JP2002153834A - Treatment method and treatment equipment for making ash and soil pollution-free - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a treatment method and treatment equipment for making ash and soil pollution-free which make hazardous materials, such as dioxins included in the ash and soil pollution-free by cracking the same. SOLUTION: This equipment is provided with an overheating means (heater) 14 which consists of a cylindrical electrode 12 and a wire electrode 13 disposed in the cylindrical electrode 12 and overheats the inside of the cylindrical electrode 12 from its outer periphery by setting the cylindrical electrode 12 as a negative pole and the wire electrode 13 as a positive pole and a pulse power source 15 which impresses pulse voltages between both electrodes 12 and 13. The dioxins precursors are expelled while the dioxins precursors in the ash pores are put into a gaseous state by heating with the heater 14 and the expelled dioxins precursor materials and the precursor materials and dioxins existing on the surface side of the ash and soil are subjected to plasma cracking and the dioxins remaining within the pores of the ash and soil are subjected to plasma cracking.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for detoxifying ash and soil. In the present invention, a radical is generated by plasma caused by discharge, and the radical and by-product ozone are used to generate radicals.
It decomposes harmful substances (such as dioxins) contained in ash and soil to make them harmless. In this specification,
The term “ash / soil” is used as a concept including ash, soil, various powders, granules, solids, and solid substances.

[0002]

2. Description of the Related Art Ashes and exhaust gases are discharged from various incinerators such as municipal waste incinerators, industrial waste incinerators, and sludge incinerators, pyrolysis furnaces, and melting furnaces. If such ash or exhaust gas contains harmful substances, it is necessary to detoxify such harmful substances.

[0003] In addition, harmful substances may be contained in exhaust gas discharged from old incinerators and the like, in which case, nearby soil was contaminated with harmful substances. It is also desired to make such contaminated soil harmless.

The harmful substances to which the present invention is applied include halogenated aromatic compounds such as dioxin, highly condensed aromatic hydrocarbons, environmental hormones, nitrogen oxides and sulfur oxides.

In order to detoxify ash and soil containing harmful substances, various kinds of powders, granules, solids and solid substances (hereinafter referred to as "ash / soil"), conventionally, Incineration method, high temperature pyrolysis method, solar radiation decomposition method, thermal desorption decomposition method,
A chemical decomposition method, a photo decomposition method, a microbial decomposition method and the like are known. Among these various treatment methods, the incineration treatment method is currently in practical use.

In this incineration method, ash containing harmful substances
The soil is incinerated in a rotary kiln incinerator, and the ash and soil are incinerated (about 900 ° C) to decompose the ash and harmful substances contained in the soil. Exhaust gas generated during incineration of ash and soil is reburned by an afterburner to detoxify harmful substances contained in the exhaust gas.

[0007]

By the way, in the conventional incineration method, the detoxification treatment requires a lot of trouble and time, and is expensive. Further, other conventional methods have not been put to practical use even though they have an effect in principle.

[0008] In view of the above prior art, the present invention detoxifies ash and soil by decomposing harmful substances such as dioxin contained in ash and soil by a novel technique (principle) that has not been used before. An object of the present invention is to provide a processing method and a detoxification processing apparatus.

An object of the present invention is to reduce dioxin to an environmental standard (soil) of 1000 pg / g or less, and in principle can reduce it to 1 pg / g or less. The decomposition rate of dioxin in ash and soil can be expected to be 99% or more.

[0010]

Means for Solving the Problems A first method for solving the above problems is described below.
The invention of a method for detoxifying ash and soil is a method for detoxifying ash and soil in which ash and soil containing harmful substances are put into a plasma reactor and the harmful substances are detoxified by plasma decomposition. The dioxin precursor present in the pores of the ash / soil is expelled from the pores of the ash / soil while being in a gaseous state, and the ejected dioxin precursor is removed from the surface of the ash / soil. The present invention is characterized in that the existing precursor substance and dioxins are plasma-decomposed, and the dioxins remaining in the pores of the ash / soil are plasma-decomposed.

