JP2003302014A - Melting furnace, its operating method and gasification melting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a melting furnace for producing less amount of exhaust of nitrogen oxide during the burning of generated gas including ashes and unburnt carbon, its operating method and a gasification melting system with the melting furnace. <P>SOLUTION: The melting furnace comprises a primary combustion chamber 3 and a secondary combustion chamber 4 provided therein and combustion gas supply means (dampers 12, 13, 14 and combustion air supply lines 15, 16, 17) for supplying combustion air to the furnace. The generated gas G including ashes and unburnt carbon is introduced into the primary combustion chamber and burnt at a high temperature through the primary combustion chamber 3 and the secondary combustion chamber 4 in sequence, and the ashes are melted. A control part 20 controls the combustion gas supply means to control the amount of the combustion air for keeping the primary combustion chamber in a reducing atmosphere of an air ratio being 1.0 or less, and combustion chambers from the secondary combustion chamber 4 on in oxidizing atmospheres of an air ratio being 1.0 or more. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a melting furnace for introducing ash and unburned product gas containing unburned carbon from a gasification furnace or the like, burning the ash at a high temperature, and collecting the ash on a wall surface of the furnace for melting. The present invention relates to an operating method and a gasification melting system.

[0002]

2. Description of the Related Art It is desired to incinerate and reduce the amount of waste such as municipal solid waste, industrial waste, medical waste, shredder dust and old tires, and to effectively utilize the incineration heat. Since the incinerated ash of waste usually contains harmful heavy metals, in order to treat the incinerated ash by landfill, it is necessary to take measures such as solidifying the heavy metal components. Furthermore, downscaling of the entire facility is also required. To cope with these problems, various metals are recovered, ash is melted to generate slag, and this slag can be recovered, and energy such as heat and electric power can be recovered. In recent years, attention has been paid to gasification and melting furnaces that enable material recycling rather than treatment.

In this gasification and melting furnace, waste is gasified in the gasification furnace to generate unburned gas containing unburned carbon (unburned carbon content) and ash and having a temperature of about 500 ° C to 600 ° C.
This produced gas is guided to the melting furnace and secondary air (combustion air) introduced into the melting furnace causes a low air ratio (1.3 to 1.
It is burned to a high temperature at about 5) and ash is collected on the furnace wall to generate a molten slag-forming flow.

FIG. 1 is a diagram showing a structural example of a gasification and melting system equipped with this kind of melting furnace. In FIG. 1, 1 is a fluidized bed gasification furnace, 2 is a melting furnace consisting of a primary combustion chamber 3, a secondary combustion chamber 4 and a tertiary combustion chamber 5, 6 is a waste heat boiler, 7 is an economizer, 8 is a bag filter, 9 is an exhaust gas reheater,
10 is a catalytic reaction tower (denitrification tower), and 11 is a chimney.

In the gasification and melting system having the above structure,
The waste M charged in the fluidized bed gasification furnace 1 is gasified and becomes a generated gas G containing ash and unburned carbon and introduced into the melting furnace 2. In the melting furnace 2, the primary combustion chamber 3 and the secondary combustion chamber 4
Combustion air A ₁ and combustion air A ₂ are introduced into the primary combustion chamber 3 and mixed with the produced gas G introduced into the primary combustion chamber 3,
Burn at a high temperature of 1400 ° C (preferably around 1350 ° C). As a result, the unburned carbon contained in the generated gas G burns, the ash melts, and the combustion air A
After mixing with ₃ and burning, the high temperature combustion exhaust gas EG of about 1350 ° C. is introduced into the waste heat boiler 6. The melting furnace 2
The ash that has been melted in 1. is discharged outside from the melting furnace 2 as molten slag D, comes into contact with the slag cooling water, and becomes granulated slag.

The high temperature combustion exhaust gas EG is cooled by passing through the waste heat boiler 6 and the economizer 7, and the temperature thereof is lowered, and the bag filter 8 removes dust such as molten fly ash contained therein. Further, the exhaust gas reheater 9 is reheated to an appropriate temperature for causing a catalytic reaction, and NOx and SOx in the combustion exhaust gas EG are reacted with ammonia in the catalytic reaction tower 10 to be removed and released into the atmosphere through the chimney 11.

