JP2000356328A - Method and facility for incinerating refuse - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce production itself of dioxins through installation of a quite simple apparatus and addition of an inexpensive material by adding a nitrogen compound to refuse before feeding it into an incinerator. SOLUTION: Refuse is thrown into a refuse hopper 11 and aqueous solution of urea is sprayed, as a nitrogen compound, from a urea spray nozzle 53 before the refuse is fed into a combustion chamber 12. In the combustion chamber 12, the charged refuse is passed through drying, combustion, and post-combustion processes and discharged in the form of ash. Since combustion air supply is restricted in the operation at the upstream side fire grate, combustion progresses under oxygen deficient state at a part of a dry stage fire grate 13a and a combustion stage fire grate 13b and dioxins are generated easily through reaction of an aromatic compound and chlorine. But since a compound having ammonia or NH2 group is generated through thermal decomposition of urea added to the refuse, reaction for generating dioxins is retarded.

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 a facility thereof.

[0002]

2. Description of the Related Art Waste such as municipal solid waste and industrial waste (hereinafter simply referred to as waste or both) is mostly disposed of by landfill after incineration. ing. In most cases, grate incinerators are provided in waste incineration facilities, but fluidized bed incinerators may be provided in some cases.

[0003] Waste incineration in an incinerator equipped with a grate incinerator is performed as follows. First, the waste is charged into an incinerator, and is heated and ignited while being dried by combustion air blown from below the grate and radiant heat in the furnace. Next, the waste is burned and ashed, and is discharged as incineration ash outside the furnace.

On the other hand, H ₂ , CO, and CH ₄ generated during the drying and heating of the waste and in the initial combustion stage are included in the combustion exhaust gas.
Since a flammable gas such as flammable gas is contained, air is blown in the secondary combustion chamber to perform a process of burning the flammable gas. Next, the combustion exhaust gas discharged from the secondary combustion chamber is sent to an exhaust gas treatment step by heat recovery in a boiler or cooling by a gas cooling device such as a gas cooler. Then, after the harmful gas removal processing and the dust removal processing are performed, the emission is performed from the chimney.

[0005] In addition, incinerators equipped with a fluidized bed incinerator are required.
Incineration of wastes is carried out as follows. Waste is flowing
Injected into a moving bed incinerator and dried in a fluidized bed
The temperature rises and burns. However, the combustion exhaust generated in the fluidized bed
H in the gas_Two, CO, CH _FourContains flammable gas such as
Air into the freeboard section of the incinerator
Only, a process for burning the combustible gas is performed. afterwards,
The flue gas is cooled by gas cooling equipment,
Sent to the treatment facility and processed for harmful gas removal and dust removal
After being released into the atmosphere.

[0006]

Recently, toxic dioxins such as chlorodibenzodioxane and chlorodibenzofuran or other organic chlorine compounds are contained in flue gas generated from equipment for incineration of wastes. It turned out to be included, and became a major environmental conservation problem. Therefore, regulations on the emission of dioxins are being strengthened.

Under such circumstances, various technical developments have been made to reduce dioxins in combustion exhaust gas. However, many of these techniques capture dioxins together with fly ash, and require separate treatment to render fly ash harmless, which is not an essential solution. Also, the technology of decomposing dioxins in exhaust gas is a large-scale treatment equipment,
When applied to existing incinerators, significant remodeling is required and implementation is difficult. For example, Japanese Patent Application Laid-Open No. 5-1
In the technology disclosed in Japanese Patent No. 61822, it is necessary to install a ceramic filter for treating combustion exhaust gas.

The present invention has been made in order to solve the above-mentioned problems, and the amount of dioxins produced can be reduced by merely installing a very simple apparatus and adding an inexpensive substance. It is an object of the present invention to provide a waste incineration method and its equipment.

[0009]

Means for Solving the Problems In the course of conducting various tests for incineration of waste, the present inventors found that dioxin contained in the combustion exhaust gas was mixed when the waste was mixed with sludge such as sewage sludge. It has been found that the content of the compounds is low. For this reason, the present inventors have conducted various studies on how the effect of reducing dioxins by the co-firing of sludge can be achieved.