[0011] The second invention is the first invention, wherein the ash
The method is characterized in that the soil is heated to 140 ° C. or higher and the dioxin precursor substance is expelled from the pores.

According to a third aspect of the present invention, in the first aspect, during the heating, a nitrogen gas is supplied into and exhausted from the plasma reaction vessel, and the vessel is heated in an N ₂ atmosphere. The dioxin precursor substance expelled from the pores is discharged to the outside of the reaction vessel along with the N ₂ gas, and then the plasma decomposition is performed while replacing the inside of the vessel from a nitrogen gas atmosphere to an oxygen-containing atmosphere. Features.

According to a fourth aspect, in the first aspect, the ash / soil is continuously or intermittently placed in the reaction vessel.

The fifth invention of the ash / soil detoxification apparatus comprises a reaction vessel having a positive electrode and a negative electrode to which a high-voltage pulse voltage having a very short pulse width is applied; Heating means for heating the soil, the ash / soil containing harmful substances is put in the reaction vessel, and after heating the inside of the reaction vessel to 140 ° C. or more, the positive electrode and the negative electrode Radicals are generated by plasma generated by a discharge generated between the electrodes, and the harmful substances are decomposed by the radicals.

In a sixth aspect based on the fifth aspect, the reaction vessel comprises a cylindrical electrode and a linear or rod-shaped electrode disposed in an internal space of the cylindrical electrode. A high-voltage pulse voltage having an extremely short pulse width is applied to the rod-shaped electrode and the cylindrical electrode.

According to a seventh aspect, in the fifth or sixth aspect,
A gas supply means for supplying nitrogen gas and / or air to the reaction vessel and a gas discharge means for discharging gas in the vessel are provided. When the heating is performed, nitrogen gas is supplied into the plasma reaction vessel. Gaseous dioxin precursor material expelled from the pores by heating to a gas atmosphere, and discharge the gaseous dioxin precursor substance to the outside of the reaction vessel by gas discharge means, and then replace the nitrogen gas atmosphere with an oxygen-containing atmosphere. It is characterized in that it is plasma-decomposed while performing.

An eighth invention of a ash / soil detoxification system is a dust removing means for removing fly ash from exhaust gas discharged from various incinerators such as a municipal garbage incinerator, an industrial waste incinerator and a sludge incinerator. And the ash / soil detoxifying apparatus according to any one of claims 5 to 7, which decomposes dioxins in fly ash removed from the dust removing means.

In a ninth aspect based on the eighth aspect, the dust removing means comprises a plurality of bag filters, and the dust removed from each of the bag filters is removed from the ash / dust according to any one of claims 5 to 7.
It is characterized in that it is supplied into a container of a soil detoxification apparatus and detoxified.

According to a tenth aspect, in the eighth or ninth aspect, an ozone treatment tank for ozone treating fly ash after the plasma treatment is provided on the downstream side of the ash / soil detoxification apparatus. Features.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings, but the present invention is not limited thereto. In the following description, dioxin will be described as an example of a harmful substance, but other harmful substances are similarly detoxified. Although ash is described as an example of ash and soil, soil and the like other than ash are similarly detoxified.

[First Embodiment] FIG. 1 shows a plasma reactor for a method for detoxifying ash and soil according to the present embodiment. FIG. 1 is a schematic diagram showing an example of a plasma decomposition processing apparatus 11 according to the present embodiment, in which a line (+ pole)
It is an example of a cylindrical (-pole) plasma processing vessel (reaction vessel). As shown in FIG. 1, a plasma decomposition apparatus 11 according to the present embodiment includes a cylindrical electrode 12 and a cylindrical electrode 12.
The cylindrical electrode 1 comprises a wire electrode 13 disposed therein.
2 is a negative electrode (-), the line electrode 13 is a positive electrode (+), and a heating means (heater) 14 for heating the inside from the outer periphery of the cylindrical electrode 12 and a pulse voltage is applied between the electrodes 12 and 13. It is provided with a pulse power supply 15 to be applied. In the present embodiment, the cylindrical electrode 12 also serves as a reaction vessel. Then, the ash / soil 16 is injected into the cylindrical electrode 12 from the outside, and thereafter, harmful substances in the ash / soil 16 input by the plasma discharge generated by pulse application are decomposed by the plasma streamer discharge.