In the gasification and melting system having the above structure,
The melting furnace 2 sets the air atmosphere in the primary combustion chamber 3, the secondary combustion chamber 4, and the tertiary combustion chamber 5 to an oxidizing atmosphere of 1.0 or more, and burns the introduced product gas G containing unburned carbon at a high temperature. Therefore, not only the fuel NOx in which a part of the nitrogen component contained in the waste M is oxidized, but also a part of the nitrogen component in the air is oxidized due to the high temperature combustion and thermal NOx is also generated. NOx) is generated. Therefore NOx
In order to achieve the emission standard of No. 1, there is a problem that a denitration device is required or a denitration device to be installed, that is, the catalytic reaction tower 10 is heavily burdened.

Further, as is well known as the denitration technique, there is a two-stage combustion method in which the furnace is made a reducing atmosphere and then the combustion is completed in an oxidizing atmosphere. For example, in a gasification and melting furnace, a reduction zone is formed in the gasification furnace, and thereafter, combustion is carried out in the melting furnace, so that two-stage combustion is being performed. However, even in this case, since the melting furnace burns at a much higher temperature, there is a problem that the amount of NOx generated increases. Therefore, the denitration capacity of the catalytic reaction tower 10 must be increased. In addition, this problem is not limited to the generated gas generated in the fluidized bed gasification furnace,
The same problem occurs when the generated gas generated in the kiln furnace, the external circulation type fluidized bed gasification furnace, etc. is burned in the melting furnace.

[0009]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above points, and is a melting furnace capable of suppressing the emission of nitrogen oxides when burning a produced gas containing ash and unburned carbon.
An object of the present invention is to provide a gasification and melting system including the operation method and the melting furnace.

[0010]

In order to solve the above problems, the invention according to claim 1 provides a combustion gas supply means for supplying combustion gas to a combustion chamber of a furnace at least in the first and second stages. Introducing a generated gas containing ash and unburned carbon into the combustion chamber, supplying a combustion gas to the first stage and the second stage in sequence, burning the generated gas at a high temperature and melting the ash. The melting furnace is characterized by comprising combustion gas control means for controlling the combustion gas supply means to maintain the first stage in a reducing atmosphere and the second and subsequent stages in an oxidizing atmosphere.

As described above, the first stage is set to a reducing atmosphere,
By providing the combustion gas control means for maintaining the oxidizing atmosphere in the second stage and thereafter, the two-stage combustion in which the produced gas containing unburned carbon is burned in the reducing atmosphere in the first stage and is completely burned in the second stage and thereafter. Therefore, the amount of nitrogen oxides (NOx) generated can be suppressed by the self-denitrification action (detailed later).

According to the second aspect of the present invention, the combustion chamber of the furnace is provided with combustion gas supply means for supplying combustion gas to at least the first and second stages, and the combustion chamber has ash and unburned gas. The generated gas containing carbon is introduced, the combustion gas is sequentially supplied to the first and second stages, and the generated gas is burned at a high temperature.
In the method of operating a melting furnace for melting the ash, the first stage is set to a reducing atmosphere, the second stage is set to an oxidizing atmosphere, and the product gas containing unburned carbon introduced in the first stage is burned in a reducing atmosphere. In addition, it is characterized by complete combustion in the second and subsequent stages.

As described above, the reducing atmosphere is used in the first stage, the oxidizing atmosphere is used in the second stage and thereafter, the generated gas is burned in the reducing atmosphere in the first stage, and the complete combustion is performed in the second stage and thereafter. As a result, the amount of nitrogen oxides discharged from the melting furnace can be suppressed as described above.

The invention according to claim 3 is a gasification furnace for gasifying waste to produce a product gas containing ash and unburned carbon, and at least the first and second stages in the combustion chamber of the furnace,
Combustion gas supply means for supplying the combustion gas is provided, and the generated gas containing ash and unburned carbon is introduced into the combustion chamber, and the combustion gas is sequentially supplied to the first stage and the second stage. In a gasification melting system comprising a melting furnace for burning the ash at a high temperature and melting the ash, the melting furnace controls the combustion gas supply means to make the first stage a reducing atmosphere and the second and subsequent stages an oxidizing atmosphere. And a combustion gas control means for maintaining the above.

