JP3825351B2 - Combustion control device and combustion control method for pyrolysis gasification melting furnace - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a combustion control device and a combustion control method for a pyrolysis gasification melting furnace in which waste such as municipal waste is pyrolyzed and gasified, and the gasified gas is combusted at a high temperature to melt ash. .
[0002]
[Prior art]
A conventional pyrolysis gasification melting furnace includes a pyrolysis furnace that thermally decomposes and gasifies waste, an ash melting furnace that is provided on the downstream side of the pyrolysis furnace, and melts ash; A secondary combustion chamber that is provided on the downstream side and combusts exhaust gas discharged from the ash melting furnace, and is taken out from the ash melting furnace as slag in order to reduce its resources, reduce its volume, and make it harmless. At the same time, exhaust gas is discharged from the secondary combustion chamber and guided to the ash gas treatment facility, and waste heat of the exhaust gas is recovered to generate steam for power generation.
[0003]
By the way, in such a pyrolysis gasification melting furnace, since it has a plurality of combustion chambers consisting of a pyrolysis furnace, an ash melting furnace and a secondary combustion chamber, the balance of the combustion air amount in each combustion chamber deteriorates. , NOx may be generated in large quantities, or the ash melting furnace auxiliary fuel required in a small-scale plant may be increased.
[0004]
[Problems to be solved by the invention]
However, in the conventional pyrolysis gasification melting furnace, since it is necessary to balance the amount of combustion air in a plurality of combustion chambers, it can be obtained only from the result of calculating the process balance from the mass balance and heat balance, It was difficult to grasp and perform the optimum operation. Therefore, there has been a problem in that it has an adverse effect on the environment due to a large amount of NOx generation, resulting in an increase in cost due to an increase in the amount of auxiliary fuel used.
[0005]
The present invention has been made in view of such a situation, and its purpose is to control the reduction combustion in the ash melting furnace by direct operation of the air ratio and the combustion rate, thereby reducing NOx and the amount of auxiliary fuel used. It is an object of the present invention to provide a combustion control apparatus and a combustion control method for a pyrolysis gasification melting furnace capable of maintaining a good environment and reducing costs by minimizing the above.
[0006]
[Means for Solving the Problems]
In order to solve the above-described problems of the prior art, the present invention provides a pyrolysis furnace that thermally decomposes and gasifies waste, an ash melting furnace provided on the downstream side of the pyrolysis furnace, and the ash melting furnace the ash in the combustion control apparatus for the pyrolysis gasification melting furnace and a secondary combustion chamber for burning exhaust gas discharged, the pyrolysis furnace, and the ash melting furnace and the secondary combustion chamber of the air-gas ratio from An arithmetic device for calculating the combustion rate of the melting furnace is provided, and the air ratio of the ash melting furnace and the secondary combustion chamber is controlled based on the calculation result of the arithmetic device.
Further, in the present invention, the arithmetic device is connected to a sand layer temperature detection device, a freeboard temperature detection device and a primary air flow rate detection device of the pyrolysis furnace, and a temperature detection device and a combustion air flow rate detection device of the ash melting furnace. And a secondary combustion chamber temperature detection device and a secondary combustion air flow rate detection device.
[0007]
On the other hand, another invention of the present invention combusts a pyrolysis furnace that thermally decomposes and gasifies waste, an ash melting furnace provided downstream of the pyrolysis furnace, and exhaust gas discharged from the ash melting furnace. In a combustion control method for a pyrolysis gasification melting furnace comprising a secondary combustion chamber and a combustion control device provided in association with the ash melting furnace and the secondary combustion chamber, the combustion control device is provided along with the combustion control device. by the air ratio and the combustion rate calculating unit, said thermal cracking furnace, comprising the steps of calculating the air-gas ratio and the combustion rate of the ash melting furnace of the ash melting furnace and the secondary combustion chamber, said secondary combustion chamber outlet Determining the level of NOx concentration, the level of combustion rate of the ash melting furnace, and the air ratio of the pyrolysis furnace and the ash melting furnace, respectively, and the ash melting furnace according to the respective determination results The air ratio in the secondary combustion chamber is controlled by the combustion control device. And a stage.