In the present invention, ash 16 containing a harmful substance is put inside the cylindrical electrode 12 of the reaction vessel. Then, a high-voltage pulse voltage having a very short pulse width (for example, a pulse width of several tens ns) is applied between the positive electrode and the negative electrode to generate a streamer discharge between the positive and negative electrodes. The discharge develops in the space between the ash particles. At this time, if the distance d between the positive and negative electrodes is set to be about 50 cm to 100 cm, the streamer discharge is likely to occur in combination with the shortening of the applied voltage.

This discharge causes plasma (electrons and ions)
Occurs. Among the generated electrons, electrons having high energy (10 eV or more) collide with gas molecules existing in the space between the ash particles to generate radicals. As radicals, oxygen radicals (O.), nitrogen radicals (N
.), Hydroxyl radical (OH.), Hydrogen radical (H
・) Etc.

Such radicals decompose harmful substances contained in the ash by radical chemical reaction to render them harmless. Also, ozone oxygen radicals (O ·) is combined with oxygen molecules (O ₃₎ is generated at the same time, the ozone (O ₃₎
Also contribute to dioxin decomposition. Although the probability of occurrence is low, electrons may collide directly with dioxin to dissociate (decompose) dioxin and render it harmless.

Since streamer discharge generates many electrons having high energy (10 eV or more), the pulse width and the distance between electrodes are devised so as to increase the rate of occurrence of streamer discharge. In particular,
Ideally, the time during which the discharge causes a short circuit between the positive electrode and the negative electrode is the pulse width. However, if the pulse width is longer than that, the energy consumption is only slightly increased. If such high-energy electrons are generated, a large amount of radicals and ozone can be generated, and the detoxification processing (decomposition processing) is efficiently performed.

Also, since the pulse width is shortened, heavy ions hardly move even if light electrons move. Since there is almost no movement of ions as described above, almost no vibrational heat is generated due to the movement of ions, and heat loss can be reduced and efficiency can be increased.

The principle of plasma decomposition of one of the harmful substances to be treated in the present invention, dioxins, is not clear at present, but an example of its decomposition mechanism will be described with reference to the following "Chemical Formula 1". First, streamer discharge plasma is generated in the above-mentioned plasma decomposition apparatus. That is, from the line electrode (+) 13 to the cylindrical electrode (−)
The streamer discharge plasma generated toward 12 causes physical collisions of high-energy electrons in the plasma to dissociate ether bonds of dioxins, which are harmful substances, or break benzene rings. In addition, high-energy electrons directly collide with dioxins, and the impact decomposes ether bonds and benzene rings of dioxins. In addition, the streamer discharge decomposes moisture and N ₂ and O ₂ in the air to form hydroxyl radicals (O 2).
H.), nitrogen radical (N.), oxygen radical (O.)
Activated substances such as are generated, and harmful substances in the exhaust gas are decomposed by these various radicals.

[0028]

Embedded image

In the present invention, since the superheating means 14 is provided, the dioxin precursor present in the pores of the ash / soil is expelled from the pores of the ash / soil while being converted to a gaseous state. Dioxin precursors,
Precursor substances and dioxins existing on the surface side of the ash / soil are decomposed by plasma, and dioxins remaining in the pores of the ash / soil are decomposed by plasma.

That is, as shown in FIG. 2, in the initial state, dioxins (×) are present in the pores 21 of ash / soil (hereinafter referred to as “ash”) and near the surface 22 thereof.
23 and a dioxin precursor (▲) 24 are present. Next, 140-
When heated to 200 ° C., the internal ash skeleton 20 is overheated, and the dioxin precursor 24
Only the gaseous state will be expelled. At this time, since the dioxins 23 are not vaporized, the pores 2
It remains in 1.

