JP2642568B2 - Secondary combustion method of refuse incinerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary combustion method for reburning residual unburned gas in exhaust gas in a refuse incinerator.

[0002]

2. Description of the Related Art In general, combustible waste discharged from households and the like is collected, incinerated in a waste incinerator and disposed of (see, for example, Japanese Patent Application Laid-Open No. 3-28617).

Such an incinerator includes a hopper to which refuse is supplied by a refuse crane, a hopper chute for guiding refuse from the hopper, and a dust supply device having a refuse extruder for transferring refuse from the hopper chute. A drying stoker for drying the refuse supplied by the dust supply device, a combustion stoker for burning refuse from the drying stoker, and a post-combustion stoker for igniting and burning refuse from the combustion stoker.

[0004] A dry stoker, a combustion stoker, and a post-combustion stoker form a combustion chamber. This combustion chamber is provided at the lower part of the furnace body. An exhaust gas cooling chamber is formed in the upper part of the furnace body, and a discharge port for discharging exhaust gas is formed in an upper end of the gas cooling chamber.

[0005] High-temperature primary combustion air is blown into the drying stoker, the combustion stoker, and the post-combustion stoker from their respective lower air inlets. The garbage is transported forward while being agitated and disentangled in the drying stoker, transported from the drying stoker to the combustion stoker, and further subjected to primary combustion while being agitated and disentangled by the combustion stoker, and then transported forward for post-combustion. It is carried to the stalker.

[0006] A blower, which is called a furnace cooling fan and is provided near the furnace outlet, is operated to blow normal-temperature air when the combustion temperature rises, and is led to the exhaust gas cooling chamber above the furnace body. The exhaust gas was cooling.

That is, only when the combustion temperature due to the primary combustion rises, combustion is controlled based on the concept of blowing cooling air as the exhaust gas temperature control at the furnace outlet of the refuse incinerator.

[0008]

As described above, the blower provided near the furnace outlet is called a furnace cooling fan, and is operated so as to blow when the furnace temperature becomes high, so that the furnace temperature is controlled. However, it was not combustion control.

In the conventional secondary combustion of a refuse incinerator, it is preferable that the high temperature exhaust gas and the unburned gas be brought into contact with each other by devising the shape of the furnace body, and that the residence time be longer. However, refueling air has not been actively blown for secondary combustion of exhaust gas.

[0010] Under these circumstances, in recent years, it has been required to achieve complete combustion of refuse due to the problem of dioxins and the like. From the conventional furnace temperature management that only requires a certain range of furnace temperature, a higher degree of complete combustion management has been required. Achieving complete combustion is evaluated based on the CO concentration in the exhaust gas, the remaining amount of carbon in the exhaust gas, and the like.

While the purification of exhaust gas is required as described above, the refuse in the combustion zone on the combustion stoker of the furnace body is burned in complete combustion or in a state close to it, and high-temperature exhaust gas almost completely burned is generated. However, in the drying band on the drying stoker, since refuse not yet sufficiently dried is burned, exhaust gas containing unburned gas of incomplete combustion and relatively low temperature is likely to be generated.

Therefore, in order to achieve complete combustion of the refuse, more stable combustion on the primary combustion side (refuse supply amount, control of the primary combustion air amount) and unburned gas in the high-temperature exhaust gas left behind in the primary combustion are performed. In the secondary combustion section, it is required to mix with secondary combustion air to promote secondary combustion.

However, even if the secondary combustion is to be promoted, in the control for sending the primary combustion air to the secondary combustion section for cooling the furnace, the secondary combustion air is not blown particularly when the furnace temperature is lowered. The supply amount of the secondary combustion air is insufficient with respect to the primary combustion air amount, or the wind speed for mixing cannot be obtained, and it is far from achieving the complete combustion. For example, the CO concentration is usually 10 to 10 at the furnace temperature. The peak value may be 100 times as large.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to reduce the residual rate of unburned gas by reburning unburned gas in exhaust gas generated by primary combustion. It is an object of the present invention to provide a secondary combustion method for a refuse incinerator that can completely burn refuse.

[0015]

According to the present invention, primary combustion air is supplied to a combustion chamber to burn refuse, and exhaust gas is supplied to the combustion chamber.
Followed led to the furnace body, the secondary combustion method incinerator burning residual unburned gas in exhaust gas generated in the combustion chamber, the furnace
In the body, supply 0.4 to 0.6 times the amount of secondary combustion air to the exhaust gas containing residual unburned gas in the vertical plane.
To create a swirling flow of air,
Causing scattered combustion, and furthermore, 0.3 to
0.4 times the amount of tertiary combustion air is supplied to exhaust gas containing residual unburned gas at a wind speed about twice that of the secondary combustion air to produce water.
Mixing by creating a swirling flow in the plane
A shall cause complete combustion of combustible gas.