[0010] It is known that one of the main causes of the generation of dioxins by incineration of waste is to burn the waste in an oxygen-deficient atmosphere. This corresponds to the condition of the stage in which the input waste is heated and heated. From this fact, it is considered that, in the initial combustion stage, the sludge pyrolyzed product acts to suppress the generation of dioxins.

Therefore, general sludge has a nitrogen content of 2 to 2.
Since it contained 10 wt% (dry basis), it was considered that the substance that suppresses the generation of dioxins was the nitrogen-containing component in sludge thermally decomposed, and an experiment was conducted. In the experiment, waste was incinerated with nitrogen compounds added,
It was recognized that dioxins in the flue gas were reduced. From this, it is assumed that the substance that suppresses the generation of dioxins is a compound having ammonia (NH ₃ ) or an NH ₂ group generated when a nitrogen-containing component in sludge is thermally decomposed.

Although the mechanism by which nitrogen compounds generated by thermal decomposition suppress the production of dioxins is not clear, it is thought that these substances have a poisoning effect on copper and other substances that serve as catalysts for the production of dioxins. Can be This poisoning effect is thought to be one of the causes of the effect of suppressing the production of dioxins.

As described above, the generation of dioxins is suppressed even when a nitrogen compound is charged together with the waste when the waste is incinerated. The present invention has been made based on findings based on the results of the above tests and studies. Therefore, the above-mentioned problem is solved by the following invention.

A first invention is a waste incineration method characterized by adding a nitrogen compound to waste and charging the waste into an incinerator.

In the present invention, since the production of dioxins is suppressed by charging the nitrogen compound together with the waste as described above, the dioxins contained in the combustion exhaust gas can be reduced only by providing a very simple device. Can be reduced.

A second invention is a method for charging sludge together with waste into an incinerator, and incinerating the waste and / or sludge with a nitrogen compound before charging the sludge into the incinerator. It is a waste incineration method characterized by adding.

The incineration of waste and sludge is generally performed in dedicated incineration facilities, respectively. However, if the waste and sludge are incinerated together, there is a merit that facility and operating costs can be reduced. Furthermore, the effect of suppressing the generation of dioxins can be obtained by incinerating the sludge. However, sludge such as sewage sludge to be incinerated is a clay-like substance containing an extremely large amount of water (65 to 90% by weight) even if dewatered. If a large amount of the dewatered sludge is charged, the combustion state in the incinerator becomes poor, so that the sludge for supplying a required amount of nitrogen may not be charged. The present invention addresses the above situation,
Nitrogen compounds are added to the waste and / or sludge and charged to the incinerator to replenish the insufficient nitrogen content.

The third invention is a method of charging sludge together with waste into an incinerator and incinerating the same, wherein a nitrogen compound is added to the waste and sludge put in the waste hopper of the incinerator. It is a method of incinerating waste.

In the present invention, since the nitrogen compound is added to both the waste and the sludge to be charged into the incinerator, the nitrogen compound is uniformly distributed in the charge in the incinerator, and the generation of dioxins is reduced. It is suppressed without bias.

According to a fourth aspect of the present invention, there is provided a waste incinerator for incinerating sludge together with waste, wherein a nitrogen compound adding means for adding a nitrogen compound to waste to be charged into an incinerator is provided. Waste incineration equipment.

In the present invention, since a nitrogen compound is added to waste, a small amount of nitrogen compound can be uniformly added to a large amount of bulky waste, and the generation of dioxins in the incinerator is reduced. It can be controlled without bias.

According to a fifth aspect of the present invention, there is provided a waste incinerator for incinerating sludge together with waste, wherein a means for adding a nitrogen compound to a sludge feeder for charging sludge into an incinerator is added, and Are mixed and charged into an incinerator.

The present invention is particularly useful when a powdered nitrogen compound is added. If the nitrogen compound is added in the form of a powder and the water content of the charge charged into the incinerator is reduced, the combustion efficiency can be increased.

In the above inventions, sludge means sewage sludge, human waste sludge, sludge generated when organic wastewater is treated with activated sludge, sludge generated when wastewater containing organic matter is separated into solid and liquid, and closed sludge. It refers to sludge generated when dredging rivers in water bodies.

