JP2003190911A - Method for treating hardly decomposable material and apparatus therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for treating a hardly decomposable material wherein even the hardly decomposable material contained in incinerated ashes can be detoxified with a high decomposition ratio, and an apparatus therefor. <P>SOLUTION: In the apparatus for treating the hardly decomposable material provided with a means 10 for separating the incinerated ashes from exhaust gas emitted from a combustion apparatus such as an incinerator, a melting furnace and a boiler and a means 14 for detoxifying the separated incinerated ashes 22 by oxidation decomposing in the presence of a hydroxyl radical, the apparatus comprises having a grinding means 12 that grinds while slurrying by supplying water 25 to the incinerated ashes 22 separated and collected by the separating means 10 and a carbon separating means 13a that separates a carbon content 30 from the slurry by carrying out specific gravity difference separation, introducing the slurry from which the carbon content is removed to the decomposing means 14, and returning the separated carbon content to the combustion apparatus. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an incinerator, a melting furnace,
Concerning the treatment of hard-to-decompose substances such as dioxins contained in incinerated ash such as main ash, fly ash, boiler-collected ash, and dust-collected ash discharged from a combustion device such as a boiler. The present invention relates to a method and an apparatus for treating a hardly decomposable substance that oxidatively decomposes incinerated ash to render it harmless.

[0002]

2. Description of the Related Art Incineration ash discharged from boilers, incinerators, melting furnaces, etc., contains harmful substances such as sulfur oxides, nitrogen oxides, hydrogen chloride, heavy metals, dioxins, etc. Is included. Among them, persistent substances such as dioxins are highly toxic and have toxicity such as carcinogenicity and teratogenicity, and thus their emission has been regulated by strict environmental standards in recent years. The dioxins include polychlorinated dibenzofuran (PCDF) and polychlorinated dibenzo-.
It refers to an organic chlorine compound such as para-dioxin (PCDD), which is unintentionally produced in the process of burning an organic compound under the condition that chlorine coexists.

Further, the above-mentioned organic chlorine compounds such as dioxins and PCBs are chemically stable and hardly decomposable substances, and are precursors such as chlorobenzene in a temperature range of about 250 to 350 ° C. in an incinerator and a melting furnace. May be resynthesized by contact with incineration ash or the like, or by contacting the unburned carbon with inorganic chlorine, air, water or the like using unburned carbon as a starting material. As a method for suppressing the emission of the hardly decomposable substance, in the combustion process, combustion control is performed to improve the combustion state and prevent re-synthesis of the hardly decomposable substance in the temperature range, and further in the temperature range for decomposable substance decomposition. Reburning and the like can be mentioned, but it is difficult to eliminate the generation of hardly decomposable substances by these methods.

Therefore, as a method of treating incineration ash containing a hardly decomposable substance, a melting method, a gas phase hydrogen reduction method, a reduction heating dechlorination method, a supercritical hydroxylation decomposition method, a metal sodium dispersion method, a photochemical decomposition method, There are various methods such as oxidative decomposition method, but among them, the oxidative decomposition method using a hydroxy radical having a strong oxidizing power is considered to be a cost effective method because of its high efficiency of removing hardly decomposable substances. To be As a technique using such a system, Japanese Patent Laid-Open No. 2001-1
37803 is a mixture of incineration ash containing a hardly decomposable substance with water to form a slurry, and at the same time as or after slurrying in an acidic state, the above-mentioned difficulty in the neutral to alkaline state and in the presence of hydroxy radicals. We propose a method to oxidize and decompose degradable substances.

Furthermore, the present inventors have proposed a processing method as shown in FIG. 4 in Japanese Patent Application No. 2001-72826 (unknown) as an invention that further develops the above technique. In this treatment method, incineration ash 04 containing a hardly decomposable substance discharged from an incinerator and waste water 05 are mixed in a fly ash dissolution tank 01 to form a slurry, and an acid 07 is added in a pretreatment tank 010.
Was added to deposit a hardly decomposable substance on the surface of the incineration ash, and then alkali 08 was added to make the reaction tank 02 an alkaline state. Hydrogen peroxide 06 and a hydroxy radical generated by ozone from the ozone generator 03 were added to the reaction tank 02. In the presence thereof, the incineration ash is rendered harmless by oxidatively decomposing the hardly decomposable substance. However, in such a method, although the hard-to-decompose substance deposited on the surface of the incinerated ash can be easily decomposed, the hard-to-decompose substance existing inside the incinerator ash takes a long time to decompose and is very difficult. is there.

