in the heat recovery unit is promoted in this way, thermal or chemical deterioration or damage of the heat transfer tube in the heat recovery unit is caused by the local high temperature phenomenon and the generation of hydrogen chloride accompanying the combustion. May promote.

B) In the above-described apparatus, waste as fuel is supplied to the main combustion section, and this fuel may enter the heat recovery section in some cases. At this time, if a considerable amount of air is supplied to the heat recovery unit, the combustion of the fuel in the heat recovery unit is promoted by oxygen contained in the air, and the local high temperature decrease and There is a risk of generating hydrogen chloride.

C) In principle, combustion is not performed in the heat recovery section, and therefore, the air supplied to the heat recovery section for fluidization is surplus air that does not contribute to combustion. As the excess air increases, the NOx concentration in the combustion exhaust gas increases, which may adversely affect the environment.

[0011] In view of such circumstances, the present invention can increase the amount of heat recovery in the sand layer without inconvenience while satisfactorily fluidizing the fluidized bed in the heat recovery section. It is an object of the present invention to provide a method and an apparatus for supplying a fluidized gas in a fluidized bed heat recovery apparatus capable of suppressing the heat transfer tube by protecting the heat transfer section and reducing the amount of NOx generated by suppressing the oxygen concentration in the heat recovery section. .

[0012]

According to the present invention, there is provided a fluidized bed formed of fluidized particles at the bottom of an apparatus body, which is divided into a main combustion section and a heat recovery section by baffles. A heat transfer tube for heat recovery is provided in the recovery unit, and a main combustion air diffuser for injecting a fluidizing gas for fluidizing the fluidized particles in the main combustion unit to the main combustion unit, and the heat recovery unit A heat-recovery diffuser for injecting a fluidizing gas for fluidizing the fluidized particles in the heat-recovery section, whereby the fluidized particles of the main combustion section pass above the baffle by these fluidized gases. A fluid that enters the heat recovery section and returns to the main combustion section through below the baffle. Conversion In which it is recycled to the heat recovery air diffuser as scan (claim 1).

In this method, the combustion exhaust gas may be partially recirculated as a fluidizing gas also to the main combustion air diffuser.

Further, according to the present invention, a fluidized bed formed of fluidized particles is divided into a main combustion section and a heat recovery section by a baffle at the bottom of the apparatus main body, and a heat transfer tube for heat recovery is provided in the heat recovery section. A main combustion air diffuser for injecting a fluidizing gas for fluidizing the fluidized particles in the main combustion section to the main combustion section; and a fluidizing device for fluidizing the fluidized particles in the heat recovery section to the heat recovery section. Equipped with a heat-recovery diffuser for injecting fluidizing gas, and by these fluidizing gases,
In the fluidized bed heat recovery apparatus, the fluidized particles of the main combustion section enter the heat recovery section above the baffle, and further form a flow returning below the baffle into the main combustion section. An exhaust gas recirculation means for recirculating flue gas generated by combustion in the fluidized bed as fluidizing gas to the heat recovery diffuser is provided (claim 3).

In this apparatus, an exhaust gas treatment device for removing a specific component in the combustion exhaust gas is provided in the exhaust gas discharge passage, and the combustion exhaust gas passing through the exhaust gas treatment device is returned to the heat recovery diffuser. It is more preferable to configure the exhaust gas recirculation means so as to circulate (claim 4).

The recirculation amount adjusting means for changing the recirculation amount of the combustion exhaust gas by the exhaust gas recirculation means, the supply source of the fluidizing gas to the main combustion air diffuser and the heat source By providing a connection passage for connecting to the collection diffuser and an opening / closing means for opening and closing the connection passage (claim 6), more excellent effects as described later can be obtained.

In the above apparatus, the exhaust gas recirculation means may be configured to partially recirculate the combustion exhaust gas as a fluidizing gas to the main combustion air diffuser.

