JP2000317266A - Wet treatment for making dioxin harmless - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make dioxins harmless at a low cost by bringing an aqueous solution acidified with hydrochloric acid and containing an iron compound in the solid state into contact with the dioxins at a specified relatively low temperature. SOLUTION: Fly ash containing dioxins is introduced through a line 11 into a solid-liquid contact apparatus 10 kept at a lower temperature than 100 deg.C and an aqueous solution acidified with hydrochloric acid and containing an iron catalyst is brought into contact with the fly ash containing dioxins to make the dioxins harmless. An aqueous solution acidified with hydrochloric acid for replenishment is introduced through a line 13 into the solid-liquid contact apparatus 10 and an aqueous alkali solution for pH adjustment is optionally introduced through a line 14. Oxygen or an oxygen-containing gas is optionally introduced through a line 102 into the solid-liquid contact apparatus 10 so as to increase the concentration of dissolved oxygen in the aqueous solution.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for wet detoxification of dioxins.

[0002]

2. Description of the Related Art Dioxins represented by 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) have a strong harmful effect on the human body. Emissions into the environment are highly regulated. The Ministry of Health and Welfare of Japan published "Guidelines on Prevention of Dioxin Generation in Waste Management" in January 1997,
It is instructed to keep the concentration of dioxins in exhaust gas discharged from the newly installed all-furnace furnace at 0.1 ng-TEQ / Nm3 or less. In addition, with the revision of the Air Pollution Control Law of December 1997, the Environment Agency has designated dioxins as designated hazardous substances and has set regulations on not only general waste but also dioxins generated during incineration of industrial waste. Was decided. Various methods for detoxifying dioxins have heretofore been proposed. Examples of such a method include an incineration method, a melting method, a thermal decomposition method, a photolysis method, an ozone decomposition method, an oxidative decomposition method using hydrogen peroxide, a hydrothermal decomposition method, and an alkali decomposition method. However, all of these conventional methods involve problems such as great difficulty in implementing them and still being unsatisfactory in terms of economic efficiency. According to JP-A-10-146574, an oxidizing acid such as concentrated sulfuric acid is added to fly ash containing dioxins to form a slurry.
A method of decomposing dioxins by heating to the above temperature has been proposed. In this method, dioxins can be detoxified relatively efficiently, but the treatment temperature is 100 ° C. or higher, preferably 200 ° C. or higher, which is higher than the boiling point of water (atmospheric pressure, the same applies hereinafter). In addition, since the treatment is performed while evaporating water, there are problems such as a high energy consumption rate and a high apparatus cost.

[0003]

An object of the present invention is to provide a wet treatment method for detoxifying dioxins, wherein the processing temperature is lower than the boiling point of water and the cost of detoxifying dioxins is low. It is the subject.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and also found that dioxins contain an iron compound in a solid state at a temperature lower than 100 ° C. They have found that they can be rendered harmless by contact with an aqueous hydrochloric acid solution, and have completed the present invention. That is, according to the present invention, there is provided a method for wet detoxification of dioxins, wherein the dioxins are brought into contact with a hydrochloric acid aqueous solution containing an iron compound in a solid state at a temperature lower than 100 ° C to convert the dioxins. A method for wet detoxification of dioxins, characterized by detoxification, is provided. Further, according to the present invention, there is provided a method for wet detoxification of incinerator exhaust gas containing dioxin-containing fly ash generated from an incinerator, wherein the incinerator exhaust gas contains 1%.
Contacting with a hydrochloric acid aqueous solution containing an iron compound in a solid state at a temperature lower than 00 ° C. to transfer fly ash in the exhaust gas to the aqueous solution and decompose and harmlessly dioxins adhered to the fly ash in the aqueous solution. The present invention provides a method for wet detoxification of incinerator exhaust gas, characterized in that the method comprises the steps of: Further, according to the present invention, there is provided a method for wet detoxification of incinerator exhaust gas at a temperature of 100 ° C. or more containing dioxin-containing fly ash generated from an incinerator, wherein the incinerator exhaust gas is cooled with a cooling liquid and a gas-liquid mixture. A cooling step of bringing the exhaust gas temperature to a temperature lower than 100 ° C. by contacting, a gas-liquid contacting step of bringing the exhaust gas obtained in the cooling step into gas-liquid contact with an aqueous hydrochloric acid solution, and a contact with the exhaust gas obtained in the cooling step The cooling liquid containing the fly ash after the contact and the hydrochloric acid aqueous solution containing the fly ash after the contact with the exhaust gas obtained in the gas-liquid contacting step, separately or in a unified state, are used to remove the iron compound in the solid state. In the presence, the concentration of the iron compound contained in the aqueous solution is maintained at 10 mmol or more per liter of water in terms of metallic iron, and the dioxin in the fly ash is maintained at a processing temperature lower than 100 ° C. To decompose and make harmless Wet detoxification method incinerator exhaust gas, characterized in that it comprises a oxine such decomposition reaction step is provided. Furthermore, according to the present invention, there is provided a method for wet detoxification of incinerator exhaust gas containing dioxin-containing fly ash generated from an incinerator, wherein the incinerator exhaust gas cooled to a temperature lower than 100 ° C. is treated with an aqueous hydrochloric acid solution. A gas-liquid contacting step, a fly ash concentration step of increasing the fly ash content in a hydrochloric acid aqueous solution containing the fly ash obtained in the gas-liquid contacting step, and a fly ash obtained in the fly ash concentration step. In the presence of an iron compound in a solid state, an aqueous solution of hydrochloric acid containing an elevated concentration is maintained at a concentration of 10 mmol or more per liter of water, in terms of metallic iron, in the presence of a solid state iron compound. A method for wet detoxification of exhaust gas from an incinerator, comprising a dioxin decomposition reaction step of decomposing dioxins contained in the fly ash under a treatment temperature condition lower than ℃. Furthermore, according to the present invention, there is provided a method for wet detoxification of incinerator exhaust gas containing dioxin-containing fly ash generated from an incinerator, wherein the exhaust gas is brought into gas-liquid contact with a first treatment liquid. The contacting step, the second gas-liquid contacting step in which the treated exhaust gas obtained in the first gas-liquid contacting step is brought into gas-liquid contact with the second treatment liquid, and the first treatment liquid trapped in the first gas-liquid contacting step Fly ash and fly ash captured by the second treatment liquid in the second gas-liquid contacting step are separately or in a combined state, at a temperature lower than 100 ° C., in the presence of a solid-state iron compound. The concentration of the iron compound contained in the aqueous solution is calculated as
A method for wet detoxification of exhaust gas from an incinerator, comprising a dioxin decomposition reaction step of decomposing dioxins contained in the fly ash by contacting with an aqueous hydrochloric acid solution while maintaining the concentration at 10 mmol per liter or more. Is provided.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The term "dioxins" as used herein refers to 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) and its analogous compounds. Polychlorodibenzo-p-dioxins (PCDDs) having 1 to 8 chlorine atoms substituted in the dibenzo-p-dioxin nucleus and polychlorodibenzofurans (PCDs) having 1 to 8 chlorine atoms substituted in the dibenzofuran nucleus
Fs) and the like.

Although dioxins include various chlorine compounds as described above, the degree of harmfulness of each type of dioxin differs depending on the specific type thereof. In order to evaluate, a scale is required to evaluate the harmfulness of different dioxins. Therefore, based on the short-term toxicity evaluation results of various dioxins, the amounts of various dioxins are reduced to 2,3,7,8-
Coefficient converted to TCDD amount (Toxicity equivalent coefficient (TE
F)) is calculated, and the sum of the actual amount of each dioxin multiplied by this toxic equivalent coefficient is called the toxicity equivalent conversion value (TEQ), and the emission of dioxins And is used to represent concentration.

The method for detoxifying dioxins according to the present invention is characterized in that a dioxin is contacted with an aqueous hydrochloric acid solution (hereinafter, also simply referred to as an aqueous solution) containing an iron compound in a solid state. In this case, the treatment temperature is lower than the boiling point of water (100 ° C.), preferably 80 ° C.
It is a temperature below ° C. The lower limit temperature is about 30 degrees. In the aqueous solution used as a reaction treatment agent in the present invention, the concentration of the iron compound is expressed in terms of metallic iron (Fe).
5 mmol or more, preferably 10
The amount is at least mmol, more preferably at least 20 mmol. Its upper limit is about 200 mmol. Its pH
Is 2 to 6, preferably 3 to 5. This aqueous solution
Other inorganic acids, such as sulfuric acid, may be included, in which case the molar ratio of Cl ⁻ ions to SO ₄ ^2- ions [Cl ⁻ ] / [SO ₄ ^2- ] in the aqueous solution is 5 or more, preferably 20
It is better to adjust above. In this case, the upper limit is not particularly limited. Examples of the method of contacting dioxins with an aqueous solution include a method of stirring dioxins or a solid containing the same in an aqueous solution, a method of spraying an aqueous solution on a dioxin or a solid containing the same, and a method of filling a column or a shelf. A method of contacting with a column tower is exemplified. In this specification, the hydrochloric acid aqueous solution refers to an acidic aqueous solution containing chloride ions. Examples of the acid for maintaining the acidity include hydrochloric acid, sulfuric acid, and nitric acid, and the use of hydrochloric acid is preferable. Decomposition of dioxins means that dioxins are converted into non-dioxins.

[0008] The aqueous hydrochloric acid solution used in the present invention contains a reaction catalyst comprising a solid iron compound which promotes the decomposition of dioxins. According to our research, 10
At a temperature lower than 0 ° C., it has been clarified that the dioxins can be rendered harmless by contacting the aqueous solution with the dioxins, but when an aqueous solution not containing the reaction catalyst is used, the dioxins are rendered harmless. Therefore, including the reaction catalyst in an aqueous solution is very important from an industrial or commercial point of view. According to our research,
It has been found that iron compounds existing in a solid state in an aqueous hydrochloric acid solution exhibit a high decomposition rate of dioxins. In order for the iron compound to be present in a solid state in the aqueous hydrochloric acid solution, the pH of the aqueous hydrochloric acid solution of the iron compound containing the iron compound in a dissolved state is adjusted to a range of pH 2.5 or more, which is a precipitation region of the iron compound. Thus, the dissolved iron compound may be precipitated. In this case, it is preferable that solid particles are present in the aqueous solution, the iron compound is precipitated on the solid fine particles, and the insoluble (solid state) iron compound is supported on the solid fine particles.

In an aqueous hydrochloric acid solution of the iron compound,
As the iron compound, a compound in which the valence of iron is lower than 3 is preferable, and a compound in which the valence of iron is divalent is more preferable. Specifically, ferrous chloride (FeCl
₂ ), ferrous sulfate (FeSO ₄ ), ferrous formate (Fe (C
OO) ₂ ), ferrous bromide (FeBr ₂ ), ferrous iodide (FeI ₂ ), ferrous phosphate (Fe ₃ (PO ₄ ) ₂ ), iron perchlorate (Fe (ClO ₄ )) ₂ ) and the like. The pH of the aqueous solution is 6 or less, preferably 3 or less, which is a region in which the iron compound dissolves, and the lower limit is not particularly limited. The chloride ion concentration in the aqueous solution is 10 mmol / L or more, preferably 100 mmol / L or more, and the upper limit is about 3000 mmol / L. The concentration of the iron compound in the aqueous solution is 5 mmol / L or more, preferably 10 mmol / L or more, more preferably 20 mmol / L or more in terms of metallic iron (Fe), and the upper limit is not particularly limited. However, it is usually about 200 mmol / liter. In the case of the present invention, when the concentration of the iron compound is 20 mmol / L or more, the decomposition reaction of dioxins is remarkably accelerated.

The pH at which the iron compound existing in a dissolved state in the hydrochloric acid aqueous solution is precipitated is 2.5 or more, preferably 3.0 or more, more preferably 3.5 or more, which is the pH of the precipitation region of the iron compound. The upper limit is not particularly limited, but is usually about 6.

In order to precipitate the iron compound in the aqueous hydrochloric acid solution, a pH adjuster is added to the aqueous solution. In this case, the pH adjuster may be an alkaline substance. These include sodium hydroxide (NaOH), sodium carbonate (Na ₂ CO ₃ ), potassium hydroxide (KOH),
Potassium carbonate (K ₂ CO ₃ ), calcium hydroxide (Ca
(OH) ₂ ), calcium carbonate, (Ca (CO ₃ ), magnesium hydroxide Mg (OH) ₂ ), and magnesium carbonate (Mg (CO ₃ )).

When solid fine particles are present in an aqueous hydrochloric acid solution upon insolubilization of the iron compound, the solid fine particles may be those which are stably present in the form of solid fine particles in the aqueous solution. Such solid fine particles include various inorganic substances, for example, incinerated ash (fly ash, furnace ash), zeolite, alumina, silica, metals or metal oxides stable in aqueous hydrochloric acid. In the case where fine particles having an alkaline solid surface are used as the solid fine particles, the iron compound may be easily insolubilized, and such solid fine particles are preferably used. Examples of such solid fine particles include incinerated ash (fly ash, furnace ash) and the like. Generally, incineration ash (fly ash, furnace ash) is alkaline, and in the process of dissolving in an acidic aqueous solution, even if the bulk pH is acidic, the incineration ash (fly ash, furnace ash) At the interface between the ash) solid surface and the bulk acidic aqueous solution, the solid surface side is considered alkaline. Therefore, the iron compound supplied through the film on the particle surface is rapidly insolubilized on the particle surface. The average particle size of the solid fine particles is 50
It is 0 μm or less, preferably 200 μm or less, and the lower limit thereof is not particularly limited, but is usually about 10 μm. The concentration of the solid fine particles in the aqueous solution is 5 to 50% by weight, preferably 10 to 30% by weight. The ratio of the iron compound to the solid fine particles is determined by the ratio of metallic iron (Fe) to the solid fine particles.
0.001 to 0.4, preferably 0.005 by weight ratio
０．２0.2.

The iron compound existing in the solid state in the aqueous hydrochloric acid solution is in the form of an insoluble iron compound, that is, iron hydroxide (F
e (OH) ₂ ) and iron hydroxide chloride Fe (ClOH).

The hydrochloric acid aqueous solution containing the insoluble iron compound is
It can also be prepared by dispersing a particulate insoluble iron compound in an aqueous hydrochloric acid solution. The average particle size of the insoluble iron compound is 10 μm or less, preferably 1 μm or less, and the lower limit thereof is not particularly limited.
It is about. The concentration in the aqueous solution is expressed in terms of metallic iron,
0.002 to 1% by weight, preferably 0.005 to 0.5
% By weight. The insoluble iron compound may be one previously supported on solid fine particles, or an iron compound complexed with another metal, for example, potassium ferric sulfate (KFe
(SO ₄ ) ₂ ), iron manganate (FeMnO ₄ ), iron molybdate (FeMoO ₄ ), and the like may be used. The concentration of the iron compound in the solid fine particles is 2 to 20% by weight, preferably 5 to 15% by weight in terms of metallic iron.