This is because dichlorobenzene, one of the dioxin precursors, is vaporized in the range of 140 to 200 ° C. as shown in FIG. 3 which shows the relationship between the vapor pressure of dioxins and dioxin precursors and temperature. However, dioxins (eg, T ₄ CCFs, P ₅ CDFs, H ₆
CCFs, H ₇ CCFs, O ₈ CCFs, etc.) do not vaporize at all in the temperature range. The dioxin precursor refers to benzene, chlorobenzene, dilobenzene, phenol, chlorophenol, and the like, but is not limited thereto.

Here, a case in which harmful substances in ash (average particle size: several tens of microns) are subjected to plasma decomposition treatment in a nitrogen atmosphere without overheating the ash will be described with reference to FIG. As shown in FIG. 4, the initial state is the same as that of FIG. 2, but N radicals are generated near the surface 22 of the ash skeleton 20 immediately after the application of the plasma in the nitrogen atmosphere. The dioxins 23 and the precursor 24 on the ash surface 22 are decomposed by the action of the generated N radicals. However, the life of the N radicals is short inside the ash pores 21, and it is difficult to reach the inside. Rate is low (32%). This is a factor that makes it impossible to improve the decomposition rate of the entire ash having a particularly large particle diameter.

FIG. 5 shows a case where a plasma decomposition treatment is performed in an atmosphere of air (N ₂ + O ₂ ) without overheating the ash.
This will be described with reference to FIG. As shown in FIG. 5, the initial state is the same as FIG. 2, but immediately after the application of the plasma in the air atmosphere, N radicals, O radicals, and ozone (O ₃ ) are generated near the surface 22 of the ash skeleton 20, The N radical and O
Ash surface 22 by the action of radicals and ozone (O ₃ )
Dioxins 23 and precursor 24 are decomposed. On the other hand, in the ash fine pores 21, the life of N radicals is short, so that the ash hardly reaches the inside of the fine pores 21 and is not decomposed. On the other hand, since O ₃ has a long life, it reaches the inside of the pores 21, and simultaneously with the decomposition of the dioxins 23, the precursor 24
May be resynthesized into dioxins 23.

For this reason, the decomposition method in which dioxins can be decomposed on the surface 22 and the inside of the pores 21 of the ash skeleton 20 and do not resynthesize into dioxins, as described above, first, the ash is overheated. Then, only the dioxin precursor 24 is expelled from the inside of the ash pores 21, and this is decomposed into plasma, whereby the detoxification treatment can be performed.

That is, in the case shown in FIG.
Since the precursor 24 is expelled from the inside of the pores 0, even if ozone (O ₃ ) generated by plasma decomposition exists in the pores 21, the precursor is not resynthesized by the action of the ozone, and the pores 2
Only the solid dioxins 23 remaining in 1 are decomposed.

The present invention is not limited to an air atmosphere, and may be a steam atmosphere or an oxygen atmosphere. In this case, when the oxygen is 100%, no N radical is generated.

In addition, the overheating treatment and the plasma decomposition treatment may not be performed continuously, but may be performed simultaneously.

Further, the plasma application atmosphere may be a nitrogen atmosphere other than the air atmosphere. An example of the plasma decomposition process in this nitrogen atmosphere will be described below.

[Second Embodiment] FIG. 6 shows a plasma reactor for a method for detoxifying ash and soil according to this embodiment. FIG. 6 is a schematic diagram showing another example of the plasma decomposition processing apparatus 11 according to the present embodiment, which has the same configuration as the apparatus of FIG.
N ₂ gas supply means 3 for supplying nitrogen gas from outside to the inside 2
1 and N ₂ gas discharging means 32 for discharging nitrogen gas inside
When, it is provided and the O ₂ gas supply means 33 for supplying an O ₂ gas therein. The process of performing a plasma decomposition process using this apparatus will be described with reference to FIG.

That is, as shown in FIG. 7, the initial state is the same as that of FIG. 2, and the inside of the pore 21 of the ash / soil (hereinafter, ash is described as an example) and the vicinity of its surface 22 are shown. , A dioxin (x) 23 and a dioxin precursor (▲) 24 are present. Next, nitrogen (N ₂ ) gas is introduced from outside through gas supply means 31. Thereafter, the inside of the cylindrical electrode 12 is heated to 140 to
When heating to 200 ° C., the ash skeleton 20 of the ash filled in the container is overheated, and only the dioxin precursor 24 is expelled from the inside of the pores 21 in a gaseous state. This expelled precursor 24 is accompanied by the discharge of nitrogen gas,
The gas is discharged to the outside of the cylindrical electrode 12 by the gas discharging means.