On the other hand, there is a method of detoxifying carbon by separating carbon content having a high abundance of hardly decomposable substances from incineration ash.
001-173937. As shown in FIG. 3, in this treatment, the pyrolysis gas discharged from the fluidized bed furnace 103 is burned in the melting furnace 104, and the combustion gas is cooled by the waste heat boiler 110 and the gas cooler 111, and then the bag filter 112. Fly ash is separated by a denitration device 11
Send to 4. Then, the separated fly ash is further separated by a separation device 116 by flotation separation or electrostatic separation to separate the carbon component A, and the separated carbon component A is returned to the fluidized bed furnace 103 or the melting furnace 104.

Further, in Japanese Patent Laid-Open No. 11-193919,
Gas produced by gasifying a solid combustible material containing chlorine in a gasification furnace is separated into unburned carbon and unburned gas, and the separated unburned gas is burned in a fluidized bed boiler. A method for contacting flue gas and the unburned carbon to adsorb dioxin in the flue gas to unburned carbon, and burning the adsorbed ignitable carbon in the fluidized bed boiler to thermally decompose the dioxin. Is proposed.

[0008]

However, in the above-mentioned prior art in which unburned carbon is separated and returned to the combustor, it is difficult to reliably separate it due to the difference in particle size of incinerated ash, and incineration. Since the carbon content contained in the ash is difficult to separate, there is a high possibility that the persistent ash will be mixed in the discharged ash. Further, in the conventional technique described in the above-mentioned JP-A-11-193919, the entire apparatus is large, the installation cost increases, and the installation place is limited. In addition, JP 2001
-173937 treats the fly ash contained in the exhaust gas from the waste heat boiler, but the fly ash contained in the exhaust gas from the waste heat boiler has a low content of persistent substances and is contained in the molten slag. There is a fear that it will be discharged to the outside of the system.

Further, in these methods, unburned carbon is merely burned again, and even if the concentration of the hardly decomposable substance is once reduced, it may be resynthesized during cooling. , It is impossible to eliminate almost no emission of persistent substances only by these methods. In view of the problems of the prior art, the present invention decomposes and removes not only the hardly decomposable substance existing near the surface of the incineration ash but also the hardly decomposable substance contained in the incineration ash with a high decomposition rate. It is an object of the present invention to provide a method for treating a hardly decomposable substance and a device therefor.

[0010]

SUMMARY OF THE INVENTION In order to solve the above problems, the invention according to claim 1 is contained in incineration ash discharged from a combustion device such as an incinerator, a melting furnace or a boiler. In the method for treating a hardly decomposable substance, which oxidizes and decomposes a hardly decomposable substance in the presence of hydroxy radicals, the incineration ash is mixed with water and slurried to be pulverized, and carbon in the pulverized slurry is used. After separating at least a part of the slurry, the hard-decomposable substance contained in the slurry is oxidatively decomposed while vigorously stirring the slurry, and the carbon content separated from the slurry is returned to the combustion device. And

Further, the invention according to claim 2 detoxifies the hardly decomposable substance contained in the incineration ash discharged from the combustion device such as the incinerator, the melting furnace, and the boiler by oxidizing and decomposing it in the presence of hydroxy radicals. In the method for treating a hardly decomposable substance, the incinerated ash is crushed, and at least a part of carbon in the crushed incinerated ash is separated, and then water is added to the incinerated ash to form a slurry and with strong stirring. It is characterized in that the hardly decomposable substance contained in the slurry is oxidatively decomposed, and the carbon content separated from the incineration ash is returned to the combustion device.