The nitrogen compound refers to an organic compound or an inorganic compound containing nitrogen. Specific examples of preferred nitrogen compounds include inexpensive compounds such as ammonia and urea. Nitrogen compounds can be used in the form of gas, liquid, solid, or aqueous solution.
An appropriate form is selected.

[0026]

FIG. 1 is an explanatory view showing a first example according to an embodiment of the present invention. The incinerator shown in this figure is equipped with a grate incinerator, 10 is a grate incinerator, 11 is a waste hopper for charging municipal waste and other waste into the furnace, and 15 is a waste hopper. This is an exhaust gas treatment process. In the exhaust gas treatment step 15, gas cooling by a boiler, a gas cooler, or the like, acid gas removal processing, dust collection processing, and the like are performed.
Further, as ancillary equipment of the incinerator 10, means 50 for adding a nitrogen compound to the waste charged into the incinerator 10 is provided. In the figure, reference numeral 51 denotes a storage tank for an aqueous solution of urea, a kind of nitrogen compound, 52 denotes a urea supply pump, and 53 denotes a urea spray nozzle. Reference numeral 70 denotes waste such as municipal waste.

In the combustion chamber 12 of the incinerator, a drying stage grate 13a and a combustion stage grate 13
b, a post-combustion stage grate 13c is provided in a stepwise manner.
Thus, in the combustion chamber, an area mainly for drying the loaded waste 70 (dry zone), an area for burning the dried waste (combustion zone), and the ash sent in the combustion state are ashed. It is divided into an area where post-combustion is performed (post-combustion zone).

In the refuse incineration plant having the above configuration,
The waste is put into the waste hopper 11, and the urea spray nozzle 53 sprays an aqueous urea solution on the waste.
The waste to which the urea is added is sent from the waste hopper 11 into the combustion chamber 12.

In the combustion chamber 12, the charged waste is charged.
Drying, burning and after the material is transported on each grate
It is ashed and discharged through each process of combustion. At this time,
Operation with a reduced supply of combustion air at the upstream grate
Is performed, the drying stage grate 13a (dry zone) and the fuel
In a part of the grate grate 13b (combustion zone), oxygen-free
Burning takes place in the state of the foot. Thus, incomplete combustion takes place.
When the reaction occurs, the reaction between the aromatic compound and chlorine
Although toxins are easily produced, in this embodiment,
Urea added to waste is thermally decomposed and ammonia
(NH_Three) Or NH _TwoAnd other compounds having a group
The progress of the dioxin generation reaction is suppressed.

Since the combustion exhaust gas generated in the combustion chamber 12 contains flammable gas generated in the drying stage grate 13a and a part of the combustion stage grate 13b, air is blown into the secondary combustion chamber 14. Thus, a process of burning the combustible gas is performed. Next, the combustion exhaust gas discharged from the secondary combustion chamber 14 is sent to an exhaust gas treatment step 15, where the exhaust gas is subjected to a cooling treatment, a harmful gas removal treatment, and a dust removal treatment, and then emitted from the chimney 16.

When urea is added to waste and incinerated as described above, the amount of dioxins generated in the incinerator is reduced, and the content of dioxins in the combustion exhaust gas is greatly reduced.

FIG. 2 is an explanatory diagram showing a second example according to the embodiment of the present invention. 2, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. In this embodiment, in addition to the same configuration as in FIG. 1, a sludge supply unit is provided so that sludge can be put into the waste hopper 11 together with the waste. 40
Is a sludge feeder. Further, the sludge feeder 40 is provided with a nitrogen compound adding means 60 so that the sludge can be mixed with the nitrogen compound and charged. 61 is a urea powder storage tank, and 62 is a urea powder feeder.

In the refuse incineration plant having the above configuration,
The waste and sludge fed into the waste hopper 11 are sent into the combustion chamber 12. In the incinerator 12, waste and sludge are ashed and discharged through each process of drying, burning, and post-burning. At this time, as described above, in the initial stage of the drying process or the combustion process, the nitrogen compound in the sludge charged together with the waste and the urea added to the sludge are thermally decomposed to produce ammonia (NH ₃ ) or NH _2. A compound having a group is generated, and the formation reaction of the dioxins is suppressed.
For this reason, the content of dioxins in the combustion exhaust gas is significantly reduced.

