JP2002147725A - Operation method for external circulating fluidized bed incinerator used for incinerator of wastes with high moisture content and volatile substance content such as sewage sludge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an operation method for a compact and low cost type circulating fluidized bed incinerator capable of the combustion with a low degree of environmental pollution of sewage and sludge having a high moisture content and a high volatile substance content with high efficiency in the circulating fluidized incinerator. SOLUTION: In a circulating fluidized incinerator forming a bubble fluidized bed from the primary air supplied from the lower side of the fluidized bed and introducing the secondary air to a splash area to reflux the particles conveyed with the particles blowing up outside the furnace by the secondary air through a freeboard to the bubble fluidized bed area through an external circulating part, the amount of the primary air is made to be 10 to 40%, by volume, of the total air amount in distributing the total supplied air amount into the primary air and secondary air. It is characterized by the primary air amount that is 0.15 to 0.5 times the theoretical amount of air required for the complete combustion of an object to be incinerated, and moreover the location at which the secondary air is blown into the bubble fluidized bed area has the height of 1.2 m or higher from a fluidized bed air dispersion plate. The fluid medium with the mean particle diameter of 0.5 mm or smaller is used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circulating fluidized bed furnace capable of completely burning a combustion medium such as sewage sludge, municipal solid waste or industrial exhaust and reducing the generation of carbon monoxide, dioxins and the like. In particular, the water content is high, the volatile matter in the combustibles is high, and the sewage sludge and the like have low CO, low DXN, low NOx,
The present invention relates to an operation method of an external circulating fluidized bed incinerator used for a waste incinerator having a high water content and a high volatility such as sewage sludge which is stably incinerated with low pollution such as low N ₂ O.

[0002]

2. Description of the Related Art Conventionally, fluidized bed incinerators have been widely used for treating sewage sludge, municipal waste, industrial waste, and the like. The most distinctive feature of fluidized bed incinerators is that they can dry and incinerate waste instantaneously, and because the hearth is constantly kept at a high temperature and has sufficient heat storage to supply waste. Is stable against instantaneous fluctuations of
Among wastes, it is particularly suitable for sewage sludge with a high water content.

[0003] Such fluidized bed incinerators include bubble fluidized bed furnaces often found in incinerators for municipal garbage and dewatered sludge, and circulating fluidized bed incinerators found in coal-fired power boilers and incinerators for mixed incineration of some wastes. are categorized. In order to briefly explain the structure of the former bubble fluidized-bed furnace, the bubble-fluidized-bed furnace is filled with a fluid medium such as sand at the bottom of the furnace, and is brought into a fluidized state by blowing high-pressure air from underneath the fluid medium. The waste put in is dried and incinerated instantly. As a result, the fluid medium is maintained at a high temperature to enable continuous instantaneous combustion, and since the fluid medium has a very large heat capacity, the heat radiation at the time of stoppage is small,
It has the characteristic of being suitable for intermittent operation, and has a high heat transfer coefficient of the fluidized medium, and therefore has a high sludge drying ability.

However, due to the recent change in sludge properties, there has been a problem that volatile components in the sludge cause active combustion on the freeboard in the upper part of the furnace, and the temperature in the furnace becomes uniform and the amount of exhaust gas decreases. For such purposes, a circulating fluidized bed furnace in which a fluidized medium is circulated in the furnace by increasing the speed of the blowing air tends to be frequently used. Such a circulating fluidized bed furnace,
The supply amount of primary air blown from the furnace bottom is 5 times the total supply air amount.
0% or more, the injected sludge and the fluidized medium are violently mixed and scattered, and the scattered fluidized medium and sludge are entrained in the free board by blowing secondary air, and burned in the system while burning. It was circulating, and the characteristic feature was that the sludge had a high drying load of moisture.

However, the exhaust gas discharged from the fluidized bed furnace is
Carbon monoxide, HCN, NH ₃Concentration of harmful substances such as
High degree of attention and attention as a greenhouse gas for global warming
Nitrous oxide (N₂O) concentration is high
There is a problem. In particular, in the case of a circulating fluidized bed furnace, the conventional bubble
Sufficient residence time due to high superficial velocity compared to fluidized furnace
Could not be secured, and carbon monoxide at the cyclone exit
The representative unburned gas concentration was high.