The pH of the aqueous hydrochloric acid solution containing the insoluble iron compound used in the present invention is from 2.0 to 6.0, preferably from 3.5 to 5.0. Is 0.003 to 3% by weight, preferably 0.008 to 0.8% by weight. The chlorine concentration in the aqueous solution is 10 to 3000 mmol / L, preferably 100 to 1000 mmol / L.
It is also preferable that the copper compound exists in a dissolved state in the aqueous solution. In this case, the amount of the copper compound in the aqueous solution is 0.3 to 150 mmol / L, preferably 3 to 80 mmol / L in terms of metallic copper (Cu).

The insoluble iron compound (hereinafter also referred to as iron catalyst) used in the present invention is preferably a compound having a valence of iron lower than 3, more preferably a compound having a valence of iron in a divalent state. Generally, these iron compounds are provided in the form of metal oxides or salts, such as chlorides, oxides, carbonates, sulfates and the like. The aqueous hydrochloric acid solution as a reaction treating agent for detoxifying dioxins used in the present invention contains these insoluble iron compounds in a solid state as a reaction catalyst. In this case, the reaction catalyst can contain dissolved components. This dissolved component is usually in the process of shifting to a solid state. Such a reaction catalyst containing dissolved components in the process of transitioning to the solid state also works effectively. As the insoluble iron compound (hereinafter also referred to as iron catalyst) used in the present invention, a metal component contained in incinerated ash such as fly ash or furnace ash can be used. Incinerated ash often contains iron that acts as a reaction catalyst as described above. In order to utilize the iron component contained in such incinerated ash as a reaction catalyst, the incinerated ash may be added to a hydrochloric acid aqueous solution under a pH condition at which the iron compound does not dissolve and stirred. And the hydrochloric acid aqueous solution containing such an iron catalyst can be used as a reaction treating agent for dioxins in the present invention.

The aqueous solution used as the reaction treating agent in the present invention may contain a substance (contact promoting agent) that promotes the contact between the aqueous solution and the dioxins. The contact promoter includes a surfactant and an alcohol. The type of surfactant in this case is not particularly limited,
Anionic, cationic, nonionic and amphoteric surfactants can be used. The amount of surfactant added is 0.00
It is 5 to 1% by weight, preferably 0.01 to 0.5% by weight. As the alcohols, lower alcohols are preferably used, and specific examples thereof include methanol, ethanol, and propanol. The added amount is 0.5
10 to 10% by weight, preferably 1 to 10% by weight. In the present invention, it is preferable to irradiate the aqueous solution with ultrasonic waves in order to promote the contact between the aqueous solution and the dioxins. As the ultrasonic wave, an ultrasonic wave generally used for preparing an emulsion or the like is used. Further, according to the present invention, if necessary, oxygen or an oxygen-containing gas can be brought into contact with the aqueous solution to increase the dissolved oxygen concentration in the aqueous solution. The presence of dissolved oxygen promotes the expression of the activity of the reaction catalyst, and effectively promotes the decomposition of dioxins. Examples of the method of contacting the aqueous solution with oxygen or an oxygen-containing gas in this case include a method of blowing oxygen or an oxygen-containing gas into the aqueous solution and a method of contacting oxygen or the oxygen-containing gas with fine droplets of the aqueous solution. . Examples of the oxygen-containing gas include air and oxygen-enriched air.

The raw material to be used in the method of the present invention is dioxins. In the detoxification treatment of dioxins, dioxins are rarely treated as a single substance, and are usually attached to solids. Is processed.
Examples of such solids to which dioxins are attached include incineration ash discharged from various incinerators. The incineration ash in this case includes fly ash contained in exhaust gas from the incinerator and furnace ash deposited on the furnace bottom. Such incinerated ash contains unburned carbon (or a carbon substance), and dioxins are present in the unburned carbon, so that it is very difficult to detoxify it. When detoxifying such incineration ash using an aqueous solution, it is preferable to use a contact promoter that promotes the contact between the aqueous solution and the dioxins, and in addition, the aqueous solution and the dioxins are easily contacted. As described above, it is also effective to perform a pretreatment such as irradiating the aqueous solution with ultrasonic waves, pulverizing incinerated ash, and burning incinerated ash to reduce the amount of unburned carbon.

When incinerated ash is used as a raw material to be treated, the incinerated ash usually contains unburned carbon or carbon material. It is difficult to detoxify it because it hinders contact with water and an aqueous solution.
Then, the difficulty of the detoxification increases as the amount of the carbon substance increases. Therefore, from this viewpoint, it is preferable to previously reduce the amount of the carbon substance contained in the incineration ash. According to the study of the present inventors, the content of the carbon substance is 2% by weight or less, preferably 1% by weight. %, More preferably 0.5% by weight or less.
For this purpose, it is preferable to reduce the carbon content in the incinerated ash discharged by adjusting the combustion conditions in a combustion furnace for incinerating waste such as refuse. Further, in the treatment of fly ash and furnace ash to which a large amount of carbon material has adhered, it is preferable to calcinate them once to reduce the content of the carbon material, and then perform detoxification treatment.

The dioxins attached to the solid include:
In addition to the above-mentioned incinerated ash such as fly ash and furnace ash, dioxin-contaminated soil and the like can be mentioned. According to the present invention, not only dioxins alone but also dioxins adhering to solids as described above can be detoxified. In this case, since the processing temperature is lower than the boiling point of water,
The energy consumption rate is very low and the equipment costs are low. The processing time is about 1 to 100 hours, and the specific processing time is the processing conditions including the state of the dioxin as the raw material to be processed and the aqueous solution composition,
Furthermore, it depends on the desired dioxin decomposition rate, etc.
It is difficult to determine uniquely. In the case of the present invention, it is an essential requirement that the decomposition is performed so that the decomposition rate of dioxins at the treatment temperature is 60% or more, preferably 80% or more, more preferably 90% or more. In other words,
In the case of the present invention, 60% or more, preferably 80% As described above, a decomposition rate of dioxins of more preferably 90% or more can be achieved.
The inventor of the present invention has developed a method for detoxifying dioxins with a high decomposition rate of 60% or more at a processing temperature significantly lower than the boiling point of water using an inexpensive reaction processing agent such as an aqueous solution. It is.

Next, the present invention will be described in detail with reference to the drawings. FIG. 1 shows an example of a flow sheet when dioxin-containing fly ash is treated according to the present invention. In FIG. 1, 10 indicates a solid-liquid contact device, 2 indicates a solid-liquid separator, 3 indicates a metal separator, and 4 indicates a copper separator.
In order to treat the dioxin-containing fly ash according to the flow sheet of FIG. 1, the dioxin-containing fly ash is introduced into the solid-liquid contact device 10 maintained at a temperature lower than 100 ° C. through the line 11. The solid-liquid contacting device 10 is for detoxifying the dioxins, where the dioxin-containing fly ash is brought into contact with an aqueous hydrochloric acid solution containing an iron catalyst. The solid-liquid contact device 10 may have any structure as long as it has a structure capable of contacting dioxin-containing fly ash with a liquid. To this solid-liquid contacting device 10, a replenishing aqueous hydrochloric acid solution for contacting with dioxin-containing fly ash is introduced through a line 13, and an alkaline aqueous solution for pH adjustment as required is supplied through a line 14. Introduced through. As the alkaline aqueous solution in this case, an aqueous solution or slurry formed by dissolving or dispersing an alkaline substance such as sodium hydroxide, sodium carbonate, calcium hydroxide, calcium carbonate, and magnesium hydroxide in water is used. In addition, oxygen or an oxygen-containing gas is introduced into the solid-liquid contact device 10 through the line 102 as necessary, so that the concentration of dissolved oxygen in the aqueous solution is increased. The gas (exhaust gas) after coming into contact with the aqueous solution is discharged through the line 103, and if necessary, subjected to a purification treatment and released to the atmosphere.

The chloride ion concentration in the aqueous solution used in the solid-liquid contact device 10 is 10 mmol / L or more.
Preferably it is 100 mmol / l or more, and its pH is 2.0 to 6.0. This aqueous solution contains an iron catalyst. The iron catalyst is supplied through the line 22. When the fly ash contains iron, the iron also acts as a catalyst. When fly ash contains copper, the copper is eluted into the aqueous solution and acts as a catalyst for decomposing dioxins or a cocatalyst for an iron catalyst. This copper source can also be supplied from line 22 if desired.

In a preferred embodiment of the present invention, an aqueous hydrochloric acid solution containing an iron compound in a dissolved state is supplied from the line 22, and the iron compound is preferably precipitated in the solid-liquid contact device 10. In this case, since the precipitated iron is carried on the fly ash, it acts effectively on the dioxins in the fly ash and decomposes the dioxins. The amount of the iron catalyst used is 0.3 to 15 parts by weight, preferably 0.5 to 10 parts by weight, more preferably 1 to 5 parts by weight in terms of metallic iron, based on 100 parts by weight of the dioxin-containing fly ash. Is the ratio of In order to save replenishment of the iron catalyst from the outside, the iron catalyst separated with the fly ash in the solid-liquid separation device 2 is circulated to the solid-liquid contact device 10 together with the fly ash or separated from the fly ash. Is preferred. It is also preferable that the aqueous hydrochloric acid solution in the solid-liquid contact device 10 contains copper ions in a dissolved state. In this case, the amount of copper ions present in the aqueous solution is 0.2 to 10 parts by weight, preferably 1 to 8 parts by weight, more preferably 2 to 10 parts by weight in terms of metallic copper, based on 100 parts by weight of dioxin-containing fly ash. -5 parts by weight. In order to save external supply of copper ions, copper is separated from the heavy metals separated in the metal separation device 3 in the copper separation device 4 and, if necessary, an active water-soluble copper compound (such as copper chloride). After the conversion, it is preferably circulated through the line 21 to the gas-liquid contact device 1.

In the solid-liquid contact device 10, the dioxin-containing fly ash is brought into contact with the aqueous solution, whereby the dioxins in the fly ash are decomposed. In the present invention, dioxins account for at least 60%, preferably 8%, of the dioxins.
Decompose at least 0%, more preferably at least 90%. For this purpose, a method of increasing the residence time of fly ash in the solid-liquid contact device 10 and adjusting the reaction time to a long time is adopted. In order to accelerate the decomposition reaction of dioxins and shorten the time required for the decomposition (reaction time), as described above, the aqueous solution contains an iron catalyst, and the properties of the aqueous solution are suitable for the decomposition of dioxins. It needs to be adjusted to something.

The dioxin-containing fly ash is discharged when incinerating municipal garbage and the like. If this is fly ash containing unburned carbon, the dioxin contained in the fly ash is decomposed and made harmless. Is quite difficult. To effectively decompose and detoxify dioxins in this fly ash, as described above,
It is effective to minimize the amount of unburned carbon adhering to the fly ash. In the present invention, as described above,
It is preferable that the amount of unburned carbon in fly ash is specified to be 2% by weight or less, preferably 1% by weight or less, more preferably 0.5% by weight or less. For this purpose, it is necessary to reduce the amount of carbon substances in fly ash by completely combusting incinerators such as refuse in the incinerator in the presence of sufficient oxygen. When the amount of unburned carbon in the fly ash is large, it is preferable to add the above-mentioned contact promoter for promoting the contact between the dioxins and the aqueous solution in the aqueous solution to be brought into contact with the fly ash.

The treated fly ash that has been brought into solid-liquid contact by the solid-liquid contact device 10 is introduced into the solid-liquid separation device 2 through the line 15, where it is subjected to solid-liquid separation. The solid-liquid separation device 2 may be of any type as long as it has a structure capable of separating a solid contained in a liquid. Examples of such a device include a filtration device, a centrifugal separator, and a sedimentation separator. In the solid-liquid separator 2, a solid substance such as fly ash contained in the aqueous solution is separated, and the aqueous solution after the solid substance is separated is introduced into the metal separator 3 through a line 16. The metal separation device 3 may have any structure as long as it can separate heavy metal ions contained in the aqueous solution. Examples of such a device include a device that precipitates metal ions as a precipitate and a device that includes a metal ion adsorbent (such as an ion exchange resin or a chelate resin).

The metal separated by the metal separation device 3 is introduced into the copper separation device 4 through a line 19, where copper ions contained in the metal are separated. This copper is introduced into the solid-liquid contact device 10 through the line 21 in a form converted to an active water-soluble copper compound (such as copper chloride) as necessary. The copper separating device 4 may have any structure as long as it has a structure capable of separating copper from metal. Examples of such a device include a device for selectively precipitating or dissolving a copper compound from metal compounds, and a device for selectively adsorbing and separating copper ions from metal ions. In the case of the present invention, the metal separation device 3 and the copper separation device 4 do not need to be separate devices, and have both functions of separating a metal from an aqueous hydrochloric acid solution and selectively separating copper from the metal. If it is a device, it may be one device. The solution (drainage) from which the metal is separated by the metal separation device 3 is neutralized, discharged through a line 18, further purified if necessary, and discharged into a river or the like.

According to the present invention, by keeping the fly ash and the aqueous solution in contact with each other for a predetermined time, the dioxins in the fly ash can be almost completely decomposed and made harmless. In this case, in order to increase the contact efficiency between the dioxins and the aqueous solution, it is preferable to add the above-mentioned contact promoter or employ the above-described ultrasonic irradiation.

FIG. 2 shows a modification of the flow sheet of FIG. FIG. 2 shows the solid-liquid contact device 1 for all flow sheets.
Only the flow sheet of the part related to 0 is shown, the flow sheet of the other parts is the same as the flow sheet of FIG.
Omitted. In FIG. 2, the same reference numerals as those shown in FIG. 1 have the same meanings as those in FIG.

In FIG. 2, the solid-liquid contact device 10 has a mixing tank 10-A and a reaction tank 10-B. In order to treat the dioxin-containing fly ash according to the flow sheet of FIG. 2, the dioxin-containing fly ash is introduced through the line 11 into the mixing tank 10-A maintained at a temperature lower than 100 ° C. The mixing tank 10-A is for mixing the dioxin-containing fly ash and the dissolved iron compound in order to render the dioxins harmless. Here, the dioxin-containing fly ash is dispersed in an aqueous hydrochloric acid solution. At the same time, some of the metal salts of the dioxin-containing fly ash are dissolved here and mixed with the dissolved iron compound. The mixing tank 10-A has a structure capable of dispersing dioxin-containing fly ash in an aqueous hydrochloric acid solution, dissolving a part of the metal salts of the dioxin-containing fly ash, and mixing with the dissolved iron compound. Any object may be used. A replenishment aqueous hydrochloric acid solution for dispersing dioxin-containing fly ash is introduced into the mixing tank 10-A through the line 13. The iron compound is supplied to the mixing tank 1 through the line 22.
0-A, the iron compound in this case does not necessarily have to be in a dissolved state, but is supplied in a solid state, and is supplied to the mixing tank 10-A in the form of a slurry dispersed in the solution in the line 21. You can also. In this case, the iron compound is dissolved in the mixing tank 10-A. In this case, the pH of the hydrochloric acid aqueous solution is a pH at which the iron compound can be maintained in a dissolved state, and is not more than pH 2.5, preferably pH 2.
0 or less. The dissolved iron compound is uniformly mixed with the dioxin-containing fly ash in the aqueous hydrochloric acid solution. The aqueous solution of hydrochloric acid acidic slurry thus uniformly mixed is sent to the next reaction tank 10-B through a line connected inside, not shown.

