JPH11294742A - Combustion controller for incinerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrict NOx in an exhaust gas instantaneously increasing associated with increase in the amount of primary combustion air and CO and a harmful organic chlorine compound generated by incomplete combustion associated with a decrease in the amount of primary combustion air while keeping the combustion state of matters to be combusted stable. SOLUTION: When the amount of steam to be detected from a steam flow meter 14 falls below the amount of steam as detected under the stable condition of combustion, a natural gas adjusting meter 16 and a primary combustion air adjusting meter 17 are controlled by a controller 18 to simultaneously increase the supply quantity regulated by both the meters. When the amount of steam increases exceeding the amount of steam to be detected under the stable condition of combustion, the natural gas adjusting meter 16 and the primary combustion air adjusting meter 17 are controlled by the controller 18 to simultaneously decrease the supply quantity regulated by both the meters.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control apparatus for an incinerator for incinerating an object to be burned such as waste (garbage). The present invention relates to a combustion control device for an incinerator in which a hydrocarbon-based fuel is supplied to remove nitrogen oxides, carbon monoxide, and the like in the combustion products of the burnable material.

[0002]

2. Description of the Related Art In recent years, the amount of refuse to be treated has been increasing in cities and the like, and most of these refuse are incinerated at refuse incineration plants. When incinerating waste at this waste incineration plant, nitrogen oxides (N
O _X), air pollutants such as dioxins is discharged,
These air pollutants have a considerable impact on urban environments.

[0003] Conventionally, in order to suppress the emission of such air pollutants, for example, as disclosed in Japanese Patent Publication No. 7-62524, hydrocarbon fuels such as natural gas (hereinafter referred to as "natural gas"). A method of reburning incineration exhaust gas using a natural gas reburning method (reburning method) has been proposed. According to this natural gas reburning method, natural gas is blown above a primary combustion zone in which an object to be burned is primarily burned by primary combustion air to form a reducing atmosphere (reburning zone), thereby removing NO _X and removing natural gas. The remaining hydrocarbons after the reduction by the gas, the hydrocarbons generated in the combustion chamber, and carbon monoxide (CO) are completely burned by the secondary combustion air. According to this natural gas reburning method, compared with the case where natural gas is not used, NO
_X and CO emissions at the same time are up to 60% and 50% respectively.
It has been demonstrated that the reduction was achieved at a% reduction rate.

[0004] Here, removal mechanism of the NO _X are as follows. That is, it is considered that the following reaction is progressing in the reburning zone. C _n H _m + O ₂ → C _n 'H _m ' + CO + H ₂ O NO + C _n 'H _m ' → C _n "H _m " + N ₂ + CO + H ₂ O or NO + C _n 'H _m ' → C _n "H _m " + NH _i + CO + H ₂ O (However, 'indicates a radical at the beginning of a chemical reaction, and NH _i indicates a nitrogen compound.)

As can be seen from this reaction equation, hydrocarbon radicals (C _n ') generated by the reaction between hydrocarbons (C _n H _m ) and residual oxygen (O ₂ ) in the primary combustion air.
_Hm ') reacts with the nitrogen oxides (NO) to reduce the NO and consequently remove it.

When the above-described natural gas reburning method is used, the amount of natural gas supplied into the combustion chamber may be excessive or insufficient depending on the type of the object to be burned. in Japanese, the concentration of the NO _X discharged concentration of CO generated in the reburning zone and its reburning zone respectively detected, the supply of natural gas and the primary combustion air, as these concentration becomes a predetermined value There has been proposed a combustion control device for an incinerator in which the temperature is controlled. According to the combustion control device, it is possible to always reduce the emissions of stable combustion is possible and becomes incomplete combustion of indicators CO and air pollutants are (an indicator of dioxins) NO _X .