[0008]
In the present invention, when the NOx concentration at the outlet of the secondary combustion chamber is low, the combustion rate of the ash melting furnace is low, and the air ratio between the pyrolysis furnace and the ash melting furnace is small, the ash melting While increasing the air ratio of the furnace, the air ratio of the secondary combustion chamber is decreased, the NOx concentration at the outlet of the secondary combustion chamber is low, the combustion rate of the ash melting furnace is low, and the thermal decomposition When the air ratio of the furnace and the ash melting furnace is large or when the NOx concentration at the outlet of the secondary combustion chamber is low and the combustion rate of the ash melting furnace is high, the air ratio of the ash melting furnace and the secondary combustion When the air ratio of the chamber is held together, the NOx concentration at the outlet of the secondary combustion chamber is high, the combustion rate of the ash melting furnace is low, and the air ratio of the pyrolysis furnace and the ash melting furnace is small Is the air ratio of the ash melting furnace and the secondary The air ratio of the firing chamber is maintained together, the NOx concentration at the outlet of the secondary combustion chamber is high, the combustion rate of the ash melting furnace is low, and the air ratio of the pyrolysis furnace and the ash melting furnace is large. Or when the NOx concentration at the outlet of the secondary combustion chamber is high and the combustion rate of the ash melting furnace is high, the air ratio of the ash melting furnace is reduced and the air ratio of the secondary combustion chamber is increased. It is preferable.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a combustion control apparatus and a combustion control method for a pyrolysis gasification melting furnace according to the present invention will be described in detail based on the illustrated embodiments. Here, FIG. 1 is a control flow diagram of the combustion control apparatus of the pyrolysis gasification melting furnace according to the embodiment of the present invention, and FIG. 2 is a diagram of each part by the arithmetic unit (process simulator) provided in the combustion control apparatus of the present embodiment. FIG. 3 is a control block chart of a combustion control method for a pyrolysis gasification melting furnace according to an embodiment of the present invention.
[0010]
As shown in FIG. 1, the pyrolysis gasification melting furnace 1 of this embodiment is provided with a pyrolysis furnace 3 that thermally decomposes and gasifies waste 2 such as waste, and a downstream side of the pyrolysis furnace 3. The ash melting furnace 4 and a secondary combustion chamber 6 for burning the exhaust gas 5 discharged from the ash melting furnace 4 are provided. The ash melting furnace 4 and the secondary combustion chamber 6 are provided with a combustion control device 7. Controlled ash melting furnace combustion air 8 and secondary combustion chamber combustion air 9 are supplied.
[0011]
A waste supply device 10 for supplying a predetermined amount of waste 2 into the furnace is provided on the side surface of the pyrolysis furnace 3. For this reason, the supply device 10 is rotated by a hopper 11 that inputs the waste 2, a screw 13 that is rotated and driven by the motor 12, and an input port (not shown) of the waste 2 to the pyrolysis furnace 3. ) Has a chute 14 for guiding to). Further, in the furnace of the pyrolysis furnace 3, a sand layer temperature detecting device 15 for detecting the temperature of the sand layer and a free board temperature detecting device 16 for detecting the temperature of the free board are provided. It communicates with the ash melting furnace 4 via a line 17. Further, a pyrolysis furnace primary air 18 which is sent from an air supply source (not shown) and used for pyrolyzing the waste 2 is supplied to the bottom of the pyrolysis furnace 3. A primary air flow rate detection device 19 for detecting the flow rate of the primary air 18 is provided between the bottom of the furnace and the air supply source.
[0012]
The ash melting furnace 4 melts ash by high-temperature combustion of a mixture of pyrolysis gas, undecomposed residue, char, ash, and the like fed from the supply line 17, from an outlet 20 at the bottom of the furnace. The taken-out molten slag 21 is discharged through a slag cooling tank (not shown). Further, an ash melting furnace temperature detecting device 22 for detecting the internal temperature is provided in the furnace of the ash melting furnace 4, and a combustion air flow rate detecting device for detecting the flow rate of the ash melting furnace combustion air 8 outside the furnace. 23 is provided.