[0018]

According to the method and the apparatus according to the first and third aspects, the combustion exhaust gas is supplied as the fluidizing gas into the heat recovery section, so that the fluidized bed in the heat recovery section is fluidized and recirculated. The amount of heat of the sensible heat of the combustion exhaust gas is recovered through the heat transfer tube, and the amount of heat recovered from the sand layer is greatly increased. Moreover, since the oxygen concentration in the flue gas is very low compared to air, the oxygen concentration in the heat recovery unit is increased even if the fluidized gas supply amount, that is, the flue gas recirculation amount is increased to sufficiently perform fluidization. Hardly rises. Therefore, the promotion of fuel combustion in the heat recovery unit and the increase in the amount of generated NOx due to the increase in the oxygen concentration are avoided.

Here, if the combustion exhaust gas is partially recirculated to the main combustion air diffuser as a fluidizing gas, the NOx in the main combustion section can be increased.
Occurrence can also be suppressed.

In the apparatus according to a fourth aspect of the present invention, an exhaust gas treatment device for removing a specific component in the combustion exhaust gas is provided in the exhaust gas discharge passage, and the combustion exhaust gas passing through the exhaust gas treatment device is used as the heat recovery dispersion gas. Because it is made to recirculate to the air system, this heat recovery air diffuser
A more preferable combustion exhaust gas from which undesirable substances (eg, hydrogen chloride, dust, etc.) have been removed in advance can be supplied as a fluidizing gas.

In the apparatus according to the fifth aspect, the amount of combustion exhaust gas recirculated by the exhaust gas recirculation means is changed by the recirculation amount adjusting means, so that combustion to the heat recovery section is performed according to the state of the heat recovery section. The supply amount of the exhaust gas (fluidizing gas) can be appropriately adjusted.

In the apparatus according to the sixth aspect, when the flow rate of the flue gas is insufficient, such as at the time of startup of the apparatus, the connecting passage is opened by the opening / closing means to supply the fluidizing gas to the main combustion air diffuser. By supplying the fluidizing gas to the heat-recovering diffuser as well, the fluidizing gas can be replenished as a fluidizing gas to the heat-recovery section. By closing the passage, the recirculated flue gas can be supplied exclusively to the heat recovery diffuser.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS.

The fluidized-bed heat recovery apparatus shown here has a heat insulating wall 1
1 is provided with a fluidized bed 12 made of sand or the like at the bottom of the incinerator 10.
The free board 14 shown in FIG. An incineration material inlet 16 is formed in the middle part of the incinerator, to which an incineration material feeder 18 is connected, and secondary air blowers 20, 22 are also provided at appropriate heights in the middle part of the incinerator. And a duct 24 is connected to the upper part of the incinerator.

The heat insulating wall 11 of the free board 14 is
At a certain height, the inner surface has a membrane structure covered with a refractory material, and is configured to absorb heat from a gas layer through a wall surface. The vapor evaporated by the membrane is stored in the steam reservoir 2
5, and the steam recovers the heat of the exhaust gas by the super heater 26 and is sent to an inlet header 47 of a heat transfer tube 46 described later. After the exhaust gas is deprived of heat by the super heater 26, it is further evaporated by an evaporator 28 having the same structure as the membrane of the furnace wall, a feed water heater 29 for avoiding low-temperature corrosion, and an air heater 30 for combustion air. Deprived of heat. After being cooled in the gas cooling chamber 32, harmful substances such as hydrogen chloride and dust are removed by a bag filter (exhaust gas treatment device) 34, and exhausted from a chimney through an exhaust fan 36 in principle.

On the other hand, the bottom of the incinerator 10 has a structure as shown in FIGS.

At the center of the furnace bottom in the left-right direction, a first dispersion plate (main combustion diffuser) 38 is provided.
Dispersion plates (which constitute a part of the main combustion air diffuser and the heat recovery air diffuser) 40 are disposed on both left and right sides of the
The dispersion plate 40 is adjacent to the heat insulating wall (side wall of the apparatus main body) 11. The first dispersion plate 38 and the second dispersion plate 40 are horizontally separated from each other, and this portion serves as an incombustible discharge portion 42. An incombustible material extracting device 44 is provided below the incombustible material discharging portion 42. The incombustible material extracting device 44 includes a screw conveyor that conveys the incombustible material-containing sand drawn out from the incombustible material discharging portion 42 to both left and right outer sides. Built-in.