Further, as a more realistic combustion control method, when the amount of heat and the amount of supply of the burnable material are within a certain control range and the amount of evaporation from the boiler attached to the incinerator is reduced. There is a combustion control method in which the primary combustion air is increased by increasing the amount of primary combustion air, assuming that the decrease in the amount of evaporation is based on poor combustion of the material to be burned. That is, if the evaporation amount decreases, the primary combustion air amount is increased, and if the evaporation amount is restored, the primary combustion air amount is decreased. Further, the primary combustion air amount is reduced when the evaporation amount is increased, and the primary combustion air amount is increased when the evaporation amount is restored. This method is an accurate and inexpensive combustion control device that senses a change in the amount of evaporation in a sensitive manner and recovers the combustion state of the material to be burned.

[0008]

However, in the combustion control method for controlling the primary combustion air amount by detecting the evaporation amount of the boiler as described above, the instantaneous combustion state when the primary combustion air amount is increased is improved. However, since the amount of oxygen in the primary combustion gas sharply increases, the NO in the primary combustion gas
_X increases. For this reason, the reducing atmosphere (reburning zone) cannot be maintained even with the amount of the natural gas supplied above the primary combustion zone, and NO _X is carried over to the secondary combustion zone, and N 2 in the combustion exhaust gas is reduced.
O _X amount there is a problem that increases. On the other hand, when the amount of evaporation increases and the amount of primary combustion air decreases,
Since the amount of oxygen in the primary combustion gas sharply decreases, incomplete combustion occurs and CO is generated, and harmful organic chlorine compounds increase.

[0009] Such a NO increase and the trend of incomplete combustion of _X include, but are not permanently be temporary,
It is not preferable due to environmental demands for strict control of harmful gases.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and while maintaining the combustion state of an object to be burned in a stable manner, the exhaust gas that increases instantaneously with an increase in the amount of primary combustion air. it is an object to provide of the NO _X and CO generated by incomplete combustion due to the decrease in the primary combustion air amount, the combustion control apparatus for an incinerator capable of suppressing harmful organochlorine compounds.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, a combustion control apparatus for an incinerator according to the present invention is provided with a carbonization device above a primary combustion zone for mainly burning an object to be burned with primary combustion air. A hydrogen-based fuel is supplied to form a reducing atmosphere, and secondary combustion air is supplied above the reducing atmosphere to completely burn unburned or incompletely burned substances reduced by the hydrocarbon-based fuel. (A) a steam amount detecting means for detecting an amount of steam generated from the heat recovery device, and (b) a steam amount detected by the steam amount detecting means. The fuel cell system further comprises a supply amount control means for controlling the supply amount of the hydrocarbon-based fuel and the supply amount of the primary combustion air such that the amount maintains a predetermined value.

In the present invention, the material to be burned is primarily burned in the primary combustion zone by the primary combustion air, and a hydrocarbon-based fuel is supplied above the primary combustion zone to form a reducing atmosphere. NO _X generated by the primary combustion of the combustibles in the reducing atmosphere is reduced by hydrocarbon fuel, unburned matters or incomplete combustion products after the reduction is supplied secondary combustion air above the reducing atmosphere As a result, the fuel is completely burned and discharged through the heat recovery device. The amount of steam generated from the heat recovery device is detected by steam amount detecting means, and when the detected steam amount falls below a predetermined value, the supply amount control means controls the supply amount of the hydrocarbon fuel and the primary combustion air. Is controlled to increase.

[0013] Such a decrease in the amount of steam is considered to be due to poor combustion of the material to be burned. Therefore, the primary combustion air is increased to improve the combustion state. Since the amount of hydrocarbon-based fuel is increased, the amount of evaporation is quickly restored, and a reducing atmosphere can be formed above the primary combustion zone without excessively increasing the primary combustion air.

On the other hand, in the present invention, when the steam amount detected by the steam amount detecting means is larger than a predetermined value, the supply amounts of the hydrocarbon-based fuel and the primary combustion air are reduced by the supply amount controlling means. Is controlled as follows.

Since such an increase in the amount of evaporation is considered to be due to excessive combustion of the material to be burned, the primary combustion air is reduced to lower the combustion state. Since there is a possibility that CO may be generated due to incomplete combustion due to the decrease in the primary combustion air supply amount, the hydrocarbon-based fuel is also reduced and complete combustion is possible, and a suitable reducing property is provided above the primary combustion zone. An atmosphere can be formed.

[0016] In this way, the N
O _X increases and CO or harmful organochlorine compounds generated due to incomplete combustion due to a reduction in the primary combustion air amount is reduced by a reducing atmosphere, these hazardous pollutants to be completely burned by the secondary combustion It is possible to suppress discharge to the outside of the incinerator.

In the present invention, the supply amount control means includes:
It is preferable to control the hydrocarbon-based fuel to increase before the primary combustion air or decrease at the same time as the primary combustion air.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a specific embodiment of a combustion control apparatus for an incinerator according to the present invention will be described with reference to the drawings.

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

In the refuse incinerator 1 of the present embodiment, a hopper 3 into which refuse 2 as a substance to be burned is charged, and a stoker 4 for burning the refuse 2 from the hopper 3.
A combustion chamber 6 provided above the stoker 4 and defined by a furnace wall 5, a primary combustion air supply device 7 for supplying primary combustion air into the combustion chamber 6 through the stoker 4,
An ash outlet 8 for taking out incinerated ash after combustion is provided. Above the combustion chamber 6, a boiler 9 is provided as a heat recovery device of the incinerator 1.

The stoker 4 is composed of a drying stoker 4a, a burning stoker 4b and a post-burning stoker 4c which are communicated with the hopper 3 in this order.
Air conduits 7a, 7b, 7c of the primary combustion air supply device 7 are provided corresponding to b, 4c, respectively. In addition,
The primary combustion air is supplied to these air conduits 7a, 7b, 7c from a forced air blower 7d.

The combustion chamber 6 is provided with a drying stoker 4a.
And post-combustion stoker 4 above and combustion stoker 4b
c, and a reburning zone 6c above the primary combustion zones 6a, 6b;
The secondary combustion zone 6 above the reburning zone 6c
d. The reburning zone 6
A supply port 5a is provided in the furnace wall 5 below c, and a natural gas supply pipe 10 and a steam supply pipe 11 are connected to the supply port 5a via a mixer 12. A supply port 5b is provided in the furnace wall 5 below the secondary combustion zone 6d, and a secondary combustion air supply pipe 13 is connected to the supply port 5b. Mixing water vapor with the natural gas supplied through the natural gas supply pipe 10 in this manner causes sufficient disturbance in the combustion chamber 6 to increase the mixing with the natural gas, and the N
This is for promoting the _Ox reduction reaction.

Further, the boiler 9 is provided with a steam flow meter 14 for detecting the amount of water vapor generated from the boiler 9, and the natural gas supply pipe 10 controls a natural gas supply amount for controlling the natural gas supply amount. The primary combustion air supply device 7 is provided with a primary combustion air regulator 17 for adjusting the primary combustion air supply amount. further,
A control device 18 for controlling the natural gas controller 16 and the primary combustion air controller 17 based on a signal from the steam flow meter 14 is provided. The natural gas supply pipe 10 includes:
A natural gas flow meter 16a and a natural gas valve 16b are provided, and the natural gas controller 16 receives the signal from the control device 18 so that the measured value of the natural gas flow meter 16a becomes the natural gas amount to be set. Gas valve 16b
Operate. Similarly, a primary combustion air flow meter 17a is provided upstream of the forced blower 7d, and a primary combustion air damper 17b is provided downstream of the forced blower 7d. The primary combustion air controller 17 receives the signal from the control device 18 and controls the primary combustion air damper 17b so that the value measured by the primary combustion air flow meter 17a becomes the set primary combustion air amount.
Operate.

In the thus configured refuse incinerator 1, refuse 2 introduced from the hopper 3 first passes over the drying stoker 4a. The refuse 2 on the drying stoker 4a is dried by the high-temperature combustion gas generated by the combustion in the post-combustion stoker 4b and the post-combustion stoker 4c, and then a part of the refuse starts burning. However, since the primary combustion air supplied to the drying stoker 4a is suppressed to a small amount in order to minimize the amount of the oxidizing substance in the primary combustion air, the dust 2 on the drying stoker 4a is reduced.
The gas generated from water is water vapor by evaporation of water, hydrocarbon gas generated by dry distillation, CO generated by incomplete combustion, and the like.