The reaction tank 10-B is used for detoxifying dioxins. Here, iron compounds are insolubilized on solid fine particles such as fly ash containing dioxins. The reaction tank 10-B may have a structure capable of controlling the pH of the hydrochloric acid acidic slurry aqueous solution so as to insolubilize the iron compound and making good contact with oxygen or an oxygen-containing gas introduced as necessary. Anything may be used. An alkaline aqueous solution for pH adjustment required for insolubilizing the iron compound is introduced into the reaction tank 10-B through the line 14.
As the alkaline aqueous solution in this case, an aqueous solution or slurry formed by dissolving or dispersing an alkaline substance such as sodium hydroxide, sodium carbonate, calcium hydroxide, calcium carbonate, and magnesium hydroxide in water is used. In addition, the solid-liquid contactor reaction vessel 10-B includes:
Oxygen or an oxygen-containing gas is introduced as needed through line 102 to increase the concentration of dissolved oxygen in the aqueous solution. The gas (exhaust gas) after coming into contact with the aqueous solution passes through line 10
3 and, if necessary, subjected to purification treatment and released to the atmosphere. The chloride ion concentration in the aqueous solution used in the reaction tank 10-B is 10 mmol / L or more, preferably 100 mmol / L or more.
Its pH is between 2.5 and 6.0.

FIG. 3 shows an example of a flow sheet when the exhaust gas containing fly ash discharged from the incinerator is treated according to the present invention. In the figure, reference numeral 40 denotes an incinerator (melting furnace). In the flow sheet shown in FIG. 3, the dust is sent to an incinerator (melting furnace) 40 from a crushed pit or a crushed hopper 41 at the upper portion by a duster 42 including a pusher using a piston, a pump, or the like. Garbage inlet 40 for crushed garbage
a is provided at the bottom, while the oxygen-enriched air separated from the air by the PSA separator is supplied to the char obtained by pyrolysis of the refuse to maintain the inside at a high temperature. A supply pipe 43 for the oxidized air and a supply pipe 44 for the auxiliary agent are connected. A secondary combustion chamber 45 for completely burning the pyrolysis gas in the reducing atmosphere generated by the pyrolysis of the refuse is provided downstream of the melting furnace 40.
Are arranged. The secondary combustion chamber 45 is provided with a pipe 51 for supplying air and a pipe 52 for supplying water (such as sewage from a garbage pit). A waste heat recovery boiler 46 is provided at the outlet side of the secondary combustion chamber 45.
A turbine (not shown) is driven by the heat recovered in 6, and the waste heat is recovered as electric power by a generator connected thereto. Downstream of the boiler 46, an exhaust gas cooling water supply pipe is provided, and the gas-liquid contact device 1 into which exhaust gas containing cooled fly ash is introduced is provided. The gas-liquid contact device 1 has a supply water supply pipe 13 and a pH adjustment alkaline water supply pipe 14.
Is attached. The solid-liquid separator 2 is connected to the gas-liquid contact device 1 via an aqueous solution transfer pipe 15, and further a metal separator 3 is connected to the solid-liquid separator 2. The separation device 4 is connected.

As shown in FIG. 3, the exhaust gas discharged from the apparatus 1 is sequentially raised along an exhaust gas flow path 30 via a mist eliminator (not shown) to an exhaust duct of the exhaust gas of the gas-liquid contact device 1. A heat exchanger 31 for heating, a bag filter (dust collector) 33 for collecting fly ash and the like remaining in the exhaust gas, and a heat exchanger for raising the temperature of the exhaust gas before emission to the atmosphere to prevent white smoke. The exhaust gas passing through the heat exchanger 34 is discharged from the chimney to the atmosphere. The bag filter 33 is provided with a circulation supply line 36 for circulating and supplying the fly ash collected here to the apparatus 1.

Next, in order to incinerate waste such as refuse and treat incinerator exhaust gas in accordance with the flow sheet shown in FIG. 3, the refuse was charged into the refuse melting furnace 40 from the input port 40a and was charged. Crushed garbage is pyrolyzed internally to form pyrolysis gas and carbonaceous, high-calorie char. Then, the char is burned by the oxygen-enriched air and the auxiliary agent supplied from the introduction pipes 43 and 44. Thus, the bottom of the refuse melting furnace 40 is maintained at a high temperature of about 1650 ° C.
As a result, the inside of the refuse melting furnace 40 has a combustion / melting zone at the bottom,
The thermal decomposition zone at the center and the dry zone at the top are kept in a continuous state, and the incombustibles in the garbage become harmless molten slag (metal or glass melt) in the combustion / melting zone at the bottom. It is continuously discharged from the bottom. In parallel with this, the high-temperature gas generated by the reaction at the bottom of the refuse melting furnace (incinerator) 40 rises inside the furnace and thermally decomposes the sequentially input refuse in a pyrolysis zone, thereby thermally decomposing the reducing atmosphere. A gas is generated, and the pyrolysis gas generates
The garbage that has just been thrown in is dried. The pyrolysis gas is supplied to the secondary combustion chamber 45 to which air is supplied through a pipe 51 through a pipe 51 and is supplied with sewage through a pipe 52, and is completely burned. Is boiler 4
The heat is exchanged with the steam in 6, and the turbine and the generator are driven by the obtained steam. Power is recovered by driving the generator. The exhaust gas from which waste heat has been recovered in this way comes into contact with water sprayed into the duct 11 from the exhaust gas cooling water supply pipe 32, is adiabatically cooled, and is cooled to a temperature lower than 100 ° C (generally, about 65 ° C). Then, it is introduced into the gas-liquid contact device 1.

In the gas-liquid contact device 1, contact between an aqueous hydrochloric acid solution containing an iron compound in a solid state and exhaust gas is carried out. Thereby, the fly ash in the exhaust gas is captured in the aqueous solution, and the metal component in the fly ash is extracted in the aqueous solution. Further, acidic gases such as hydrogen chloride gas contained in the exhaust gas are absorbed in the aqueous solution. In the gas-liquid contact device 1, by taking the residence time of the fly ash trapped in the aqueous solution for a predetermined time, the dioxins in the fly ash are almost completely decomposed and made harmless. A part of the liquid component (slurry solution) in the device 1 is withdrawn from the device 1 and introduced into the solid-liquid separation device 2 via the pipe 15. On the other hand, make-up water corresponding to the liquid withdrawal amount is introduced into the apparatus 1 through the pipe 13 such that the amount of water retained in the system is constant. When the volume of the exhaust gas to be treated is large or the concentration of the hydrogen chloride gas is high with the treatment of the exhaust gas in the apparatus 1, the acidity of the hydrochloric acid aqueous solution increases with time, and the pH becomes higher than 2. Although it is conceivable that the pH may decrease, in such a case, based on the detection signal from the detector of the pH control device, an appropriate amount of alkaline water for maintaining the pH in a predetermined range is added to the aqueous hydrochloric acid solution. Introduced through 14.

The concentration of the particulate matter in the exhaust gas discharged from the gas-liquid contact device 1 is usually about 0.1 to 0.3 (g / Nm ³ ), but this exhaust gas is a mist eliminator (not shown). In (), the mist is removed and sent to the heat exchanger 31. In this heat exchanger 31, the next bag filter 3
In order to obtain a temperature sufficient to avoid a trouble due to local condensation in 3, the temperature is raised to a temperature 20 ° C. or more higher than the water saturation temperature, and then sent to the bag filter 33. In the bag filter 33, fly ash remaining in the exhaust gas is removed, and the detoxified exhaust gas is further heated in the heat exchanger 34 and discharged from the chimney to the atmosphere. The bag fly ash collected in the bag filter 33 is separated and removed and sent to the gas-liquid contact device 1 through the return pipe 36, where the dioxins in the fly ash are decomposed and made harmless.

In the solid-liquid separation device 2, fly ash in the aqueous solution is separated. The separated fly ash is decomposed and detoxified in the dioxins contained therein, and has enhanced safety. On the other hand, the aqueous solution from which the fly ash has been separated is sent to the metal separation device 3 through the pipe 16 to separate heavy metal components dissolved in the aqueous solution. The separated metal is sent to the copper separation device 4 through the pipe 20, where the copper is separated.
The separated copper is converted into a water-soluble copper compound (such as copper chloride) as needed, and then circulated to the gas-liquid contact device 1 through the pipe 21. The metal after the copper is separated is discharged through the pipe 20. On the other hand, the aqueous solution after the metal is separated by the metal separation device 3 is discharged through the pipe 18.

When detoxifying incinerator exhaust gas according to the present invention, when the exhaust gas contains hydrogen chloride and the fly ash contained in the exhaust gas contains a sufficient amount of catalytic metal such as iron, The addition of a reaction catalyst from the outside or the addition of an acidic aqueous solution containing chlorine ions is not particularly required, and the exhaust gas can be detoxified only by the addition of industrial water from the outside. In addition, the step of holding the aqueous solution containing the fly ash (dioxin decomposition reaction step) can be performed in a gas-liquid contact device, and the reaction is performed after the aqueous solution containing the fly ash is extracted from the gas-liquid contact device. The reaction can be carried out in a container. When the reaction is carried out in a reaction vessel, it is easy to optimize processing conditions such as temperature, pH conditions, chloride ion concentration and reaction catalyst concentration. Detoxifying and detoxifying dioxins in fly ash is a preferred method.

FIG. 4 shows that the incinerator exhaust gas contains hydrogen chloride,
In the treatment of incinerator exhaust gas when the fly ash contained in the exhaust gas contains a reaction catalyst metal, when dioxins in the fly ash are rendered harmless in a reaction vessel installed separately from the gas-liquid contactor 1 shows an example of the flow sheet. In FIG.
0 is a boiler, 71 is a cooling device, 72 is a gas-liquid contact device,
73 is a heat exchanger, 74 is a dust collector, 75 is a reaction vessel, 76
Denotes a solid-liquid separation device, and 77 denotes a wastewater treatment device.

In order to treat the exhaust gas according to the flow sheet shown in FIG. 4, high temperature (about 900 ° C.) from the incinerator system is used.
The exhaust gas is introduced into the boiler 70 through the line 81, and the calorie in the exhaust gas is recovered here. This lowers the temperature of the exhaust gas to about 250 ° C. This exhaust gas is then sent to a cooling device 71, where it is further cooled,
The temperature of the exhaust gas drops to about 65 ° C. The cooling device 71 is a device having a structure in which cooling water supplied from a line 83 is sprayed to form fine droplets, and the droplets and exhaust gas are brought into contact with each other to perform adiabatic cooling. This cooling device 71
The cooling treatment of the exhaust gas in step (1) produces cooled exhaust gas and cooling water that contacts the exhaust gas and captures a part of pollutants such as hydrogen chloride and fly ash in the exhaust gas. In this case, the cooling water after contact with the exhaust gas absorbs hydrogen chloride in the exhaust gas and is a hydrochloric acid acidic aqueous solution.
The exhaust gas and the hydrochloric acid aqueous solution from the cooling device 71 are introduced into a gas-liquid contact device (smoke washing device) 72 through lines 84 and 85, respectively. Gas-liquid contact device 72 in this case
Has a liquid dispersion type structure such as a spray tower or a packed tower, or a gas dispersion type structure such as a bubble tower or a plate tower. By the contact treatment between the exhaust gas and the hydrochloric acid aqueous solution in the device 72, the pollutants such as the acidic gas and fly ash contained in the exhaust gas are almost completely transferred into the hydrochloric acid aqueous solution. The exhaust gas thus purified enters the heat exchanger 73 through a line 86, is heated at a temperature of 20 ° C. or higher, and is then introduced into a dust collector 74 through a line 87, where it is contained in the exhaust gas. The remaining fly ash is removed. The exhaust gas from which fly ash has been removed is discharged through line 88. Dust collector 7
The fly ash collected in step 4 is separated and removed, and the return pipe 93 or 9
4 and sent to the gas-liquid contact device 72 or the reaction vessel 75.

On the other hand, the hydrochloric acid aqueous solution containing fly ash after contacting with the exhaust gas obtained by the gas-liquid contact device 72 is supplied to the line 8.
9 and introduced into the reaction vessel 75. In the reaction vessel 75, detoxification of dioxins contained in fly ash is achieved. At this time, an iron compound is supplied to the reaction vessel 75 through the lines 100 and 89, and p
An aqueous alkali solution for adjusting H is introduced through a line 101. Further, oxygen or an oxygen-containing gas is introduced into the reaction vessel 75 as needed through the line 102 to increase the concentration of dissolved oxygen in the aqueous solution. The gas after contact with the aqueous solution is combined with the gas in line 86 through line 103. That is, the aqueous solution containing fly ash is stirred in the reaction vessel for a predetermined time, during which the dioxins in the fly ash are decomposed and made harmless. The aqueous solution in this case absorbs the hydrogen chloride gas contained in the exhaust gas and dissolves the reaction catalyst contained in the fly ash, and exhibits a good decomposition and detoxifying effect on dioxins. is there. The reaction time depends on the amount of the carbonaceous material contained in the fly ash, so it is difficult to determine the reaction time uniquely. When the amount of the substance is 0.5% by weight or less, 24
About 48 hours, and 5% in the case of about 1.5% by weight.
It is about 0 to 60 hours. On the other hand, in the case of about 1.5% by weight, in the presence of a contact accelerator such as methanol, about 20 to
It is about 30 hours. The reaction product obtained in the reaction vessel 75 is sent to the solid-liquid separator 76 through the line 90,
The solid material (fly ash) obtained after the solid-liquid separation treatment is discharged through a line 92, while the separated aqueous solution is sent through a line 91 to a wastewater treatment step including a metal separation treatment and the like. Can be

FIG. 5 shows another example of a flow sheet when the exhaust gas containing fly ash discharged from the incinerator is treated according to the present invention. In FIG. 5, 1 is an incinerator, 2 is a waste heat boiler, 3 is a cooling tower, 4 is a gas-liquid contact device, 5 is a dust collector, 6
Denotes a storage tank, 7 denotes a thickener, 8 denotes a dioxin decomposition reaction device, and 9 denotes a solid-liquid separation device.