[0006] This is closely related to the fuel ratio of waste (fixed carbon content / volatile content), and when substances having a high water content ratio such as sludge are incinerated, most of the combustion products are gasified. Since combustion occurs on the free board above the fluidized bed, there is a problem that the mass exchange around the unburned gas does not remain, oxygen is not sufficiently supplied, and combustion is not completed in the free board. On the other hand, when the waste is incinerated in the circulating fluidized bed furnace, since the superficial velocity after mixing the primary air and the secondary air is high, the sludge particles (char particles) during gasification are reduced to the riser section. (Free board portion), and a sufficient residence time for burning carbon monoxide generated from the unburned char cannot be secured, and the unburned gas concentration at the cyclone outlet is increased as described above. Has problems. That is, in the conventional circulating fluidized bed, since the primary air amount is relatively large and the superficial velocity at the lower part of the riser is large, the large diameter of sludge particles, sludge particles in the drying process, and char particles generated after drying and gasification are large. There was a problem that the combustion time could not be secured due to the blow-up of things.

[0007] When the superficial velocity at the lower part of the riser is high, the amount of sand blown up is increased, so that the sand concentration at the lower part of the riser is reduced, and it becomes difficult to secure the heat quantity required for drying high-moisture sludge. There is a problem that the temperature is lowered. Furthermore, when the whole combustion air amount is constant (constant air ratio), since the primary air amount is relatively large (usually 50% or more of the whole), the secondary air amount is reduced (secondary air blowing flow rate). And the mixing / stirring power of the unburned gas and air in the riser section (free boat section) tends to be small. Therefore, there is a problem that unburned gas such as CO and DXN and nitrogen oxides such as NOx and N ₂ O increase at a cyclone outlet (furnace outlet).

[0008]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above-mentioned problems in the prior art, and enables sewage sludge having a high water content and a high volatile content to be efficiently combusted in a circulating fluidized bed furnace with low pollution. An object of the present invention is to provide a method for operating a circulating fluidized bed furnace.

[0009]

In order to solve the above-mentioned problems, the present invention provides a primary air supply means for forming a fluidized bed by primary air supplied from below a riser, and a primary air supply means provided on a riser furnace wall above the fluidized bed. In a circulating fluidized bed furnace equipped with secondary air supply means for forming an airflow layer on a freeboard by blowing secondary air, a bubble fluidized bed (rich layer portion) is formed by primary air supplied from below the fluidized bed. Let
Secondary air is introduced into the splash area where the particles of the fluid medium are blown up by the rupture of the bubbles on the surface of the fluidized sand layer in the bubble fluidized bed (dense layer portion) area, and the blow-up particles are freed by the secondary air. An external circulating fluidized bed furnace that entrains and transports the entrained particles out of the furnace through the board and recirculates the entrained particles to the bubble flow area through an external circulating section is incinerated with a high moisture content and highly volatile waste such as sewage sludge. The first point is that an external circulating fluidized bed furnace is used for the furnace.

According to the first aspect of the present invention, in distributing the total supply air amount to the primary air and the secondary air, the primary air amount is set to 10 to 40% (volume ratio) of the total supply air amount. At the same time, the primary air amount is 0.15 to stoichiometric air amount required for complete combustion of the complete combustion of the incineration target.
It is characterized in that it is set to 0.5 times and thermal decomposition is performed while maintaining the bubble fluidized bed region in a reducing atmosphere.

That is, according to the present invention, the amount of primary air supplied from below the riser is reduced to 10 to 40% of the total air amount to form a stable dense layer portion, and coarse dry sludge and char particles are discharged to the free board side. And the primary air amount is 0.1% of the theoretical air amount necessary for complete combustion of the incineration object.
By making the ratio 5 to 0.5 times, gasification by the drying and reduction combustion of the sewage sludge in the primary combustion region, which is the rich layer, is positively generated, and the secondary combustion region in the freeboard portion is multi-stage gas. By setting it as a combustion field, it is possible to stabilize and improve the efficiency of combustion and achieve low-pollution combustion.