[0013]
The secondary combustion chamber 6 is provided to burn the exhaust gas 5 again, and is provided in communication with an upper position on the downstream side of the ash melting furnace 4. In addition, a secondary combustion chamber temperature detecting device 24 for detecting the internal temperature is provided at the upper portion of the secondary combustion chamber 6. Further, a secondary combustion chamber air flow rate detection device 25 for detecting the flow rate of the secondary combustion chamber combustion air 9 is provided outside the upper and lower intermediate positions of the secondary combustion chamber 6, and the exhaust gas 5 is provided downstream at the top outlet. An exhaust gas duct 26 leading to an exhaust gas treatment facility (not shown) on the side is connected, and in the middle of the exhaust gas duct 26, a concentration detection device 27 that detects the O ₂ concentration and the NOx concentration at the outlet of the secondary combustion chamber 6. Is provided. Moreover, the concentration detection device 27 is electrically connected to the combustion control device 7.
[0014]
On the other hand, the combustion control device 7 of the pyrolysis gasification melting furnace 1 according to this embodiment includes a pyrolysis furnace sand layer temperature, a pyrolysis furnace freeboard temperature, an ash melting furnace temperature, a secondary combustion chamber temperature, and a secondary combustion chamber. outlet O ₂ concentration, the pyrolysis furnace primary air flow rate, calculate the process balance than ash melting furnace combustion air flow rate and the secondary combustion chamber air flow rate, pyrolysis furnace 3, air in the ash melting furnace 4 and the secondary combustion chamber 6 A calculation device (process simulator) 28 for calculating the ratio and the combustion rate of the ash melting furnace 4 is provided. The combustion control device 7 is based on the calculation result of the calculation device 28 and the ash melting furnace 4 and the secondary combustion chamber 6. The air ratio is controlled.
For this reason, the arithmetic unit 28 is electrically connected to the sand layer temperature detection device 15, the freeboard temperature detection device 16 and the primary air flow rate detection device 19 of the pyrolysis furnace 3 as shown by the dotted line in FIG. 4 is electrically connected to the temperature detection device 22 and the combustion air flow rate detection device 23, and is also electrically connected to the temperature detection device 24 and the secondary combustion chamber air flow rate detection device 25 of the secondary combustion chamber 6. Yes. Moreover, the calculation device 28 is electrically connected to the combustion control device 7 as indicated by the arrow in FIG.
[0015]
A specific example of the calculation method of the combustion air ratio and the combustion rate of each part by the arithmetic unit 28 will be described below with reference to FIG. Here, the mass flow rate is represented by G, the volume flow rate by V, the temperature by T, and the specific heat by Cp.
(1) Calculation of combustion air ratio (1) Total combustion air ratio λ = 21 / (21−O ₂ )
Here, 21 represents the proportion of O _{2 in} the air.
(2) Pyrolysis furnace air ratio λ ₁ = V ₁₁ / (V ₁₁ + V ₃₁ + V ₄₁ ) · λ
(3) Pyrolysis furnace to ash melting furnace air ratio λ ₁₂ = (V ₁₁ + V ₃₁ ) / (V ₁₁ + V ₃₁ + V ₄₁ ) · λ
[0016]
(2) Calculation of the burning rate of each part
[1] Pyrolysis furnace sand layer Material balance: GR + G11 = G12
Heat balance: GRCpRTR + G11Cp11 + η1 · LHVR / GR = G12Cp12T12 + Q1
η1: Pyrolysis furnace sand layer burning rate LHVR: Waste lower heating value Q1: Pyrolysis furnace sand layer heat release Burning rate: η 1 = (G 12 Cp 12 T 12 + Q 1 -G 11 C p11 T 11 ) / (LHV R · G R ) = G 11 / G 0 · η l1
ηl1: Combustion rate for the combustion air in the pyrolysis furnace sand layer (oxygen consumption rate)
[2] Pyrolysis furnace free board Material balance: G21 = G22
Heat balance: G21Cp21T21 + η2, LHVR, GR = G22Cp22T22 + Q2
η2: Pyrolysis furnace free board burning rate Q2: Pyrolysis furnace free board heat dissipation Burning rate: η2 = (G22Cp22T22 + Q2−G21Cp21T21) / (LHVR · GR) = (G21 + (1-ηl1) G11) / G0 · ηl2
ηl2: Combustion rate (combustion rate of oxygen) in the pyrolysis furnace freeboard
[3] Ash melting furnace Material balance: G22 + G31 = G32
Heat balance: G22Cp22T22 + G31Cp31T31 + η3 ・ LHVR ・ GR = G32