In order to detoxify the exhaust gas from the incinerator in accordance with the flow sheet shown in FIG.
After passing through 1, it is introduced into the waste heat boiler 2, where its heat is recovered, and then introduced into the cooling tower 3 through the line 12.
The exhaust gas introduced into the cooling tower 3 is brought into contact with fine droplets of the cooling liquid sprayed upward in the tower through the lines 13 and 14. The exhaust gas is humidified and cooled by this contact, and is reduced to a saturation temperature of about 60 to 75 ° C. depending on the amount of water in the incineration exhaust gas before cooling. The cooled exhaust gas is introduced into the gas-liquid contact device 4, where it is brought into contact with a hydrochloric acid aqueous solution. By this gas-liquid contact, fly ash contained in the exhaust gas is captured by the aqueous solution and removed from the exhaust gas. On the other hand, the exhaust gas
It is discharged from the device 4 through 3. This exhaust gas is introduced into a heat exchanger 24, where the exhaust gas is heated to a relative humidity at which moisture does not condense in a downstream bag filter 5, and then introduced into the bag filter 5, where residual fly ash in the exhaust gas is removed. Is done. The exhaust gas that has passed through the bag filter 5 is introduced into a heat exchanger 26 through a line 25, where it is further heated to prevent white smoke, and, if necessary, subjected to further appropriate treatment. Released to The pH of the aqueous hydrochloric acid solution is 7 or less, preferably 2 to 6. As the gas-liquid contact device 4, any device having a function of capturing fly ash in exhaust gas in a liquid can be used. Such devices include, for example,
A tank filled with an aqueous solution can be used. In order to contact the exhaust gas with the aqueous solution using such a tank, the exhaust gas may be blown into the aqueous solution filled in the tank via a nozzle.

In the gas-liquid contact device 4, contact between an aqueous hydrochloric acid solution containing an iron compound in a solid state and exhaust gas is performed. Thereby, the fly ash in the exhaust gas is captured in the aqueous solution, and the metal component in the fly ash is extracted in the aqueous solution. Further, acidic gases such as hydrogen chloride gas contained in the exhaust gas are absorbed in the aqueous solution. The liquid component (slurry solution) in the device 4 is withdrawn from the device 4 and introduced into the thickener 7 through a line 28.
Replenishing cooling water is introduced into the cooling tower 3 via lines 15 and 14 so that the amount of liquid retained in the system is constant. A part of the cooling liquid used in the cooling tower 3 is introduced into the gas-liquid contact device 4 through the line 16. In addition, with the treatment of the exhaust gas in the gas-liquid contact device 4, when the volume of the exhaust gas to be treated is large or when the concentration of the hydrogen chloride gas is high, the acidity of the hydrochloric acid aqueous solution increases with time, and the pH is increased. However, in such a case, a suitable amount of alkaline solution for maintaining the pH within a predetermined range is added to the aqueous hydrochloric acid solution based on the detection signal from the detector of the pH control device. Water is introduced.

The thickener 7 functions as a concentrator for increasing the fly ash concentration in the aqueous solution containing fly ash obtained by the gas-liquid contact device 4. That is, in this thickener 7,
Fly ash in the aqueous solution settles due to its gravity, and the fly ash concentration in the aqueous solution on the surface is reduced, while the fly ash concentration in the aqueous solution on the bottom is increased. The aqueous solution (fly ash concentrate) having the increased fly ash concentration is introduced into the dioxin decomposition reaction device 8 via the line 29 and the pump. on the other hand,
The fly ash dilute aqueous solution having a low fly ash concentration on the surface of the thickener is circulated to the cooling tower 3 as a cooling liquid through the storage tank 6, the pump and the line 21, and further through the line 20. Further, a part of the fly ash dilute aqueous solution passing through the line 21 can be introduced into the gas-liquid contact device 4 through the line 19. Further, a part thereof can be introduced into the cooling tower 3, and the remaining part can be introduced into the gas-liquid contact device 4. The fly ash concentration rate by the thickener 7 is 2 to 60 times, preferably 3 to 50 times. The fly ash concentration in the fly ash concentrate discharged from the thickener 7 is preferably 1% by weight or more. The upper limit is not particularly limited, but is usually about 30% by weight. On the other hand, the fly ash concentration in the diluted fly ash aqueous solution having a reduced fly ash concentration discharged from the thickener 7 is:
It is at most 0.5% by weight, preferably at most 0.1% by weight.

As described above, the fly ash-containing aqueous solution is concentrated by the thickener 7 and the concentrated fly ash solution is introduced into the dioxin decomposition reactor 8, thereby reducing the size of the reactor 8 and increasing the efficiency of the reactor. Can be. When dioxins are decomposed and made harmless by the reactor 8, it is necessary to make the residence time (reaction time) of fly ash in the reactor 8 as long as possible in order to increase the decomposition rate. Low fly ash concentrations in the contained aqueous solution necessitate an increase in the equipment volume corresponding to the extended residence time. In the case of the present invention, the fly ash-containing aqueous solution introduced into the reactor 8 has a high fly ash concentration, so that the amount of fly ash per volume in the reactor increases, and The device can be reduced in size. The fly ash dilute aqueous solution having a reduced fly ash concentration obtained by the thickener 7 is suitable as a cooling liquid used in the cooling tower 3 and as a processing liquid used in the gas-liquid contact device 4. That is, the fly ash dilute aqueous solution has a low fly ash concentration and an extremely fine particle size of the fly ash, so that when the pump, the pipe, and the nozzle are allowed to flow, friction and clogging troubles occur. It does not occur and can be handled almost in the same manner as ordinary industrial water.

The aqueous solution containing fly ash with an increased fly ash concentration obtained by the thickener 7 is sent to the dioxin decomposition reactor 8 by a line 29 and a pump. An iron compound is supplied to the dioxin decomposition reaction device 8 through a line 100, and an alkaline aqueous solution for pH adjustment is introduced through a line 101 as necessary. Further, if necessary, oxygen or an oxygen-containing gas is introduced into the dioxin decomposition reactor 8 through the line 102 to increase the concentration of dissolved oxygen in the aqueous solution. The gas after coming into contact with the aqueous solution is combined with the gas in the line 23 through the line 103.

In the dioxin decomposition reactor 8, detoxification of dioxins contained in fly ash is achieved. That is, the aqueous solution containing fly ash is stirred in the reaction tank for a predetermined time, during which the dioxins in the fly ash are decomposed and made harmless. The aqueous solution in this case is an aqueous hydrochloric acid solution containing an iron compound in a solid state, and exhibits a good detoxifying effect on dioxins. It is preferable that the fly ash residence time in the reactor 8 is longer from the viewpoint of the decomposition rate of dioxins, but generally, the treatment conditions are adjusted to be about 1 to 100 hours. The dioxin decomposition reactor 8 is operated so that the decomposition rate of dioxins is usually 60% or more, preferably 80% or more, more preferably 90% or more.

The reaction product obtained in the reaction device 8 is sent to a solid-liquid separation device 9 through a pump and a line 31, where it is subjected to a solid-liquid separation treatment, and the obtained solid substance (fly ash, etc.)
Is discharged through a line 32, while the separated aqueous solution is sent through a line 33 to a wastewater treatment step including a metal separation treatment and the like. A part of the catalytic metal such as copper recovered by the metal separation treatment is converted into a dioxin decomposition reactor 8
Can also be returned to In this case, the concentration of the reaction catalyst in the dioxin decomposition reaction device is increased, which is more effective. The dioxin decomposition reaction device 8 may be composed of one reaction vessel, or may be composed of a plurality of reaction vessels. In the case of the present invention, since the reaction tank is close to a complete mixing tank, a reaction device with high reaction efficiency can be obtained by connecting a plurality of reaction tanks in series. When a plurality of reaction vessels are used, the reaction conditions such as the concentration of the reaction catalyst, the chloride ion concentration, and the pH in each vessel can be appropriately changed, thereby enabling an efficient decomposition reaction of dioxins. It is.

When detoxifying incinerator exhaust gas according to the present invention, if the exhaust gas contains hydrogen chloride and the fly ash contained in the exhaust gas contains a sufficient amount of catalytic metal such as iron, The addition of a reaction catalyst from the outside or the addition of an acidic aqueous solution containing chlorine ions is not particularly required, and the exhaust gas can be detoxified only by the addition of industrial water from the outside. Further, in the present invention, as a cooling liquid used in the cooling step and an aqueous solution used in the gas-liquid contacting step, an aqueous hydrochloric acid solution containing an iron compound in a solid state is used, and during the cooling and during the gas-liquid contacting. Can also decompose and remove dioxins. Therefore,
In this case, the residence time of the fly ash-containing aqueous solution in the dioxin decomposition reaction apparatus can be shortened, so that there is an advantage that the reaction tank can be downsized. In the present invention,
A hydrocyclone can be used instead of the thickener. When using a liquid cyclone, as in the case of the thickener, an aqueous solution with an increased fly ash concentration and an aqueous solution with a reduced fly ash concentration are obtained, and the aqueous solution with a high fly ash concentration is introduced into a dioxin decomposition reactor, The dilute aqueous solution having a low fly ash concentration is introduced into a cooling tower and / or a gas-liquid contact device.

FIG. 6 shows a modification of the flow sheet shown in FIG. 6, the same reference numerals as those shown in FIG. 5 have the same meaning. In FIG. 5, reference numeral 10 denotes an aqueous solution concentrator (multiple-effect can). The flow sheet shown in FIG.
Line 3 after separating fly ash obtained by solid-liquid separator 9
4 differs from the method shown in FIG. 4 in that the aqueous solution withdrawn through 3 is introduced into the concentration device 10 and a part of the concentrated solution is returned to the dioxin decomposition reaction device 8. The concentrating device 10 is composed of a multi-effect can, into which heated steam is introduced through a line 43 and an aqueous solution after fly ash is separated is introduced through a line 33. The heated steam and the aqueous solution introduced into the apparatus 10 are indirectly contacted by the first evaporator a, the aqueous solution is indirectly heated by the heated steam, and the steam corresponding to the heating amount is evaporated from the aqueous solution. Thus, the aqueous solution is concentrated. In this case, due to the indirect contact between the aqueous solution and the heated steam, the steam is condensed to generate condensed water. This condensed water is withdrawn from the bottom of the evaporator a through the line 34.

The aqueous solution that has been subjected to the evaporative concentration treatment in the evaporator a is then introduced into the evaporator b, and the water vapor evaporated in the evaporator a is also introduced into the evaporator b. And the aqueous solution is indirectly heated by the water vapor, and the water vapor corresponding to the heating amount evaporates from the aqueous solution, whereby the aqueous solution is concentrated. The condensed water generated by the indirect contact between the water vapor and the aqueous solution is supplied to line 3
Withdrawn through 5. The concentrated liquid and the vapor in the evaporator b are introduced into the evaporator c in the same manner as described above, and are indirectly contacted in the same manner as described above. The condensed water generated in the evaporator c is extracted through a line 36. On the other hand, evaporator c
The evaporating steam in the tank passes through a line 37 and is condensed in a cooler 38, and then passes through a line 39 and a line 42 to form the cooling tower 3
Will be introduced. Each condensed water extracted from the evaporators a, b, and c is introduced into the cooling tower 3 through the line 39 and the line 42. The concentrated liquid extracted from the evaporator c through the line 40 is introduced into the subsequent wastewater treatment device through the line 41, and after being subjected to appropriate wastewater treatment, is discharged. In this case, a part of the concentrate is transferred to lines 40 and 4
4 and is returned to the dioxin decomposition reactor 8. By returning the concentrated liquid to the dioxin decomposition reaction device 8, the concentration of the reaction catalyst and chlorine ion in the device 8 can be increased, which contributes to reducing the volume of the decomposition reaction device or improving the decomposition rate. At this time, the reaction catalyst may be recycled after being subjected to an activation treatment as required. In the concentration device 10, it is preferable that the aqueous solution from the solid-liquid separation device 9 be concentrated within a range in which the chlorine compound in the concentrated solution does not precipitate.

FIGS. 5 and 6 show an example in which a cooling tower using a cooling liquid is used to cool the incinerator exhaust gas to a temperature lower than 100 ° C. However, the present invention is not limited to this, and can be performed using other means, for example, a heat exchanger. As described above, the higher the fly ash concentration in the aqueous fly ash-containing solution supplied to the dioxin decomposition reaction device 8, the higher the device efficiency of the reaction device 8. For example, when the residence time of the fly ash-containing aqueous solution in the apparatus is the same, if the fly ash concentration in the aqueous solution is doubled, the internal volume of the reaction device 8 can be reduced to about 1/2. Then, in order to increase the fly ash concentration in the aqueous solution supplied to the reaction device 8, it is necessary to improve the concentration ratio in the thickener 7. However, the aqueous solution contains salts generated from the acid gas in the exhaust gas and salts extracted from the fly ash, and it is necessary to discharge these from the system. When the fly ash is concentrated to a high concentration, the amount of the discharged aqueous solution is reduced, thereby increasing the salt concentration in the system. If the salt concentration is close to the saturation solubility, there will be problems such as precipitation of salts in places where the system is partially cooled, and incomplete extraction of salts from fly ash. Therefore, in order to concentrate fly ash to a high concentration, it may be necessary to adjust the concentration of salts in the system in some cases.

FIG. 7 shows a modification of the flow sheet of FIG. FIG. 7 shows only the flow sheet of the portion related to the thickener 7 of the entire flow sheet, and the other portion of the flow sheet is the same as the flow sheet of FIG. 5 and is omitted. In FIG. 7, the same reference numerals as those shown in FIG. 4 have the same meanings as those in FIG.

According to the flow sheet shown in FIG. 7, FIG.
The fly ash-containing aqueous solution withdrawn from the gas-liquid contact device 4 shown in (1) is introduced into the thickener 7 through a line 28, where it is concentrated. The concentrated liquid having an increased fly ash concentration passes through a line 29 and a pump, and is supplied to a dioxin decomposition reaction apparatus 8.
Where dioxins are decomposed and made harmless. The dioxin decomposition reactor 8 has a line 10
0, an iron compound is supplied, and an alkaline aqueous solution for pH adjustment is introduced through a line 101 as necessary. Further, if necessary, oxygen or an oxygen-containing gas is introduced into the dioxin decomposition reactor 8 through the line 102 to increase the concentration of dissolved oxygen in the aqueous solution. The gas (exhaust gas) after coming into contact with the aqueous solution is discharged through the line 103, and if necessary, subjected to a purification treatment and released to the atmosphere. The aqueous solution discharged from the dioxin decomposition reaction device 8 is introduced into the solid-liquid separation device 9 through a pump and a line 31, where fly ash and the like in the aqueous solution are removed from a line 32.
Separated through. The separated aqueous solution, such as fly ash, is sent to the next drainage treatment device through the line 33, subjected to appropriate treatment, and discharged. Meanwhile, thickener 7
The aqueous solution with reduced fly ash concentration obtained in
Through the storage tank 6 and the line 51 to be introduced into the solid-liquid separation device 52 where the fly ash and the like in the aqueous solution are separated and introduced into the storage tank 56 through the line 53. The separated aqueous solution such as fly ash obtained by the solid-liquid separator 52 is withdrawn through a line 54, a part of which is introduced into a storage tank 56 through a line 55, and the remaining part is connected to a line 57. Through to line 33. The aqueous solution containing fly ash in the storage tank 56 is circulated through the line 58 to the cooling tower 3 and / or the gas-liquid contact device 4. According to the method of FIG. 7, since the discharged water from the system is discharged from the line 57 in addition to the aqueous solution extracted from the line 29, the fly ash can be concentrated while adjusting the salt concentration in the system. Becomes possible.