According to this invention, by crushing the incinerated ash, the carbon content existing in the same particle and the incinerated ash are separated, and the separation efficiency in the subsequent carbon separation treatment is improved. In addition, the persistent substances that remain in the incineration ash are decomposed and rendered harmless by the strong oxidizing power of hydroxy radicals.
Almost no persistent substances can be emitted. Further, in the invention according to claim 1, since the steps after the crushing treatment are carried out by a wet method, the treatment can be carried out at room temperature, and there is no concern about the contamination of the hardly decomposable substance due to the scattering of incinerated ash or dust. In the invention according to claim 2, since the carbon content recovered by the carbon separation treatment is in a dry state, it does not cause a local temperature drop or the like even when introduced into the combustion device,
It does not become a factor in the generation of new persistent substances. Further, since the decomposition treatment of the hardly decomposable substance in the incineration ash is carried out by a wet method, there is no concern about the contamination of the hardly decomposable substance due to the scattering of the incineration ash or dust.

The carbon separation according to claim 1 or 2 is characterized in that the carbon separation is performed by specific gravity difference separation or electrostatic separation. In the specific gravity difference separation, separation is possible because the specific gravity of carbon content is smaller than water and the specific gravity of incineration ash is larger than water, and in the electrostatic separation, separation is possible because carbon content has good conductivity. Therefore, according to this method, the carbon content can be easily and surely separated from the incinerated ash.

The invention according to claims 4 to 6 is an invention relating to a treatment device for hardly decomposable substances, and the invention according to claim 4 is contained in incineration ash discharged from a combustion device such as an incinerator, a melting furnace or a boiler. In a treatment device for a hardly decomposable substance, which comprises a decomposing means for oxidatively decomposing a hardly decomposable substance in the presence of hydroxy radicals, pulverizing means for pulverizing while inducing slurry by supplying water to the incinerated ash, and from the slurry And a carbon separation means for separating at least a part of carbon content,
It is characterized by comprising an introduction path for guiding the slurry from which the carbon content has been separated to the decomposition means, and a return path for returning the separated carbon content to the combustion device.

Further, the invention according to claim 5 is a decomposing means for oxidatively decomposing a hardly decomposable substance contained in incineration ash discharged from a combustion device such as an incinerator, a melting furnace or a boiler in the presence of hydroxy radicals. In the apparatus for treating hardly decomposable substances, the ash means for crushing the incinerated ash and the carbon separating means for separating at least a part of carbon content from the crushed incinerated ash are provided, and the carbon content is separated. An introductory path for guiding the incinerated ash together with water to the decomposition means and a return path for returning the separated carbon content to the combustion device are provided.

Further, as described in claim 6, it is preferable that the carbon separating means is a specific gravity difference separator or an electrostatic separator. According to these inventions, it is possible to obtain the same effects as those of the inventions according to claims 1 to 3.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be exemplarily described in detail below with reference to the drawings. However, the dimensions, materials, shapes, relative positions, etc. of the components described in this embodiment are not intended to limit the scope of the present invention thereto unless specifically stated otherwise, and are merely illustrative examples. Not too much. In the present embodiment, the object to be treated is fly ash discharged from the incinerator, but the main ash discharged from a combustion device such as a boiler, an incinerator, or a melting furnace, fly ash, boiler recovered ash, and dust ash incinerated. Any ash can be treated. FIG. 1 is an overall schematic configuration diagram of an apparatus for treating a persistent substance according to a first embodiment of the present invention, and FIG. 2 is an overall schematic configuration diagram of a second embodiment which is another embodiment.

In FIGS. 1 and 2, reference numeral 10 denotes exhaust gas 20.
The bag filter for separating the fly ash 22 from the exhaust gas may be any device capable of solid-gas separation such as an electrostatic precipitator or a multi cyclone. Reference numeral 11 is a scrubber for spraying makeup water 24 to remove soot dust and acid gas in the exhaust gas. Even if the makeup water 24 contains an alkaline agent to treat the acid gas in the exhaust gas with a high removal rate. Good. Reference numeral 14 is a decomposition tank equipped with a strong stirring means 18 and a hydroxy radical generating means such as a diffusion hole for ozone 28 and a supply hole for hydrogen peroxide 26, and 12 is a crusher for crushing the fly ash.

