JP2002267133A - Method and apparatus for incinerating waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To more efficiently obtain an effect of a re-burning method by suppressing the amount of a hydrocarbon fuel used which invites in rise a high cost. SOLUTION: A method for incinerating a waste comprises the step of switching a flow rate of a primary combustion air for burning an object 12 to be incinerated in a primary combustion chamber 1 by an air flow regulator 9 controlled by a timer 11. The method further comprises the step of increasing the flow rate of the primary air until a predetermined time elapses after charging. The method also comprises the step of reducing an air introducing amount after a predetermined time has elapsed. The method also comprises the steps of decreasing the air introducing amount as a whole, and reducing a residual oxygen amount. Thus, the amount of dioxins generated or the like can be decreased even when the amount of a city gas used to add from an adding gas nozzle 4 is not increased.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste incineration method and apparatus for performing reburning operation.

[0002]

2. Description of the Related Art Conventionally, wastes such as refuse are incinerated to remove combustible components, and only remaining incombustible components are finally treated by landfilling. Wastes contain substances that may generate harmful substances such as nitrogen oxides (NOx) and dioxins when burned. Therefore, it is necessary to reduce the generation of these harmful substances during incineration. is there.

[0003] Harmful substances such as nitrogen oxides and dioxins generated in the incineration process are contained in the exhaust gas and discharged. As a conventional method for reducing harmful substances in combustion exhaust gas, a reburning method in which a hydrocarbon-based fuel is added into a combustion zone of an incinerator is known. In the reburning method, a hydrocarbon-based fuel such as natural gas is caused to flow into a primary combustion zone or a flue to create a region of a reducing atmosphere to reduce nitrogen oxides, and then to perform a secondary combustion. This is a combustion technique using two combustion zones for completely burning unburned substances such as carbon monoxide (CO) by sending secondary air to a burnout zone which is a zone.
At this time, unburned substances such as dioxins and their precursors can be completely oxidized at the same time, and an air ratio of 1
Dioxins can also be decomposed by reaction with radicals such as OH, H, O, and CH ₃ generated in the following combustion process.

[0004]

In the conventional reburning method, the amount of the hydrocarbon-based fuel to be added differs depending on the oxygen concentration in the primary combustion gas in the combustion zone. It is generally said that a fuel having a calorific value equal to or more than about 5% of the original calorific value per 1% of the residual oxygen concentration is required. The amount of this fuel corresponds to an amount at which the residual oxygen concentration becomes 0% when all the oxygen in the exhaust gas is used for combustion.

In a typical incinerator, 6 to 8%
Contains about oxygen. Therefore, about 30 to 40% of theoretically necessary hydrocarbon fuel is required. For this reason, when trying to blow to obtain an effective reduction area,
This will cause a significant increase in processing costs. Also,
For complete combustion, the oxygen concentration at the furnace outlet is required to some extent, and the combustion air ratio cannot be simply reduced.

[0006] Furthermore, in a batch incinerator, the atmosphere in the furnace differs greatly between the time of charging the object to be treated and the time of normal combustion. Although the oxygen concentration is low due to intense combustion for a while after the introduction, the combustion reaction becomes slow and the oxygen concentration increases as the combustion proceeds. Therefore, the oxygen concentration in the exhaust gas changes significantly. As a result, although the residual oxygen concentration often temporarily drops below 1%,
It may exceed 10% during the incineration process.

As described above, in the reburning method, the required amount of hydrocarbon fuel differs in proportion to the residual oxygen concentration. Therefore, in order to always obtain an effective reduction region, the highest residual oxygen concentration is assumed. Therefore, the amount of the hydrocarbon fuel to be added is determined, which causes a problem that the cost is increased and the waste is increased when the oxygen concentration is low.

[0008] An object of the present invention is to solve such a problem by suppressing the amount of use of a hydrocarbon-based fuel which causes an increase in processing cost, and more efficiently obtaining the effect of the reburning method. Incineration method and apparatus.

[0009]

SUMMARY OF THE INVENTION The present invention is directed to a furnace for incinerating waste such as refuse, wherein a primary combustion zone is provided.
After supplying and burning the secondary air, a hydrocarbon-based fuel is added to form a reducing atmosphere, and in a secondary combustion zone downstream of the reducing atmosphere, secondary air for combustion is supplied. In an incineration method of waste for performing a reburning operation by burning in two combustion zones by completely burning unburned components, the average residual oxygen concentration in the reducing atmosphere is set to 4%.
% Or less, wherein the supply amount of the primary air for combustion supplied in the first stage is controlled in a stepwise manner so as to be less than or equal to a predetermined upper limit value.