FIG. 8 shows a flow sheet when the thickener 7 is used to concentrate the fly ash concentration in the aqueous solution. 8, reference numeral 60 denotes a fly ash slurry preparation tank. 8, the same reference numerals as those shown in FIG. 7 have the same meaning. In the flow sheet shown in FIG. 8, a fly ash slurry liquid prepared in a fly ash slurry preparation tank is used instead of the fly ash-containing aqueous solution extracted from the gas-liquid contact device 4 shown in FIG. The flow sheet shown in FIG. 8 is different from the flow sheet in the case of actually treating exhaust gas from an incinerator in that a fly ash slurry preparation tank is included, but the flow sheet of FIG. This is adopted because the concentration experiment of the contained aqueous solution can be easily performed. In FIG. 8, reference numeral 60 denotes a fly ash slurry preparation tank, and the same reference numerals as those shown in FIG. 6 have the same meanings as those of FIG.

In the flow sheet shown in FIG. 8, a thickener supernatant liquid from line 21 and industrial water and line 6 from line 61 are supplied to fly ash slurry preparation tank 60.
Hydrochloric acid and sulfuric acid simulating acidic gas removed from the exhaust gas from 2 are added, and fly ash is further added from a line 63, and then a pH adjuster is added from a line 64 while stirring to prepare a slurry liquid. This slurry liquid is supplied to the thickener 7 through a line 28. The iron compound is supplied to the fly ash slurry preparation tank 60 or the dioxin decomposition reactor 8 by the line 100. When the fly ash is supplied to the fly ash slurry preparation tank 60, the decomposition reaction by the iron compound preliminarily proceeds even in the process until the fly ash is concentrated by the thickener 7, and the decomposition reaction is accelerated in the dioxin decomposition reaction device 8. Is completed. When the iron compound is supplied to the dioxin decomposition reactor 8 through the line 100, the iron compound is supplied after the fly ash is concentrated by the thickener 7 and the decomposition treatment is performed in the dioxin decomposition reactor 8. Is shown.

FIG. 9 shows an example of a flow sheet when the exhaust gas containing fly ash discharged from the incinerator is treated by the method of the present invention including two gas-liquid contacting steps. In FIG. 8, 1 is a first gas-liquid contact step, 2 is a second gas-liquid contact step, 3
Is a dioxin decomposition reaction step, 4 is a solid-liquid separation step, 5
Denotes a wastewater treatment step, and 6 denotes a fly ash treatment step. In order to detoxify the incinerator exhaust gas according to the flow sheet shown in FIG.
, And brought into contact with the first treatment liquid, so that the acid gas and fly ash contained in the exhaust gas are captured by the first treatment liquid and separated from the exhaust gas. The first processing liquid used in the first processing step 1 is:
It is mainly for trapping hydrogen chloride (HCl) and fly ash contained in the exhaust gas in the liquid. As the first treatment liquid, industrial water, an acidic aqueous solution, an aqueous hydrochloric acid solution containing a catalyst for decomposing dioxins such as iron compounds in a solid state, or the like is used. When an acidic aqueous solution or an aqueous hydrochloric acid solution containing a reaction catalyst is used, the pH is preferably adjusted to a range of 2 to 4. Such a pH of 2 as the first treatment liquid
When an acidic aqueous solution of (4) to (4) is used, HCl in exhaust gas can be effectively absorbed by the treatment liquid and removed from the exhaust gas.

When the exhaust gas from the incinerator is brought into contact with the first treatment liquid, the temperature and the amount of the first treatment liquid depend on the temperature and the amount of the exhaust gas. And the amount used is such that the temperature of the treatment liquid is lower than 100 ° C., preferably 80 ° C. or lower. When the temperature of the exhaust gas is 100 ° C. or more, for example, 110 to 300
In the case of ° C, the first processing liquid needs to have a function as a cooling liquid for the exhaust gas, and the first processing liquid uses a relatively large amount of the processing liquid having a low temperature, or has a large number of spray nozzles. It is necessary to improve the gas-liquid contact. In the gas-liquid contacting step using the first treatment liquid, 30 to 95%, preferably 80 to 95%, of fly ash in the exhaust gas is captured and separated in the treatment liquid. In such fly ash separation, fly ash having a large particle diameter is preferentially captured in the first processing liquid. Most of the HCl in the exhaust gas is absorbed by the first processing liquid. The apparatus for performing the first gas-liquid contacting step 1 may have any structure as long as fly ash in the exhaust gas can be captured and separated in the processing liquid. Such a device has a liquid spray nozzle and has a structure in which fine droplet particles ejected from the spray nozzle are brought into contact with a gas, and a gas injection nozzle is used to eject a gas into the liquid. An apparatus having a structure is used. The treated exhaust gas that has been subjected to the contact treatment with the first treatment liquid in the first gas-liquid contacting step 1 is introduced into the second gas-liquid contacting step 2 through the line 12, where the acidic gas remaining in the exhaust gas is introduced. Gas and fly ash are removed. The second gas-liquid contacting step is mainly for separating SO ₂ and fly ash remaining in the exhaust gas from the exhaust gas.

As a first method for carrying out this, the exhaust gas is brought into contact with a second treatment liquid to remove SO ₂ and fly ash remaining in the exhaust gas. At the same time, in the second gas-liquid contacting step, the exhaust gas is cooled to a temperature lower than that of the exhaust gas at the inlet of the second gas-liquid contacting step to condense the water in the exhaust gas. It is removed by a mist separator installed above the liquid contacting step. In this case, since water mist is generated with fly ash fine particles remaining in the exhaust gas passing through the first gas-liquid contacting step as a nucleus, the weight and the particle size of the fine particles increase, and the fine particles are easily captured by the mist separator. . As the mist separator, a demister that removes by collision, a wet electrostatic precipitator, or the like can be used, but a wet electric precipitator is preferable. As the cleaning liquid for the wet electrostatic precipitator, industrial water or the second treatment liquid can be used, and it is preferable to use the same temperature as or lower than the exhaust gas passing through the wet electric precipitator. As a method of cooling the exhaust gas in the second gas-liquid contacting step to a temperature lower than the exhaust gas at the inlet of the second gas-liquid contacting step, the second processing liquid is cooled to a temperature lower than the exhaust gas at the second gas-liquid contacting step to contact the exhaust gas. For example, a direct cooling method in which a heat exchanger is disposed in the second gas-liquid contacting step and an indirect cooling of exhaust gas can be used. In this case, condensed water from the exhaust gas can be used as it is, or an acidic aqueous solution or an aqueous hydrochloric acid solution containing a reaction catalyst for a decomposition reaction of dioxins such as iron compounds in a solid state can be used as the second treatment liquid.

It is preferable that the pH of the second treatment liquid is adjusted in the range of 4 to 6, whereby the SO 2 remaining in the exhaust gas is adjusted.
₂ can be effectively removed from the exhaust gas. Further, even in contact with the second treatment liquid, fly ash remaining in the exhaust gas is removed, and the fly ash is almost completely removed together with the above-described removal by the water mist. The cooling temperature of the exhaust gas in the second gas-liquid contacting step 2 may be a temperature at which moisture condenses at a temperature lower than the exhaust gas temperature at the inlet of the second gas-liquid contacting step. 5-4
A temperature lower by about 0 ° C, preferably by about 5 to 30 ° C is used. As an apparatus for performing the second gas-liquid contacting step 2, a commonly used apparatus for contacting a gas and a liquid, for example, a spray tower, a packed tower, or the like can be used. When performing indirect cooling by the above-described heat exchanger, the heat exchanger may be disposed at an appropriate place in a tower such as a spray tower or a packed tower. Further, the wet electrostatic precipitator may be installed at an upper part in the tower or may be arranged outside the tower.

As a second method, a packed tower filled with activated carbon is used in the second gas-liquid contacting step to adsorb and remove gaseous dioxins in addition to SO ₂ and residual fly ash in exhaust gas. Furthermore, the dioxins adsorbed on the activated carbon are decomposed by bringing the second treatment liquid comprising a hydrochloric acid aqueous solution containing a reaction catalyst such as an iron compound in a solid state into contact with the activated carbon packed bed. Further, SO ₂ remaining in the exhaust gas is adsorbed by activated carbon, and then converted into sulfuric acid by its catalytic oxidation action and removed. The generated sulfuric acid absorbs moisture in the exhaust gas to become diluted sulfuric acid, and overflows from inside the activated carbon to flow down the activated carbon packed bed. Further, fly ash remaining in the exhaust gas is also removed by contact with the second treatment liquid. In this case, the contact temperature in the second gas-liquid contacting step 2 may be the same as the exhaust gas temperature at the inlet of the second gas-liquid contacting step, and is usually 30 to 80 ° C, preferably 50 to 7 ° C.
0 ° C. PH of the second processing liquid in the second gas-liquid contacting step 2
Need not be a high pH for SO ₂ is removed by adsorption and catalytic oxidation with activated carbon, preferably adjusted to a range of valid pH2~6 the decomposition of the adsorbed dioxins on activated carbon.

The activated carbon to be used is preferably in the form of granules, honeycombs or the like having a small pressure loss of exhaust gas. The granular activated carbon preferably has an average particle diameter of 2 mm or more, and activated carbon usually used for gas treatment or water treatment can be used. These activated carbons are preferably subjected to a hydrophobic treatment, and may be subjected to a heat treatment, a fluoridation treatment, or a support of hydrophobic particles such as a polypropylene, a vinyl chloride resin, and Teflon. The loading amount of the hydrophobic particles is 1 to 15
%, Preferably 3 to 10%. As the honeycomb-shaped activated carbon, those obtained by mixing activated carbon powder and a dispersant of hydrophobic particles such as Teflon dispersion and forming the mixture into a honeycomb shape can be used. The content of the hydrophobic particles is 3 to 20%, preferably 5 to 15%. When such activated carbon is used, dioxins are effectively adsorbed on the hydrophobic surface thereof, and further contact with a hydrochloric acid aqueous solution containing a reaction catalyst such as a solid iron compound to remove dioxins from the exhaust gas. Detoxification is achieved.
The treated exhaust gas obtained in the second gas-liquid contacting step is
And then, if necessary, subjected to treatments such as white smoke prevention and released to the atmosphere. In the case of the method of cooling the exhaust gas in the second gas-liquid contacting step, since the moisture concentration in the treated exhaust gas is reduced, the heat load required for the heat treatment of the exhaust gas that is usually performed to prevent white smoke can be reduced. . The second processing liquid (second processing drainage) discharged from the second gas-liquid contacting step 2 circulates through the line 23 to the first gas-liquid contacting step 1,
It is preferable to use it as at least a part of the first processing liquid. Also, a part of the circulating liquid can be directly introduced into the decomposition reaction step 3.

Fly ash trapped in the first processing liquid (first processing waste liquid) obtained in the first gas-liquid contacting step 1 and the second processing liquid (second processing liquid) obtained in the second gas-liquid contacting step 2 The fly ash trapped in the treated effluent) is brought into contact with an aqueous hydrochloric acid solution (treating agent) containing the iron compound in a solid state in the dioxin decomposition reaction step 3 separately or in a united state. As a method for this, in addition to the method of adding the processing liquid containing the fly ash to the processing agent and stirring for a predetermined time, at least the first processing liquid of the first processing liquid and the second processing liquid is used as the first processing liquid. ,
The gas-liquid contact treatment is performed using a hydrochloric acid aqueous solution containing a reaction catalyst such as a solid state iron compound, and the treatment liquid containing fly ash after the gas-liquid contact treatment is treated for a predetermined time in a reaction vessel used in the decomposition reaction step 3. Stirring can be mentioned. In an aqueous hydrochloric acid solution containing this reaction catalyst used at least as the first treatment liquid, an iron compound or the like as the reaction catalyst can be added from the outside, and when fly ash is brought into contact with the aqueous hydrochloric acid solution, Metal ions eluted from the ash can be used. Hydrogen chloride (HCl) necessary for forming an aqueous hydrochloric acid solution can be added from the outside, and hydrogen chloride contained in exhaust gas can be used. . When the exhaust gas contains hydrogen chloride and the catalyst metal-containing fly ash, the aqueous hydrochloric acid solution containing the reaction catalyst can be prepared by contacting the exhaust gas with industrial water in the first gas-liquid contacting step.

In the dioxin decomposition reaction step 3, the decomposition rate of the dioxins adhering to the fly ash is:
Usually, the operation is performed so as to be at least 60%, preferably at least 80%, more preferably at least 90%. In the dioxin decomposition reaction step 3, an iron compound is supplied through a line 100, and an alkaline aqueous solution for pH adjustment is introduced through a line 101 as needed. Further, in the dioxin decomposition reaction step 3, if necessary, oxygen or an oxygen-containing gas is introduced through the line 102 to increase the concentration of dissolved oxygen in the aqueous solution. The gas (exhaust gas) after coming into contact with the aqueous solution is discharged through the line 103, and if necessary, subjected to a purification treatment and released to the atmosphere. As the decomposition reaction vessel used in the decomposition reaction step 3, a normal stirring type reaction vessel can be used. In addition, this decomposition reaction step can be performed in a single-stage processing step, or can be performed in a series multi-stage processing step. The decomposition treatment liquid obtained in the decomposition reaction step 3 is separated into fly ash contained in the liquid in the solid-liquid separation step 4 and the obtained fly ash is introduced into the fly ash processing step 6 through the line 16. And process.

In the solid-liquid separation step 4, fly ash in the treatment liquid is separated. As a device for this, a filtration device, a centrifugal separation device or the like is used. This solid-liquid separation step 4
The solid (cake-like) separated fly ash obtained in (1) is dried in the fly ash processing step 6. The dry fly ash thus obtained is withdrawn through the line 18 and recovered as stabilized fly ash. The separated liquid (drainage) obtained in the solid-liquid separation step 4 is withdrawn through the line 17, subjected to necessary treatment in the wastewater treatment step 5, and discharged as required. In addition, a part of the separated liquid separated in the solid-liquid separation step 4 passes through the first gas-liquid contacting step 1
Alternatively, it is circulated to the second gas-liquid contacting step 2, and the first processing liquid and / or
Alternatively, it is used as at least a part of the second processing liquid. Thereby, the reaction catalyst accumulated in the first processing liquid can be used in the second gas-liquid contacting step. Further, a reaction catalyst can be added to the second treatment liquid as needed. In addition,
The line 22 shown in connection with the second gas-liquid separation step 2 is a line for supplying a part of the second processing liquid to the wet dust collector provided in the second gas-liquid contact step. When the incinerator exhaust gas is detoxified as described above, the processing liquid containing fly ash obtained in the first gas-liquid contacting step 1 is used after increasing the fly ash concentration in the processing liquid in the concentration step. It can also be introduced into the decomposition reaction step 3.

In this case, a thickener, a cyclone or the like is used as a concentrator used in the concentrating step. In this concentration step, fly ash has a high concentration, usually 1 to 20% by weight,
A slurry containing preferably 4 to 20% by weight and a dilute solution having a fly ash concentration of 0.5% by weight or less, and preferably substantially zero%, are obtained. Introduced to the step 3, the diluted liquid is sent to the first gas-liquid contact step 1 and / or the second gas-liquid contact step 2, and is used as a part of the first processing liquid and / or the second processing liquid.