The crusher 12 is, for example, a high-speed rotary impact crusher such as a disc mill or a pin mill, a roller mill, a ball mill, a stirring type crusher, a jet mill, a colloid mill, a disperser, and a mixer. Machines, etc. can also be used to disperse and mix the incinerated ash to a predetermined particle size, but especially fly ash and balls are inserted into a high-hardness container and rotated by a motor. A ball mill in which the fly ash collides with the balls, the wall of the container, and the fly ash to crush the incinerated ash in a short time by vibrating is preferable, and a rolling ball mill, a vibrating ball mill, a planetary ball mill, or the like is suitable. . It should be noted that these devices may be of batch type, continuous type, or semi-batch type.

Explaining the treatment process in the first embodiment shown in FIG. 1, first, the exhaust gas 20 discharged from a combustor such as an incinerator, a melting furnace, or a boiler is sprayed with slaked lime 21 at an exhaust gas flue to be discharged. After the harmful substances such as the acidic gas therein are removed, it is guided to the bag filter 10 and is solid-gas separated into fly ash, 22 and exhaust gas by the bag filter 10. The separated exhaust gas is sprayed with makeup water 24 by the scrubber 11 to remove residual acidic gas and harmful substances such as hardly decomposable substances, and is discharged as exhaust gas 23.

On the other hand, the separated fly ash 22 is crushed by the crusher 1.
It is mixed with the scrubber wastewater 25 from the scrubber 11 that is introduced into the crusher 12 and supplied to the crusher 12, slurried and crushed, and then fed to the carbon separator 13a in the subsequent stage. Here, the fly ash 22 may be pulverized to a particle size of about 10 μm or less, preferably about 5 μm or less, whereby carbon separation, which will be described later, can be efficiently performed. The carbon separator 13a has a structure capable of separating the carbon content by using a specific gravity difference separation, and the slurry introduced into the carbon separator 13a is retained for a predetermined time and the carbon content floated up is not shown in the scraper. The carbon content 30 scraped and collected is returned to the incinerator. The carbon separator 13a is not limited to the above-described specific gravity separation, and may be any device capable of separating the carbon content and the fly ash, such as flotation sorting utilizing the difference in wettability of the solid particle surface. .

The carbon content 30 returned to the incinerator is burned again in the incinerator so that the hardly decomposable substance contained in the carbon content is decomposed and rendered harmless. Then, the slurry from which the carbon content has been separated is introduced into the decomposition tank 14, and the hard-to-decompose substance contained in the slurry in the presence of the hydroxy radicals generated by the hydrogen peroxide 26 and the ozone 28 while being strongly stirred by the stirrer 18. Is oxidatively decomposed.

In this embodiment, hydrogen peroxide 26 and ozone 28 are used as the hydroxyl radical generating means.
However, it is not particularly limited as long as it is a means for generating hydroxy radicals, and for example, a reaction between hydrogen peroxide and ozone can be performed by using at least two of hydrogen peroxide, ozone, a catalyst, a photocatalyst or ultraviolet irradiation. , Ozone oxidation at high pH, ozone oxidation under UV irradiation, UV irradiation in the presence of hydrogen peroxide, UV irradiation in the presence of hypochlorite, photooxidation in the presence of photocatalyst, by Fenton's reagent Hydroxyl radicals can be generated by oxidation or the like. In particular, ozone oxidation in the coexistence of hydrogen peroxide or ozone oxidation under high pH is preferable because it is difficult for ultraviolet rays to pass through the incinerated ash made into a slurry.
Of course, it is not limited to this, and decomposition treatment by a single oxidizing action of hydrogen peroxide, ozone or the like is also possible.

At this time, it is preferable that the decomposition tank 14 is in an alkaline state, whereby the generation efficiency of hydroxy radicals is improved. The slurry that has been subjected to the oxidative decomposition treatment is drained after the hard-to-decompose substance is sufficiently removed.
It may be returned to the makeup water 24 after solid-liquid separation as 7, or may be discharged to the outside of the system after being guided to equipment for treating other harmful substances and treated. According to this invention,
It is possible to reduce the hardly decomposable substance by selectively separating the carbon content including unburned carbon having a high content rate of the hardly decomposable substance, returning it to the combustion device, and reburning it.