Cp32T32 + Q3
η3: Ash melting furnace combustion rate Q3: Ash melting furnace heat dissipation combustion rate: η3 = (G32Cp32T32 + Q3− (G22Cp22T22 + G31Cp31T31
)) / (LHVR · GR) = ((1-ηl2) (G21 + (1-
ηl1) G11) + G31) / G0 · ηl3
ηl3: Combustion rate for ash melting furnace combustion air (oxygen consumption rate)
[4] Secondary combustion chamber Material balance: G32 + G41 = G42
Heat balance: G32Cp32T32 + G41Cp41T41 + η4 ・ LHVR ・ GR = G42Cp42
T42 + Q4
η4: secondary combustion chamber combustion rate Q4: secondary combustion chamber heat dissipation combustion rate: η4 = (G42Cp42T42 + Q4− (G32Cp32T32 + G41Cp41T41)) / (LHVR · GR) = (1−η1−η2−η3)
[0017]
In the pyrolysis gasification melting furnace 1 according to the embodiment of the present invention, as shown in FIG. 1, when waste 2 such as waste is supplied to the pyrolysis furnace 3 by the supply device 10, the waste 2 is Partial combustion is performed in the furnace to which the primary air 18 is fed, and dry pyrolysis is performed with the heat. Then, a mixture of pyrolysis gas, undecomposed residue, char, ash and the like generated in the pyrolysis furnace 3 is introduced into the ash melting furnace 4 through a supply line 17 from an unillustrated inlet, and combustion air 8 is supplied. The ash is heated and melted in a high temperature furnace. Further, when the exhaust gas 5 discharged from the ash melting furnace 4 flows into the upper secondary combustion chamber 6, it is burned again in the chamber supplied with the combustion air 9, and passes through the exhaust gas duct 26 to downstream exhaust gas treatment equipment (see FIG. (Not shown).
[0018]
Next, a combustion control method for the pyrolysis gasification melting furnace 1 according to the embodiment of the present invention will be described.
In the pyrolysis gasification melting furnace 1 of the present embodiment, the reduction combustion of the ash melting furnace 4 is controlled by the combustion control method using the combustion control device 7 and the arithmetic device 28. That is, the combustion control method of the present embodiment uses the temperature, O ₂ concentration, and numerical value of the air flow rate obtained from the detection device provided in each part, and the calculation method of the combustion air ratio and combustion rate of each part described above. a step of then, the process balance calculated by the air ratio and combustion rate calculating unit 28, a pyrolysis furnace 3 calculates the air-gas ratio and combustion rate of ash melting furnace 4 ash melting furnace 4 and the secondary combustion chamber 6, Stages of determining the level of NOx concentration at the outlet of the secondary combustion chamber 6, the level of combustion rate of the ash melting furnace 4, and the magnitude of the air ratio between the pyrolysis furnace 3 and the ash melting furnace 4, respectively, Accordingly, a step of controlling the air ratio of the ash melting furnace 4 and the secondary combustion chamber 6 by the combustion control device 7 is included.
[0019]
In the combustion control method including such a stage, as shown in FIG. 3, first, the arithmetic unit 28 calculates the air ratios of the pyrolysis furnace 3, the ash melting furnace 4, and the secondary combustion chamber 6, The combustion rate of the ash melting furnace 4 is calculated. Next, the NOx concentration at the outlet of the secondary combustion chamber 6 is detected by the concentration detection device 27, the NOx concentration is low, the combustion rate of the ash melting furnace 4 is low from the calculation results, and the pyrolysis furnace 3 and ash melting furnace 4 When the air ratio is small, the air ratio of the ash melting furnace 4 is increased and the air ratio of the secondary combustion chamber 6 is decreased. Further, the NOx concentration at the outlet of the secondary combustion chamber 6 detected by the concentration detector 27 is low, the combustion rate of the ash melting furnace 4 is low from the calculation result, and the air ratio of the pyrolysis furnace 3 and ash melting furnace 4 is large. If the NOx concentration at the outlet of the secondary combustion chamber 6 detected by the case or the concentration detector 27 is low and the combustion rate of the ash melting furnace 4 is high from the calculation result, the air ratio of the ash melting furnace 4 and the secondary combustion chamber 6 The air ratio of both is maintained.