As described above, the melting furnace is equipped with the combustion gas control means for controlling the combustion gas supply means to maintain the first stage in the reducing atmosphere and the second and subsequent stages in the oxidizing atmosphere, thereby making the unburned gas unburned. Since the generated gas containing carbon will be burned in two stages, the amount of nitrogen oxides discharged from the melting furnace can be suppressed,
It is possible to realize a gasification and melting system that can reduce the load on the denitration device in the latter stage of the melting furnace. Further, since the denitrification capacity of the denitrification device is small, the scale of the denitrification device can be reduced.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a diagram showing a configuration example of the melting furnace according to the present invention. As illustrated, the melting furnace 2 includes a primary combustion chamber 3, a secondary combustion chamber 4, and a tertiary combustion chamber 5. Combustion air A ₁ is supplied to the primary combustion chamber 3 from a combustion air supply line 15 as a combustion gas through a damper 12.
Combustion air A ₂ from the combustion air supply line 16 to the secondary combustion chamber 4 via the damper 13, and combustion air A ₂ to the tertiary combustion chamber 5 from the combustion air supply line 17 via the damper 14.
₃ can be supplied. Also, each damper 1
The openings 2, 13, and 14 can be controlled by the control unit 20. An O ₂ sensor 18 for detecting the oxygen concentration in the combustion exhaust gas EG discharged from the melting furnace 2 is provided at the exhaust gas outlet of the tertiary combustion chamber 5 or the flue portion of the waste heat boiler 6 (see FIG. 1). The output is transmitted to the control unit 20.

The produced gas G containing ash and unburned carbon from the fluidized bed gasification furnace 1 (see FIG. 1) is introduced from a gas inlet (not shown) of the melting furnace 2 in the tangential direction of the furnace wall surface of the primary combustion chamber 3. At the same time, the combustion air A _{1 is} also introduced tangentially to the furnace wall surface of the primary combustion chamber 3. As a result, the produced gas G containing ash and unburned carbon and the combustion air A ₁ are mixed while forming a swirling flow.
It burns and moves to the secondary combustion chamber 4. In the secondary combustion chamber 4, the combustion air A ₂ is introduced in the tangential direction of the furnace wall surface of the secondary combustion chamber 4 to form a swirling flow, and burns while being mixed with the swirling flow of the combustion gas of the mixed gas. Move to 5. In the tertiary combustion chamber 5, combustion air A ₃ is introduced in the tangential direction of the furnace wall surface of the tertiary combustion chamber 5 to form a swirling flow, and burns while being mixed with the swirling flow of the combustion gas from the secondary combustion chamber 4. It becomes combustion exhaust gas EG and flows into the waste heat boiler 6 (see FIG. 1).

In the melting furnace 2, the combustion air amount AQ ₁ introduced into the primary combustion chamber 3, the combustion air amount AQ ₂ introduced into the secondary combustion chamber 4, the combustion air introduced into the tertiary combustion chamber 5 The quantity AQ ₃ is obtained by setting the air ratio AR ₁ in the primary combustion chamber 3 to a reducing atmosphere of AR ₁ = 0.9 to 1.0 and the air ratio AR ₂ in the secondary combustion chamber 4 to AR ₂ = 1, for example. .. in an oxidizing atmosphere, the air ratio AR ₃ in the tertiary combustion chamber 5 is set to, for example, AR ₃ = 1.
The opening degree of each of the dampers 12, 13, 14 is controlled by the control of the control unit 20 so as to maintain the oxidizing atmosphere of No. 3. As a result, the produced gas G containing unburned carbon introduced into the primary combustion chamber is burned in the reducing atmosphere in the primary combustion chamber 3, and then completely in the oxidizing atmosphere in the secondary combustion chamber 4 and the tertiary combustion chamber 5. So-called two-stage combustion, in which combustion is performed, can also be realized in the melting furnace 2.

FIG. 3 is a block diagram showing the function of the control unit 20. As shown in the figure, the control unit 20 includes a calculator Y and three PID ₁ to PID ₃ calculators. The operation unit Y has O
₂ Oxygen concentration O in combustion exhaust gas EG detected by sensor 18
_{2 (EG)} , exhaust gas flow rate M _(EG) , the amount of air supplied to each of the primary combustion chamber 3, the secondary combustion chamber 4, and the tertiary combustion chamber 5, A _{1 (PV)} , A _{2 (PV)} , A _{3 (PV)} is input. The calculator Y calculates the oxygen concentration O _{2 (EG)} , the exhaust gas flow rate M _(EG), and the amount of air supplied to each combustion chamber A _{1 (PV)} , A _{2 (PV)} , and A _{3 ( PV)} for each combustion. Actual air ratio AR _{1 (PV)} , AR in chambers 3, 4, 5
_{2 (PV)} , AR _{3 (PV)} are calculated, and each PID calculator PID ₁ ,
Output to PID ₂ and PID ₃ .