Further, since the fly ash is crushed into fine particles and then the carbon is separated, the carbon content and fly ash existing in the same particle are separated, and the carbon separation efficiency is improved. Further, since the hardly decomposable substance existing in the remaining fly ash is decomposed and rendered harmless by the hydroxy radical, the emission of the hardly decomposable substance to the outside of the system can be greatly reduced.
Further, in such an embodiment, since all the treatments after the crusher 12 are carried out by a wet method, there is no concern about contamination of the hardly decomposable substance due to fly ash or dust scattering.

The second embodiment shown in FIG. 2 is the same as the first embodiment.
As in the embodiment, the exhaust gas separated by the bag filter 10 is washed by the scrubber 11 and discharged as the exhaust gas 23 to the outside of the system. On the other hand, the fly ash 22 separated and collected is the crusher 1
Introduced into No. 2 and subjected to dry pulverization. Similar to the first embodiment, the crushing may be performed to about 10 μm or less, preferably about 5 μm or less, and the crushed fly ash is guided to the electrostatic separator 13b.

The electrostatic separator 13b has a structure for separating carbon by electrostatic screening, and the electrostatic screening may be performed by any of electrostatic type, corona discharge type, combination type of both types, and friction charging type. Is also good. A drum type electrostatic type (not shown) is preferable
This method is provided with a rod-shaped high-voltage electrode parallel to the rotating cylindrical grounding roll, an electrostatic field is formed between the two, and conductive carbon is transferred from the grounding roll to the high-voltage electrode side. The fly-out and fly ash are free-falled or adhered to the grounding roll as they are, and when they fly out of the electrolysis by rotation, they are dropped from the roll to separate them.

The fly ash from which the carbon content has been removed in this way is supplied with the scrubber wastewater 25 from the scrubber 11 and guided to the decomposition tank 14, where it is mixed and slurried and stirred by the stirrer 18. The hard-to-decompose substance in the slurry is decomposed and rendered harmless in the presence of the hydroxy radicals while vigorously stirring. According to such an embodiment, since the carbon content discharged from the carbon separator 13b is in a dry state, a local temperature decrease does not occur even when the carbon content is put into an incinerator, and a new factor of generation of a hardly decomposable substance. There is no fear of becoming. further,
Since the hardly decomposable substance in the fly ash is oxidatively decomposed by the wet method, there is no concern about the contamination of the hardly decomposable substance due to fly ash or dust scattering.

[0029]

As described above, according to the present invention, by crushing the incinerated ash discharged from the combustion device, the carbon content present in the same particle and the incinerated ash are separated, and the carbon separation treatment in the latter stage is performed. The separation efficiency at Further, since the persistent substance that remains in the fly ash is decomposed and rendered harmless by the strong oxidizing power of the hydroxy radical, the amount of the persistent substance that is discharged can be greatly reduced. Further, according to the invention described in claim 1, since the steps after the crushing treatment are carried out by a wet method, the treatment can be carried out at room temperature, and there is no concern about the contamination of the hardly decomposable substance due to the scattering of incinerated ash or dust. Further, according to the second aspect of the present invention, since the carbon content recovered by the carbon separation treatment is in a dry state, it does not cause a local temperature drop or the like even if it is introduced into the combustion device, and a new problem is caused. It does not become a factor in the generation of degradable substances. Further, since the decomposition treatment of the hardly decomposable substance in the incineration ash is carried out by a wet method, there is no concern about the contamination of the hardly decomposable substance due to the scattering of the incineration ash or dust.

[Brief description of drawings]

FIG. 1 is an overall schematic configuration diagram of an apparatus for treating a persistent substance according to a first embodiment of the present invention.

FIG. 2 is an overall schematic configuration diagram of a second embodiment which is another embodiment of FIG.