The first dispersion plate 38 is inclined in a mountain shape so as to become lower toward the left and right non-combustible material discharge portions 42, and the second dispersion plate 40 also becomes lower as it goes toward the non-combustible material discharge portion 42. It is inclined.

Above both second dispersion plates 40, a plurality of heat transfer tubes 46 are arranged at equal intervals in the depth direction in FIG. 2 (the vertical direction in FIG. 3). Each heat transfer tube 46 penetrates the lower part of the heat insulating wall 11 to the side, faces the inside of the furnace, meanders on the second dispersion plate 40, and penetrates the heat insulating wall 11 above the penetrating part to the outside of the furnace. Both ends are connected to an inlet header 47 and an outlet header 48 extending in the depth direction of FIG. 2, respectively. Then, the steam sent from the super heater 26 to the inlet header 47 flows through the heat transfer tube 46 as an incineration heat recovery medium, and is recovered by the outlet header 48.

In this furnace, a plurality of diffuser tubes 50 are provided as shown in FIG.
Are arranged side by side in the depth direction. Each diffuser tube 50 includes an upper portion 51 located above the heat transfer tube 46 and an upright portion extending from the upper portion 51 in a substantially vertical direction through the side of the heat transfer tube 46 to reach the second distribution plate 40. 52, a number of gas injection holes are formed in the side surface of the tube wall of the upper portion 51 and in the vicinity thereof. The upper part 51 is provided with the incombustible discharge part 4.
2, the upper surface of the fluidized bed 12 is located slightly above the upper portion 51.

A baffle 54 made of a refractory material, a jacket, or the like is provided around an intermediate portion of the upright portion 52. By the baffle 54, the fluidized bed 12 is divided into a central main combustion portion 12A and left and right outer heat recovery portions 12B, and the second distribution plate 40 forms a floor of the heat recovery portion 12B. The part serves as a diffuser plate of the heat recovery diffuser according to the present invention. A minute gap 55 is secured between the baffles 54, and sand particles can flow through the gap 55 slightly.

The distance between the diffuser tubes 50 is determined by the heat transfer tubes 4.
6 is set to be equal to the arrangement interval of the air diffusion tubes 5, but the air diffusion tubes 5 are larger than the heat transmission tubes 46 by the diameter of the air diffusion tubes 50.
The gaps between the heat transfer tubes 46 are smaller than the gaps between the heat transfer tubes 46. The gap between the air diffusers 50 is a baffle 54.
It is also smaller than the vertical distance between the first and second dispersion plates 40 (ie, the exit width of the heat recovery unit).

A number of fluidizing gas injection holes are formed in the dispersion plates 38 and 40. A plurality of gas chambers 41 b are provided below the first dispersion plate 38, and a plurality of gas chambers 41 b are provided below the second dispersion plate 40. Gas chambers 40a, 41, 40b, and 40c are provided side by side in the left-right direction. Of these gas chambers, a specific gas chamber 41 located below the second dispersion plate 40 and near the incombustible substance discharge section 42 supplies fluidized gas into the air diffuser 50. It has become. Further, the fluidizing gas injected from the gas chamber 40a closer to the incombustible substance discharge section 42 than the gas chamber 41 through the fluidizing gas injection port is supplied to the incombustible substance discharge section 4.
2, and passes through the baffle 54 near the surface facing the first dispersion plate 38 side. The fluidizing gas injected from the gas chambers 40b and 40c through the fluidizing gas injection port is supplied to the heat recovery unit 1
2B.

Next, a facility for supplying a fluidizing gas to each gas chamber, which is a feature of this apparatus, will be described.

First, a primary air blower (gas injection means) 60A as a fluidizing gas (here, air) supply source is provided in the gas chambers 40a and 41b constituting the main combustion air diffuser through a branch pipe 57A. It is connected. The air discharged from the primary air blower 60A is injected from the fluidizing gas injection port toward the main combustion section 12A in the furnace. This air has both a role as combustion air in the main combustion section 12A and a role as fluidization air.