According to the present invention, in a reburning operation in which combustion is performed in two combustion zones, when a hydrocarbon-based fuel is added to form a reducing atmosphere, the supply amount of the primary air for combustion is gradually increased. The residual oxygen concentration in the furnace is maintained at a low level of 4% or less on average, and the effect of the reburning method can be efficiently obtained with a small amount of hydrocarbon fuel. In the combustion in the primary combustion zone, a sufficient amount of the primary air for combustion is blown when the incinerated material requiring a large amount of oxygen is injected, so that the combustion for the entire primary combustion zone is performed.
Even if the amount of secondary air blown is adjusted to be small, the generation of unburned substances such as carbon monoxide and dioxins can be suppressed. You can not be invited.

Further, according to the present invention, in a furnace for incinerating waste such as refuse, in a primary combustion zone, after supplying and burning primary air for combustion, hydrocarbon fuel is added. In the secondary combustion zone that forms a reducing atmosphere and is downstream of the reducing atmosphere, secondary air for combustion is supplied to completely burn unburned components, and reburning due to combustion in the two combustion zones. In the waste incineration method for performing the operation, the amount of the hydrocarbon-based fuel added is controlled such that the average residual oxygen concentration in the reducing atmosphere is equal to or less than a predetermined upper limit. It is an incineration method.

According to the present invention, the amount of the hydrocarbon-based fuel can be controlled in accordance with the residual oxygen concentration in the furnace, and the amount of use can be suppressed.

In the present invention, the average residual oxygen concentration is
It is characterized in that it is calculated based on the residual oxygen concentration estimated from the elapsed time after the input of the waste to be incinerated.

According to the present invention, since the residual oxygen concentration is estimated from the elapsed time after the waste to be incinerated is introduced, it is not necessary to measure the oxygen concentration, and low-cost incineration can be performed. Further, even if the oxygen concentration in the combustion gas changes, the change can be ignored and the low oxygen concentration can be maintained.

In the present invention, the average residual oxygen concentration is
It is characterized in that the oxygen concentration in the furnace is measured and calculated.

According to the present invention, since the average residual oxygen concentration is calculated by measuring the residual oxygen concentration, highly accurate control can be performed.

In the present invention, the average residual oxygen concentration is
Of the carbon monoxide, carbon dioxide or nitrogen in the furnace,
Measuring at least one concentration, estimating the oxygen concentration from the measured concentration value based on the correlation between the concentration value and the oxygen concentration determined in advance, and calculating from the estimated value of the oxygen concentration. .

According to the present invention, instead of directly measuring the oxygen concentration, at least one of carbon monoxide, carbon dioxide and nitrogen is measured to control the average residual oxygen concentration to be low. Can be.

In the present invention, the average residual oxygen concentration is
The gas temperature in the furnace is measured, and the oxygen concentration is estimated from the measured gas temperature value based on the correlation between the gas temperature and the oxygen concentration determined in advance, and the oxygen concentration is calculated from the estimated value of the oxygen concentration. Features.

According to the present invention, instead of directly measuring the oxygen concentration, the gas temperature in the furnace can be measured to control the average residual oxygen concentration to be low.

Further, according to the present invention, in a furnace for incinerating waste such as refuse, primary air for combustion is supplied and burned in a primary combustion zone, and then hydrocarbon-based fuel is added. In the secondary combustion zone that forms a reducing atmosphere and is downstream of the reducing atmosphere, secondary air for combustion is supplied to completely burn unburned components, and reburning due to combustion in the two combustion zones. In operation, waste incinerator, in advance,
A correlation setting means for setting a correlation between the elapsed time after the input of the waste to be incinerated and the oxygen concentration in the furnace, a timer for measuring the elapsed time after the input of the waste to be incinerated, and a timer. A concentration estimating means for estimating oxygen by referring to the correlation set in the correlation setting means based on the measured elapsed time; and an average in the reducing atmosphere based on the oxygen concentration estimated by the concentration estimating means. In order to keep the residual oxygen concentration at 4% or less and below a predetermined upper limit,
Control means for controlling the supply amount of the primary air for combustion to be supplied to the first stage combustion by decreasing the supply amount in a stepwise manner.