Therefore, according to the present invention, the supply amount of primary air
To 10 to 40% of the total supply air volume,
The fluidized bed (dense layer) is formed stably,
Secondary sludge of dry sludge and pyrolysis char particles (free board
Part) and burn while suppressing high-speed sand circulation.
As a result, the amount of heat in the bubble fluidized bed (dense bed) can be secured.
High load drying of water in sludge has been achieved,
The combustion of the char of the furnace can be miniaturized, and the combustion gas
To significantly reduce the gas concentration, that is, to achieve complete combustion.
It is possible. In addition, the present invention is intended for
0.15 to 0.5 times the theoretical air volume required for complete combustion of objects
The lower part in the primary combustion zone
Proactively generate gasification by water sludge drying and reduction combustion
In other words, gasification combustion in the primary combustion section is promoted. Sewage pollution
Mud gasification is the pyrolysis gasification of volatile combustibles due to high temperatures.
And the steam and char generated from the sewage sludge shown below
Aquatic gasification reaction occurs simultaneously. Aquatic moth
Reaction: C + H₂O → CO + H₂ As a result, under the riser
From the primary combustion zone (rich layer) to the secondary combustion zone
-Combustible gas is mainly transferred to the
The amount of char that jumps out of the ship has been significantly reduced.

According to a second aspect of the present invention, the total amount of air, which is the sum of the amount of supply of the primary air and the amount of secondary air, is 1.15 to 1.15 of the theoretical amount of combustion air with respect to all incinerated materials including auxiliary fuel.
When the total supply air amount is set to 1.45 times and the total supply air amount is distributed to the primary air and the secondary air, the primary air amount is set to 10 to 40% (volume ratio) of the total supply air amount. Features.

That is, according to the present invention, the amount of primary air supplied from below the riser is reduced to 10 to 40% of the total amount of air to form a stable dense layer portion, and coarse dry sludge and char particles are discharged to the freeboard side. And the total air amount, which is the sum of the supply amount of the primary air and the secondary air amount, is 1.1 of the theoretical combustion air amount for all incinerated materials including the auxiliary fuel.
By setting the ratio to 15 to 1.45 times, that is, the above-mentioned advantage by the reduction combustion in the primary combustion region and the multi-stage gas combustion by increasing the amount of air in the secondary combustion region, complete combustion and high load combustion can be achieved. This is achieved, and unburned gases such as CO and DXNs and nitrogen oxides such as Nox and N ₂ O at the cyclone outlet (furnace outlet) are greatly suppressed.

According to a third aspect of the present invention, the position of the secondary air to be injected into the bubble fluidized bed region is set at a height close to a splash region of 1.2 m or more from the fluidized bed air dispersion plate, and the average particle size is adjusted. The method is characterized in that a superficial velocity of exhaust gas in a freeboard section (riser section) after mixing primary air and secondary air is 3 to 10 m / s using a fluid medium having a diameter of 0.5 m or less.

That is, according to the present invention, the height of the blowing of the secondary air into the bubble fluidized bed region (dense layer portion) is close to the splash region of 1.2 m or more from the air dispersion plate or the air dispersion nozzle. In addition, by using a fluid medium having an average particle size of 0.2 m or less, even if the superficial velocity of the primary air is reduced, the sand circulation is stabilized, and a high water content and a high volatile content such as sewage sludge are obtained. It is possible to achieve low-pollution combustion with high efficiency of the incinerated material.

According to the invention, the secondary air blowing height is set to 1.2 m or more from the air dispersion plate or the nozzle, and by using a fluid medium having an average particle diameter of 0.2 mm or less, the dense layer having high sand concentration can be obtained. Because there is enough space,
Drying and gasification by high-temperature sand is promoted. Further, when the secondary air blowing height is low as in the conventional case, the amount of scattered char can be significantly reduced by increasing the secondary air blowing height.

Hereinafter, the present invention will be described in detail with reference to an embodiment shown in the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention but to merely illustrative examples. Absent. FIG. 1 is an overall schematic configuration diagram of an external circulating fluidized bed furnace used in a waste incinerator having a high water content and a high volatility such as sewage sludge according to an embodiment of the present invention.

In FIG. 1, the external circulating fluidized bed furnace includes a riser 1 in which a combustion reaction of sewage sludge is performed, a cyclone 11 for collecting a fluid medium, a downcomer 12 and a blow-through of unburned gas in the furnace to the cyclone. Seal pot 13 to prevent
Consists of In the hearth of the riser 1, a riser-like box 2
The fluid medium filled in the lower part 4 of the riser is fluidized by the primary air 17 introduced from the air, and the bubble fluid medium layer (rich layer) 18 is further formed on the fluidized sand layer surface of the bubble fluid bed region (rich layer portion). A splash area 29 is formed in which particles of the fluid medium are blown up with the bursting of the bubbles.