On the other hand, the gas chambers 40b, 40c and the gas chamber 41, which constitute the heat recovery diffuser, are disposed downstream of the exhaust fan 36 in the exhaust passage via an exhaust gas recirculation pipe 58 and a branch pipe 57B. The parts are connected. In the middle of the exhaust gas recirculation pipe 58, a damper (recirculation amount adjusting means) 59 and an exhaust gas recirculation blower 60B are provided. , 57B through the gas chambers 40b, 40c, 41, and the amount of recirculation is adjustable by a damper 59.

The discharge side of the primary air blower 60A and the discharge side of the exhaust gas recirculation blower 60B are connected via a pipe 61 which is a connection passage, and a damper (opening / closing means) is provided in the middle of the pipe 61. 62 are provided.

In this embodiment, the injection amount of the fluidizing gas from the gas chamber 41b in the vicinity of the non-combustible substance discharge section 42 is basically set relatively large among all the gas chambers. The amount of fluidizing gas injected from the gas chamber 41 located below the heat transfer tube 46 in the central portion of the chevron and the second dispersion plate 40 is set relatively small. Due to such setting of the injection amount, the sand particles rise near the side of the baffle 54 on the main combustion part side, as shown by the white arrow in FIG. The flows which overflow to the 51 side and settle are formed.

In this apparatus, wastes (objects to be treated) such as municipal solids introduced from the incineration material inlet 16 fall into the main combustion section 12A and burn. In the main combustion portion 12A, the fluidizing gas injected from the gas chamber 41b through the gas injection port of the first distribution plate 38 and the fluidizing gas injected from the gas chamber 40a through the gas injection port of the second distribution plate 40 are used. The sand particles violently move up and down repeatedly, and the sand particles that have risen through the vicinity of the baffle 54 overflow to the center of the furnace and the upper portion 51 of the diffuser 50 and settle.

More specifically, the particles overflowing toward the upper portion 51 pass through the gap between the upper portions 51 and pass through the baffle 5.
After sinking between the heat transfer tubes 46 in the heat recovery portion 12B sandwiched between the heat transfer tube 4 and the heat insulating wall 11, the heat transfer tubes 46 are given incineration heat (that is, after the heat transfer tubes 46 collect the incineration heat). Then, it slides down along the inclined surface of the second dispersion plate 40 toward the non-combustible material discharge portion 42 side. Further, the particles overflowing to the center of the furnace settle as they are at the center of the chevron of the first dispersing plate 38, and the first dispersing plate 38
Along the inclined surface toward the incombustible discharge part 42 side. Here, the gas chamber 41 immediately before the incombustibles discharge section 42
Since a strong fluidizing gas is injected from b, some sand particles are pushed up by the fluidizing gas and recirculated to the main combustion section, and the other sand particles are mixed with noncombustibles (solids). It falls into the incombustible discharge part 42 and is carried out to the left and right outer sides by the incombustible substance extracting device 44. This discharge is sieved and only fine sand particles are resupplied to the fluidized bed 12.

At this time, the gas chambers 41b and 40a constituting the main combustion air diffuser are supplied with the fluidizing gas as
The air discharged from the primary air blower 60A is supplied as it is, and is injected from the fluidizing gas injection port to the main combustion section 12A.

On the other hand, a part of the combustion exhaust gas flowing through the exhaust passage is recirculated as a fluidizing gas to the gas chambers 40b, 40c and the gas chamber 41 constituting the heat recovery diffuser. The gas is injected from the gas injection port into the heat recovery unit 12B. Since the oxygen concentration in the flue gas thus recirculated is very low as compared with air, even if the supply amount of the fluidizing gas (that is, the recirculation amount of the flue gas) is increased for sufficient fluidization, the heat The oxygen concentration in the recovery unit 12B hardly increases, and the combustion of the fuel in the heat recovery unit 12B is hardly promoted. Accordingly, it is possible to prevent the heat transfer tube from being thermally damaged due to the local high temperature phenomenon and the generation of hydrogen chloride accompanying the promotion of combustion, and it is also possible to suppress the generation of NOx.
Moreover, since the sensible heat of the recirculated combustion exhaust gas can be recovered through the heat transfer tube 46, the amount of heat recovery is greatly increased as compared with the related art, and a sufficient amount of heat can be recovered even when the in-layer combustion rate is low. .

