JPH07119942A - Recombustion furnace and combustion furnace incorporating the same - Google Patents

Abstract

PURPOSE:To obtain surely and with a good combustion efficiency combustion ashes having a merit which is large in recovering resource because of a complete combustibility of such impurities as an unburnt carbon and the like in burnup ashes. CONSTITUTION:A recombustion furnace 20 consists of a vessel 21 having an opening 22 which exhausts exhausted gases after an execution of a recombustion and opens, at an upper section, in a fluidized combustion room 4, and having a predetermined height, wherein burnt ashes are reburnt in an inside section, a burnt ashes taking-out device 24 arranged at an upper section of the vessel 21, and supplying the burnt ashes into the vessel 21, a burnt ashes taking-out device 25 arranged at a lower section of the vessel 21 and taking-out reburnt ashes, and an air supplying device 26 supplying an air for combustion and arranged at an upper section than the lower-situated burnt ashes taking-out device 25 in the vessel 21. This air supplying device 26 is positioned and set in the fluidized combustion room 4 of a fluidized bed incineration furnace. Besides, a fluidized bed incineration furnace 1 is composed wherein the recombustion furnace 20 is incorporated by positioning and setting the recombustion furnace 20 having the composition as this in the fluidized combustion room 4.

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention is capable of completely burning and removing impurities such as unburned carbon in combustion ash, and is capable of efficiently and reliably obtaining combustion ash, which has a large merit of resource recovery. And a combustion furnace such as a fluidized bed incinerator incorporating the re-combustion furnace.

[0002]

2. Description of the Related Art In recent years, disposal costs have risen due to a shortage of disposal sites for industrial waste, and securing disposal sites has become difficult. In order to solve this problem, a method of incinerating industrial waste to reduce its volume has been widely adopted. Conventionally, combustible industrial waste has been reduced in volume by incineration and finally disposed of. However, recycling of resources has begun to be emphasized, and in recent years, many companies have begun to install equipment for collecting valuables contained in industrial waste.

As a technique for recovering valuable substances in the combustion ash of industrial waste, a valuable substance extracting technique and an impurity removing technique are generally used. The equipment for extracting valuables is a complicated and expensive equipment and can be applied when high value-added recovered materials such as rare metals can be obtained, but when resources are recovered as raw materials for industrial products, impurities contained in combustion ash We have equipment to remove For the technology of removing impurities in combustion ash, magnetic separation equipment for removing metals, centrifugal separation equipment, thermal decomposition equipment for harmful substances (dioxin), electric field separation equipment for unburned carbon, reburning furnace, etc. are industrially used. Has been done. What is especially in demand is a device for removing unburned carbon,
The mainstream method is to install a combustion ash reburning furnace.

[0004]

In the method of installing the reburning furnace for combustion ash as described above, in order to reburn unburned carbon in the combustion ash, the reburning is performed separately from the combustion furnace such as the incinerator. A reburning furnace that maintains the required temperature and residence time had to be installed, and fuel for reburning was also required.
Therefore, the facility cost and the operating cost increase, and there is no merit of resource recovery. Further, as a method for reducing equipment costs and operating costs, a method of recycling combustion ash into an incinerator to maintain a long residence time at high temperature is used. With this method, it is possible to completely burn the unburned carbon in the reburned combustion ash, but since the combustion ash containing unburned carbon that has not been reburned is mixed with the recovered combustion ash, it is possible to completely burn it. It is impossible to recover the burned ash.

The present invention eliminates the disadvantages of the conventional apparatus for completely burning and removing unburned carbon in the combustion ash, reduces the facility cost and the operating cost, and has the advantage of resource recovery. An object of the present invention is to obtain a combustion furnace such as a recombustion furnace and an incinerator equipped with the recombustion furnace, which can efficiently and reliably obtain large combustion ash.