FIG. 10 is a flow sheet showing a specific embodiment of the flow sheet of FIG. In FIG. 10, 31 is an incinerator, 32 is a waste heat boiler, 33 is a first gas-liquid contact device,
34 is a second gas-liquid contact device, 35 is a wet electric dust collector, 3
Reference numeral 6 denotes a dioxin decomposition reaction device, and 37 denotes a solid-liquid separation device.

In order to detoxify the incinerator exhaust gas according to the flow sheet shown in FIG. 10, the incinerator exhaust gas containing dioxin-containing fly ash generated in the incinerator 31 is passed through a line 41 to a waste heat boiler 32. After collecting the heat, the heat is introduced into the first gas-liquid contact device 33 through the line 42. The exhaust gas introduced into the first gas-liquid contact device 33 comes into contact with the fine droplet particles of the first processing liquid sprayed into the tower through the line 45 and is rapidly cooled, and at the same time, fly ash in the exhaust gas. And most of the HCl are trapped in the first treatment liquid and separated from the exhaust gas. The exhaust gas has a temperature of 45 to 45 by the first gas-liquid contact treatment.
75 ° C, preferably reduced to 50-70 ° C. The treated exhaust gas which has been cooled and from which a part of the fly ash and most of the HCl have been removed is introduced into the second gas-liquid contact device 34 via the line 43, where it is brought into contact with the second treated liquid. . By this gas-liquid contact, residual fly ash and SO ₂ contained in the exhaust gas are captured by the second treatment liquid and removed from the exhaust gas.

The first gas-liquid contact device 33 shown in FIG.
It has a structure in which a liquid spray nozzle is provided at the top of the tower, and the first treatment liquid stored at the bottom of the tower is sprayed from the spray nozzle via the line 45 and brought into contact with the gas. The apparatus is not limited to a simple apparatus, and may be, for example, a structure in which gas is ejected into a liquid in a tank containing the liquid through a gas blowing nozzle to perform gas-liquid contact. The second gas-liquid contact device 34 shown in FIG. 10 has a structure in which a filling layer is formed inside, and has a liquid spray nozzle 57 above the filling layer F. Known materials such as teralet can be used as the filler for the filling layer. Further, above the packed bed F of this device, a wet-type electrostatic precipitator 35 is provided.
Is attached. The wet electric precipitator 35 in this case
Need not necessarily be disposed above the packed layer F, and may be disposed independently of the second gas-liquid contact device 34.

In the first gas-liquid contacting device 33, a hydrochloric acid aqueous solution containing a reaction catalyst such as a solid iron compound is stored at the bottom of the device as a first treatment liquid. Is sprayed from the upper part of the apparatus through the apparatus, and the inside of the apparatus is filled with fine droplet particles of the aqueous solution. The incinerator exhaust gas introduced through the waste heat boiler 32 and the line 42 (the temperature is typically
(Approximately 0-300 ° C.) comes into contact with the fine droplet particles of the aqueous solution, and most of fly ash and HCl contained in the gas are captured by the droplet particles and separated from the exhaust gas. The droplet particles capturing the fly ash and the like descend in the apparatus and are united with the stored liquid at the bottom of the apparatus. In the first gas-liquid contact processing, the pH of the first processing liquid used in the first gas-liquid contact device is
Is adjusted to the range of 2 to 4, HCl contained in the exhaust gas can be efficiently captured and separated in the treatment liquid. By performing the first gas-liquid contact treatment of the exhaust gas as described above, 30 to 95 of the fly ash contained in the exhaust gas can be obtained.
%, Preferably 80 to 95%, is captured and removed by the first processing liquid. In addition, 90% or more of HCl contained in exhaust gas,
Preferably, 95% or more is captured and removed by the first processing liquid.

A part of the waste water obtained by the solid-liquid separation device 37 is circulated through the line 51 to the second gas-liquid contact device 34 as a second treatment liquid. This circulating fluid is introduced into the lower part of the device 34 and is united with the stored liquid at the bottom of the device. The liquid stored at the bottom of the apparatus is introduced into a cooler 55 through a line 52 and a pump.
After the temperature has been lowered to a certain degree, a part thereof is sprayed from a liquid spray nozzle 57 through a line 56 and the remainder is sprayed from a liquid spray nozzle 59 through a line 58. In the second gas-liquid contacting step 34, the second processing liquid flows downward from above in the packed layer F, and contacts the exhaust gas rising from below during that time. By this contact, the remaining fly ash and SO ₂ in the exhaust gas are captured by the flowing-down processing liquid, and the processing liquid that has captured the fly ash descends from the packed bed F to the storage liquid at the bottom of the apparatus and is united. . In the space above the packed bed F of the second gas-liquid contact device 34, the cooled second
Since the processing liquid is sprayed and the temperature of the space is lower than the temperature of the exhaust gas introduced into the device 34 through the line 43, the moisture in the exhaust gas existing below the space is condensed mist. Is done. At this time, since the water in the exhaust gas generates a water mist with the remaining fly ash fine particles as nuclei, a mist having a large weight and a large particle size is easily generated.

The exhaust gas containing the condensed mist that has passed through the second gas-liquid contact device 34 is introduced into a wet-type electrostatic precipitator 35, where the water condensed mist and the water condensed mist containing fly ash are removed. The removed mist is washed away from the electrode surface by the cooled second processing liquid (mist processing liquid) descending in the apparatus formed by spraying from the spray nozzle 59 above the mist, and the lower filling layer is removed. After passing through, it falls to the stored liquid at the bottom of the second gas-liquid contact device 2 and is united. The exhaust gas that has passed through the wet electrostatic precipitator 35 passes through a line 44, and if necessary, is subjected to a treatment for preventing white smoke, and is then discharged to the atmosphere. The second treatment liquid, its is preferred to adjust pH to 4-6, thereby the SO ₂ efficiently capture and removal contained in the exhaust gas. A part of the stored liquid at the bottom of the second gas-liquid contact device 34 is circulated to the first gas-liquid contact device 33 through a line 52, a pump and a line 53, and is used as a first treatment liquid.

A part of the first processing liquid containing fly ash stored at the bottom of the apparatus obtained by the first gas-liquid contacting apparatus 33 is supplied to the line 4
6, the dioxin is introduced into the dioxin decomposition reaction device 36, where it is stirred and maintained for a predetermined time to decompose and remove dioxins adhering to fly ash. An iron compound is supplied to the dioxin decomposition reactor 36 through a line 100, and an alkaline aqueous solution for pH adjustment is introduced through a line 101 as necessary. Further, if necessary, oxygen or an oxygen-containing gas is introduced into the dioxin decomposition reactor 36 through the line 102 to increase the concentration of dissolved oxygen in the aqueous solution. The gas after coming into contact with the aqueous solution is combined with the gas in the line 43 through the line 103. The processing liquid obtained in the dioxin decomposition reaction device 36 is introduced into a solid-liquid separation device 37 through a line 47 and a pump, where fly ash in the liquid is separated. Exhausted through. On the other hand, the separated water (drain) passes through the line 49 and the pump, and
1 and the first gas-liquid contact device 33 through the line 61 and / or
Alternatively, it is circulated to the second gas-liquid contact device 34, and the remaining portion passes through the line 70, and is discharged after performing appropriate drainage treatment as necessary. The processing liquid for replenishment is introduced from the line 60 to the line 51 as needed.

FIG. 11 shows another example of a flow sheet showing a specific embodiment of the flow sheet of FIG. In FIG.
31 is an incinerator, 32 is a waste heat boiler, 33 is a first gas-liquid contact device, 34 is a second gas-liquid contact device, 36 is a dioxin decomposition reaction device, and 37 is a solid-liquid separation device.

In order to make the incinerator exhaust gas harmless according to the flow sheet shown in FIG. 11, the incinerator exhaust gas containing dioxin-containing fly ash generated in the incinerator 31 is passed through a line 41 to a waste heat boiler 32. After the heat is recovered, the heat is introduced into the first gas-liquid contact device 33 through the line 42. The exhaust gas introduced into the first gas-liquid contact device 33 comes into contact with the fine droplet particles of the first processing liquid sprayed into the tower through the line 45 and is rapidly cooled, and at the same time, fly ash in the exhaust gas. And most of the HCl are trapped in the first treatment liquid and separated from the exhaust gas. The temperature of the exhaust gas is 45 to 45 by the first gas-liquid contact treatment.
75 ° C, preferably reduced to 50-70 ° C. The cooled exhaust gas from which part of the fly ash and most of the HCl have been removed is introduced via a line 43 into a second gas-liquid contact device 34, where it is brought into contact with a second treatment liquid. By this gas-liquid contact, residual fly ash and SO ₂ contained in the exhaust gas are captured by the second processing liquid and removed from the exhaust gas.

The first gas-liquid contact device 33 shown in FIG.
It has a structure in which a liquid spray nozzle is provided at the top of the tower, and the first treatment liquid stored at the bottom of the tower is sprayed from the spray nozzle via the line 45 and brought into contact with the gas. The apparatus is not limited to a simple apparatus, and may be, for example, a structure in which gas is ejected into a liquid in a tank containing the liquid through a gas blowing nozzle to perform gas-liquid contact. The second gas-liquid contact device 34 shown in FIG. 11 has a structure in which an activated carbon layer F is formed inside, and has a liquid spray nozzle 57 above the activated carbon layer F.

In the first gas-liquid contact device 33, a hydrochloric acid aqueous solution containing a reaction catalyst such as a solid iron compound is stored at the bottom of the device as a first treatment liquid. Is sprayed from the upper part of the apparatus through the apparatus, and the inside of the apparatus is filled with fine droplet particles of the aqueous solution. The incinerator exhaust gas introduced through the waste heat boiler 32 and the line 42 (the temperature is typically
(Approximately 0-300 ° C.) comes into contact with the fine droplet particles of the aqueous solution, and most of fly ash and HCl contained in the gas are captured by the droplet particles and separated from the exhaust gas. The droplet particles capturing the fly ash and the like descend in the apparatus and are united with the stored liquid at the bottom of the apparatus. In the first gas-liquid contact processing, the pH of the first processing liquid used in the first gas-liquid contact device is
Is adjusted to the range of 2 to 4, the hydrogen chloride contained in the exhaust gas can be efficiently captured and separated in the treatment liquid. By performing the first gas-liquid contact treatment of the exhaust gas as described above, 30 to 9 of fly ash contained in the exhaust gas can be obtained.
5%, preferably 80-95%, is captured and removed by the first processing solution. 90% or more of HCl contained in exhaust gas,
Preferably, 95% or more is captured and removed by the first processing liquid.

A part of the waste water obtained by the solid-liquid separator 37 is circulated through the line 51 to the second gas-liquid contact device 34 as a second treatment liquid. This circulating fluid is introduced into the lower part of the device 34 and is united with the stored liquid at the bottom of the device. The stored liquid at the bottom of the apparatus is sprayed from a liquid spray nozzle 57 through a line 52, a pump and a line 54. In the second gas-liquid contacting step 34, the second processing liquid flows down from above in the activated carbon layer F, and during that time, comes into contact with the exhaust gas descending from above. By this contact, the remaining fly ash in the exhaust gas is captured by the flowing down processing liquid, and the processing liquid that has captured the fly ash descends from the activated carbon layer F to the storage liquid at the bottom of the apparatus and is united. On the other hand, SO ₂ in the exhaust gas is adsorbed on the activated carbon and then converted into sulfuric acid by the catalytic oxidation action and removed. The generated sulfuric acid absorbs the moisture in the exhaust gas to become diluted sulfuric acid, overflows from the inside of the activated carbon, flows down the activated carbon layer, and is united with the stored liquid at the bottom of the apparatus. The exhaust gas that has passed through the second gas-liquid contact device 34 passes through a line 44, is subjected to further processing if necessary, and is discharged to the atmosphere. The second treatment liquid is a hydrochloric acid aqueous solution containing a reaction catalyst such as a solid state iron compound.
Is preferably adjusted to 2 to 6, whereby the dioxins adsorbed on the activated carbon can be efficiently decomposed. A part of the stored liquid at the bottom of the second gas-liquid contact device 34 is circulated to the first gas-liquid contact device 33 through a line 52, a pump and a line 53, and is used as a first treatment liquid.

A part of the first processing liquid containing fly ash stored at the bottom of the apparatus obtained by the first gas-liquid contacting device 33 is supplied to the line 4
5 and a line 46 to introduce it into a dioxin decomposition reactor 36, where it is stirred and held for a predetermined time to decompose and remove dioxins adhering to fly ash. An iron compound is supplied to the dioxin decomposition reactor 36 through a line 100, and an alkaline aqueous solution for pH adjustment is introduced through a line 101 as necessary. Further, if necessary, oxygen or an oxygen-containing gas is introduced into the dioxin decomposition reactor 36 through the line 102 to increase the concentration of dissolved oxygen in the aqueous solution. The gas after coming into contact with the aqueous solution is combined with the gas in the line 43 through the line 103. The processing liquid obtained in the dioxin decomposition reaction device 36 is introduced into a solid-liquid separation device 37 through a line 47 and a pump, where fly ash in the liquid is separated. Exhausted through. On the other hand, the separated water (drain) passes through a line 49 and a pump, and a part thereof is circulated to a second gas-liquid contact device 34 through a line 51,
The remainder passes through a line 70 and is discharged after being subjected to appropriate drainage treatment as required. The processing liquid for replenishment is introduced from the line 60 to the line 51 as needed.

FIG. 12 shows still another example of the flow sheet showing a specific embodiment of the flow sheet of FIG. FIG.
, The same reference numerals as those shown in FIG. 11 have the same meaning.

In order to detoxify incinerator exhaust gas in accordance with the flow sheet shown in FIG. After collecting the heat, the heat is introduced into the first gas-liquid contact device 33 through the line 42. The exhaust gas introduced into the first gas-liquid contact device 33 comes into contact with the fine droplet particles of the first processing liquid sprayed into the tower through the line 45 and is rapidly cooled, and at the same time, fly ash in the exhaust gas. And most of the HCl are trapped in the first treatment liquid and separated from the exhaust gas. The temperature of the exhaust gas is 45 to 45 by the first gas-liquid contact treatment.
75 ° C, preferably reduced to 50-70 ° C. The cooled exhaust gas from which part of the fly ash and most of the HCl have been removed is introduced via a line 43 into a second gas-liquid contact device 34, where it is brought into contact with a second treatment liquid. By this gas-liquid contact, residual fly ash and SO ₂ contained in the exhaust gas are captured by the second processing liquid and removed from the exhaust gas. The first gas-liquid contact device 33 shown in FIG. 12 has a liquid spray nozzle at the top of the tower, and sprays the first processing liquid stored at the bottom of the tower from the spray nozzle via the line 45. Although it has a structure in which it is brought into contact with gas, it is not necessarily limited to such a device. It can be of a structure that performs The second gas-liquid contact device 34 shown in FIG. 12 has a structure in which an activated carbon layer F is formed therein, and has a liquid spray nozzle 57 above the activated carbon layer F.