The damper 62 may be opened during a period when the flow rate of the combustion exhaust gas is insufficient such as when the apparatus is started. Thereby, the shortage of the supply amount of the fluidizing gas to the gas chambers 40b, 40c, 41 can be supplemented by the discharge air of the primary air blower 60A.

* Experimental data: FIG. 4 shows the heat recovery amount when the above-mentioned exhaust gas recirculation was not performed (that is, when air was supplied as a fluidizing gas to the heat recovery unit 12B), and the amount of the total combustion exhaust gas. A graph showing the ratio to the amount of heat recovery (that is, the rate of increase in the amount of heat recovery) when 10% is recirculated (that is, when the exhaust gas recirculation rate is 10%) is shown in a graph in relation to the heat generation amount of the waste. Things. As shown in this graph, the waste heat value is 3000
In the range of 40004000 kcal / kg, heat recovery can be increased by about 1.2 to 1.4 times by performing exhaust gas recirculation.

FIG. 5 shows the relationship between the exhaust gas recirculation rate and the NOx reduction rate in the combustion exhaust gas at the furnace outlet (the NOx generation amount when the NOx generation amount is 1 when the exhaust gas recirculation amount is 0). The relationship is shown in a graph. In this experiment, when the exhaust gas recirculation rate was 10%, the content of the combustion exhaust gas in the fluidized gas to the heat recovery unit 12B was 100%, and the exhaust gas recirculation rate was 10% or more. In some cases, a part of the fluidized gas for the main combustion section is also used.

As is apparent from this graph, the execution of the exhaust gas recirculation can suppress the generation of NOx and contribute to the improvement of the environment.

FIG. 6 shows a second embodiment. In this embodiment, a pipe 64 is branched from the exhaust gas recirculation pipe 58 and connected to the gas chamber 41b constituting the main combustion air diffuser, and a damper 65 is provided in the middle of the pipe 64. The combustion exhaust gas is also partially recirculated to the chamber 41b.

According to such a configuration, the combustion exhaust gas is appropriately mixed into the air supplied from the primary air blower 60A to the gas chamber 41b within a range where a sufficient combustion efficiency can be obtained, so that the main combustion section 12A It is also possible to suppress the generation of NOx.

It should be noted that the present invention is not limited to this embodiment, and the following embodiments can be taken as examples.

(1) In the present invention, regardless of the specific internal structure of the apparatus, it can be widely applied to those in which the fluidized bed is divided into a main combustion section and a heat recovery section. For example, in the above embodiment, the first dispersing plate 38 is disposed at the center of the furnace, and the second dispersing plate 40 is disposed on both outer sides thereof. However, the first dispersing plate 38 is disposed on one side of the furnace. Arrange the second dispersion plate 40 on one side,
The incombustible discharge part 42 may be arranged substantially at the center of the furnace. In addition, the shape of the furnace is cylindrical, and the first
The dispersing plate 38 is disposed, a second donut-shaped dispersing plate 40 is disposed radially outward of the dispersing plate 38, and an incombustible substance discharge portion 42 is formed between the dispersing plates 38 and 40 over the entire circumference. Good. In this case, the heat transfer tube 46 and the air diffuser tube 50 may also be provided side by side in the circumferential direction.

(2) In the present invention, the point at which the combustion exhaust gas for recirculation is extracted from the exhaust passage may be appropriately set. However, as shown in the above embodiment, if the flue gas is recirculated from the downstream side of the bag filter 34 which is an exhaust gas treatment device, the more preferable flue gas from which harmful components have been removed by the bag filter 34 is fluidized. There is an advantage that it can be supplied as a gas.

(3) The structure of the baffle in the present invention is not particularly limited, and the fluidized bed 12 is composed of the main combustion section 12A and the heat recovery section 12B.
Any material can be used as long as the fluidized particles can move above and below it. For example, a device in which the entire baffle is integrally formed of a single plate may be specially provided. In this case, a column different from the diffuser tube 50 may be erected on the second dispersion plate 40, and the column may be supported by the column. In the present invention, the air diffuser 5 is not necessarily used.
0 is not required.