The sewage sludge 19 introduced into the riser 1 from the sludge introduction port 5 is repeatedly mixed and agitated in the fluidized bed 18 while repeatedly colliding with the fluidized medium to be atomized, dried and thermally differentiated. You. Then, the water content, unburned gas, and light sludge particles scattered from the fluidized bed 18 are transported together with the fluidized medium to the free board section 8 by the secondary air 20 introduced from the secondary air supply port 6, and the free It burns in the board section 8. The fluid medium passing through the free board section 8 is heated here to a high temperature, and the cyclone 11
, Collected via downcomer-12 and sealed pot 1
3 and is formed into a moving bed by the air supplied from the seal pot lower wind box 14, and is returned to the fluidized bed 7 of the riser 2.

The following is a circulating fluidized-bed furnace similar to that of the prior art. In this embodiment, as shown in FIGS. 3 and 4, the primary air is changed depending on the properties and amount of the sewage sludge introduced or the combustion state in the furnace. By adjusting the distribution ratio of the primary air 17 and the secondary air 20 to make the primary air amount 10 to 40% (volume ratio) of the total air amount, a stable fluidized bed 18 (rich layer portion) is formed. As a result, The combustible gas mainly migrates from the primary combustion zone (rich portion) at the lower part of the riser to the freeboard part 8 as the secondary combustion zone, and the amount of coarse dry sludge and char particles that jump out from the lower part of the riser is remarkable. Diminished. That is, as shown in FIG. 3, the primary air ratio (primary air amount / theoretical air amount) is equal to 0.
In both cases of 2 and 0.3, a sufficiently thick layer was formed in the lower part of the furnace, but when the air ratio was 0.6, almost no thick layer was formed, and the air layer had a thickness of 50 to 70 kg / m ³ over the entire riser.
Therefore, the scattering of the char particles into the free board portion 8 cannot be suppressed. Primary air ratio
2 is 15% when expressed as (primary air amount / total air amount), 0.3
It is understood that it is better to set the (primary air amount / total air amount) to 10 to 40% in view of the allowance. FIG. 2 shows the relationship between the CO concentration and the furnace height. In this figure, primary air ratio (primary air amount / theoretical air amount)
Is 0.3 and the CO concentration is sufficiently reduced, but the primary air ratio is 0.1 (primary air amount / total air amount: 8%) 0.6 (primary air amount / total air amount: 46%) 0 At 0.7 (primary air amount / total air amount: 55%), the CO concentration did not decrease sufficiently. From this point (primary air amount / total air amount) is 10
It can be understood that it is better to set to に 40%. As a result, a bubble fluidized bed portion (thick layer portion) is formed stably, and coarse dry sludge and pyrolysis char particles are prevented from scattering to the secondary combustion portion (free board portion) and burned.
Because high-temperature sand circulates, the amount of heat in the bubble fluidized bed (dense layer) can be secured, high-load drying of moisture in sludge can be achieved, and the combustion of char in the primary combustion zone can be miniaturized.
The gasified gas transferred to the free board unit 8 can improve the mixing / stirring power by increasing the secondary air supplied to the free board unit (60 to 90%), and greatly reduce the generation of HCN, DXN, etc. That is, it is possible to achieve complete combustion.

According to the present embodiment, the primary air amount is
0.15 of the theoretical air volume required for complete combustion of the incineration object
By making it 0.5 times, the primary combustion in the rich layer
Of sewage sludge drying and gasification by reduction combustion in the area
Thermal decomposition of volatile combustibles due to high temperatures
Along with gasification, the following steam generated from sewage sludge
The aquatic gasification reaction is simultaneously generated by
To accelerate char combustion (solid combustion), which is slower than
It becomes possible to plan. Aquatic gasification reaction: C (char) + H₂O (steam) → C
O + H₂  As a result, a large amount of secondary air is
Mix and stir actively with air to promote gas combustion.
Achieves stable combustion, high efficiency, and low-pollution combustion
I can do it.