Each PID operator PID ₁ , PID ₂ , PID
₃ , the set air ratios AR _{1 (SV)} , AR _{2 (SV) of} each combustion chamber,
AR _{3 (SV)} is input to each PID calculator PID ₁ ,
Air ratio AR of each combustion chamber 3, 4, 5 for PID ₂ and PID _{3
1 (PV)} , AR _{2 (PV)} , AR _{3 (PV)} are set air ratio AR _{1 (SV)} ,
Damper operation signal S that makes AR _{2 (SV)} , AR _{3 (SV)
1 (MV)} , S2 _(MV) , S3 _(MV) to each damper 12, 13, 1
4 to operate each of the dampers 12, 13, and 14. As a result, the combustion chambers of the primary combustion chamber 3, the secondary combustion chamber 4, and the tertiary combustion chamber 5 are set to the set air ratios AR _{1 (SV)} , AR
Maintain _{2 (SV)} and AR _{3 (SV)} .

As described above, the product gas G containing unburned carbon
By burning in a reducing atmosphere in the primary combustion chamber 3, a reducing gas such as NH ₃ or carbon monoxide (CO) is generated. This reducing gas is NH in the non-catalytic denitration method.
Performs the same action as the blowing agent such as ₃ and reduces nitrogen oxide NOx (or NO intermediate) to nitrogen (N ₂ ) and oxygen (O ₂ ) by burning in an oxidizing atmosphere in the secondary combustion chamber 4. Disassemble. As described above, the two-stage combustion of the combustion in the reducing atmosphere in the primary combustion chamber 3 and the combustion in the oxidizing atmosphere after the secondary combustion chamber 4 causes the self-denitration reaction to reduce the nitrogen oxides in the combustion exhaust gas EG. Can be made.

In the above example, the generated gas G generated in the fluidized bed gasification furnace 1 is burned in the melting furnace 2. However, the generated gas G is not limited to the generated gas G generated in the fluidized bed gasification furnace 1. Instead of the above, a generated gas generated in a kiln furnace, a shaft furnace, an external circulation type fluidized bed gasification furnace or the like may be used.

Further, the structure of the melting furnace is not limited to a melting furnace having three combustion chambers of primary, secondary, and tertiary, and in the combustion chamber, at least the first stage and the second stage, Combustion air supply means for supplying combustion air is provided, the first stage is maintained in a reducing atmosphere with an air ratio of 1.0 or less, and the second stage and subsequent stages are maintained in an oxidizing atmosphere with an air ratio of 1.0 or greater, and the second stage and subsequent stages are maintained. It suffices if it is a structure that completely burns. In addition, the upper part of the primary combustion chamber is the first stage, the lower part is the second stage, the first stage of the upper part is a reducing atmosphere with an air ratio of 1.0 or less, and the second and lower stages of the lower part are with an air ratio of 1.0 or more. The oxidizing atmosphere may be maintained.

A melting furnace having the structure shown in FIG. 2 is used as the melting furnace 2 of the gasification melting system having the structure shown in FIG. 1, and the air ratio AR of each of the primary combustion chamber 3, the secondary combustion chamber 4 and the tertiary combustion chamber 5 is increased. By burning the generated gas G containing ash and unburned carbon while maintaining ₁ , AR ₂ and AR ₃ as described above, so-called two-stage combustion of the generated gas G can be realized.
Nitrogen oxides (NO in flue gas EG emitted from
x) can be suppressed. As a result, the scale can be reduced without imposing an excessive burden on the catalytic reaction tower 10 and without requiring the catalytic reaction tower 10 to have an excessive denitration capacity.

In the above example, air is used as the combustion gas, but the combustion gas may be oxygen activated air or oxygen. The combustion gas may be preheated and used.

[0026]

As described above, according to the invention described in each claim, the following excellent effects can be expected.