[0016]

According to the present invention, secondary combustion air is blown into the lower part of the secondary combustion chamber, and the unburned gas generated in the drying zone and the high-temperature combustion gas from the combustion zone are projected vertically in the lower part of the secondary combustion chamber. Mixing by creating a swirling flow within
Thus, the unburned gas is dispersed and burned, and the unburned gas is reburned while suppressing the generation of thermal NOx due to rapid partial combustion.

Next, in the upper part of the secondary combustion chamber, rapid horizontal mixing with the tertiary combustion air is performed, and complete combustion of the unburned gas in the secondary combustion chamber is almost achieved, so that CO can be reduced.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a refuse incinerator according to an embodiment of the present invention.

In FIG. 1, reference numeral 1 indicates a refuse incinerator. The refuse incinerator 1 includes a hopper 2 to which refuse is supplied by a refuse crane (not shown),
A hopper chute 3 for guiding refuse, a dust supply device having a refuse extruder 4 for transferring refuse from the hopper chute 3, a drying stoker 5 for drying refuse supplied by the dust supply device, and a drying stoker 5 A combustion stoker 6 for burning refuse and a post-combustion stoker 7 for igniting and burning refuse from the combustion stoker 6 are provided.

The refuse extruder 4 is provided below the hopper chute 3. Dry stoker 5, Burning stoker 6,
The post-combustion stoker 7 is housed in a furnace body 8,
A discharge port 9 for discharging combustion gas is formed at the upper end of the furnace, and a cooling water supply port 10, a secondary combustion air blower 11, a cooling water supply port 10, A tertiary combustion air blower 12 is provided between the air blowers 11, and an auxiliary burner 13 is provided at a lower end of the furnace body 8.

The interior of the furnace body 8 includes the primary combustion chamber 1 above the drying stoker 5, the combustion stoker 6, and the post-combustion stoker 7.
4 and the secondary combustion chamber 15 near the secondary combustion air blower 11
And a tertiary combustion chamber 16 above the secondary combustion chamber 15 and a gas cooling chamber 17 above the tertiary combustion chamber 16.

The secondary combustion air blower 11 is provided immediately above the primary combustion chamber 14 of the furnace body 8. The secondary combustion air blowing nozzle 11A is provided on the upper side and the lower side of the secondary combustion chamber 15.

The secondary combustion air blown from the secondary combustion air blowing nozzle 11A vertically extends while drawing a substantially S-shape (meandering) from the lower part to the upper part of the secondary combustion chamber 15 of the furnace body 8. It is mixed with the upward flow of exhaust gas.

The tertiary combustion chamber 16 and the gas cooling chamber 17 of the furnace body 8
The cross section in the vicinity is formed in a circular shape, and as shown in FIG. 2, a plurality of tertiary combustion air blowing nozzles 12A to which air is sent from the tertiary combustion air blower 12 are provided on the wall surface of the tertiary combustion chamber 16 of the furnace body 8. They are provided circumferentially at predetermined intervals.

The blowing direction of each of the tertiary combustion air blowing nozzles 12A has a predetermined inclination angle with respect to the wall surface of the furnace body 8 and the same inclination angle with respect to the tangential direction of the furnace body 8, respectively. A vortex of the secondary combustion air is generated in the inside 8.

When the diameter of the tertiary combustion chamber 16 is increased, it is preferable to change the blowing angle of the tertiary air blowing nozzle 12A in order to prevent blow-through at the center and to improve the mixing efficiency.

One end of the air supply pipe 18 is connected to the refuse pit 19, and the other end is branched on the way, and connected to the lower portion 8A of the drying stoker 5 of the furnace body 8, the first branch pipe 18A, The second branch pipe 18B connected to the lower part 8B of the stalker 6 and the third branch pipe 18B connected to the lower part 8C of the post-combustion stoker 7
The branch pipe 18C is constituted.

An air flow adjusting damper 18D, a primary combustion air blower 20, and a primary combustion air temperature adjusting damper 20A are provided in the middle of the air supply pipe 18. In the middle of the first branch pipe 18A, the primary combustion air distribution first damper 21
A, a primary combustion air distribution second damper 21B is provided in the middle of the second branch pipe 18B, and a primary combustion air distribution third damper 21C is provided in the middle of the third branch pipe 18C.