The combustion exhaust gas generated in the combustion chamber 12 is subjected to a secondary combustion treatment, a gas cooling treatment, a harmful gas removal treatment, and a dust removal treatment as in the case of the equipment shown in FIG.
Dissipated from 6.

FIG. 3 is an explanatory diagram showing a third example according to the embodiment of the present invention. 3, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals, and description thereof will be omitted. In this embodiment, the waste hopper 11
Means 50 for adding a nitrogen compound to the waste and the sludge introduced into the inside is provided. 51 is a urea aqueous solution storage tank,
52 is a urea supply pump and 53 is a urea spray nozzle.

In the refuse incineration plant having the above configuration,
A urea aqueous solution is sprayed from the spray nozzle 52 onto the waste and the sludge introduced into the waste hopper 11. The waste and sludge to which the urea is added are sent from the waste hopper 11 into the combustion chamber 12. In the incinerator 12, waste and sludge are ashed and discharged through each process of drying, burning, and post-burning. At this time, as in the case of the equipment in FIG.
Nitrogen compounds in sludge charged together with waste and urea added separately are thermally decomposed to ammonia (NH ₃ ) or
A compound having an NH ₂ group or the like is generated, and the generation reaction of dioxins is suppressed, and the content of dioxins in the combustion exhaust gas is significantly reduced.

The flue gas generated in the combustion chamber 12 is treated in the same manner as in the case of the equipment shown in FIG.

FIG. 4 is an explanatory diagram showing a fourth example according to the embodiment of the present invention. The incineration equipment shown in this figure is equipped with a fluidized bed incinerator.
Is a sludge feeder, and 20 is a fluidized bed incinerator. Also, 26
Is an exhaust gas treatment process for performing gas cooling by a boiler, a gas cooler, etc., acid gas removal treatment, dust removal treatment, and the like.

Inside the fluidized bed incinerator 20, the wind box 2
1 is divided into a fluidized bed portion 23 in which a fluidized bed is formed by air supplied to 1 and a free board 24 thereon. The free board 24 is provided with an air blowing nozzle 25. . Reference numeral 22 denotes a dispersion plate for rectifying air blown from the wind box 21 into the fluidized bed. The sludge feeder 40 is provided with a nitrogen compound adding means 60, and the sludge is mixed with the nitrogen compound and charged. 61 is a urea powder storage tank, and 62 is a urea powder feeder.

In the refuse incineration plant having the above configuration,
Waste is charged into the incinerator 20 from the waste supply device 30, and sludge is charged from the sludge supply device 40. At this time, urea powder is supplied from the urea supply device 62 to the sludge supply device 40, and sludge mixed with urea is charged. The charged waste and sludge are heated in a fluidized bed while drying and burning.

Since the amount of air blown in the fluidized bed is suppressed, the fluidized bed is in a combustion state in which dioxins are easily generated. In the present invention, the nitrogen compound in the sludge charged together with the waste and the urea added to the sludge are thermally decomposed to produce ammonia (NH ₃ ), a compound having an NH ₂ group, and the like. The reaction is suppressed. Incombustibles in the waste are extracted from the bottom of the incinerator.

The combustion exhaust gas generated in the fluidized bed contains H ₂ ,
Since a flammable gas such as CO and CH ₄ is contained, air is blown from the nozzle 25 in the freeboard section 24 to perform a secondary combustion process for burning the flammable gas. Next, the combustion exhaust gas discharged from the secondary combustion chamber 14 is sent to an exhaust gas treatment step 26, where the exhaust gas is subjected to a cooling treatment, a harmful gas removal treatment, and a dust removal treatment, and then emitted from a chimney 27.

As described above, sludge is charged together with waste, and urea, a kind of nitrogen compound, is added to the sludge and incinerated, so that the content of dioxins in the combustion exhaust gas is greatly reduced. Can be done.