[0006]

In order to achieve the above object, the present invention provides (1) reburning combustion ash of a combustion furnace such as an incinerator which is provided in a combustion chamber of the combustion furnace. A re-combustion furnace for allowing the re-combustion furnace to have an opening in the upper part for discharging exhaust gas after re-combustion, the container having a predetermined height for internally burning the combustion ash; A combustion ash supply device provided in the upper part of the container for supplying the combustion ash into the container, a combustion ash extraction device provided in the lower part of the container for extracting ash after re-combustion, and a lower part of the container in the container. The air supply device is provided above the combustion ash extraction device and supplies combustion air. (2) In a combustion furnace such as an incinerator, a recombustion furnace is provided in the combustion chamber of the combustion furnace, and the recombustion furnace is opened in the upper part of the combustion chamber to form exhaust gas after recombustion. A container having a predetermined height for internally burning the combustion ash of the combustion furnace, and a combustion ash supply device that is provided above the container and that supplies the combustion ash of the combustion furnace into the container. A combustion ash extraction device provided at a lower portion of the container for extracting ash after re-combustion, and an air supply device provided in a lower position in the container above the combustion ash extraction device for supplying combustion air And a re-combustion furnace as a built-in combustion furnace.

[0007]

When the combustion furnace is a fluidized bed incinerator, for example, a recombustion furnace is installed inside the fluidized combustion chamber of the incinerator.
In the fluidized combustion chamber, the fluidized medium such as sand is fluidized by the hot air supplied from the lower air chamber through the air dispersion plate to form a fluidized bed, and the waste to be incinerated is put into the fluidized bed. And burned. The fluidized bed is kept at a high temperature by heating the fluidized medium by the hot air supplied from the air chamber and the heat of combustion of the waste. The combustion exhaust gas after combustion is discharged outside the fluidized combustion chamber along with unburned carbon along with combustion ash and flows into a dust collector such as a bag filter where it is separated into exhaust gas and combustion ash containing unburned carbon.
The combustion ash is supplied to the recombustion furnace installed in the fluidized combustion chamber by the combustion ash supply device of the recombustion furnace. On the other hand, the exhaust gas separated by the dust collector is discharged to the atmosphere, for example.

Combustion ash is supplied to the container constituting the furnace wall of the reburning chamber from above the container by the combustion ash supply device. The combustion ash supplied in the container is filled in the container,
The filled combustion ash forms a moving layer by the combustion ash extraction action of the combustion ash extraction device provided in the lower portion of the container, and descends in the container. Then, the container is heated by effectively absorbing heat from the high temperature atmosphere of the fluidized bed or the combustion exhaust gas heated by the combustion heat of the incineration material in the fluidized combustion chamber to heat the moving bed, and during this descending operation. The combustion ash is supplied with combustion air from the lower part of the container, and the unburned carbon is burned into the completely burned ash. The complete combustion ash is extracted from the lower part of the re-combustion furnace by the combustion ash extraction device and collected.
On the other hand, the combustion gas of unburned carbon burned in the container is discharged into the fluidized combustion chamber through the opening in the upper part of the container.

In the reburning furnace of the present invention and the combustion furnace incorporating the reburning furnace, however, only the completely burned ash is extracted from the lower portion of the reburning furnace, so that the reburning is performed as in the conventional case. As a result, the completely burned combustion ash and the combustion ash containing unburned carbon are not mixed together. Therefore,
It is possible to reliably obtain reusable combustion ash,
It is possible to improve the quality of recycled materials. Further, in obtaining this completely combusted ash, the combustion heat of the fuel such as incineration materials in the combustion furnace can be effectively used as a heat source for recombustion, so fuel for recombustion is not required, and fuel cost is saved. It is possible to reduce the operating cost. Moreover, the heating burner for the reburning furnace, the heat retention / heat retention facility, the waste heat recovery facility, the dust treatment facility, etc. are not required, and the facility cost and facility site can be significantly reduced.

In addition to the above, the reburning furnace of the present invention can be easily incorporated into any existing combustion furnace, and the unburned carbon and other unburned components generated from the existing combustion furnace. It is possible to completely burn (impurities). Further, it is possible to burn unburned components (impurities) such as unburned carbon discharged from other combustion equipment.

In addition to the above, in a combustion furnace incorporating the re-combustion furnace, since the combustion ash completely burned by the combustion furnace is discharged, the amount of ash discharged from the combustion furnace is reduced. In addition, the combustion efficiency of the combustion furnace is improved.

[0012]

The present invention will now be described in detail with reference to the embodiments shown in the drawings. 1 is an enlarged perspective view showing an embodiment in which the reburning furnace according to the present invention is incorporated into a fluidized bed incinerator as a combustion furnace, and FIG. 2 is a combustion furnace incorporating the reburning furnace according to the present invention. It is a figure which shows the whole flow of the waste incinerator provided with the fluidized bed incinerator.