The discharge port 9 of the furnace body 8 has a discharge pipe 22
Is connected, and the air preheater 23 and the electric precipitator 2
4 are interposed in order. Primary combustion of air supply pipe 18
Air preheaters are installed on both sides of the air temperature adjustment damper 20A.
23 are connected.
You. Through the air preheater 23, the exhaust pipe 22Exhaust gas
And the primary combustion air in the heat exchange air pipes 25
The primary combustion air in the air supply pipe 18 becomes hot.
With the discharge pipe 22Exhaust gasIs cooled.

Next, a combustion control method using the refuse incinerator thus configured will be described with reference to FIGS. In the present embodiment, high-temperature primary combustion air is blown into the lower portion 8A of the drying stoker 5, the lower portion 8B of the combustion stoker 6, and the lower portion 8C of the post-combustion stoker 7, respectively. The refuse on the drying stoker 5, the combustion stoker 6, and the post-combustion stoker 7 is stably burned to generate exhaust gas.
Inside the secondary combustion chamber 15.

Usually, the flow rate of the upward flow of the exhaust gas is about 2
３3 m / sec. On the other hand, the amount of the secondary combustion air corresponding to the primary combustion air from the secondary combustion air blower 11 is set to about 6 to 8 times the flow rate of the ascending flow of the exhaust gas so that the secondary combustion chamber 15 In the lower part of the secondary combustion chamber 15, the unburned gas generated in the drying zone and the high-temperature combustion gas from the combustion zone generate a swirling flow in the vertical plane.
Mixing causes the unburned gas to disperse and burn.
Then , the unburned gas is reburned while suppressing the generation of thermal NOx due to rapid partial combustion.

Here, the amount of secondary combustion air to be blown is 1: 0.4 to 0.6, where the amount of primary combustion air is 1.
In addition, as for the secondary combustion air, air of normal temperature is conventionally used for the purpose of cooling the furnace temperature, whereas in the present embodiment, the secondary combustion air is mainly used for the secondary combustion. Because it blows, the secondary combustion air is also set to a high temperature,
Makes secondary combustion more effective.

Further, the exhaust gas generated by the secondary combustion rises together with the exhaust gas generated by the primary combustion,
The tertiary combustion chamber 16 is reached. On the other hand, the tertiary combustion air blower 1
The tertiary combustion air is blown into the tertiary combustion chamber 16 through the plurality of tertiary combustion air blowing nozzles 12A at a blowing speed of about twice the blowing speed of the secondary combustion air.

Here, the amount of tertiary combustion air to be blown is 1: 0.3 to 0.4, assuming that the amount of primary combustion air is one.
In the tertiary combustion chamber 16, the mixing of the tertiary combustion air and the residual unburned gas in the exhaust gas that has not yet been burned by the secondary combustion is promoted.

In this case, the tertiary combustion air is at a normal temperature, which makes the cooling of exhaust gas more effective, and the tertiary combustion air at a normal temperature swirls into the furnace body 8 through the plurality of tertiary combustion air blowing nozzles 12A. As a result, the mixing of the tertiary combustion air and the residual unburned gas in the exhaust gas is effectively promoted.

In this state, tertiary combustion is promoted in the tertiary combustion chamber 16. Then, the exhaust gas generated by the primary combustion, the secondary combustion, and the tertiary combustion is guided to the gas cooling chamber 17, cooled by the cooling water sprayed from the cooling water supply port 10, guided to the discharge port 9, and further discharged. The air is cooled from the discharge pipe 22 through the air preheater 23 and reaches the electric precipitator 24. In addition, the cooling operation of the furnace temperature when the furnace temperature is increased is appropriately controlled by controlling the amount of waste.

According to the above configuration, an amount of secondary combustion air corresponding to the primary combustion air is vertically mixed into the furnace body 8 so as to promote the mixing with the residual unburned gas in the exhaust gas. since it supplied as slowly vertical plane and a residual unburnt gas and hot combustion gases in the exhaust gas generated in the primary combustion
To create a swirling flow of air,
Thermal NO due to diffuse combustion and rapid partial combustion
Unburned gas is reburned while suppressing generation of x.

Therefore, the residual ratio of unburned gas in the exhaust gas can be reduced, and the refuse can be more completely burned.
In particular, even when the furnace temperature decreases, the secondary combustion air is blown in, and the supply amount of the secondary combustion air becomes an amount corresponding to the primary combustion air amount, so that the amount of the secondary combustion air does not run short.
Alternatively, the wind speed of the secondary combustion air for mixing can be obtained, which is close to achieving complete combustion, and for example, the CO concentration can be reduced.