According to the first aspect of the present invention, by providing the combustion gas control means for maintaining the reducing atmosphere in the first stage and the oxidizing atmosphere in the second and subsequent stages, the produced gas containing unburned carbon is provided. Is performed in the reducing atmosphere of the first stage and complete combustion is performed in the second stage and thereafter, so that the amount of nitrogen oxides (NOx) generated can be suppressed by the self-denitration action.

According to the second aspect of the invention, the reducing atmosphere is used in the first stage, the oxidizing atmosphere is used in the second and subsequent stages, and the generated gas is burned in the reducing atmosphere in the first stage and the second stage is used. By completely burning after the eyes, the amount of nitrogen oxides discharged from the melting furnace can be suppressed as in the above.

According to the third aspect of the invention, in the melting furnace, the combustion gas control means for controlling the combustion gas supply means to maintain the reducing atmosphere in the first stage and the oxidizing atmosphere in the second and subsequent stages. By providing the
Since the staged combustion is performed, the amount of nitrogen oxides discharged from the melting furnace can be suppressed, and a gasification and melting system that can reduce the load on the denitration device in the latter stage of the melting furnace can be realized. Further, since the denitrification capacity of the denitrification device is small, the scale of the denitrification device can be reduced.

[Brief description of drawings]

FIG. 1 is a structural example of a gasification and melting system.

FIG. 2 is a diagram showing a configuration example of a melting furnace according to the present invention.

FIG. 3 is a diagram showing a functional block configuration of a control unit of the melting furnace according to the present invention.

[Explanation of symbols]

1 Fluidized Bed Gasification Furnace 2 Melting Furnace 3 Primary Combustion Chamber 4 Secondary Combustion Chamber 5 Tertiary Combustion Chamber 6 Waste Heat Boiler 7 Economizer 8 Bag Filter 9 Exhaust Gas Reheater 10 Catalytic Reaction Tower 11 Chimney 12 Damper 13 Damper 14 Damper 15 Combustion Air supply line 16 Combustion air supply line 17 Combustion air supply line 18 O ₂ sensor 20 Control unit

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F27B 17/00 B09B 3/00 303L (72) Inventor Masaaki Irie 11-1 Haneda Asahi-cho, Ota-ku, Tokyo F term in EBARA CORPORATION (reference) 3K061 AA07 AA11 AA16 AB03 AC01 AC03 AC14 AC19 BA06 DB16 EA03 EB16 3K078 AA06 BA03 CA02 CA12 4D004 AA36 AC04 CA27 CA29 CB04 CB05 CB34 CC02 DA02 DA10

Claims (3)

[Claims] 1. A combustion gas supply means for supplying a combustion gas to at least a first stage and a second stage in a combustion chamber of a furnace, and introducing a produced gas containing ash and unburned carbon into the combustion chamber. However, in the melting furnace that sequentially supplies the combustion gas to the first stage and the second stage, burns the produced gas at a high temperature, and melts the ash, the combustion gas supply unit is controlled to control the first stage. To a reducing atmosphere, and a combustion gas control means for maintaining the second and subsequent stages in an oxidizing atmosphere. 2. A combustion gas supply means for supplying a combustion gas to at least the first and second stages in a combustion chamber of the furnace, and introducing a produced gas containing ash and unburned carbon into the combustion chamber. However, in a method for operating a melting furnace in which a combustion gas is sequentially supplied to the first and second stages, the produced gas is burned at a high temperature, and the ash is melted, the first stage is set to a reducing atmosphere, and The second stage is set to an oxidizing atmosphere, and the produced gas containing the unburned carbon introduced in the first stage is burned in a reducing atmosphere.
A method for operating a melting furnace, which is characterized in that complete combustion is performed after the first stage. 3. A gasification furnace for gasifying waste to produce a product gas containing ash and unburned carbon, and combustion for supplying combustion gas to a combustion chamber of the furnace at least in first and second stages. And a combustion gas is introduced into the combustion chamber, the combustion gas is sequentially supplied to the first and second stages, and the combustion gas is burned at a high temperature.
In a gasification and melting system including a melting furnace for melting the ash, the melting furnace controls the combustion gas supply means to maintain the first stage in a reducing atmosphere and the second and subsequent stages in an oxidizing atmosphere. A gasification / melting system, comprising: