JP2001241629A - Low-pollution combustion equipment for waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide low-pollution combustion equipment for waste capable of reducing the amount of dioxin, CO, and NOx in an oxygen-deficient gas such as an exhaust gas by effectively combining primary air and secondary air at an appropriate temperature, an oxygen-riched gas and the oxygen-deficient re-circulation gas such as exhaust gas for burning at a high temperature without charging any chemicals, without increasing the amount of blown air and the amount of oxygen more than required, and without complicating the furnace structure or increasing the furnace size. SOLUTION: Oxygen-deficient primary air due to the increase in temperature is introduced from the lower portion of a stoker where an object to be burnt is thrown to create reduction atmosphere to thereby prevent NOx from being generated, and at the same time oxygen-enriched air (or normal air) is mixed, as secondary air, with a thermally decomposed gas that is generated by primary combustion, by agitation operation caused by the blowing of an oxygen-deficient gas such as a low-temperature re-circulation exhaust gas that is introduced as secondary air similarly, thus completely combusting the thermal decomposition gas while controlling temperature, and preventing harmful substances from being generated in the stoker furnace.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a stoker type incinerator by controlling primary air and secondary air.
The present invention relates to a low-pollution waste combustion device capable of reducing the amount of harmful substances in oxygen-deficient gas such as exhaust gas generated when burning waste.

[0002]

2. Description of the Related Art In recent years, harmful gases generated by incineration of garbage, including dioxins designated as harmful air pollutants by amendments to the Waste Management Law and the Air Pollution Control Law, have become a social problem and the environmental awareness has increased. Improvements and developments have been made in incinerators to achieve regulation of harmful gases from exhaust gas generated by incineration. Generally, stoker-type incinerators and fluidized-bed incinerators are used as refuse incinerators. In the stoker type incinerator, the grate of the fixed stage and the movable stage are alternately arranged, and the garbage input by stirring and moving forward by reciprocating the movable stage with a hydraulic device,
An incinerator for drying and burning the refuse. In addition, a fluidized bed incinerator is an incinerator in which refuse is charged into fluidized sand heated to a high temperature, and combustion air is supplied from below to be mixed violently to form a carbonized gas in a short time to burn.

[0003] However, in the fluidized bed type, the supply of waste is intermittent due to its configuration, and the incineration of the waste is instantaneous. Therefore, the residence time of the incineration is not sufficient, and the fluidized bed type has a fluidized bed as compared with the stoker type incinerator. It is known that dioxin is generated in larger amounts in waste incineration using an incinerator.
It is difficult to reduce pollution.

The invention disclosed in Japanese Patent Application Laid-Open No. 6-313534 is a method for incinerating combustibles, particularly refuse, using a stoker-type incinerator. According to this, the combustion intensity on the stoker is increased by introducing oxygen-enriched primary air from below the stoker, and the oxygen ratio is reduced by circulating exhaust gas as secondary air and using it.
The combustion intensity of the secondary combustion zone is suppressed, and the exhaust gas is circulated and repeatedly used as secondary air, thereby reducing carbon monoxide, dioxin, NOx, etc. of the exhaust gas discharged from the incinerator.

[0005]

However, since the primary air is enriched with oxygen, the temperature of the refuse combustion section becomes high,
Further, since the oxygen-excess atmosphere continues from the primary combustion chamber to the freeboard, there is a problem that NOx is easily generated when the nitrogen substance present in the refuse is incinerated. Furthermore, since the circulated exhaust gas with a low oxygen content is used as the secondary air, the atmosphere above the stoker becomes a reducing atmosphere, and the pyrolysis gas that is immediately transported upward without being oxidized by the primary air also lacks oxygen. Therefore, there is a problem that CO and HCl are generated.

[0006] The secondary air is repeatedly circulated, but the primary air is introduced, and the secondary air is exhausted, so that the amount of oxygen-deficient gas such as exhaust gas is small but the amount of harmful substances such as exhaust gas is concentrated. Since the oxygen-deficient gas is emitted, no substantial improvement has been achieved in preventing the generation of harmful substances in the incinerator.

[0007] Therefore, the present invention has been made in view of the technical problems that cannot be solved by the above-mentioned conventional technology, and does not require the injection of chemicals and the like, without increasing the amounts of air and oxygen to be injected more than necessary. Combustion at high temperatures by effectively combining primary and secondary air at appropriate temperatures and oxygen enrichment and recirculation of oxygen-deficient gas such as exhaust gas without complicating or enlarging the furnace structure. Dioxin, CO, in oxygen-deficient gas
It is another object of the present invention to provide a low-pollution waste combustion device capable of reducing the amount of NOx.

[0008]

According to the first aspect of the present invention,
Primary air is introduced from below the stoker into which the material to be burned is injected, and after primary combustion is performed, secondary air is introduced into the secondary combustion chamber space above the stoker, and unburned or pyrolyzed components on the primary combustion side are introduced. In a stoker-type incinerator that performs secondary combustion of gas (hereinafter, referred to as pyrolysis gas), the secondary air blowing nozzle is disposed to face the furnace wall on the side where the burnable material is input and on the opposite side thereof. The secondary air is characterized by oxygen-enriched air (or ordinary air), and the secondary air from the opposite nozzle is an oxygen-deficient gas such as exhaust gas.

According to the invention, in the primary combustion, a large amount of pyrolysis gas is generated on the drying stoker on the side where the burned material is input (see FIG. 2). Is introduced to efficiently burn the pyrolysis gas and oxidize it to prevent generation of harmful gas. In addition, it is possible to control the combustion distribution in the secondary combustion chamber by pressing the pyrolysis gas generated in the primary combustion process in the direction of the injection side nozzle by the oxygen-deficient gas such as exhaust gas introduced from the opposite side nozzle. At the same time, the air in the secondary combustion chamber space is agitated, whereby the mixing of the pyrolysis gas and air (oxygen) is improved, and the combustion of the pyrolysis gas can be completed.

Further, according to the present invention, the oxygen-deficient gas such as the exhaust gas described in the above-mentioned claim 1 is maintained at about 100 ° C.
It is a middle-temperature heating gas at ~ 200 ° C. This is because, by introducing a medium-temperature gas, it is possible to alleviate the increase in temperature due to combustion in the secondary combustion chamber space, thereby preventing the generation of NOx generated in a high-temperature state.

According to a third aspect of the present invention, the primary air according to the first aspect is a primary air having a high temperature of about 300 ° C. to 400 ° C. In other words, since the volume of atmospheric air at room temperature is expanded, the ratio of oxygen to air volume is reduced without changing the oxygen content weight, so that the stoker's empty tower due to volume expansion is increased. While maintaining the speed and stirring power, and by reducing the ratio of the amount of oxygen to the air volume, a substantial oxygen deficiency state becomes possible, and a reducing atmosphere is created when refuse is burned on the stoker. Thus, generation of NOx can be prevented.

In addition, even if the amount of air is small in the primary air introduction, the air is expanded by increasing the temperature, and the volume of the air is increased, so that the blowing speed is easily maintained at a certain level or more. However, the agitation and combustion of the refuse put on the stoker can be performed more reliably.

Further, the invention according to claim 4 is characterized in that the grate constituting the stoker of the present invention is water-cooled. In other words, in the present invention, the furnace temperature is set to a high temperature (about 1200
(° C or higher), it is assumed that combustion is performed in a state of sufficient oxygen, and it is necessary to prevent the stoker grate from becoming hot and burning due to high temperature by cooling with water while increasing the temperature by enriching oxygen. You.

Finally, a fifth aspect of the present invention is directed to the first aspect.
A plurality of nozzles for blowing out oxygen-deficient gas such as the exhaust gas described above are arranged vertically, and the supply amount of each nozzle is controlled according to the NOx concentration. By controlling the exhaust gas injection position from the nozzle positions located above and below, it is possible to create a reducing atmosphere space in accordance with the NOx concentration, and complete combustion of the pyrolysis gas without waste with a minimum amount of oxygen. In addition, the temperature of the space in the secondary combustion chamber can be maintained at an optimum temperature.

The invention described in claim 6 is the first invention of the present invention.
The waste low-pollution combustion apparatus described above, wherein the secondary air blowing nozzle pitch is set to 200 to 300 mm / piece or less. This is to improve the mixing of the pyrolysis gas and air (oxygen) in the secondary air chamber space by narrowing the pitch between the nozzles, achieve complete combustion of the unburned components, and thereby reduce the generation of harmful substances. Will be prevented. In this case, preferably, by setting the blowing nozzle pitch on the oxygen-deficient gas side to 200 to 300 mm / piece or less, the stirring power is improved without unnecessarily increasing the supplied oxygen.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to an embodiment shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not merely intended to limit the scope of the present invention, but are merely illustrative examples unless otherwise specified. Absent.

(First Embodiment) A low-pollution combustion apparatus for waste according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 shows a schematic configuration of a stoker-type waste low-pollution combustion apparatus 1 of the present invention, and stokers 6, 7, and 8 are laid at the bottom of the stoker furnace 2 and the refuse hopper 3 inlet, respectively. The primary air 31 can be supplied from below. A primary combustion chamber 30 is formed above the stokers 6 to 8, and a secondary combustion chamber 33 is formed above the stoker 6-8.
Are constituted by secondary air blowing nozzles 17, 18 and the like at the inlet. In the stokers 6 to 8, a moving grate is arranged between fixed grates, and drying, finally burning, and finally burning are performed by reciprocating motion of the moving grate. This is an example in which three stokers for performing combustion, combustion, and combustion respectively are used (this technique can be applied to a stoker that cannot clearly distinguish drying, combustion, and combustion).

The refuse 4 introduced from the refuse hopper 3 is introduced into the stoker furnace 2 while being quantitatively controlled by a refuse quantitative supply device 5. The introduced refuse is first dried on the drying stoker 6 by radiant heat or the like, and partial surface combustion occurs. Next, while the garbage is moved forward by the reciprocating movement of the stoker 6, the garbage is stirred by blowing the primary air 31 kept at a constant speed from below the stokers 6 to 8,
Due to the supply of oxygen, partial combustion by gasification starts at the rear of the drying stoker 6 and at the front of the combustion stoker 7. At this time, the air introduced as the primary air is the above-mentioned high-temperature air and is expanded, so that the amount of oxygen in the volume is small, the pyrolysis gas is generated, and the generation of NOx is suppressed.

Next, refuse is burned on the combustion stoker 7. At this point, the pyrolysis gas is oxidized by oxygen in the supplied primary air 31 to generate CO ₂ and a small amount of NOx, but the combustion is performed at a high temperature while supplying a minimum amount of oxygen. A reducing atmosphere is formed above the combustion stoker 7, and the generated NOx is reduced. Next, the refuse carried to the post-combustion stoker 8 is ignited, discharges excess oxygen and the like, completes the combustion, becomes ash, and is discharged outside the incinerator.

At the inlet of the secondary combustion chamber 33 above the stoker 6, 7, 8 the secondary air from the opposite side of the secondary combustion chamber space 33 for secondary combustion of the pyrolysis gas generated in the primary combustion. Blowing nozzles 17 and 18 for taking in are installed. That is, the oxygen-enriched air (or ordinary air) is taken in by the blow-out nozzle 17 provided on the combustion object input side, whereby the pyrolysis gas, particularly CO 2
By supplying oxygen to the gas, secondary combustion (reburning) is performed to promote oxidation, that is, conversion to CO ₂ or decomposition of HCl, and harmful gas can be changed to harmless gas in the furnace. The blow-out nozzle 18 installed on the opposite side of the dust hopper 3 inlet so as to face the blow-out nozzle 17 is for introducing oxygen-deficient gas such as recirculated exhaust gas as secondary air.

Exhaust gas discharged from the outlet of the secondary combustion chamber of the stoker furnace 1 is heated to about 600 to 500 ° C. by a superheater 9 for heating boiler steam.
After removing fly ash etc. at 0, some exhaust gas
The temperature of the recirculated exhaust gas is adjusted to a temperature of about 100 to 200 ° C. by heat exchange with boiler water, and the recirculated exhaust gas is converted into an oxygen-deficient gas (EG).
(R oxygen content about 12%) is used as the secondary air. The recirculated exhaust gas is used for controlling the combustion distribution in the secondary combustion chamber 33 because the oxygen content is small. That is, by blowing the recirculated exhaust gas from the blowing nozzle 18 to the facing blowing nozzle 17 side via the secondary combustion chamber 33, the pyrolysis gas generated in the primary combustion is pressed against the blowing nozzle 17 side, By actively mixing with the oxygen-enriched air taken in by the blowing nozzle 17, complete combustion of the pyrolysis gas can be efficiently achieved.

Further, since the recirculated exhaust gas is not too high in temperature and is moderately heated to about 100 to 200 ° C., it is possible to prevent the combustion temperature from becoming higher than necessary due to oxygen enrichment in the secondary combustion chamber. And the intermediate temperature prevents the temperature of the secondary combustion chamber from lowering and prevents the resynthesis of dioxin and the like. This is to prevent a large amount of NOx from being generated by supplying oxygen to an atmosphere of 1300 ° C. or higher.

Exhaust gas which has not been recirculated after passing through the dust removing means 10 is recovered by the heat recovery facility 12, and then is drawn into the chimney 15 by the suction suction fan 14 and discharged to the atmosphere.

On the other hand, the air (atmosphere) taken in by the push-in blower 13 is heat-exchanged in the heat recovery equipment 12 so that 300-400
The temperature is raised to ° C. and introduced from below the stoker as primary air.

(Second Embodiment) A low-pollution waste combustion apparatus according to a second embodiment of the present invention will be described with reference to FIG. FIG. 2 shows a stoker-type low-pollution combustion apparatus 1 according to a second embodiment of the present invention. This embodiment includes a plurality of secondary air blowing nozzles in which the nozzle pitch of the nozzles for discharging exhaust gas is set to 200 to 300 mm / line, a NOx detection device 19, a controller 20, and the like in addition to the first embodiment. I have. The present embodiment is almost the same as the first embodiment, and a detailed description is omitted.

In the present embodiment, secondary air blowing nozzles 18a, 18b and 18c for introducing oxygen-deficient gas such as exhaust gas into the secondary combustion chamber space 16 are subdivided and a plurality of upper and lower secondary air blowing nozzles are installed. NOx mounted above furnace 2
The NOx concentration detected by the detection device 19 is input to the controller 20 by an input signal, and the exhaust gas supply amount and the supply position can be controlled in accordance with the NOx concentration in the stoker furnace 2.

When NOx is generated by combustion, NOx is created by creating an oxygen-deficient environment, a so-called reducing atmosphere.
x is reduced, thereby reducing the generation of the harmful substance NOx. In other words, since the reducing atmosphere is formed in the space from the primary combustion section to the secondary combustion section, when the NOx concentration is detected by the NOx detection device to be high, the blowing of the exhaust gas introduction blowing nozzles installed in the upper and lower parts is performed. By adjusting the amount and the supply position, exhaust gas is actively supplied to the portion of the stoker furnace 2 where the temperature of the secondary combustion is the highest, and the temperature of the secondary combustion chamber is set to be equal to or lower than the NOx generation temperature. A wider atmosphere is formed, and more NOx can be reduced.

Further, the nozzle pitch is set to 2
By narrowing to a diameter of 00 to 300 mm / piece or less and subdividing, the pyrolysis gas and the oxygen-enriched secondary air can be more reliably stirred and mixed, and the complete combustion of the pyrolysis gas can be performed efficiently. Will be

(Third Embodiment) A low-pollution waste combustion apparatus according to a third embodiment of the present invention will be described with reference to FIG. FIG. 3 shows a water-cooled grate 24 in a stoker-type waste low-pollution combustion apparatus 1 according to a third embodiment of the present invention.
In the present invention, in order to reduce pollution, an incineration temperature of about 1 is used.
The temperature is as high as 200 ° C. or more, and the stoker grate can be water-cooled to prevent burnout due to the stoker's high temperature.

The structure of the stoker furnace according to the present invention has first and second structures.
Since it is as described in the embodiment, it is not described here. The stoker is constituted by a plurality of grate, and a cooling water pipe 27 is buried in the grate, and the cooling water of about 80 ° C. taken in from the cooling water inlet 25 passes while cooling the inside of the grate, By discharging the cooling water heated to approximately 110 ° C. from the cooling water outlet 26, even if the surface of the stoker becomes hot due to combustion, it is cooled to prevent burning and prolong the life of the stoker. Becomes possible.

[0031]

As described above, according to the stoker type waste low-pollution combustion apparatus of the present invention, primary air and secondary air are utilized by utilizing heat recovered from oxygen-deficient gas such as exhaust gas or oxygen-deficient gas such as exhaust gas. At an appropriate temperature and effectively combine oxygen enrichment and oxygen-deficient gas recirculation such as exhaust gas, thereby enabling high-temperature combustion and thus preventing emissions of harmful substances in the incinerator. It has become possible to reduce the amount of harmful substances causing air pollution problems contained in oxygen-deficient gas such as exhaust gas. Furthermore, by using a water-cooled grate having cooling water pipes embedded in the grate of the stoker, even if high-temperature combustion is performed with the stoker-type waste low-pollution combustion device of the present invention, burning of the waste while preventing burning of the stoker is achieved. It became possible to do.

[Brief description of the drawings]

FIG. 1 shows a schematic configuration of a stoker type waste low-pollution combustion apparatus according to a first embodiment of the present invention.

FIG. 2 shows a schematic configuration of a stoker-type waste low-pollution combustion apparatus according to a second embodiment of the present invention.

FIG. 3 shows a configuration of a water-cooled grate in a stoker-type waste low-pollution combustion apparatus according to a third embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stalker type waste low-pollution combustion apparatus 2 Stalker furnace 3 Waste hopper 4 Garbage 5 Garbage fixed-quantity supply apparatus 6 Stalker 7 Stalker 8 Stalker 9 Superheater 10 Dust removing means 11 Boiler 12 Heat recovery 13 Push-blower 14 Induction suction fan 15 Chimney 16 2 Next combustion chamber space 17 Nozzle (oxygen-enriched) 18 Nozzle (oxygen-deficient gas such as exhaust gas) 19 NOx detector 20 Controller 21, 22, 23 Control valve 24 Water-cooled grate 25 Cooling water inlet 26 Cooling water outlet 27 Cooling water pipe

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F23L 9/02 F23L 9/02 (72) Inventor Hirotoshi Hirotoshi 1-8-8 Koura, Kanazawa-ku, Yokohama-shi, Kanagawa 1 Mitsubishi Heavy Industries, Ltd. Yokohama Research Laboratory F-term (reference) 3K078 AA04 AA07 AA08 BA03 BA22 BA24 BA26 CA03 CA13 CA21 3K091 AA01 AA03 BB06 BB22 DD01 DD03 DD04 GA29 GA44

Claims (6)

[Claims] 1. A primary air is introduced from below a stoker into which a substance to be burned is introduced, and after primary combustion is performed, secondary air is introduced into a secondary combustion chamber space above the stoker, and the primary combustion side air is introduced. In a stoker-type incinerator that performs secondary combustion of fuel or pyrolysis gas, the secondary air blowing nozzle is disposed to face the furnace wall on the side where the burnable material is input and on the opposite side thereof, and oxygen is enriched from the input side nozzle. Air (or normal air), exhaust gas (E
A low-pollution combustion device for waste, wherein oxygen-deficient gas such as GR) is blown out. 2. An oxygen-deficient gas such as the exhaust gas is substantially 100
The low-pollution combustion device for waste according to claim 1, wherein the device is a medium-temperature heating gas at a temperature of from 200C to 200C. 3. The primary air according to claim 1, wherein the primary air is a primary air having a high temperature of about 300 ° C. to 400 ° C.
The low-pollution combustion device of the described waste. 4. A method according to claim 1, wherein a plurality of blow-off nozzles on the side of the oxygen-deficient gas such as the exhaust gas are arranged above and below, and the supply amount from each nozzle is controlled according to the NOx concentration. Waste low-pollution combustion equipment. 5. The pitch of the secondary air outlet nozzle, preferably the outlet nozzle pitch on the oxygen-deficient gas side, is 200 to 30.
2. The low-pollution waste combustion apparatus according to claim 1, wherein the apparatus is set to 0 mm / piece or less. 6. The low-pollution waste combustion apparatus according to claim 1, wherein the grate constituting the stoker is water-cooled.