Next, while applying plasma, O ₂ or air or water vapor is supplied into the inside from the O ₂ supply means from the outside to generate N radicals, O radicals, and ozone (O ₃ ) near the surface 22 of the ash skeleton 20. Let it.

By the heating, the dioxin precursor 24 is expelled from the pores 21 of the ash skeleton 20, and the gaseous precursor 24 is also entrained from the ash surface 22 by the nitrogen gas to the outside. Since it has been expelled, even if an oxygen-containing atmosphere is used, long-life ozone and hydrogen peroxide (H ₂ O ₂ ) completely re-synthesize dioxins.
It can be disassembled without breaking. In the case of steam, hydrogen peroxide will be generated. As a result, hydrogen peroxide and ozone enter the pores, and the remaining dioxins can be completely decomposed.

The mechanism for oxidatively decomposing the dioxins 23 adsorbed in the pores 21 by the entry of peroxide (peroxide) into the ash pores will be described below. By separately introducing steam, hydrogen peroxide (H ₂ O ₂ ) is generated in addition to ozone (O ₃ ) generated from oxygen molecules. The reaction for producing each peroxide is as follows.

Ozone: O ₂ + high-energy electron → 2OH + low-energy electron O ₂ + O → O ₃ ... Formula (1) Hydrogen peroxide: H ₂ O + high-energy electron → OH + H + low-energy electron OH + OH + M (neutral particles) → H ₂ O ₂ + Neutral particles Formula (2) The neutral particles referred to here are stable molecules such as oxygen, water vapor, and nitrogen.

Since these peroxides have an excessive amount of oxygen, they release oxygen atoms and have an extremely large oxidizing effect. Incidentally, the reaction rate of the formula (2) is about 1000 times faster than that of the formula (1), and the production amount of hydrogen peroxide can be increased. Since this reaction can be performed at a low temperature, it is not necessary to maintain this temperature after the temperature is raised to 150 ° C. or more to eliminate the precursor 24.

The ash / soil may be continuously or intermittently placed in the reaction vessel and treated.

The above-mentioned plasma decomposition apparatus 11 was removed from dust removing means for removing fly ash in exhaust gas discharged from various incinerators such as municipal waste incinerators, industrial waste incinerators, and sludge incinerators. It can be treated to decompose dioxins in fly ash.

[Third Embodiment] FIG. 8 shows an embodiment of a system for continuously detoxifying ash. FIG.
As shown in the figure, the detoxification treatment system is provided with two decomposers as described above and the supply line 3 for the ash / soil 16.
5, the line 35 is divided into two, and the first disassembly processing device 11A according to the first embodiment as described above and the second
Is disposed in each of the dividing lines 35A and 35B, and the ash 16 is alternately supplied to perform the ash detoxification processing. Thereby, the ash can be continuously detoxified. Note that the disassembling apparatus of the second embodiment may be used instead of the disassembling apparatus of the first embodiment.

[Fourth Embodiment] FIG. 9 shows an embodiment of a system for continuously and efficiently detoxifying ash. FIG. 9 shows a detoxification system that completely detoxifies the dioxin remaining after plasma decomposition in the system of the third embodiment as described above. As shown in FIG. 9, the system of the fourth embodiment is different from the third system in that an ozone treatment tank 42 having an ozone generator 41 is connected to a supply line 37 for supplying detoxified treated ash 17. It is what you wear. In the case where undecomposed dioxins still exist in the plasma treatment, the treatment ash 17 of the above-described ozone treatment device is filled as a post-treatment, and ozone (O ₃ ) from the ozone generator 41 is injected into the inside. Then, the ozonolysis may be performed. This ozonolysis may be performed over a long period of time.