First, a fluidized bed incinerator and a reburning furnace will be described with reference to FIGS. 1 and 2. Fluidized bed incinerator 1
Is provided with an air chamber 2 at a lower portion, and a fluidized combustion chamber 4 for burning an incineration object is formed above the air chamber 2 through an air dispersion plate 3.
Further, a secondary combustion chamber 8 is formed on the upper part of the gas dispersion plate 7 and configured. 5 is a fluidized bed formed by fluidizing a fluid medium such as sand in the fluidized combustion chamber 4 by air supplied from the air chamber 2 through the air dispersion plate 3.
a is a freeboard which is an upper space of the fluidized bed 4, 6 is a waste (material to be incinerated) supply port provided in the fluidized combustion chamber 4, 9
Is a combustion exhaust gas discharge port provided in the secondary combustion chamber 8.

Thus, the fluidized combustion chamber 4 of the fluidized bed incinerator 1
A re-combustion furnace 20 is provided inside the. Reburning furnace 2
Reference numeral 0 denotes a container 21 constituting the furnace body, a combustion ash supply device 24 provided at the upper part thereof, a combustion ash hopper 23 provided in connection with the combustion ash supply device 24, and combustion provided at the bottom of the container 21. It is composed of an ash extraction device 25 and an air supply device 26 provided inside the container 21 above the combustion ash extraction device 25.

The structure of the reburning furnace 20 will be described in more detail.
A vessel 21 forming a furnace wall of the reburning furnace 20 is a vessel having a rectangular cross section and a predetermined height and having a space inside. The vessel 21 has a bottom plate as an air dispersion plate 3 at the lower end of the fluidized combustion chamber 4. It is placed on the upper side, and the side on the narrow side is located substantially in the center of the fluidized combustion chamber 4 and installed in the fluidized combustion chamber 4.

The container 21 is formed with an opening 22 expanding upward at the upper end thereof, and the height thereof is made lower than the height of the fluid combustion chamber 4 by a predetermined length, and the opening 22 is formed. The combustion exhaust gas of the combustion ash that is opened inside and is recombusted in the container 21 is discharged into the fluidized combustion chamber 4. Further, the container 21 has a flat and elongated cross section with a rectangular cross section in which one side is considerably shorter than the other side, so that heat from the outside inside the fluidized combustion chamber 4 can be easily transferred to the internal combustion ash for complete combustion. It is formed to be easy.

Inside the opening 22 of the container 21, a combustion ash supply device 24 consisting of a screw feeder in which a screw 24a is inserted in a casing extending in the longitudinal direction of the container 21 penetrates through the furnace body of the fluidized bed incinerator 1. The combustion ash supply port of the combustion ash supply device 24 is fixed to the furnace body and communicates with a combustion ash hopper 23 installed outside the fluidized bed incinerator 1. A plurality of combustion ash drop openings 24b are provided at the bottom of the casing of the combustion ash supply device 24 at intervals in the longitudinal direction of the container 21. Reference numeral 24c is a screw driving device including an electric motor or the like.

On the other hand, at the bottom of the container 21, a combustion ash extraction device 25 comprising a screw 25a for extracting completely burned ash is extended in the longitudinal direction of the container 21, and the screw 25a is in a fluidized bed incinerator. It penetrates through one furnace body and is inserted into a screw casing fixedly provided to the furnace body outside the furnace body. The screw casing is provided with a complete combustion ash discharge port 25b. The screw 25a is rotationally driven by a driving device 25c including an electric motor or the like.

Then, inside the container 21 above the combustion ash extraction device 25, a pipe extending in the longitudinal direction of the container 21 and penetrating the furnace body of the fluidized bed incinerator 1 and fixed to the furnace body. An air supply device 26 is provided for supplying combustion air. A large number of air ejection ports 26a are formed in the pipe.

Next, with reference to FIG. 2, a waste incinerator to which a fluidized bed incinerator incorporating the above-described reburning furnace is applied will be described. The waste incinerator is sequentially supplied to the fluidized bed incinerator 1, the exhaust gas discharge port 9 of the fluidized bed incinerator 1 and its downstream side to the air chamber 2 of the fluidized bed incinerator 1 and the air supply device 26 of the reburning furnace 20. The bag filter 12, which is a dust collector, which separates and collects the combustion ash containing unburned carbon discharged from the waste heat recovery device 11 and the fluidized bed incinerator 1 for preheating the combustion air Duct 1
0 are connected and provided. The outlet of the combustion ash containing unburned carbon below the bag filter 12 is connected to the combustion ash hopper 23 of the reburning furnace 20 by the combustion ash feed pipe 14.