(4) In each of the above embodiments, the air diffuser for injecting the fluidizing gas from the furnace bottom is provided with the dispersing plates 38 and 40 and the means for injecting the gas from these dispersing plates 38 and 40 (gas , Etc.), but instead of the dispersion plate,
A diffuser tube similar to the diffuser tube 50 may be arranged at the bottom of the apparatus in a horizontal state. In this case, the incombustibles fall from the gaps between the air diffusers, and the lower part of these air diffusers serves as an incombustible discharge unit.

[0054]

As described above, according to the present invention, in a fluidized bed heat recovery apparatus in which a fluidized bed is divided into a main combustion section and a heat recovery section, combustion exhaust gas is supplied as the fluidizing gas supplied to the heat recovery section. Since the recirculation is performed, by recovering the sensible heat of the recirculated combustion exhaust gas through the heat transfer tube, the heat recovery amount can be greatly increased. In addition, while increasing the supply amount of the fluidizing gas, that is, the recirculation amount of the combustion exhaust gas, to sufficiently perform the fluidization, the oxygen concentration in the heat recovery unit can be suppressed to be low, and the combustion of the fuel in the heat recovery unit can be suppressed. Therefore, deterioration and damage of the heat transfer tube due to the combustion can be prevented, and generation of NOx can be suppressed.

Further, in the method and the device according to the second and seventh aspects, the combustion exhaust gas is partially recirculated to the main combustion air diffuser as a fluidizing gas. There is an effect that generation of NOx can be suppressed.

In the apparatus according to a fourth aspect of the present invention, an exhaust gas treatment device for removing a specific component in the combustion exhaust gas is provided in the exhaust gas discharge passage, and the combustion exhaust gas passing through the exhaust gas treatment device is dispersed into the heat recovery dispersion gas. Because it is made to recirculate to the air system, this heat recovery air diffuser
There is an effect that a more preferable combustion exhaust gas from which undesirable substances (eg, hydrogen chloride, dust and the like) are removed in advance can be supplied as a fluidizing gas.

In the apparatus according to the fifth aspect, the amount of combustion exhaust gas recirculated by the exhaust gas recirculation means is changed by the recirculation amount adjusting means, so that the combustion to the heat recovery section is performed according to the state of the heat recovery section. There is an effect that the supply amount of the exhaust gas (fluidizing gas) can be appropriately adjusted.

The apparatus according to claim 6, wherein a connecting passage connecting the supply source of the fluidizing gas to the main combustion air diffuser and the heat recovery air diffuser, and an opening / closing means for opening and closing the connection passage. When the flow rate of the flue gas is insufficient, such as when the apparatus starts up, the connection passage is opened to recover part of the fluidized gas to the main combustion air diffuser. It can be replenished as a fluidizing gas to the air diffuser for use, and has the effect that fluidization of the fluidized bed in the heat recovery section can always be performed well.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a fluidized bed heat recovery device according to a first embodiment of the present invention.

FIG. 2 is a sectional front view showing a main part of the fluidized bed heat recovery device.

FIG. 3 is a partial sectional plan view showing the main part.

FIG. 4 is a graph showing a relationship between a calorific value of a waste and an increase rate of a heat recovery amount due to exhaust gas recirculation.

FIG. 5 is a graph showing a relationship between an exhaust gas recirculation rate and a NOx reduction rate at a furnace outlet.