[Fifth Embodiment] FIG. 10 shows an embodiment of a detoxification system in which a dust remover and a detoxification device of this embodiment are integrated. FIG. 10 shows a specific example of the detoxification processing system using the processing apparatus of the first or second embodiment as described above. FIG.
As shown in the figure, the detoxification processing system is configured such that a detoxification processing device 52 is integrally provided at a lower end side of a plurality of bag filters 51 as dust removing devices. Reference numeral 15 in FIG. 10 indicates a pulse power supply. As shown in FIG. 10, the detoxification treatment devices 11 are independently installed directly below the filter 51, and trapped ash (approximately once per hour) that falls periodically from the bag filter 51. Gather
Decomposition is performed on the spot through a series of plasma decomposition processes as described above. Further, even in the above-mentioned processing, when there is residual dioxins, the ozone treatment tank 42 may be provided on the downstream side as the post-processing shown in FIG.

FIG. 11 is an example of a plasma decomposition processing apparatus 52 which is a detoxification processing apparatus. A plurality of cylindrical electrodes (reaction vessels) 12 are erected in a casing 54 having an upper lid 54a and a lower lid 54b. And each cylindrical electrode 12
A wire electrode 13 is disposed in the inside, and the reaction space 55 is filled with ash or the like, and the above-described plasma processing is performed by heating by the heater 14.

In this embodiment, the treated ash 17 subjected to the plasma treatment is treated by the treated ash transport means 53 by the ozone treatment tank 42.
The inside is led to treated ash, where ozone treatment is further performed to complete dioxin treatment.

According to each embodiment of the present invention described above,
There are the following effects and features. (1) The regulation value of the dioxin concentration in ash of 1 ng-TEQ / g can be satisfied, and even if the regulation is strengthened, it can be sufficiently coped with. (2) Significantly reduce what used to require 10,000 yen per ton of ash to treat (less than 1/5). (3) The heat treatment can be performed at a low temperature of 200 ° C. or less, and a combination of a reaction vessel and a pulse power source can be used, so that the initial investment cost can be reduced. (4) Dioxin can be decomposed in high-concentration dioxin pollutants (solids), and can be applied to ash and pollutants other than soil. For example, dioxin decomposition of RDF (Refuse Derive Fuel) before an incinerator becomes possible. (5) It can be applied to the decomposition of solid dioxin by separating dioxin in liquid (eg, incinerator wastewater). (6) Dioxin decomposition rate in ash and soil can be expected to be 99% or more. (7) Dry processing.

[0054]

As described above with reference to the embodiments,
According to the first invention of the ash / soil detoxification method, ash / soil containing a harmful substance is put into a plasma reaction vessel, and the harmful substance is detoxified by plasma decomposition.
A method for detoxifying soil, in which dioxin precursors present in ash / soil pores are expelled from the ash / soil pores while being converted to a gaseous state, thereby removing the dioxin precursors. In addition, the precursor substances and dioxins existing on the surface side of the ash / soil can be plasma-decomposed, and the dioxins remaining in the pores of the ash-soil can be subjected to plasma decomposition.

According to the second aspect, in the first aspect, the ash / soil is heated to 140 ° C. or higher to drive out the dioxin precursor substance from the pores, so that only the precursor is driven out of the pores. .

According to the third invention, in the first invention, in the above-mentioned heating, a nitrogen gas is supplied into and exhausted from the plasma reaction vessel during the heating, and the inside of the vessel is heated in an N ₂ atmosphere. The dioxin precursor substance expelled from the inside of the pores is discharged out of the reaction vessel with the N ₂ gas accompanying the N ₂ gas, and then the plasma is decomposed while replacing the inside of the vessel from a nitrogen gas atmosphere to an oxygen-containing atmosphere. Therefore, plasma decomposition can be performed without resynthesis in a state where no precursor is present in the container.

According to a fourth aspect, in the invention according to any one of the first to third aspects, the ash / soil is continuously or intermittently put into the reaction vessel, so that the ash / soil is efficiently used.
Decomposes soil.