According to the present invention, the waste incineration apparatus includes a correlation setting unit, a timer, a concentration estimating unit, and a control unit, and performs a reburning operation. The correlation setting means includes:
The correlation between the elapsed time after the introduction of the waste to be incinerated and the oxygen concentration in the furnace is set in advance, and the control unit controls the concentration estimation unit based on the oxygen concentration estimated from the elapsed time measured by the timer. The primary air for combustion is controlled so that the average residual oxygen concentration becomes low. Since the residual oxygen concentration is estimated from the elapsed time after the input of the waste to be incinerated, it is not necessary to measure the oxygen concentration, and low-cost incineration can be performed. Further, even if the oxygen concentration in the combustion gas changes, the change can be ignored and the low oxygen concentration can be maintained.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a schematic configuration of a waste incinerator that performs a reburning operation in a batch system as an embodiment of the present invention. The incinerator of this embodiment is
It has a primary combustion chamber 1 and a secondary combustion chamber 2, and the primary combustion chamber 1 and the secondary combustion chamber 2 are connected by a flue 3. In the primary combustion chamber 1, waste such as refuse is charged as a substance to be burned to form a primary combustion zone. The exhaust gas in the primary combustion zone is completely burned in the secondary combustion chamber 2 to form a secondary combustion zone. A hydrocarbon-based fuel such as city gas containing natural gas as a main component is added to the latter stage of the primary combustion zone or the flue 3 from an additional gas nozzle 4. By adding a hydrocarbon-based fuel, a reducing atmosphere is formed and nitrogen oxides can be reduced.

In order to assist combustion in the primary combustion chamber 1 and the secondary combustion chamber 2, a primary combustion burner 5 and a secondary combustion burner 6 which operate as auxiliary combustion burners are provided, respectively. The air for combustion is sent from the blower 7 and supplied into the primary combustion chamber 1 through the primary air supply pipe 8 as primary air for combustion. In the present embodiment, the flow rate of the primary air for combustion is adjusted by the air flow rate regulator 9. The secondary air supply pipe 10 supplies secondary air for combustion from the blower 7 to the secondary combustion chamber 2. The air flow controller 9 controls the combustion
Adjust the flow rate of the secondary air. The timer 11 is used until a certain time elapses from the time when the incineration object 12 is charged.
The flow rate of the primary air for combustion is increased and thereafter decreased.

FIG. 2 shows the relationship between the flow rate control in this embodiment and the change in oxygen concentration when control is not performed. In a batch incinerator, it has been found that there is a close relationship between the combustion state in the furnace and the charging of the incineration target 12. In FIG. 2, a broken line indicates a change in the change in the oxygen concentration, and a solid line indicates a change in the supply amount of the primary air for combustion. If the operation is performed in a state where the supply amount of the primary air for combustion is constant, as is usually performed, as shown by a broken line, gasification and combustion are performed rapidly immediately after introduction, so that oxygen is rapidly supplied. The concentration decreases. Thereafter, as time elapses, the combustion becomes slower, so that the oxygen concentration increases. In the present embodiment, the fluctuation of the oxygen concentration is suppressed, the average residual oxygen concentration is suppressed to 4% or less, and dioxin is reduced.

The amount of the incineration object 12 to be charged at one time and the charging interval can be calculated from the incineration capacity of the incinerator. For example, if an incinerator 12 having an incinerator having an incineration capacity of 30 kg / h is to be charged every 30 minutes, the amount to be charged once is 15 kg. Every minute. In any case, the processing amount per time is constant, and the tendency of the oxygen concentration fluctuation as shown in FIG. 2 is the same even if the time interval and the upper and lower limits of the oxygen concentration are different. Therefore, in the present embodiment, the charging amount and charging interval of the incineration object 12 can be determined according to the actual operation of the incinerator.

There are several methods for calculating the incineration capacity. Expressing using the combustion chamber load, one of which, is expressed by the following equation (1). The combustion chamber load is about 1,046,500 kJ / m ³ h (25
00,000 kcal / m ³ h). Incineration capacity and 1
If you maintain the time interval required from the input amount,
The same concept can be applied to different incineration objects 12.

[0028]

(Equation 1)

Hereinafter, results of an operation experiment using the incinerator of the embodiment of FIG. 1 will be described. [Experiment 1] An incineration target 12 containing 10 g of PVDC (food packaging material) per 1 kg of newsprint was prepared, and placed in an incinerator having an incineration capacity of 20 (kg / h) every 7.5 minutes.
It was charged at a rate of 5 kg and burned. At this time, the primary air for combustion and the secondary air for combustion are sent into each combustion chamber from an air supply blower 7. The primary air for combustion has an air ratio λ ₁ = 1.1 with respect to the incineration object 12, and the secondary air for combustion has an air ratio λ ₂ = with respect to the incineration object 12.
Driving at 1.0. In addition, both the primary combustion burner 5 and the secondary combustion burner 6 were operated by supplying city gas of 4 m ³ / h so as to burn at an air ratio of 1.15. However, the reburning operation in which the city gas is added from the additional gas nozzle 4 is not performed.