In the first gas-liquid contact device 33, a hydrochloric acid aqueous solution containing a reaction catalyst such as a solid iron compound is stored in the bottom of the device as a first treatment liquid. Is sprayed from the upper part of the apparatus through the apparatus, and the inside of the apparatus is filled with fine droplet particles of the aqueous solution. The incinerator exhaust gas introduced through the waste heat boiler 32 and the line 42 (the temperature is typically
(Approximately 0-300 ° C.) comes into contact with the fine droplet particles of the aqueous solution, and most of fly ash and HCl contained in the gas are captured by the droplet particles and separated from the exhaust gas. The droplet particles capturing the fly ash and the like descend in the apparatus and are united with the stored liquid at the bottom of the apparatus. In the first gas-liquid contact processing, the pH of the first processing liquid used in the first gas-liquid contact device is
Is adjusted to the range of 2 to 4, the hydrogen chloride contained in the exhaust gas can be efficiently captured and separated in the treatment liquid. By performing the first gas-liquid contact treatment of the exhaust gas as described above, 30 to 9 of fly ash contained in the exhaust gas can be obtained.
5%, preferably 80-95%, is captured and removed by the first processing solution. 90% or more of HCl contained in exhaust gas,
Preferably, 95% or more is captured and removed by the first processing liquid.
For the second gas-liquid contact device 34, a thickener 61
Is circulated as the second processing liquid via the storage tank 63, the line 64, and the line 66. This circulating fluid is introduced into the lower part of the device 34 and is united with the stored liquid at the bottom of the device. The stored liquid at the bottom of the apparatus is sprayed from a liquid spray nozzle 57 through a line 52, a pump and a line 54.

In the second gas-liquid contacting step 34, the second processing liquid flows down from above in the activated carbon layer F, and comes in contact with the exhaust gas descending from above during that time. By this contact, the remaining fly ash in the exhaust gas is captured by the flowing down processing liquid, and the processing liquid that has captured the fly ash descends from the activated carbon layer F to the storage liquid at the bottom of the apparatus and is united. On the other hand, SO ₂ in the exhaust gas is adsorbed on the activated carbon and then converted into sulfuric acid by the catalytic oxidation action and removed. The generated sulfuric acid absorbs the moisture in the exhaust gas to become diluted sulfuric acid, overflows from the inside of the activated carbon, flows down the activated carbon layer, and is united with the stored liquid at the bottom of the apparatus. The exhaust gas that has passed through the second gas-liquid contact device 34 passes through a line 44, is subjected to further processing if necessary, and is discharged to the atmosphere. The second treatment liquid is a hydrochloric acid aqueous solution containing a reaction catalyst such as a solid state iron compound.
Is preferably adjusted to 2 to 6, whereby the dioxins adsorbed on the activated carbon can be efficiently decomposed. A part of the stored liquid at the bottom of the second gas-liquid contact device 34 is circulated to the first gas-liquid contact device 33 through a line 52, a pump and a line 53, and is used as a first treatment liquid. A part of the first treatment liquid containing fly ash stored in the bottom of the apparatus obtained by the first gas-liquid contacting device 33 is introduced into the concentration device (thickener) 61 through the lines 45 and 46.

The thickener 61 includes the first gas-liquid contact device 33
It acts as a concentrating device for increasing the fly ash concentration in the aqueous solution containing the fly ash obtained in the above. That is, in the thickener 61, the fly ash in the aqueous solution settles down due to its gravity, and the fly ash concentration in the aqueous solution on the surface is reduced, while the fly ash concentration in the aqueous solution on the bottom is increased. The aqueous solution (fly ash concentrate) having the increased fly ash concentration is introduced into the dioxin decomposition reaction device 36 via the line 67 and the pump. On the other hand, the fly ash dilute aqueous solution having a low fly ash concentration on the surface of the thickener is supplied to the storage tank 63, the pump and the line 6.
4 and further circulates through the line 66 to the second gas-liquid contact device 34 as a second processing liquid. Further, a part of the fly ash dilute aqueous solution passing through the line 64 can be introduced into the first gas-liquid contact device 33 through the line 65. The fly ash concentration rate by the thickener 61 is 2 to 60 times, preferably 3 to 50 times. The fly ash concentration in the fly ash concentrate discharged from the thickener 61 is preferably 1% by weight or more. The upper limit is not particularly limited, but is usually about 30% by weight. On the other hand, the fly ash concentration in the diluted fly ash aqueous solution with a reduced fly ash concentration discharged from the thickener 61 is:
It is at most 0.5% by weight, preferably at most 0.1% by weight. As described above, while the fly ash-containing aqueous solution is concentrated by the thickener 61 and the fly ash concentrate is introduced into the dioxin decomposition reaction device 36, the reaction device 36
And the efficiency of the apparatus can be increased. When dioxins are decomposed and made harmless by the reactor 36, the residence time (reaction time) of the fly ash in the reactor 36 must be as long as possible in order to increase the decomposition rate. Low fly ash concentrations in the contained aqueous solution necessitate an increase in the equipment volume in response to the extended residence time. In the case of the present invention, the reactor 36
Since the fly ash-containing aqueous solution introduced into the reactor has a high fly ash concentration, the amount of fly ash per volume in the reaction apparatus increases, and the apparatus can be downsized accordingly. The fly ash dilute aqueous solution having a reduced fly ash concentration obtained by the thickener 36 is suitable as a cooling liquid used in the first gas-liquid contact device 33 and a processing liquid used in the second gas-liquid contact device 34. It is. That is, the fly ash dilute aqueous solution has a low fly ash concentration and an extremely fine particle size of the fly ash, so that when the pump, the pipe, and the nozzle are allowed to flow, friction and clogging troubles occur. It does not occur and can be handled almost in the same manner as ordinary industrial water.

In the dioxin decomposition reactor 36, dioxins contained in fly ash are decomposed and removed.
An iron compound is supplied to the dioxin decomposition reactor 36 through a line 100, and an alkaline aqueous solution for pH adjustment is introduced through a line 101 as necessary.
Further, if necessary, oxygen or an oxygen-containing gas is introduced into the dioxin decomposition reactor 36 through the line 102 to increase the concentration of dissolved oxygen in the aqueous solution. The gas after contact with the aqueous solution flows through line 103 through line 43
Gas. The processing liquid obtained in the dioxin decomposition reaction device 36 is introduced into a solid-liquid separation device 37 through a line 47, where fly ash in the liquid is separated, and the separated fly ash is passed through a line 48. Is discharged. On the other hand, the separated water (drainage) passes through the line 49, and is discharged after performing appropriate drainage treatment as needed. Replenishing industrial water is introduced from line 68 to the first gas-liquid contact device as needed. Further, the processing solution for replenishment is supplied to the line 60 as needed.
To the second gas-liquid contact device 34.

[0087]

Next, the present invention will be described in more detail by reference examples and examples. The experiments shown in Examples 1 to 8 were performed using the experimental device shown in FIG. The container shown in FIG. 13 is a glass flask having a content of 2000 ml. This flask has a structure in which a stirrer can be connected so as to be able to stir, and a structure in which a cooling pipe for preventing the liquid in the container from escaping due to evaporation can also be connected. In addition, the vessel is equipped with hydrochloric acid and air inlet pipes,
A thermometer and thermometer are inserted. In order to keep the reaction temperature constant, the vessel was fixed in a constant temperature bath.

Example 1 A treatment for detoxifying dioxins contained in fly ash having the following properties separated and recovered from the exhaust gas from an incinerator was performed as follows. (Properties of fly ash) (i) Carbonaceous substance content: 1.2% by weight (ii) Iron content: 1.4% by weight (iii) Copper content: 0.12% by weight (iv) Dioxins Content: 0.87 ng-TEQ / g

(Experimental method and result) 200 g of fly ash
Was added to 2 liters of pure water, hydrochloric acid was added while stirring with heating, air was introduced into the solution at 800 Ncc / min, and the mixture was maintained at 65 ° C. and pH 3.5 for 24 hours. At this time, the Cl concentration in the aqueous solution was (845) mmol / L, and [Cl] / [SO ₄ ] was (68). The total Fe concentration in the slurry was 1,400 mg /
And the total Cu concentration was 120 mg / liter. After stirring for 24 hours, the slurry was subjected to suction filtration to analyze dioxins contained in the fly ash after the treatment. Dioxin decomposition rate was calculated by the following equation. As a result, a decomposition rate of 72% was obtained.

[0090]

[Number 1] _{R = (a 0 × c 0} -a × c) / a 0 c 0 × 100 (1) R: Dioxins decomposition rate (%) a _0: untreated fly ash weight (g (Dry)) a: Weight of treated fly ash (g (Dry)) c ₀ : DXN concentration in untreated fly ash (ng-TEQ / g) c: DXN concentration in treated fly ash (ng-TEQ / g)

Example 2 An experiment was conducted in the same manner as in Example 1 except that the reaction time was changed. As a result, 43 hours at a reaction time of 10 hours.
% And a decomposition rate of 72% was obtained in a reaction time of 24 hours.

Example 3 The detoxification treatment of dioxins contained in fly ash having the following properties separated and recovered from incinerator exhaust gas was performed as follows.

(Properties of Fly Ash) (i) Content of carbonaceous substance: 1.2% by weight (ii) Iron content: 1.4% by weight (iii) Copper content: 0.12% by weight (iv) ) Dioxin content: 0.87 ng-TEQ / g

(Experimental method) Ferrous chloride tetrahydrate (FeCl ₂ .4H ₂ O: special grade reagent) in 2 liters of pure water 21.3
g was dissolved. At this time, the pH of the aqueous solution was about 2.0. Here, 200 g of the fly ash was added, hydrochloric acid was added while stirring with heating, and air was added to 800 Ncc /
The solution was then introduced into the solution in min., and maintained at 65 ° C. and pH 3.5 for 24 hours. At this time, the Cl concentration in the aqueous solution is (950)
In mmol / l, the [Cl] / [SO ₄ ] molar ratio was (76). The total Fe concentration in the slurry was 4,400 mg / liter, and the total Cu concentration was 120 mg / L.
mg / liter. After stirring for 24 hours, the slurry was subjected to suction filtration to analyze fly ash after treatment, treatment liquid, exhaust gas, and dioxins contained in fly ash (raw fly ash) before treatment. Further, iron precipitated on the ash after the treatment was quantified by atomic absorption spectrometry and X-ray fluorescence analysis. For the quantitative analysis by atomic absorption spectrophotometry, model SAS7 manufactured by Seiko Denshi Co., Ltd.
A 500 atomic absorption spectrophotometer was used, and a fluorescent X-ray analyzer of model PW1400 manufactured by PHILIPS was used for quantification by X-ray fluorescence analysis.

(Experimental Results) (1) The change in weight of the fly ash before and after the wet treatment is as shown in Table 1. 200 g before the treatment was reduced to 160 g (80% of that before the treatment) after the treatment. This is because soluble salts such as NaCl were dissolved and the added iron salt was precipitated.

[0096]

[Table 1]

(2) The concentrations of dioxins in the fly ash before and after the wet treatment are as shown in Table 2, and the concentration in the fly ash after the treatment is generally lower than the concentration in the fly ash before the treatment. And it became quite low. The abbreviations in Tables 2 and 3 have the following meanings. T4CDDs: tetrachlorodibenzoparadioxin P5CDDs: pentachlorodibenzoparadioxin H6CDDs: hexachlorodibenzoparadioxin H7CDDs: heptachlorodibenzoparadioxin O8CDD: octachlorodibenzoparadioxin Total PCDDs: all polychlorodibenzoparadioxin T4CDFs: tetrachlorodibenzofuran Pentachlorodibenzofuran H6CDFs: Hexachlorodibenzofuran H7CDFs: Heptachlorodibenzofuran O8CDFs: Octachlorodibenzofuran Total PCDFs: Total polychlorodibenzofuran Total Total dioxins

[0098]

[Table 2]

(3) Table 3 shows the dioxin removal rate (decomposition rate) (%). The removal rate was calculated by the formula (1) described in Example 1 in consideration of the fact that the fly ash weight after treatment was 80% of the original weight. Rate was obtained. Since the amount of dioxins in the exhaust gas and the treatment liquid was sufficiently negligible, the removal rate was calculated only from the analysis value of the concentration of dioxins in fly ash.

[0100]

[Table 3]

(4) Further, when iron precipitated on the ash after the treatment was quantified by atomic absorption spectrometry and X-ray fluorescence analysis, an iron salt corresponding to 81% by weight of the added iron was precipitated.

Example 4 Dioxins contained in fly ash having the following properties separated and recovered from the exhaust gas of an incinerator were detoxified as follows. (Properties of fly ash) (i) Carbonaceous substance content: 1.2% by weight (ii) Iron content: 1.4% by weight (iii) Copper content: 0.12% by weight (iv) Dioxins Content: 0.87 ng-TEQ / g

(Experimental method) Ferrous chloride tetrahydrate (FeCl ₂ .4H ₂ O: special grade reagent) in 2 liters of pure water 21.3
g was dissolved. At this time, the pH of the aqueous solution was about 2.0. Here, 200 g of the fly ash was added, hydrochloric acid was added while stirring with heating, and air was added to 800 Ncc /
min, and maintained at 65 ° C. and pH 5.2 for 24 hours. The Cl concentration in the slurry at this time was (95
0) mmol / l and the [Cl] / [SO ₄ ] molar ratio was (76). The total Fe concentration in the slurry was 4,400 mg / liter, and the total Cu concentration was 12 mg / L.
It was 0 mg / liter. After stirring for 24 hours, the slurry was subjected to suction filtration, the dioxins contained in the fly ash after the treatment were analyzed, and the decomposition rate of dioxins was calculated by the formula (1) described in Example 1, and as a result, the decomposition was 89%. Rate was obtained. At this time, when dioxins in the aqueous solution after filtration were analyzed, the amount was sufficiently negligible. Further, the amount of iron precipitated in the ash after the treatment was quantified by atomic absorption spectrometry and X-ray fluorescence analysis. As a result, an iron salt corresponding to 97% by weight of the added iron was precipitated. For the quantitative analysis by atomic absorption spectrometry, model SA manufactured by Seiko
S7500 Atomic Absorption Spectrophotometer and Quantification by X-ray Fluorescence Spectrometry
X-ray fluorescence analyzer was used.

Example 5 The detoxification treatment of dioxins contained in fly ash having the following properties separated and recovered from incinerator exhaust gas was performed as follows. (Properties of fly ash) (i) Carbonaceous substance content: 1.2% by weight (ii) Iron content: 1.4% by weight (iii) Copper content: 0.12% by weight (iv) Dioxins Content: 0.87 ng-TEQ / g

(Experimental method) Ferrous chloride tetrahydrate (FeCl ₂ .4H ₂ O: special grade reagent) in 2 liters of pure water 21.3
g, 6.2 g of cuprous chloride (CuCl: reagent grade)
Was dissolved. At this time, the pH of the aqueous solution was about 2.0. Here, 200 g of the fly ash is added, hydrochloric acid is added while heating and stirring, and air is added at 800 Ncc / m.
Introduced into the solution at in and maintained at 65 ° C., pH 3.5 for 24 hours. At this time, the Cl concentration in the aqueous solution was (980) mmol / L, and the [Cl] / [SO ₄ ] molar ratio was (78). The total Fe concentration in the slurry was 4,400 mg / liter, and the total Cu concentration was 2.1.
It was 20 mg / liter. After stirring for 24 hours, the slurry was subjected to suction filtration, the dioxins contained in the fly ash after the treatment were analyzed, and the decomposition rate of dioxins was calculated by the formula (1) described in Example 1, and as a result, the decomposition was 98%. Rate was obtained. At this time, when dioxins in the aqueous solution after filtration were analyzed, the amount was sufficiently negligible. Further, when iron and copper deposited on the ash after the treatment were quantified by atomic absorption spectrometry and X-ray fluorescence analysis, an iron salt equivalent to 79% by weight of the added iron was deposited. The amount of copper deposited was negligible. For the quantitative analysis by atomic absorption spectrophotometry, model SAS manufactured by Seiko
An X-ray fluorescence spectrometer of model PW1400 manufactured by PHILIPS was used for quantification by X-ray fluorescence analysis using a 7500 atomic absorption spectrophotometer.