According to the fifth invention of the ash / soil detoxification apparatus, a reaction vessel having a positive electrode and a negative electrode to which a high-voltage pulse voltage having a very short pulse width is applied; Heating means for heating the ash / soil, the ash / soil containing a harmful substance is put into the reaction vessel, and the inside of the reaction vessel is heated to 140 ° C. or more, and then the positive electrode and the negative electrode are heated. Radicals are generated by the plasma resulting from the discharge generated between the above and the harmful substances are decomposed by the radicals, so the expelled dioxin precursor substances, the precursor substances present on the ash / soil surface side and Dioxins can be plasma-decomposed, and at the same time, dioxins remaining in the pores of the ash / soil can be plasma-decomposed.

According to a sixth aspect, in the fifth aspect, the reaction vessel comprises a cylindrical electrode, and a wire electrode or a rod-shaped electrode disposed in an internal space of the cylindrical electrode. Since a high-voltage pulse voltage having an extremely short pulse width is applied to the electrode or rod-shaped electrode and the cylindrical electrode, a streamer discharge is easily generated, and the decomposition efficiency of dioxins is improved.

According to a seventh aspect, in the fifth or sixth aspect, a gas supply means for supplying nitrogen gas and / or air to the reaction vessel and a gas discharge means for discharging gas in the vessel are provided. During the heating, a nitrogen gas is supplied into the plasma reaction vessel under a nitrogen gas atmosphere, and the gaseous dioxin precursor substance expelled from the pores by the heating is reacted by the gas discharging means. Since the gas is discharged to the outside of the container and then subjected to plasma decomposition while replacing the nitrogen gas atmosphere with an oxygen-containing atmosphere, plasma decomposition can be performed without resynthesis in a state where no precursor is present in the container.

According to the eighth invention of the ash / soil detoxification system, fly ash is removed from exhaust gas discharged from various incinerators such as municipal waste incinerators, industrial waste incinerators, and sludge incinerators. The ash / soil detoxifying apparatus according to any one of claims 5 to 7, which decomposes the dioxins in the fly ash removed from the dust removing means, so that the detoxifying process is performed efficiently. Can be done well and quickly.

According to a ninth aspect, in the eighth aspect, the dust removing means comprises a plurality of bag filters, and the dust removed from each bag filter is ash / soil according to any one of claims 5 to 7. Since it is supplied into the container of the detoxification apparatus and detoxified, dioxins can be efficiently decomposed.

According to a tenth aspect, in the eighth or ninth aspect, an ozone treatment tank for ozone treating fly ash after the plasma treatment is provided on the downstream side of the ash / soil detoxification treatment apparatus. Therefore, decomposition treatment can be performed even when there is undecomposed dioxins.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a detoxification processing apparatus according to a first embodiment of the present invention.

FIG. 2 is a process chart of an ash plasma decomposition process according to the first embodiment.

FIG. 3 is a graph showing the relationship between vapor pressure and temperature of dioxins and dioxin precursors.

FIG. 4 is a process diagram of a plasma decomposition process of ash under an N ₂ atmosphere.

FIG. 5 is a process chart of a plasma decomposition treatment of ash in an N ₂ + O ₂ atmosphere.

FIG. 6 is a schematic view of a detoxification processing apparatus according to a second embodiment of the present invention.

FIG. 7 is a process diagram of the ash plasma decomposition process according to the second embodiment.

FIG. 8 is a schematic diagram of a detoxification processing apparatus according to a third embodiment of the present invention.

FIG. 9 is a schematic diagram of a detoxification processing system according to a fourth embodiment of the present invention.

FIG. 10 is a schematic diagram of a detoxification processing system according to a fifth embodiment of the present invention.

FIG. 11 is a schematic view of a detoxification processing apparatus according to a fifth embodiment of the present invention.