FIG. 3 is an explanatory diagram showing a configuration of a conventional waste treatment facility.

FIG. 4 is an overall schematic configuration diagram showing a conventional treatment device for a hardly decomposable substance.

[Explanation of symbols]

10 Bug filter 11 scrubber 12 crusher 13a Carbon separator (specific gravity difference separator) 13b Carbon separator (electrostatic separator) 14 Decomposition tank 18 stirrer 25 scrubber drainage 26 Hydrogen peroxide 28 Ozone 30 carbon

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F23G 5/033 F23J 1/00 A 7/00 103 B09B 3/00 304G F23J 1/00 ZAB (72) Invention Yusuke Kawasaki 1-8-1 Sachiura, Kanazawa-ku, Yokohama-shi 1 Mitsubishi Heavy Industries, Ltd. Yokohama Research Laboratory (72) Inventor Kotoshi Kose 1-8, Sukiura, Kanazawa-ku, Yokohama Mitsubishi Heavy Industries Ltd. ) 2E191 BA12 BC01 BD11 3K061 AA24 AB01 AC03 BA05 DA02 NA01 NA02 NA05 NA13 3K065 AA24 AB01 AC03 BA05 CA01 CA02 4D004 AA36 AB07 AC04 CA09 CA10 CA13 CA15 CA35 CA36 CB02 CB13 CB26 CC01 CC11 4H006 AA04 BD84 AC13 AC84 BD84 AC13

Claims (6)

[Claims] 1. A method for treating a hardly decomposable substance, which oxidizes and decomposes a hardly decomposable substance contained in incinerator ash discharged from a combustion device such as an incinerator, a melting furnace, or a boiler in the presence of hydroxy radicals. In, in the incineration ash is mixed with water and slurried to pulverize,
After separating at least a part of the carbon content in the crushed slurry, the hard-decomposable substance contained in the slurry is oxidatively decomposed while vigorously stirring the slurry, and the carbon content separated from the slurry is A method for treating a hardly decomposable substance, characterized in that the substance is returned to the combustion device. 2. A method for treating a hardly decomposable substance, which oxidizes and decomposes a hardly decomposable substance contained in incinerator ash discharged from a combustion device such as an incinerator, a melting furnace, or a boiler in the presence of hydroxy radicals. In the above, after the incinerated ash is crushed and at least a part of carbon content in the crushed incinerated ash is separated, water is added to the incinerated ash to make a slurry and the hard decomposition is contained in the slurry while vigorously stirring. A method for treating a hardly decomposable substance, which comprises oxidizing and decomposing a volatile substance and returning the carbon content separated from the incinerated ash to the combustion device. 3. The method for treating a hardly decomposable substance according to claim 1, wherein the carbon separation is performed by specific gravity difference separation or electrostatic separation. 4. Treatment of a hardly decomposable substance comprising a decomposing means for oxidatively decomposing a hardly decomposable substance contained in incinerator ash discharged from a combustion device such as an incinerator, a melting furnace or a boiler in the presence of hydroxy radicals. In the apparatus, crushing means for supplying water to the incinerated ash and crushing while making it into a slurry, and carbon separating means for separating at least a part of carbon content from the slurry are provided, and the slurry separating the carbon content is decomposed. An apparatus for treating a hardly decomposable substance, comprising: an introduction path leading to the means; and a return path for returning the separated carbon content to the combustion device. 5. A decomposable substance comprising a decomposing means for oxidatively decomposing a decomposable substance contained in incinerator ash discharged from a combustion device such as an incinerator, a melting furnace or a boiler in the presence of hydroxy radicals. In the processing device, a crushing unit for crushing the incinerated ash and a carbon separating unit for separating at least a part of carbon content from the crushed incinerated ash are provided, and the incinerated ash in which the carbon content is separated is decomposed together with water. An apparatus for treating a hardly decomposable substance, comprising: an introduction path leading to the means; and a return path for returning the separated carbon content to the combustion device. 6. The treatment device for a hardly decomposable substance according to claim 4 or 5, wherein the carbon separation means is a specific gravity difference separator or an electrostatic separator.