Next, after passing through the drying stoker 4a,
The dried refuse 2 is passed through an air conduit 7 on a combustion stoker 4b.
The main combustion is performed by the primary combustion air supplied from b.
It is. Primary combustion air supplied to combustion stoker 4b
Because this amount is necessary and sufficient for refuse combustion,
The gas generated from the refuse 2 from above the _X
Is contained at a high concentration.

Next, the refuse 2 that has passed through the dry stoker 4a and the combustion stoker 4b is separated into post-combustion stoker 4c
Supplied to After this, the refuse 2 on the combustion stoker 4c is
In order to prevent a large amount of unburned solid matter or incompletely burned solid matter from remaining in the incineration ash, the primary combustion air is set to have a relatively large air-fuel ratio as compared with the dry stoker 4a and the combustion stoker 4b. Supplied and burned.

Accordingly, the combustion gas in the primary combustion zone 6b above the post-combustion stoker 4c has a temperature of 50 ° C.
At about 0 to 800 ° C., about 15 to 19% of oxygen remains and has an oxidizing atmosphere. However, a possible combustion gas is relatively low, because the nitrogen component in the dust is gone almost gone, in the state NO _X is in which was suppressed less generated at the portion of the rear combustion stoker 4c. Recently, in order to suppress dioxins in incineration ash, combustion is performed at a temperature as high as possible.

As described above, the combustion gas in the primary combustion zones 6a and 6b in the lower part of the combustion chamber 6 is mixed, so that the temperature distribution becomes uniform and the atmosphere of relatively low oxygen is maintained. Here, the natural gas supplied through the natural gas supply pipe 10 and the steam supplied through the water vapor supply pipe 11 are mixed by the mixer 12, and this mixed gas is ejected from the supply port 5a. 6c, a complete reducing atmosphere is formed. Therefore, NO _X generated during the primary combustion is also reduced in the reburning zone 6c and reduced at a maximum reduction rate of 60% or more.

Thus, in the combustion gas by the primary combustion
Generated hydrocarbon gas, CO gas or surplus carbon
Hydrogen gas, etc., in the secondary combustion zone 6d
The combustion chamber 6 is completely burnt by the combustion air (fresh air).
The boiler 9 and a not-shown discharge
It is released to the atmosphere by a chimney via a gas treatment device. What
In the secondary combustion zone 6d, natural gas is blown.
NO already _XIs reduced, and 80
Because combustion is performed at a relatively low temperature of 0 to 1000 ° C
New NO_XGeneration of N2 in exhaust gas
O_XIs suppressed to 50 ppm or less.

In such a state, the refuse 2 is supplied with substantially constant primary combustion air, natural gas, and secondary combustion air to maintain a stable combustion state. The amount of water vapor from the boiler 9 detected by the flow meter 14 is substantially constant.

When the amount of steam from the boiler 9 detected by the steam flow meter 14 is lower than the amount of steam detected in the stable combustion state, the controller 18 controls the natural gas controller 16 and the primary combustion air controller. 17 is controlled so that the natural gas supply and the primary combustion air supply are increased simultaneously or in advance of natural gas.

As described above, when the amount of water vapor decreases, not only the primary combustion air amount increases as in the conventional case, but also the natural gas supply amount corresponding to the decrease in the amount of water vapor increases. , minimizes the increase of the primary combustion air amount, the primary combustion zone 6a, less increase in the amount of oxygen 6b, it is possible to maintain the reburning zone 6c to a reducing atmosphere, suppressing the instantaneous increase of the NO _X it can.

On the other hand, when the amount of steam from the boiler 9 detected by the steam flow meter 14 is larger than the amount of steam detected in the stable combustion state, the controller 18 controls the natural gas controller 16 and the primary combustion air. Controller 17
Is simultaneously controlled to reduce the natural gas supply and the primary combustion air supply.