FIGS. 1 to 4 show a waste incinerator equipped with a grate incinerator or a fluidized bed incinerator. The incinerator to which the present invention can be applied is the above two incinerators. The type is not limited, and for example, a kiln type may be used.

FIGS. 1 to 3 show a grate-type incinerator having a structure in which fire grates are arranged in a stepwise manner. However, the present invention is not limited to this, and the grate may be arranged horizontally.

In addition, in the equipment shown in FIGS. 1 to 4, two methods are described in which the state of adding urea as a nitrogen compound is a powder state and an aqueous state, but in the present invention, The state of the nitrogen compound at the time of addition is not limited. When a nitrogen compound is added to a bulky waste, it is preferable that the nitrogen compound be added in the form of an aqueous solution and adhered to the waste so as to be added as evenly as possible. When the nitrogen compound is added to the sludge, it is preferable that the nitrogen compound is added in the form of a powder and mixed with the sludge in the sludge feeder so that the water content of the charge is not increased.

(Example 1) Next, the result of incineration of waste by a test facility having the same configuration as the grate incineration facility shown in FIG. 2 will be described. Municipal waste was used as a waste sample, and sewage sludge (moisture 77 wt%, N content 6 wt% (dry basis)) was used as a sludge sample. Urea powder was added to the sludge. And municipal waste 2000kg / H, sewage sludge 200kg / H, urea 1k
g / H was charged and incinerated.

During the incineration under the above conditions, when the concentration of dioxins in the combustion exhaust gas was measured, the average value of the equivalent concentration of 2,3,7,8-TCDD of the dioxins was equivalent to the incineration of municipal solid waste. Was a low value corresponding to about 20% of the value obtained when only the exhaust gas treatment was performed.

As described above, it has been confirmed that the content of dioxins in the combustion exhaust gas is greatly reduced by adding sludge or further adding a nitrogen compound when incinerating waste.

[0050]

According to the present invention, when loading waste into an incinerator, a nitrogen compound is added, or sludge and a nitrogen compound are added, and sludge and the added nitrogen compound are thermally decomposed to obtain dioxins. Therefore, the amount of dioxins generated in the incinerator is reduced, and the content of dioxins in the combustion exhaust gas is significantly reduced.
Further, the waste incineration equipment provided with the apparatus for adding a nitrogen compound makes it possible to add the nitrogen compound to the incinerator to be charged into the incinerator, and the above-mentioned effects are obtained.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a first example according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a second example according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a third example according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a fourth example according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Grate incinerator 11 Waste hopper 12 Combustion chamber 13a Dry stage grate 13b Combustion stage grate 13c Post-combustion stage grate 14 Secondary combustion chamber 15, 26 Exhaust gas treatment process 20 Fluidized bed incinerator 21 Wind box 23 Fluidized bed section 24 Free board 30 Waste feeder 40 Sludge feeder 50 Nitrogen compound adding means 51 Urea aqueous solution storage tank 52 Urea supply pump 53 Urea spray nozzle 60 Nitrogen compound adding means 61 Urea storage tank 62 Urea feeder 70 Waste

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshinari Fujisawa 1-2-2 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) 3K065 AA02 AB01 AC01 AC02 AC20 BA04 BA10 CA04 CA15

Claims (5)

[Claims] A waste incineration method comprising adding a nitrogen compound to waste and charging the waste into an incinerator. 2. A method for charging sludge together with waste into an incinerator and incinerating the waste and / or sludge, wherein a nitrogen compound is added to the waste before charging the sludge. Characteristic waste incineration method. 3. A method for charging sludge together with waste into an incinerator, wherein the nitrogen compound is added to the waste and the sludge put in the waste hopper of the incinerator. Waste incineration method. 4. A waste incineration facility for incinerating sludge together with waste, characterized in that a nitrogen compound addition means for adding a nitrogen compound to waste charged into an incinerator is provided. Facility. 5. A waste incineration facility for incinerating sludge together with waste, wherein a means for adding a nitrogen compound is added to a sludge feeder for charging sludge into an incinerator, wherein the sludge and the nitrogen compound are mixed. Waste incineration equipment characterized by being configured to be charged into an incinerator.