[0020]
On the other hand, the NOx concentration at the outlet of the secondary combustion chamber 6 detected by the concentration detector 27 is high, the combustion rate of the ash melting furnace 4 is low from the calculation results, and the air ratio between the pyrolysis furnace 3 and the ash melting furnace 4 is small. In this case, both the air ratio of the ash melting furnace 4 and the air ratio of the secondary combustion chamber 6 are maintained. Further, the NOx concentration at the outlet of the secondary combustion chamber 6 detected by the concentration detector 27 is high, the combustion rate of the ash melting furnace 4 is low from the calculation results, and the air ratio between the pyrolysis furnace 3 and the ash melting furnace 4 is large. In the case where the NOx concentration at the outlet of the secondary combustion chamber 6 detected by the case or the concentration detector 27 is high and the combustion rate of the ash melting furnace 4 is high from the calculation result, the air ratio of the ash melting furnace 4 is reduced and The air ratio of the next combustion chamber 6 is increased.
[0021]
Combustion control apparatus 7 of the pyrolysis gasification melting furnace 1 according to the embodiments of the invention, the pyrolysis furnace 3, the air-gas ratio and combustion rate of ash melting furnace 4 ash melting furnace 4 and the secondary combustion chamber 6 operation And the air ratio of the ash melting furnace 4 and the secondary combustion chamber 6 is controlled based on the calculation result of the calculation device 28, so that the ash melting furnace 4 and the secondary combustion chamber are controlled. The air ratio of 6 and the combustion rate of the ash melting furnace 4 can be directly manipulated. As a result, the reduction combustion in the ash melting furnace 4 can be controlled, and the NOx concentration of the exhaust gas 5 can be reduced. Moreover, if the combustion control device 7 of this embodiment is applied, the combustion efficiency in the ash melting furnace 4 can be increased, the amount of auxiliary fuel used for the ash melting furnace 4 can be reduced, and the cost can be reduced. Can do.
[0022]
While the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications and changes can be made based on the technical idea of the present invention.
[0023]
【The invention's effect】
As described above, the combustion control apparatus for a pyrolysis gasification melting furnace according to the present invention includes a pyrolysis furnace for pyrolyzing waste to gasify, an ash melting furnace provided on the downstream side of the pyrolysis furnace, be those with a secondary combustion chamber for burning exhaust gas discharged from the ash melting furnace, said thermal cracking furnace, the ash melting furnace and the secondary combustion chamber air-gas ratio and the ash melting furnace An arithmetic device for calculating the combustion rate is provided, and the air ratio of the ash melting furnace and the secondary combustion chamber is controlled based on the calculation result of the arithmetic device. The reduction combustion in the ash melting furnace can be controlled by direct manipulation of the air ratio, reducing NOx and minimizing the amount of auxiliary fuel used, maintaining a good environment, and producing Cost can be reduced.
[0024]
A combustion control method for a pyrolysis gasification melting furnace according to the present invention includes a pyrolysis furnace for pyrolyzing waste to gasify, an ash melting furnace provided on the downstream side of the pyrolysis furnace, and the ash melting furnace And a combustion control device provided in association with the ash melting furnace and the secondary combustion chamber, and provided in association with the combustion control device. the obtained air ratio and combustion rate calculating unit, said thermal cracking furnace, comprising the steps of calculating the air-gas ratio and the combustion rate of the ash melting furnace of the ash melting furnace and the secondary combustion chamber, said secondary combustion chamber A step of determining the level of NOx concentration at the outlet, the level of combustion rate of the ash melting furnace, and the air ratio of the pyrolysis furnace and the ash melting furnace, and the ash melting furnace according to the respective determination results And the combustion control device controls the air ratio of the secondary combustion chamber. Because it contains a step, on the same effect as the invention can be obtained, while balancing the combustion air quantity of each part, the pyrolysis gasification melting furnace can be operated operated at optimum conditions.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing a control flow of a combustion control apparatus for a pyrolysis gasification melting furnace according to an embodiment of the present invention.
FIG. 2 is a conceptual diagram illustrating a method for calculating a combustion air ratio and a combustion rate of each part by an arithmetic unit provided in the combustion control apparatus according to the embodiment of the present invention.