The residual unburned gas in the exhaust gas generated by the primary combustion is secondarily burned, and the temperature of the exhaust gas after the secondary combustion is about 800 ° C. to 900 ° C. By feeding the tertiary combustion air into the inside and remixing, the residual unburned gas in the exhaust gas can be reburned.

Therefore, the residual rate of unburned gas in the exhaust gas can be reduced, and the refuse can be more completely burned.
Moreover, even if the residual unburned gas is almost completely eliminated from the exhaust gas after the secondary combustion, the cooling effect by blowing the tertiary combustion air can be obtained. Therefore, the supply amount of the cooling water to the gas cooling chamber 17 of the furnace body 8 can be reduced, the moisture in the exhaust gas can be reduced, and the amount of white smoke discharged from the refuse incinerator 1 can be reduced.

Further, as a measure against dioxin, for example, even in an existing refuse incinerator, the discharge pipe 22 of the furnace body 8 may be used.
If the exhaust gas temperature at the inlet of the electrostatic precipitator 24 provided in the middle of the equipment is designed to be about 300 ° C.
In order to control the temperature to a target value of 0 ° C. to 280 ° C., it is often necessary to modify the cooling water spray equipment including the capacity of the gas cooling chamber 17 and the cooling water supply port 10.

Even in such an existing incinerator,
By providing the tertiary combustion air supply together with the above-mentioned secondary combustion air supply, the overall cooling capacity of the refuse incinerator is improved, and the exhaust gas temperature can be reduced without modifying the capacity of the gas cooling chamber 17 or the cooling water spray equipment. The cooling target value can be achieved.

As shown in FIG. 5, the gas cooling water may be of a separate type. Next, the refuse incinerator of the present invention will be described with reference to FIG. The capacity of the refuse incinerator is 25
t / 16h x 2 furnace = 50 t / day, type was quasi-continuous combustion type incinerator. The flow is as shown in FIG.

First, FIG. 7 shows a time-dependent change in the CO concentration at the time of startup. The dashed line indicates the CO concentration when activated by the conventional method (hereinafter, referred to as the conventional system) in which the mixing was performed in one stage,
The case where the refuse incinerator of the present invention is used is indicated by a dashed line.

In the conventional system, a peak of the CO concentration exceeding 1000 ppm was generated at the time of startup. As a measure for reducing the CO concentration at startup, the peak of the CO concentration can be reduced to about 700 ppm by using the burner temperature and the tertiary combustion air together.

Further, by using together with an automatic combustion control system using fuzzy control for controlling the amount of waste supplied and controlling the amount of primary combustion air at the time of startup, the peak of the CO concentration at startup can be reduced by 30%.
It can be reduced to 0 ppm.

Next, FIG. 8 shows the measurement results of the time-dependent changes in the CO concentration and the NOx concentration during the steady operation when the conventional system and the dust incinerator of the present invention are used. FIG. 9 shows changes over time when the refuse incinerator of the present invention is used and when the refuse incinerator of the present invention is used together with an automatic combustion control system.

When the refuse incinerator of the present invention is used in comparison with the conventional system, the CO concentration is reduced to about 2/3 and NOx
The concentration was also reduced to about 2/3. From this, it was confirmed that the refuse combustion furnace of the present invention was a system capable of controlling the NOx concentration at a low level while performing mixing for reducing the CO concentration.

Further, when the automatic combustion control system was used together, the NOx concentration was the same level as when the refuse incinerator of the present invention was used alone, but the CO concentration was reduced to about 1/2.

When the conventional system and the refuse incinerator of the present invention were used, and when the automatic combustion control system was used in combination, the measurement results of the amount of organic carbon (TC) (%) in the collected ash were as follows: It was 1.9% with the conventional system, 1.4% with the present invention, and 0.75% with the automatic combustion control system.

This data is obtained when the 16-hour operation is steady.
The sample was sampled four times every hour and the composite material was analyzed. In the conventional system,
1.9%, but when using the refuse combustion furnace of the present invention
It was 1.4%, which was reduced to about 2/3 similarly to the CO concentration. 0.75% when combined with automatic combustion control system
And it was further reduced to about 1/2.

From this, the waste incinerator of the present invention improved the mixing efficiency in the secondary combustion chamber, thermally decomposed most of the unburned components in the exhaust gas, and was able to approach the complete combustion.