The exhaust gas was sampled at the flue 3 and at the outlet of the secondary combustion chamber 2 to measure the CO concentration and the O ₂ concentration, and at the same time the temperature of the combustion chamber. At the outlet of the secondary combustion chamber 2, the analysis of the concentration of dioxins was also performed. The results obtained are shown in Table 1 below. The concentration of dioxins is
Toxic equivalent (TEQ) based on dibenzodioxin tetrachloride (TCDD), taking into account the toxicity of other isomers.
It is shown in terms of mass ng (nanogram) per m ³ .

[0031]

[Table 1]

[Experiment 2] Next, an experiment under the same conditions as in Experiment 1 was carried out by blowing a city gas into the furnace from an additional gas nozzle 4 for adding a city gas on the downstream side of the primary combustion chamber 1. The burning operation was performed. Reburning is performed based on the prior art. The added amount of city gas was 3 m ³ / h, which corresponds to about 30% of the total input of the primary combustion chamber. The results of Experiment 2 are shown in Table 2 below.

[0033]

[Table 2]

[Experiment 3] Next, an experiment was performed under the same conditions as in Experiment 2 by applying the present invention and changing the flow rate of the primary air for combustion as shown in FIG. The primary air for combustion is operated at an air ratio λ _1a = 1.2 when the incineration object 12 is charged, and then controlled to increase or decrease the air ratio λ _1b = 0.6 four minutes after the charging. went. The result obtained in Experiment 3 is
The results are shown in Table 3 below.

[0035]

[Table 3]

It can be said that the average oxygen concentration in the primary combustion chamber was reduced from 5.7% to 3.6% by controlling the flow rate of the primary air for combustion. Dioxins also decreased from 11.4 ng to 7.8 ng. It can be seen that the average oxygen concentration should be 4% or less in order to keep dioxins below 10 ng in accordance with environmental standards.

From Tables 2 and 3, it can be seen that when performing the reburning operation, the average oxygen concentration in the secondary combustion chamber corresponds to the average carbon monoxide concentration. It has been found that it corresponds not only to carbon monoxide but also to concentrations of carbon dioxide and nitrogen. Therefore, the average remaining oxygen concentration, carbon monoxide in the furnace (CO), carbon dioxide (C ₂ O)
Alternatively, at least one concentration of nitrogen (N ₂ ) is measured, and the oxygen concentration is estimated from the measured concentration value based on the correlation between the concentration value and the oxygen concentration determined in advance, and the oxygen concentration is estimated. It can also be calculated from the value. Furthermore, the gas temperature in the furnace is measured, the oxygen concentration is estimated from the measured gas temperature value based on the correlation between the gas temperature and the oxygen concentration determined in advance, and the average residual oxygen is estimated from the estimated oxygen concentration value. The concentration can also be calculated.

FIG. 3 shows another embodiment of the present invention.
Components corresponding to those in the embodiment shown in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted. In the present embodiment, the oxygen concentration in the gas is measured in the flue 3 using the oximeter 13. In order to reduce the average residual oxygen concentration as much as possible,
The fuel flow rate adjuster 14 adjusts the flow rate of the city gas added from the addition gas nozzle 4. The flow rate of city gas is
According to the oxygen concentration detected by the oxygen concentration meter 13, the flow rate of the city gas is adjusted to increase when the oxygen concentration is high, and to decrease when the oxygen concentration is low, so that the usage amount of the city gas can be reduced as a whole.

The results of an operation test using the incinerator of the embodiment shown in FIG. 3 are shown below. [Experiment 4] Under the same conditions as in Experiment 3 described above, instead of adjusting the flow rate of the primary air for combustion in Experiment 3, the flow rate of city gas added from the addition gas nozzle 4 was adjusted. The city gas flow rate was controlled by monitoring the residual oxygen concentration in the flue 3 with the oximeter 13 and controlling the instantaneous value of the residual oxygen concentration in the flue 3 to 0.5% or less. However, the supply amount of the instantaneous city gas, was not to exceed the 3m ³ / h at the most. The primary air for combustion and the secondary air for combustion are air ratios with respect to the incineration object 12, respectively, λ ₁ = 1.
The operation was performed so that 1 and λ ₂ = 1.0. The experimental results are shown in Table 4 below.