FIG. 3 is a control block chart showing a combustion control method for a pyrolysis gasification melting furnace according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Pyrolysis gasification melting furnace 2 Waste 3 Pyrolysis furnace 4 Ash melting furnace 5 Exhaust gas 6 Secondary combustion chamber 7 Combustion control device 8 Ash melting furnace combustion air 9 Secondary combustion chamber combustion air 10 Waste supply device 15 Sand layer temperature Detection device 16 Free board temperature detection device 17 Supply line 18 Pyrolysis furnace primary air 19 Primary air flow rate detection device 22 Ash melting furnace temperature detection device 23 Combustion air flow rate detection device 24 Secondary combustion chamber temperature detection device 25 Secondary combustion chamber air Flow rate detection device 26 Exhaust gas duct 27 O ₂ concentration and NOx concentration detection device 28 Air ratio and combustion rate calculation device

Claims (4)

A pyrolysis furnace that thermally decomposes and gasifies waste, an ash melting furnace provided downstream of the pyrolysis furnace, and a secondary combustion chamber that burns exhaust gas discharged from the ash melting furnace In the pyrolysis gasification melting furnace combustion control device,
Said thermal cracking furnace, an arithmetic unit is provided for calculating the air-gas ratio and the combustion rate of the ash melting furnace of the ash melting furnace and the secondary combustion chamber, the ash melting furnace and on the basis of the calculation result of the arithmetic unit A combustion control apparatus for a pyrolysis gasification melting furnace, characterized in that the air ratio in the secondary combustion chamber is controlled. The arithmetic unit is connected to a sand layer temperature detection device, a freeboard temperature detection device and a primary air flow rate detection device of the pyrolysis furnace, and is connected to a temperature detection device and a combustion air flow rate detection device of the ash melting furnace. The combustion control device for a pyrolysis gasification melting furnace according to claim 1, wherein the combustion control device is connected to a temperature detection device and a secondary combustion air flow rate detection device for the secondary combustion chamber. A pyrolysis furnace for pyrolyzing waste to gasify, an ash melting furnace provided on the downstream side of the pyrolysis furnace, a secondary combustion chamber for combusting exhaust gas discharged from the ash melting furnace, and the ash In a combustion control method for a pyrolysis gasification melting furnace comprising a combustion control device provided in association with a melting furnace and a secondary combustion chamber,
By the air ratio is provided in association with the combustion control device and combustion rate calculating unit, said thermal cracking furnace, to calculate the air-gas ratio and the combustion rate of the ash melting furnace of the ash melting furnace and the secondary combustion chamber Determining the level of NOx concentration at the outlet of the secondary combustion chamber, the level of combustion rate of the ash melting furnace, and the magnitude of the air ratio between the pyrolysis furnace and the ash melting furnace, And controlling the air ratio of the ash melting furnace and the secondary combustion chamber by the combustion control device in accordance with the determination result. When the NOx concentration at the outlet of the secondary combustion chamber is low, the combustion rate of the ash melting furnace is low, and the air ratio between the pyrolysis furnace and the ash melting furnace is small, the air ratio of the ash melting furnace is increased. In addition, the air ratio of the secondary combustion chamber is reduced, the NOx concentration at the outlet of the secondary combustion chamber is low, the combustion rate of the ash melting furnace is low, and the pyrolysis furnace and the ash melting furnace If the NOx concentration at the outlet of the secondary combustion chamber is low and the combustion rate of the ash melting furnace is high, both the air ratio of the ash melting furnace and the air ratio of the secondary combustion chamber are On the other hand, if the NOx concentration at the outlet of the secondary combustion chamber is high, the combustion rate of the ash melting furnace is low, and the air ratio between the pyrolysis furnace and the ash melting furnace is small, the ash melting furnace The air ratio of the secondary combustion chamber and the air ratio of the secondary combustion chamber are both maintained. And when the NOx concentration at the outlet of the secondary combustion chamber is high, the combustion rate of the ash melting furnace is low, and the air ratio of the pyrolysis furnace and the ash melting furnace is large, or in the secondary combustion chamber 4. When the NOx concentration at the outlet is high and the combustion rate of the ash melting furnace is high, the air ratio of the ash melting furnace is decreased and the air ratio of the secondary combustion chamber is increased. A combustion control method for a pyrolysis gasification melting furnace as described in 1. above.

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