Next, the reburning furnace 2 constructed as described above.
0 and the operation of the fluidized bed incinerator 1 incorporating the reburning furnace 20 will be described with reference to FIGS. 1 and 2. Waste is introduced into the fluidized combustion chamber 4 of the fluidized bed incinerator 1 from the waste supply port 6 and is introduced into the fluidized bed 5 which is fluidized on the air dispersion plate 3 and burned. The fluidized bed 5 is formed by fluidizing a fluidized medium such as sand by high-temperature air supplied from the air chamber 5 through the gas dispersion plate 3, and the temperature is, for example, 9 by burning waste.
It is heated to 00 ° C and kept at a high temperature. And fluidized bed 5
From the freeboard 4
The gas is discharged to a and flows upward in the free board 4a, reaches the gas dispersion plate 7, passes through this, and flows into the secondary combustion chamber 8. Therefore, the fluidized combustion chamber 4 is kept in a high temperature atmosphere.

The combustion exhaust gas discharged from the fluidized bed 5 is accompanied by combustion ash containing unburned carbon. In the secondary combustion chamber 8, a part of the unburned carbon in this combustion ash is burned. Exhaust gas accompanied by the remaining unburned carbon and combustion ash flows into the exhaust gas discharge port 9 at the upper part of the secondary combustion chamber 8 and is introduced into the exhaust gas duct 10, and reaches the waste heat recovery device 11, where the fluidized bed incinerator is. After being used for preheating the combustion / fluidization air supplied to the first air chamber and the combustion air supplied to the air supply device 26 of the reburning furnace 20, the air is introduced into the bag filter 12.

The bag filter 12 captures and separates the combustion ash containing unburned carbon from the combustion exhaust gas, and the combustion ash is discharged from the lower portion of the bag filter 12 and burned in the reburning furnace 20 by the combustion ash feed pipe 14. Air is conveyed to the ash hopper 23. Combustion ash containing unburned carbon is stored in the combustion ash hopper 23. The exhaust gas after the combustion ash is separated by the bag filter 12 is discharged from the upper part of the bag filter 12.

A drive unit 24 is provided in the container 21 of the reburning furnace 20.
The combustion ash containing unburned carbon stored in the combustion ash hopper 23 is sent to the upper opening 22 by the screw 24a of the combustion ash supply device 24 that is rotationally driven by c, and the intervals are set in the longitudinal direction of the opening 22. From a plurality of combustion ash drop openings 24b provided at the bottom of the casing, which are dropped into the container 21 substantially evenly in the longitudinal direction of the container 21,
The container 21 is filled so that the upper surface thereof has a height as shown by a broken line in FIG. The combustion ash thus filled is lowered downward by the discharging action of the combustion ash extraction device 25 at the bottom of the container 21 to form the moving bed ML.

However, as shown in FIGS. 1 and 2, the container 21 has a temperature of the fluid combustion chamber 4 of about 9 at the lower portion of its outer wall surface.
The moving bed ML is heated to a high temperature by being brought into contact with the high temperature fluidized bed 5 at 00 ° C. and being brought into contact with the high temperature exhaust gas rising in the freeboard 4 a to be exposed to a high temperature atmosphere and heated. The unburned carbon in the combustion ash of the moving bed ML heated to this high temperature is located in the lower part of the container 21 while descending from the upper part to the lower part.
The unburned carbon is burned by the supply of the preheated combustion air ejected from the above, and the combustion ash is made into complete combustion ash.

The completely burned ash is rotated by the drive device 25c of the combustion ash extraction device 25 and is rotated by the screw 25.
It is discharged from the lowermost part of the container 21 by a and is taken out of the furnace through the discharge port 25b of the combustion ash extracting device 25. On the other hand, the combustion gas of unburned carbon burned in the container 21 is discharged into the fluidized combustion chamber 4 through the opening 22 in the upper part of the container 21,
It merges with the exhaust gas discharged from the fluidized bed 5, moves up the freeboard 4a, and is sent to the secondary combustion chamber 8.