As described above, when the amount of steam increases, not only does the amount of primary combustion air decrease as in the prior art, but also
The natural gas supply has been reduced in proportion to the increase in water vapor. Since the amount of natural gas decreases along with the amount of primary combustion air, there is no sudden generation of CO, and the reburning zone 6c can be maintained in an appropriate reducing atmosphere.

In this embodiment, the steam supply pipe 1
The steam supplied through 1 may be circulated and used after the amount of steam is detected by the steam flow meter 14, and the medium for disturbing and mixing natural gas into the combustion chamber 6 may be:
Not limited to steam, for example, flue gas (6 to 12% of oxygen remaining), primary combustion gas (about 2% of oxygen remaining), a mixed gas of flue gas and primary combustion gas, and the like may be used.

In the present embodiment, the supply port 5a, which is the point where natural gas is blown into the combustion chamber 6, may be located at least below the supply port 5b of the secondary combustion air. The number is not limited to one, and may be two or more. The number of the secondary combustion air supply ports 5b is also 1
Not limited to two places, there may be two or more places.

In this embodiment, the natural gas supply amount and the primary combustion air supply amount are simultaneously increased or decreased by the respective controllers 16 and 17, but the natural gas supply amount is increased prior to the primary combustion air. Or it may be reduced.

In this embodiment, the natural gas supply amount and the primary combustion air supply amount are controlled by the respective controllers 16 and 17 to control the valve 16b and the damper 17b.
The valves and dampers may be directly controlled by the controller 18 without using a controller.

[Brief description of the drawings]

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Garbage incinerator 2 Garbage 3 Hopper 4 Stalker 4a Dry stoker 4b Burning stoker 4c Post-burning stoker 5 Furnace wall 5a Supply port (natural gas, steam) 5b Supply port (secondary combustion air) 6 Combustion chamber 6a, 6b Primary combustion zone 6c Reburning zone 6d Secondary combustion zone 7 Primary combustion air supply device 7a, 7b, 7c Air conduit 7d Push blower 8 Ash discharge 9 Boiler 10 Natural gas supply pipe 11 Steam supply pipe 12 Mixer 13 Secondary combustion air supply pipe 14 Steam flow meter 16 Natural gas controller 16a Natural gas flow meter 16b Natural gas valve 17 Primary combustion air regulator 17a Primary combustion air flow meter 17b Primary combustion air damper 18 Controller

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Nao Ito 6-16, Kamigaharajubancho, Nishinomiya City, Hyogo Prefecture (72) Inventor Ryoji Samejima 2-33, Kinrakujimachi, Amagasaki City, Hyogo Prefecture Takuma (72) Inventor Tomonori Aso 2-33, Kinrakuji-cho, Amagasaki City, Hyogo Prefecture Inside Takuma Co., Ltd. (72) Inventor Kazuhisa Yamamoto 1-7-89 Minami Kohoku, Suminoe-ku, Osaka City Inventor Mamoru Kondo 1-7-89 Minami Kohoku, Suminoe-ku, Osaka

Claims (2)

[Claims] 1. A reducing atmosphere is formed by supplying a hydrocarbon-based fuel above a primary combustion zone in which an object to be burned is primarily burned by primary combustion air, and a secondary combustion air is supplied above the reducing atmosphere. The combustion control device of an incinerator which completely burns unburned matter or incompletely burned matter after being reduced by the hydrocarbon-based fuel and discharges generated exhaust gas through a heat recovery device, (a) generated from the heat recovery device (B) a supply amount of the hydrocarbon-based fuel and a supply amount of the primary combustion air such that the amount of steam detected by the amount-of-steam detector maintains a predetermined value. A combustion control device for an incinerator, comprising a supply amount control means for controlling. 2. The combustion control apparatus for an incinerator according to claim 1, wherein the supply amount control means controls the hydrocarbon-based fuel to increase or decrease prior to the primary combustion air.