[0040]

[Table 4]

The amounts of city gas used in Experiments 1, 2, 3, and 4 are shown in Table 5 below. The amount of city gas used does not change between Experiment 2 and Experiment 3. In Experiment 4, it can be seen that the usage of city gas is reduced.

[0042]

[Table 5]

In the embodiment of FIG. 1, it is also possible to adjust the flow rate of the primary air for combustion by measuring the oxygen concentration as shown in FIG. Further, in the embodiment of FIG. 3, as in the embodiment of FIG. 1, the oxygen concentration is estimated with the passage of time, and the flow rate of the city gas is switched after a lapse of a certain time after the incineration object 12 is charged. You can also. Since the residual oxygen concentration is estimated from the elapsed time after the input of the waste to be incinerated, it is not necessary to measure the oxygen concentration, and low-cost incineration can be performed. Further, even if the oxygen concentration in the combustion gas changes, the change can be ignored and the low oxygen concentration can be maintained. Furthermore, the flow rate of the added city gas can be controlled by estimating the oxygen concentration from the concentration values of carbon monoxide, carbon dioxide, nitrogen, and the like, and estimating the oxygen concentration from the temperature.

In the present invention, the embodiments of FIGS. 1 and 3 can be combined. That is, to keep the average residual oxygen concentration in the reducing atmosphere at 4% or less,
In the reburning operation in which combustion is performed in two combustion zones, when a hydrocarbon-based fuel is added to form a reducing atmosphere, the supply amount of the primary air for combustion is controlled by gradually decreasing the supply amount. The residual oxygen concentration is maintained at a low level of 4% or less on average, and the effect of the reburning method can be efficiently obtained with a small amount of hydrocarbon fuel. In the combustion in the primary combustion zone, a sufficient amount of the primary air for combustion is blown at the time of incineration which requires a large amount of oxygen, so that the primary air for combustion as the whole primary combustion zone is blown. Even if the injection amount is adjusted to be small, generation of unburned substances such as carbon monoxide and dioxins can be suppressed, and even if the apparent air ratio is kept low, the incineration capacity does not decrease. Can be

Further, from Table 3, although the average O ₂ concentration is less than 4%, it is sufficiently possible to suppress the average value of the residual oxygen concentration in the furnace to 2% or less in a large incinerator. is there.

[0046]

As described above, according to the present invention, the residual oxygen concentration in the furnace is maintained at a low level of 4% or less on average in a reburning operation in which two stages of combustion are performed in two combustion zones.
The effect can be obtained efficiently with a small amount of hydrocarbon fuel. In the combustion in the primary combustion zone, a sufficient amount of primary air for combustion is blown when incinerated materials that require a large amount of oxygen are injected, and the generation of unburned substances such as carbon monoxide and dioxins is suppressed. Can be. The amount of the primary air for combustion as the whole primary combustion zone is adjusted so as to be small,
Even if the apparent air ratio is kept low, it is possible to prevent the incineration capacity from being lowered.

Further, according to the present invention, the amount of the hydrocarbon-based fuel to be added can be controlled so as to lower the oxygen concentration, thereby reducing the amount of use.

Further, according to the present invention, it is not necessary to measure the oxygen concentration by estimating the residual oxygen concentration from the elapsed time after the introduction of the waste, so that low-cost incineration can be performed.

Further, according to the present invention, since the average residual oxygen concentration is calculated by measuring the residual oxygen concentration, highly accurate control can be performed.

Further, according to the present invention, the concentration of another gas such as carbon monoxide can be measured in the furnace to control the average residual oxygen concentration to be low.

Further, according to the present invention, it is possible to control the gas temperature in the furnace so as to reduce the average residual oxygen concentration.

Further, according to the present invention, in order to perform a reburning operation by burning in two combustion zones in a furnace for incinerating waste such as refuse, a hydrocarbon-based fuel is added to reduce the reducing atmosphere. Form. In the correlation setting means, a correlation between the elapsed time after the introduction of the waste to be incinerated and the oxygen concentration in the furnace is set in advance, and the control means estimates the concentration estimation means from the elapsed time measured by the timer. On the basis of the oxygen concentration, combustion 1
The secondary air is controlled by gradually decreasing it. Since the residual oxygen concentration is estimated from the elapsed time after the input of the waste to be incinerated, it is not necessary to measure the oxygen concentration, and low-cost incineration can be performed. Further, even if the oxygen concentration in the combustion gas changes, the change can be ignored and the low oxygen concentration can be maintained.