Next, according to this embodiment, the height of the secondary air to be blown is set at the position of the dense layer close to the splash area of 1.2 m or more from the air distribution plate or nozzle, and the average particle diameter is 0.5 mm or less. By using the fluid medium of
Even if the superficial velocity of the primary air is reduced, it is possible to stabilize the sand circulation and sufficiently secure a dense layer with high sand concentration. Gasification is promoted, that is, even low-pollution incineration with high water content and high volatility such as sewage sludge can be achieved with high efficiency. In the demonstration test, the secondary injection position was set at 1.2 m and the dense layer position near the splash area of 1.2 m or more, but in the latter case, the pressure gradient at the bottom of the furnace was large, and the sand concentration was high in the dense layer, It can be understood that the CO concentration is also significantly improved as compared with 60 ppm in the case of 20 ppm and 1.2 m. In addition, by making the secondary air blowing height as high as 1.2 m or more, the scattering amount can be significantly reduced.

In this embodiment, in order to achieve complete combustion of the unburned gas and to reduce the amount of exhaust gas from the furnace, the total supply air amount including the primary air and the secondary air must be reduced by the auxiliary fuel. 1.15-Theoretical combustion air amount for all incinerated materials including
1.45 times, preferably 1.25 to 1.35 times.
That is, as is apparent from FIG.
At 5 times, the furnace outlet CO concentration is 40 ppm, and at 1.3 times, the furnace outlet CO concentration is greatly reduced to 20 ppm.
On the other hand, it is understood that the Nox concentration increases significantly at 1.45 times or more of the theoretical combustion air amount.

Further, in order to stabilize the operation of the furnace, particularly the sand circulation, the superficial velocity of the exhaust gas in the freeboard section 8 after mixing the primary air and the secondary air is 3 to 10 m / s, preferably Is controlled to be 4 to 7 m / s. As a result, the exhaust gas treatment facility can be made compact by reducing the amount of exhaust gas, the furnace can be made compact by high-efficiency combustion, the sand circulation can be stabilized, and the operation operability can be stabilized and simplified.

[0026]

As described below, according to the present invention, the primary air flow rate is reduced to 10 to 40% of the total air flow rate, so that the primary air blow-up flow rate is reduced and sludge and pyrolysis charcoal during drying are reduced. By suppressing the blowing of coarse particles into the freeboard section (secondary combustion section), complete combustion of unburned gas and the like is promoted, so that carbon monoxide, HCN, NH ₃
And significant reduction of dioxins and the like. Further, by making the primary air amount 0.15 to 0.5 times the theoretical air amount necessary for complete combustion of the incineration object, the drying and pyrolysis gasification reaction in the primary combustion field is promoted,
The water gasification reaction is also caused to occur, and the mixing and agitation of the secondary combustion section by the secondary air are promoted, so that the gas combustion is made more efficient and stable, and low-pollution combustion is achieved. Further, the height of the secondary air blown into the bubble fluidized bed region (dense layer portion) is at least 1.2 m close to the splash region from the air dispersion plate or the air dispersion nozzle, and particularly a fluid medium having an average particle size of 0.5 mm or less. By using, it is possible to have a margin for the above-mentioned reduction of the primary air amount, and it is possible to expand the range of flow velocity for stabilizing the sand circulation. Therefore, even incineration products having a high water content and a high volatile content such as sewage sludge can achieve low-pollution combustion with high efficiency. In the operation of the invention, the total supply air amount is 1.15 to 1.45 of the theoretical combustion air amount.
Times, preferably 1.3 times, and the superficial velocity of the exhaust gas in the freeboard section is 3 to 10 m / s, preferably,
By controlling so as to be 4 to 7 m / s, exhaust gas treatment equipment can be made compact by reducing the amount of exhaust gas, furnaces can be made compact by high-efficiency combustion, sand circulation can be stabilized, and operation operability can be stabilized and simplified. Is achieved. As described above, the control of the fluidized bed furnace is simple, and even in the combustion of sewage sludge having a high water content, high efficiency and low pollution combustion can be achieved without impairing the combustion speed, and thus the incinerator can be made more compact, and Contributes to reduction of exhaust gas volume.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an overall schematic configuration of an external circulating fluidized bed furnace according to an embodiment of the present invention.

FIG. 2 is a CO temperature distribution in a furnace axial direction at a primary air ratio using the partial circulation fluidized bed furnace.

FIG. 3 is a distribution of suspended density in a furnace axial direction at a primary air ratio using the partial circulation fluidized bed furnace.

FIG. 4 is a distribution diagram showing a secondary air blowing height and an axial pressure distribution in the furnace using the partially circulating fluidized bed furnace.