Further, by using the automatic combustion control system together, the amount of exhaust gas and the temperature of exhaust gas entering the secondary combustion chamber are always stabilized, and the mixing in the secondary combustion chamber works more effectively, and It was confirmed that it was a very effective combination (total system).

In the state where the exhaust gas temperature at the inlet of the electrostatic precipitator using the automatic combustion system is controlled at 220 ° C., the case where the tertiary combustion air is not used and the case where the operation is performed using the tertiary combustion air are as follows.
The concentration of homologs of dioxins in the exhaust gas at the outlet of the electrostatic precipitator was measured. The result is shown in FIG.

When tertiary combustion air was used, in PCDF, H ₇ CDD _S and O ₇ CDD were slightly increased, but other homologues were reduced, and dioxins were reduced as a whole. Since the cooling process and the cooling conditions of the exhaust gas are made the same, it is considered that dioxins generated up to the outlet of the secondary combustion chamber were reduced by using the tertiary combustion air.

The TEQ when operated without using the tertiary combustion air was 3.3 ng / Nm ³ , and when not used was 2.6 ng / Nm ^3.
Nm ³ and decreased. From the above, it was confirmed that by using the tertiary combustion air, complete combustion was further achieved at the outlet of the secondary combustion chamber, and it was also confirmed that dioxins were effective.

[0057]

As described above, according to the present invention,
First, an amount of secondary combustion air corresponding to the primary combustion air is supplied to the residual unburned gas in the exhaust gas to generate a swirling flow in the vertical plane.
Mixing causes the unburned gas to disperse and burn.
Was Runode, gently burned without causing sudden partial combustion and non燃排gas and hot combustion gases, thermal NOx
The unburned gas can be re-burned while suppressing the generation of the gas.

Next, 0.3 to 0.4 times the primary combustion air
The tertiary combustion air is supplied to the residual unburned gas in the exhaust gas at a wind speed approximately twice the wind speed of the secondary combustion air to produce a swirling flow in the horizontal plane.
Since mixing by causing, can be brought close to the rapid combustion to complete combustion of residual unburned gas in <br/> horizontal plane becomes possible to reduce the CO concentration.

Therefore, dioxin can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a refuse incinerator according to an embodiment of the present invention.

FIG. 2 is a sectional view of the furnace body showing a tertiary combustion air injection nozzle of the furnace body of FIG. 1;

FIG. 3 is a perspective view showing an outline of a refuse incinerator according to an embodiment of the present invention.

FIG. 4 is a system schematic diagram of a refuse incinerator according to an embodiment of the present invention.

FIG. 5 is a perspective view showing a modification of the refuse incinerator according to the embodiment of the present invention.

FIG. 6 is a processing flow based on a refuse incinerator system according to an embodiment of the present invention.

FIG. 7 is a graph showing a change over time in CO concentration at the time of startup based on the refuse incinerator system according to the example of the present invention.

FIG. 8 is a graph showing changes over time in CO and NOx concentrations during steady operation based on the system of the refuse incinerator according to the embodiment of the present invention.

FIG. 9 is a graph showing a normal operation time C when the refuse incinerator system according to the embodiment of the present invention is used together with an automatic combustion control system.
It is a graph which shows O, NOx concentration time-dependent change.

FIG. 10 is a graph showing the I-TEQ homolog concentration when the refuse incinerator system according to the embodiment of the present invention is used in combination with an automatic combustion control system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Garbage incinerator 5 Dry stoker 6 Burning stoker 7 Post-burning stoker 8 Furnace 14 Primary combustion chamber 15 Secondary combustion chamber 16 Tertiary combustion chamber

Continuation of the front page (56) References JP-A-59-9419 (JP, A) JP-A-56-100221 (JP, A) JP-A-50-111981 (JP, U) JP-A-4-108128 (JP , U)

Claims (1)

(57) [Claims] 1. A refuse incinerator that supplies primary combustion air to a combustion chamber to burn refuse, guides exhaust gas to a furnace body following the combustion chamber, and burns residual unburned gas in the exhaust gas generated in the combustion chamber. in the secondary combustion method, vertical plane and fed into exhaust gas containing 0.4 to 0.6 times the amount of secondary combustion air residual unburned gas of the primary combustion air in the furnace body
Mixing by generating a swirling flow in the
Dispersed combustion is caused , and tertiary combustion air in an amount of 0.3 to 0.4 times that of the primary combustion air is left unburned at a wind speed approximately twice that of the secondary combustion air.
Swirl flow in horizontal plane due to supply into exhaust gas containing gas
A secondary combustion method for a refuse incinerator, wherein the unburned gas remaining after mixing is completely burned .