In the combustion of the combustion ash inside the container 21, as described above, in this embodiment, the container 21 has a rectangular cross section whose one side is considerably elongated compared to the other side. 4) Heat from the inner moving bed ML
The combustion ash is retained in the container 21 for a shorter period of time because it is easily transmitted to the combustion ash and completely combusted.

Next, a description will be given of a test example conducted by using a waste incinerator having a fluidized bed incinerator incorporating the reburning furnace of this embodiment shown in FIGS. 1 and 2. Waste diatomaceous earth generated in a food company was incinerated in a fluidized bed incinerator 1, and combustion ash containing unburned carbon discharged from the fluidized bed incinerator 1 was supplied to a reburning furnace 20 and burned. The re-combustion furnace 20 uses a container 21 having a width of 300 mm, a length of 1,500 mm and a height of 1,500 mm, and the amount of recycled diatomaceous earth recycled (the amount supplied to the fluidized combustion chamber 4 of the fluidized bed incinerator 1) is set. At 1000 Kg / h, 500 Kg / h was recovered as pure diatomaceous earth that could be completely burned and reused. At this time, waste diatomaceous earth combustion ash (combustion ash discharged from the fluidized bed incinerator 1,
No new fuel was used for complete combustion of diatomaceous earth with unburned carbon). The recovered diatomaceous earth was of a quality that could be used again in the manufacturing process.

Although diatomaceous earth is used as a filter aid when filtering vegetable oils after squeezing edible oil in a food company or the like, the diatomaceous earth contains impurities used as the filter aid. The diatomaceous earth, that is, the waste diatomaceous earth is incinerated to return it to the original diatomaceous earth, and is used again as a filter aid to effectively utilize resources.

As described above, in the fluidized bed incinerator 1 having the re-combustion furnace 20 of this embodiment incorporated therein, impurities such as unburned carbon discharged from the fluidized combustion chamber 4 and the secondary combustion chamber 8 are contained. Burning ash without the need for new fuel,
In addition, the heat can be reburned in the reburning furnace 20 with good heat transfer efficiency. Then, reusable combustion ash having improved quality can be surely obtained without mixing combustion ash completely burned by re-combustion with combustion ash containing unburned carbon. Then, since the ash discharged from the fluidized bed incinerator 1 is completely burned, the amount of ash discharged from the incinerator 1 is small, and the ash treatment becomes easy. Moreover, since complete combustion can be performed, the combustion efficiency as an incinerator can be improved.

Using the fluidized bed incinerator 1 of this embodiment, in addition to the above-mentioned waste diatomaceous earth as waste, for example, defective products of IC substrates discharged in the IC substrate manufacturing process are incinerated,
The epoxy resin contained in the substrate and the epoxy resin component of silica are incinerated to obtain high-purity silica as a product, and the beer lees discharged from a beer factory are incinerated to remove phosphorus (P ) It is also possible to obtain a minute and use this as a component of fertilizer.

The cross-sectional area of the reburning furnace 20 according to the present invention is the amount of air required for complete combustion of the combustion ash and the reburning furnace (container 2
The gas passage speed in 1) is determined to be a predetermined value. The required amount of air can be obtained from the amount of unburned carbon (heat generation amount) in the combustion ash. Further, the gas passage rate is determined to be a value less than the minimum fluidization rate from the particle size distribution of the combustion ash and the true specific gravity. Further, the height of the reburning furnace (container 21) can be obtained from the amount of combustion ash generated, the apparent specific gravity and the required residence time.

The container 21 forming the furnace wall of the reburning furnace 20 is made of a material such as a ceramic plate that easily emits far infrared rays, so that the unburned carbon in the combustion ash in the reburning furnace 20 is completely burned. The effect of promoting can be given.

In the above embodiment, the case where the combustion furnace is the fluidized bed incinerator 1 is shown, but as the combustion furnace, other types of incinerator other than the fluidized bed type, a stoker furnace, a coal-fired fluidized bed boiler, and a heavy oil burning furnace are used. It may be a combustion furnace such as a boiler or a pulverized coal burning boiler. The re-combustion furnace 20 can easily be installed in various newly installed incinerators such as those described above, or in a combustion furnace such as a boiler, but can also be installed in these existing combustion furnaces. In this case, an existing incinerator or the like can be converted into, for example, an incinerator for incinerating waste diatomaceous earth as described above to obtain combustion ash with high added value. In addition, of course, the combustion efficiency of the existing combustion furnace can be improved.