FIG. 12 is a schematic diagram of a detoxification processing apparatus according to a fifth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Plasma decomposition processing apparatus 12 Cylindrical electrode 13 Wire electrode 14 Superheating means (heater) 15 Pulse power supply 16 Ash / soil 17 Treated ash

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B09C 1/06 B09B 3/00 303L C07D 319/24 ZAB H05H 1/42 303P (72) Inventor Kohei Kawazoe Nagasaki 5-717-1, Fukabori-cho, Nagasaki City, Nagasaki Prefecture, Nagasaki Research Laboratory, Ltd. (72) Inventor Katsuhiko Kobayashi 12, Nishikicho, Naka-ku, Yokohama-shi, Kanagawa Prefecture Mitsubishi Heavy Industries, Ltd. 1-8-1, Koura, Kanazawa-ku, Yokohama-shi, Kanagawa F-term (reference) 2E191 BA12 BB00 BB01 BD18 4D004 AA36 AA41 AB05 AB07 CA12 CA27 CA43 CA50 CB32 CC01 DA06 4D058 JA04 KB02 RA19 SA20 TA01 UA30 4G75 AA37 BA01 BA05 BD05 BD12 CA02 CA63 EA02 EA06 EB21 EB41 EC21 FC02

Claims (10)

[Claims] An ash / soil detoxification method for putting ash / soil containing a harmful substance into a plasma reactor and detoxifying the harmful substance by plasma decomposition. The dioxin precursor substance present in the pores is expelled from the pores of the ash / soil while forming a gaseous state, and the displaced dioxin precursor substance, the precursor substance present on the surface side of the ash / soil, and the dioxins A method for detoxifying ash and soil, comprising decomposing plasma and dioxins remaining in the pores of the ash and soil. 2. The ash / soil detoxification method according to claim 1, wherein the ash / soil is heated to 140 ° C. or higher to drive out the dioxin precursor substance from the pores. 3. The method according to claim 1, wherein, during the heating, a nitrogen gas is supplied and exhausted into the plasma reaction vessel, and the plasma reaction vessel is heated while being kept in an N ₂ atmosphere. Discharging the dioxin precursor material together with the N ₂ gas to the outside of the reaction vessel, and then performing plasma decomposition while replacing the inside of the vessel from a nitrogen gas atmosphere to an oxygen-containing atmosphere. Detoxification method of soil. 4. The method for detoxifying ash / soil according to claim 1, wherein the ash / soil is continuously or intermittently put into the reaction vessel. 5. A reaction vessel having a positive electrode and a negative electrode to which a high-voltage pulse voltage having a very short pulse width is applied, and heating means for heating ash and soil in the reaction vessel, Put ash / soil containing harmful substances into the above-mentioned reaction vessel, heat the inside of the reaction vessel to 140 ° C or higher, and then generate radicals due to plasma generated by the discharge generated between the positive and negative electrodes. And detoxifying the harmful substance by the radicals. 6. The reaction vessel according to claim 5, wherein the reaction vessel includes a cylindrical electrode, and a linear or rod-shaped electrode disposed in an internal space of the cylindrical electrode. An apparatus for detoxifying ash and soil, wherein a high-voltage pulse voltage having an extremely short pulse width is applied to a cylindrical electrode. 7. The method according to claim 5, further comprising: gas supply means for supplying nitrogen gas and / or air to the reaction vessel; and gas discharge means for discharging gas in the vessel. Then, a nitrogen gas is supplied into the plasma reaction vessel to form a nitrogen gas atmosphere, and the gaseous dioxin precursor substance expelled from the pores by heating is discharged to the outside of the reaction vessel by gas discharge means. A ash / soil detoxification apparatus characterized by performing plasma decomposition while replacing the atmosphere under a nitrogen gas atmosphere with an oxygen-containing atmosphere. 8. A dust removing means for removing fly ash in exhaust gas discharged from various incinerators such as a municipal garbage incinerator, an industrial waste incinerator, a sludge incinerator, and the like, and fly ash removed from the dust removing means. An ash detoxification system comprising the ash / soil detoxification treatment apparatus according to any one of claims 5 to 7, which decomposes dioxins therein. 9. The container of the ash / soil detoxifying apparatus according to claim 5, wherein the dust removing means comprises a plurality of bag filters, and dust removed from each bag filter is provided. A detoxification system for ash, which is supplied inside and subjected to detoxification processing. 10. The ash treatment device according to claim 8, wherein an ozone treatment tank for ozone treatment of fly ash after the plasma treatment is provided downstream of the ash / soil detoxification treatment device. Detoxification system.