FIG. 5 is a distribution diagram showing the air ratio and the CO and NOx concentrations at the furnace outlet when the partial circulation fluidized bed furnace is used.

[Brief description of the code]

 Reference Signs List 1 riser 3 riser dispersion plate 5 sludge inlet 6 secondary air inlet 8 free board section 9 riser top 17 primary air 18 rich layer section 20 secondary air 29 splash area

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) F23G 5/50 ZAB F27B 15/02 F27B 15/02 15/10 15/10 F23C 11/02 311 (72) Inventor Tsuneki Yamauchi 1-8-1 Koura, Kanazawa-ku, Yokohama-shi Yokohama Research Institute, Mitsubishi Heavy Industries Co., Ltd. Shiro No.12 Nishikicho, Naka-ku, Yokohama-shi F-term in Mitsubishi Heavy Industries, Ltd.Yokohama Works 3K062 AA11 AB01 AC01 AC02 BB03 DB06 DB09 DB30 3K064 AA01 AA04 AB03 AC03 AC06 AD08 AE01 AE04 AE11 BA07 BA17 BB09 4K046 HA12 JC04 J06 LA04

Claims (3)

[Claims] 1. An external circulating fluidized bed furnace for a waste incinerator having a high water content and high volatility such as sewage sludge, and a bubble fluidized bed (dense layer portion) with primary air supplied from below the fluidized bed furnace.
Is formed, and secondary air is introduced into a splash area where particles of a fluid medium are blown up along with bursting of bubbles on the surface of the fluidized sand layer in the bubble fluidized bed area (dense layer portion), and the secondary air blows up the air. In a circulating fluidized bed incinerator in which particles are entrained and transported to the outside of the furnace via a free board and the entrained particles are returned to the bubble flow region via an external circulation section, the total amount of supplied air is reduced by two times with the primary air. When distributing to the primary air, the primary air amount is 10 to 40% of the total supply air amount.
(Volume ratio), and the amount of primary air is 0.1% of the theoretical amount of air required for complete combustion of the completely burned material to be incinerated.
15 to 0.5 times, thermal decomposition is carried out while maintaining the bubble fluidized bed area in a reducing atmosphere, and is used for waste incinerators with high water content and high volatility such as sewage sludge. Operating method of circulating fluidized bed furnace. 2. An external circulating fluidized bed furnace for a waste incinerator having a high water content and a high volatility such as sewage sludge, and a bubble fluidized bed (dense layer portion) with primary air supplied from below the fluidized bed furnace.
Is formed, and secondary air is introduced into a splash area where particles of a fluid medium are blown up along with bursting of bubbles on the surface of the fluidized sand layer in the bubble fluidized bed area (dense layer portion), and the secondary air blows up the air. In a circulating fluidized bed incinerator in which particles are entrained and transported outside the furnace via a free board and the entrained particles are recirculated to the bubble flow region via an external circulation section, the supply amount of the primary air and the secondary air amount Is set to 1.15 to 1.45 times the theoretical combustion air amount for all incinerated materials including auxiliary fuel, and the total supply air amount is set to the above-described primary air and secondary air amount. When used for incinerators with high water content and high volatility such as sewage sludge, the primary air amount is 10 to 40% (volume ratio) of the total supply air amount when distributing to air. Operating method of circulating fluidized bed furnace. 3. An external circulating fluidized bed furnace for a waste incinerator having a high water content and a high volatility such as sewage sludge, and a bubble fluidized bed (dense layer portion) with primary air supplied from below the fluidized bed furnace.
Is formed, and secondary air is introduced into a splash area where particles of a fluid medium are blown up along with bursting of bubbles on the surface of the fluidized sand layer in the bubble fluidized bed area (dense layer portion), and the secondary air blows up the air. The secondary air is blown into the bubble fluidized bed region in a circulating fluidized bed incinerator in which particles are transported out of the furnace via a free board and the entrained particles are returned to the bubble flowed region through an external circulation section. The freeboard section after mixing the primary air and the secondary air, using a fluid medium having an average particle size of 0.5 m or less, while setting the position of the fluidized bed close to the splash area of 1.2 m or more from the fluidized-bed air dispersion plate. The superficial velocity of the exhaust gas at the riser is 3 to 10 m
/ S, the method for operating an external circulating fluidized bed furnace used for a waste incinerator having a high water content and a high volatility such as sewage sludge.