The re-combustion furnace 20 of the present invention has the re-combustion furnace 20 installed in a combustion chamber of a new or existing combustion furnace,
In addition to reburning only the combustion ash discharged from the combustion furnace, the combustion ash containing impurities such as unburned carbon obtained in other equipment is put into the combustion ash hopper 23 of the recombustion furnace 20. It can also be applied to a case where complete combustion is performed in the reburning furnace 20 to obtain complete combustion ash.

[0036]

As is apparent from the above description, according to the present invention, the following effects can be obtained. (1) In the re-combustion furnace of the present invention and the combustion furnace incorporating the re-combustion furnace, only the completely burned ash can be extracted from the lower portion of the re-combustion furnace, so that the complete combustion is achieved by re-combustion as in the conventional case. The combustion ash and the combustion ash containing unburned carbon do not mix with each other, so that reusable combustion ash can be reliably obtained and the quality of the recycled material can be improved. Further, in obtaining this completely combusted ash, the combustion heat of the fuel such as incineration materials in the combustion furnace can be effectively used as a heat source for recombustion, so fuel for recombustion is not required, and fuel cost is saved. It is possible to reduce the operating cost. Then, in the re-combustion furnace, by installing the container in the combustion chamber, high heat in the combustion chamber is efficiently transmitted to the container, and re-combustion can be performed with high combustion efficiency. Further, the heating burner for the reburning furnace, the heat retention / heat retention facility, the waste heat recovery facility, the dust treatment facility, etc. are not required, and the facility cost and facility site can be greatly reduced.

(2) In addition to the effect of (1) above, the reburning furnace of the present invention can be easily incorporated into any existing combustion furnace, and the unburned gas generated from the existing combustion furnace can be easily incorporated. It is possible to completely burn unburned components (impurities) such as carbon. Further, it is possible to burn unburned components (impurities) such as unburned carbon discharged from other combustion equipment.

(3) In the combustion furnace incorporating the re-combustion furnace of the present invention, in addition to the effect of (1) above, since combustion ash completely burned by the combustion furnace is discharged, the combustion ash is discharged from the combustion furnace. The amount of ash generated can be reduced, and the combustion efficiency of the combustion furnace can be improved.

[Brief description of drawings]

FIG. 1 is a cutaway enlarged perspective view showing an embodiment in which a reburning furnace according to the present invention is incorporated into a fluidized bed incinerator as a combustion furnace.

FIG. 2 is a diagram showing an overall flow of a waste incinerator including a fluidized bed incinerator as a combustion furnace incorporating the re-combustion furnace of the present invention.

[Explanation of symbols]

 1 fluidized bed incinerator (combustion furnace) 2 air chamber 4 fluidized combustion chamber 5 fluidized bed 6 waste supply port 8 secondary combustion chamber 11 waste heat recovery device 12 bag filter 14 combustion ash feed pipe 20 reburning furnace 21 container ( Furnace wall) 22 opening 23 combustion ash hopper 24 combustion ash supply device 25 combustion ash extraction device 26 air supply device ML moving bed (combustion ash)

Claims (2)

[Claims] 1. A re-combustion furnace which is disposed in a combustion chamber of a combustion furnace such as an incinerator and re-combusts combustion ash of the combustion furnace, wherein the re-combustion furnace is provided in an upper part of the combustion chamber. A container having an opening for discharging the exhaust gas after re-combustion and having a predetermined height inside which the combustion ash is burned, and a combustion ash supply device which is provided above the container and supplies the combustion ash into the container And a combustion ash extraction device provided at the bottom of the container for extracting ash after re-combustion, and an air supply provided at a position above the combustion ash extraction device in the lower part of the container to supply combustion air. A reburning furnace characterized by being configured with a device. 2. A re-combustion furnace is provided in a combustion chamber of a combustion furnace such as an incinerator, and the re-combustion furnace has an opening in the upper part thereof for discharging exhaust gas after re-combustion. A container of a predetermined height inside which burns the combustion ash of the combustion furnace, a combustion ash supply device which is provided on the upper part of the container to supply the combustion ash of the combustion furnace into the container, and a lower part of the container And a combustion ash extraction device for extracting the ash after re-combustion, and an air supply device provided in a lower position in the container above the combustion ash extraction device to supply combustion air. Combustion furnace with built-in re-combustion furnace.