[Brief description of the drawings]

FIG. 1 is a simplified front cross-sectional view showing a schematic configuration of a waste incinerator according to an embodiment of the present invention.

FIG. 2 is a time chart showing a state of adjusting a flow rate of primary air for combustion in the incinerator of FIG. 1;

FIG. 3 is a simplified front sectional view showing a schematic configuration of a waste incinerator according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Primary combustion chamber 2 Secondary combustion chamber 3 Flue 4 Additive gas nozzle 7 Blower 9 Air flow regulator 11 Timer 12 Incineration target 13 Oxygen concentration meter 14 Fuel flow regulator

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) F23G 5/44 ZAB F23G 5/44 ZABF F term (reference) 3K062 AA18 AB01 AC01 AC19 BA02 BB04 CB06 CB08 DA01 DA22 DA23 DA24 DA25 DB06 DB13 3K065 AA18 AA24 AB01 AC01 AC19 BA04 BA09 GA03 GA12 GA22 GA32 HA01 3K078 AA04 AA08 AA09 BA03 BA24 CA02 CA12

Claims (7)

[Claims] 1. In a furnace for incinerating waste such as garbage, the first
In the secondary combustion zone, after supplying and burning the primary air for combustion, a hydrocarbon-based fuel is added to form a reducing atmosphere, and in the secondary combustion zone downstream of the reducing atmosphere,
Supplying secondary air for combustion to completely burn unburned components,
A waste incineration method for performing reburning operation by combustion in two combustion zones, wherein a first step is performed so that an average residual oxygen concentration in the reducing atmosphere is 4% or less and a predetermined upper limit or less. A waste incineration method, characterized in that the supply amount of the primary air for combustion supplied in the step (1) is reduced and controlled stepwise. 2. In a furnace for incinerating waste such as refuse, the first
In the secondary combustion zone, after supplying and burning the primary air for combustion, a hydrocarbon-based fuel is added to form a reducing atmosphere, and in the secondary combustion zone downstream of the reducing atmosphere,
Supplying secondary air for combustion to completely burn unburned components,
In a waste incineration method for performing a reburning operation by burning in two combustion zones, the amount of the hydrocarbon-based fuel added is controlled so that the average residual oxygen concentration in the reducing atmosphere is equal to or less than a predetermined upper limit. A waste incineration method characterized by controlling. 3. The incineration of waste according to claim 1, wherein the average residual oxygen concentration is calculated based on a residual oxygen concentration estimated from an elapsed time after charging the waste to be incinerated. Method. 4. The waste incineration method according to claim 1, wherein the average residual oxygen concentration is calculated by measuring an oxygen concentration in the furnace. 5. The average residual oxygen concentration is obtained by measuring at least one concentration of carbon monoxide, carbon dioxide, or nitrogen in the furnace and obtaining a correlation between a concentration value obtained in advance and the oxygen concentration. The waste incineration method according to claim 1 or 2, wherein the oxygen concentration is estimated from the measured concentration value based on the measured oxygen concentration, and the oxygen concentration is calculated from the estimated oxygen concentration value. 6. The average residual oxygen concentration is obtained by measuring the gas temperature in the furnace and estimating the oxygen concentration from the measured gas temperature value based on a correlation between the gas temperature and the oxygen concentration determined in advance. The method for incinerating waste according to claim 1 or 2, wherein the method is calculated from an estimated value of the oxygen concentration. 7. In a furnace for incinerating waste such as refuse, the first
In the secondary combustion zone, after supplying and burning the primary air for combustion, a hydrocarbon-based fuel is added to form a reducing atmosphere, and in the secondary combustion zone downstream of the reducing atmosphere,
Supplying secondary air for combustion to completely burn unburned components,
In a waste incineration system that performs reburning operation by combustion in two combustion zones, a correlation is set in advance to set the correlation between the elapsed time after the input of the waste to be incinerated and the oxygen concentration in the furnace. Setting means, a timer for measuring the elapsed time after the input of waste to be incinerated, and a concentration for estimating oxygen by referring to the correlation set in the correlation setting means based on the elapsed time measured by the timer. Based on the estimation means and the oxygen concentration estimated by the concentration estimation means,
The supply amount of the primary combustion air supplied to the first-stage combustion is controlled by gradually decreasing the average residual oxygen concentration in the reducing atmosphere to 4% or less and to a predetermined upper limit or less. A waste incineration apparatus comprising a control means.