FIG. 6 is an overall configuration diagram of a fluidized bed heat recovery device according to a second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Incinerator 12 Fluidized bed 12A Main combustion part 12B Heat recovery part 36 Bag filter (exhaust gas treatment device) 38 1st dispersion plate (constituting the main combustion air diffuser) 40 2nd dispersion plate (of main combustion air diffuser 40a, 41b Gas chambers (constitutes main combustion diffuser) 40b, 40c Gas chambers (constitutes heat recovery diffuser) 46 Heat transfer tube 54 Baffle 57B Branch pipe (Exhaust gas recirculation means) 58 Exhaust gas recirculation pipe (Exhaust gas recirculation means) 59 Damper (Recirculation amount adjusting means) 60A Primary air blower (Fluidized gas supply source to main combustion diffuser) 60B Exhaust gas recirculation Blower (exhaust gas recirculation means) 61 piping (connection passage) 62 damper (opening / closing means)

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location F23G 5/30 ZAB F23G 5/30 ZABB ZABH

Claims (7)

(57) [Claims] A fluidized bed formed of fluidized particles at the bottom of an apparatus main body is divided into a main combustion section and a heat recovery section by a baffle, and a heat transfer tube for heat recovery is provided in the heat recovery section. A main-combustion diffuser for injecting a fluidizing gas for fluidizing the fluidized particles in the main combustion section, and a fluidizing gas for fluidizing the fluidized particles in the heat recovery section to the heat recovery section. And a diffuser for heat recovery that injects the fluidized gas.The fluidized gas causes the fluidized particles of the main combustion section to pass through above the baffle, enter the heat recovery section, and further pass below the baffle to pass through the baffle. In a fluidized bed heat recovery device configured to form a flow returning into the main combustion section, it is possible to recirculate combustion exhaust gas generated by combustion in the fluidized bed as a fluidized gas to the heat recovery diffuser. Features and For supplying a fluidized gas in a fluidized bed heat recovery apparatus. 2. The method for supplying a fluidized gas in a fluidized bed heat recovery apparatus according to claim 1, wherein the combustion exhaust gas is partially recirculated as a fluidized gas also to the main combustion air diffuser. For supplying a fluidized gas in a fluidized bed heat recovery apparatus. 3. A fluidized bed formed of fluidized particles at the bottom of the apparatus body is divided into a main combustion section and a heat recovery section by a baffle, and a heat transfer tube for heat recovery is provided in the heat recovery section. A main-combustion diffuser for injecting a fluidizing gas for fluidizing the fluidized particles in the main combustion section, and a fluidizing gas for fluidizing the fluidized particles in the heat recovery section to the heat recovery section. And a diffuser for heat recovery that injects the fluidized gas.The fluidized gas causes the fluidized particles of the main combustion section to pass through above the baffle, enter the heat recovery section, and further pass below the baffle to pass through the baffle. In a fluidized bed heat recovery device configured to form a flow returning into the main combustion section, an exhaust gas recirculation system is used in which flue gas generated by combustion in the fluidized bed is recirculated as a fluidizing gas to the heat recovery diffuser. Circulation Means for supplying a fluidized gas in a fluidized-bed heat recovery apparatus, characterized by comprising means. 4. A fluidized gas supply device in a fluidized bed heat recovery device according to claim 3, wherein an exhaust gas treatment device for removing a specific component in the combustion exhaust gas is provided in the exhaust gas exhaust passage, and the exhaust gas is provided. An apparatus for supplying a fluidized gas in a fluidized bed heat recovery apparatus, wherein the exhaust gas recirculation means is configured to recirculate the combustion exhaust gas that has passed through the processing apparatus to the heat recovery diffuser. 5. The fluidized gas supply device in the fluidized bed heat recovery device according to claim 3, further comprising a recirculation amount adjusting means for changing a recirculation amount of the combustion exhaust gas by the exhaust gas recirculation means. A fluidized gas supply device in a fluidized bed heat recovery device. 6. The fluidizing gas supply device in the fluidized bed heat recovery device according to claim 3, wherein the fluidizing gas supply source to the main combustion air diffuser and the heat recovery gas supply device. A fluidized gas supply device in a fluidized bed heat recovery device, comprising: a connection passage connecting the air diffuser; and an opening / closing means for opening and closing the connection passage. 7. The fluidizing gas supply device in the fluidized bed heat recovery device according to claim 3, wherein the combustion exhaust gas is partially recycled to the main combustion diffuser as a fluidizing gas. A fluidized gas supply device in a fluidized bed heat recovery device, wherein the exhaust gas recirculation means is configured to circulate.