Example 6 Dioxins contained in fly ash having the following properties separated and recovered from incinerator exhaust gas were detoxified as follows.

(Properties of Fly Ash) (i) Carbonaceous substance content: 3.0% by weight (ii) Iron content: 1.53% by weight (iii) Copper content: 0.17% by weight (iv) ) Dioxin content: 17.4 ng-TEQ / g

(Experimental method) Ferrous chloride tetrahydrate (FeCl ₂ .4H ₂ O: reagent grade) was added to 2 liters of an aqueous solution in which 10 wt% of methanol was added to pure water as a contact promoter.
g, 3.1 g of cuprous chloride (CuCl: reagent grade)
Was dissolved. At this time, the pH of the aqueous solution was about 2.0. Here, 200 g of the fly ash is added, hydrochloric acid is added while heating and stirring, and air is added at 800 Ncc / m.
Introduced into the solution at in and maintained at 65 ° C., pH 3.5 for 24 hours. At this time, the Cl concentration in the aqueous solution was (560) mmol / L, and the [Cl] / [SO ₄ ] molar ratio was (34). The total Fe concentration in the slurry was 4,520 mg / liter, and the total Cu concentration was 2.1.
70 mg / liter. After stirring for 24 hours, the slurry was subjected to suction filtration, the dioxins contained in the fly ash after the treatment were analyzed, and the decomposition rate of dioxins was calculated by the formula (1) described in Example 1, and as a result, the decomposition was 78%. Rate was obtained. At this time, when dioxins in the aqueous solution after filtration were analyzed, the amount was sufficiently negligible.

Example 7 An experiment was conducted in the same manner as in Example 6, except that the aqueous solution was irradiated with ultrasonic waves. In this case, a decomposition rate of 83% was obtained. In addition, the ultrasonic wave generated from the ultrasonic processing device UP-50H manufactured by Kubota Corporation was used as the ultrasonic wave.

Example 8 An experiment was conducted in the same manner as in Example 6, except that 8 g of a sulfosuccinate-type anionic surfactant and 4 g of a special ether-based nonionic surfactant were added instead of methanol as a contact promoter. . In this case, a decomposition rate of 74% was obtained.

Example 9 The detoxification treatment of incinerator exhaust gas will be described with reference to the flow sheet shown in FIG. The main operating conditions in this case are shown below in relation to FIG. It should be noted that the data in this example is based on the results obtained in individual small-scale experiments.

(1) Line 82 Temperature: 250 ° C. Gas amount: 15,000 Nm 3 / h Fly ash amount in gas: 19,000 g / h Fly ash concentration in gas: 1.27 g / Nm 3 Dioxins in fly ash Concentration (abbreviated as DXN):
1.0 ng-TEQ / g (2) Cooling device 71-Coolant: industrial water Cooling temperature: 65 ° C (3) Line 84-Temperature: 65 ° C-Fly ash in gas: 12,000 g / h (4) Line 85 ・ Temperature: 65 ° C. ・ Amount of fly ash in the liquid: 7,000 g / h (5) Gas-liquid contact device 72 ・ Temperature: 65 ° C. ・ Properties of treatment liquid Cl ion concentration: 845 mmol / l Cl / SO ₄ Molar ratio: 100 pH: 3.5 (6) Line 88-Temperature: 95 ° C-Fly ash amount in gas: 152 g / h (7) Line 89 Temperature: 65 ° C Fly ash concentration in liquid: 1.1 wt% DXN concentration in fly ash: 2.1 ng-TEQ / g Liquid composition Cl ion concentration: 845 mmol / l Cl / SO ₄ molar ratio: 100 (8) Reaction vessel 75 pH: 3.5 Residence time: 24 hours ( 9) Line 90 Temperature: 65 ° C Fly ash concentration in the liquid: 1. wt% DXN concentration in fly ash: 0.16 ng-TEQ / g DXN decomposition rate: 94% (10) Line 92 temperature: 65 ° C. Cake amount: 7.2 kg / h DXN concentration of fly ash in cake: 0. 16ng-TEQ /
g

Example 10 Fly ash separated and recovered from the exhaust gas of an incinerator was used, and a detoxification treatment was performed as follows using the flow sheet shown in FIG. The main operating conditions in this case are shown in relation to FIG.

(Experimental method) Fly ash slurry preparation tank 6 shown in FIG.
0, a thickener supernatant from line 21 and industrial water are added to line 61 and hydrochloric acid and sulfuric acid simulating an acidic gas removed from exhaust gas at a molar ratio of 7: 1 from line 62, and fly ash is further added to 50 g. / H from the line 63, and magnesium hydroxide was added from the line 64 with stirring to prepare a slurry liquid having a pH of 3.5. The residence time of the liquid in the fly ash slurry preparation tank 60 was simulated as the residence time in the cooling tower 3 and the gas-liquid contact device 4 in FIG.

(1) Line 63 • Fly ash amount: 50 g / h • Dioxin concentration in fly ash: 1.0 ng-TEQ /
g (2) Line 28-Temperature: 65 ° C-pH: 3.5-Fly ash concentration: 0.5 wt%-Extraction amount: 4,900 g / h (3) Line 27-Temperature: 65 ° C-Fly ash concentration: 0.1 wt%-Overflow: 3,500 g / h (4) Line 29-Temperature: 65 ° C-Fly ash concentration: 1.5 wt%-Dioxin concentration in fly ash: 1.8 ng-TEQ /
g-Withdrawal amount: 1,400 g / h (5) Line 100 Ferrous chloride equivalent to 2.80 g / h as Fe is supplied to the fly ash slurry preparation tank 60 through the line 100. (6) Dioxin decomposition reaction tank 8-Temperature: 65 ° C-pH: 3.5-Fly ash concentration: 1.5 wt%-Residence time: 24 hours (7) Line 31-Temperature: 65 ° C-Fly ash concentration: 1.5wt% ・ Dioxin concentration in fly ash: 0.12ng-TEQ
/ G-Dioxin decomposition rate: 95% (8) Line 32-Fly ash amount: 21 g / h-Dioxin concentration in fly ash: 0.12 ng-TEQ
/ G Dioxin decomposition rate: 95%

Example 11 Using fly ash separated and recovered from incinerator exhaust gas, detoxification treatment was performed as follows using the flow sheet shown in FIG. The main operating conditions in this case are shown in relation to FIG.

(Experimental method) An experiment was conducted under the same conditions as in Example 10 except that ferrous chloride was supplied to the reactor inlet line. (1) Line 63-Fly ash amount: 50 g / h-Dioxin concentration in fly ash: 1.0 ng-TEQ /
g (2) Line 28-Temperature: 65 ° C-pH: 3.5-Fly ash concentration: 0.5 wt%-Extraction amount: 4,900 g / h (3) Line 27-Temperature: 65 ° C-Fly ash concentration: 0.1 wt%-Overflow: 3,500 g / h (4) Line 29-Temperature: 65 ° C-Fly ash concentration: 1.5 wt%-Dioxin concentration in fly ash: 1.8 ng-TEQ /
g-Withdrawal amount: 1,400 g / h (5) Line 100 Ferrous chloride corresponding to 2.80 g / h as Fe is supplied to the line 29 through the line 100. (6) Dioxin decomposition reaction tank 8-Temperature: 65 ° C-pH: 3.5-Fly ash concentration: 1.5 wt%-Residence time: 24 hours (7) Line 31-Temperature: 65 ° C-Fly ash concentration: 1.5wt% ・ Dioxin concentration in fly ash: 0.12ng-TEQ
/ G-Dioxin decomposition rate: 95% (8) Line 32-Fly ash amount: 21 g / h-Dioxin concentration in fly ash: 0.12 ng-TEQ
/ G ・ Dioxin decomposition rate: 95%

Example 12 Fly ash was rendered harmless according to the flow sheet shown in FIG. In this method, a fly ash concentration of 4
The concentration was reduced to wt%, but the decomposition reaction tank for dioxins was reduced to about 1 / 2.5 of Example 10, and the residence time was the same as in Example 10. (1) Line 63-Fly ash amount: 50 g / h-Dioxin concentration in fly ash: 1.0 ng-TEQ /
g (2) Line 28-Temperature: 65 ° C-pH: 3.5-Fly ash concentration: 0.5 wt%-Extraction amount: 5,120 g / h (3) Line 27-Temperature: 65 ° C-Fly ash concentration: 0.1 wt%-Overflow: 4,595 g / h (4) Line 29-Temperature: 65 ° C-Fly ash concentration: 4.0 wt%-Dioxin concentration in fly ash: 1.7 ng-TEQ /
g-Withdrawal amount: 525 g / h (5) Line 100 Ferrous chloride equivalent to 2.80 g / h as Fe is supplied to the fly ash slurry preparation tank 60 through the line 100. (6) Dioxin decomposition reactor 8-Temperature: 65 ° C-pH: 3.5-Fly ash concentration: 4.0 wt%-Residence time: 24 hours (7) Line 31-Temperature: 65 ° C-Fly ash concentration: 4.0 wt%-Dioxin concentration in fly ash: 0.095 ng-TE
Q / g-Dioxin decomposition rate: 96% (8) Line 32-Cake amount: 21 g / h-Dioxin concentration in fly ash in cake: 0.095 n
g-TEQ / g Dioxin decomposition rate: 96%

Comparative Example In Example 10, no fly ash concentration was obtained without using a thickener.
The result of supplying 5 wt% to the dioxin decomposition reactor 8 is shown below. (1) Dioxin decomposition reactor supply liquid (line 2
9) Temperature: 65 ° C pH: 3.5 Fly ash concentration: 0.5 wt% Dioxin concentration in fly ash: 2.1 ng-TEQ /
g ・ Supply liquid amount: 4,200 g / h (2) Dioxin decomposition reaction tank device 8 ・ Temperature: 65 ° C. ・ pH: 3.5 ・ Fly ash concentration: 0.5 wt% ・ Dwell time: 8 hours (3) Dioxin decomposition reactor outlet liquid (line 3
1) Temperature: 65 ° C Fly ash concentration: 0.5 wt% Dioxin concentration in fly ash: 0.95 ng-TEQ
/ G-Dioxin decomposition rate: 60% (4) Line 32-Cake amount: 21 g / h-Dioxin concentration in fly ash in cake: 0.95 ng
-TEQ / g-Dioxin decomposition rate: 60%

Example 13 In accordance with the flow sheet shown in FIG.
The harming process will be described. Coal-based in the second gas-liquid contactor
Activated carbon powder contains Teflon dispersion
Activated carbon Hani formed by mixing so as to have a content of 10 wt%
The packed bed of the cam was placed. The main operating conditions in this case are
Shown in connection with No. 12. The data of the present embodiment is
Based on results obtained from small-scale experiments. (1) Line 42-Temperature: 250 ° C-Gas amount: 15,000 Nm^Three/ H (dry base) ・ Concentration of hydrochloric acid in gas: 580ppm ・ SO in gas_TwoConcentration: 100 ppm-Fly ash amount in gas: 19,000 g / h-Fly ash concentration in gas: 1.27 g / Nm^Three  -Dioxin concentration in fly ash: 1.0 ng-TEQ /
g-Total dioxin concentration in gas: 1.33 ng-TE
Q / Nm^Three  (2) First gas-liquid contact device 33-Cooling temperature: 70 ° C (3) Line 43-Temperature: 70 ° C-Hydrochloric acid concentration in gas: 10 ppm-SO in gas_TwoConcentration: 80 ppm-Fly ash amount in gas: 1,900 g / h (4) Line 44-Temperature: 70 ° C-Hydrochloric acid concentration in gas: 0 ppm-SO in gas_TwoConcentration: 7 ppm-Fly ash amount in gas: 200 g / h-Total dioxin concentration in gas: 0.023 ng-T
EQ / Nm^Three  ・ Removal rate of total dioxins in gas: 98.3% (5) Line 54 ・ Temperature of second treatment liquid: 70 ° C. (6) Line 46 ・ Temperature: 70 ° C. ・ Fly ash concentration: 0.5 wt% (7) Line 62 ・ Temperature: 70 ° C. ・ Fly ash concentration: 0.1 wt% (8) Line 67 ・ Temperature: 70 ° C. ・ Properties of extracted liquid Cl ion concentration: 99000 ppm-w (based on weight)
Concentration) Cl / SO_FourMolar ratio: 250 pH: 3.5-Fly ash concentration: 4 wt%-Dioxin concentration in fly ash: 1.8 ng-TEQ /
g (9) Ferrous chloride equivalent to 2.80 g / h as line 100 Fe
To the line 67 through the valve 100. (10) Dioxin decomposition reaction tank 36-Temperature: 70 ° C-pH: 3.5-Fly ash concentration: 4 wt%-Residence time: 24 hours (11) Line 47-Temperature: 70 ° C-Fly ash concentration: 4 wt% -Dioxin concentration in fly ash: 0.095 ng-TE
Q / g (12) Line 48-Fly ash amount: 8.0 kg / h-Dioxin concentration in fly ash: 0.095 ng-TE
Q / g-Decomposition rate of dioxins in fly ash: 96% (13) Line 49-Dioxin concentration in wastewater: 0.001 ng-TE
Q / kg-Decomposition rate of all dioxins removed: 96% According to the present invention, dust in fly ash contained in incinerator exhaust gas
Decompose and detoxify ioxins with low cost and high efficiency
be able to.

[0121]

According to the present invention, dioxins can be decomposed and made harmless at low temperature at a temperature lower than the boiling point of water.

[Brief description of the drawings]

FIG. 1 shows an example of a flow sheet when dioxin-containing fly ash is treated according to the present invention.

FIG. 2 shows a modified example of the flow sheet of FIG.

FIG. 3 shows an example of a flow sheet when exhaust gas containing fly ash discharged from an incinerator is treated according to the present invention. In the figure, reference numeral 40 denotes an incinerator (melting furnace).

FIG. 4 shows a treatment of incinerator exhaust gas when the incinerator exhaust gas contains hydrogen chloride and the fly ash contained in the exhaust gas contains a reaction catalyst metal. Fig. 1 shows an example of a flow sheet in the case where dioxins in fly ash are detoxified.

FIG. 5 shows another example of a flow sheet when the exhaust gas containing fly ash discharged from the incinerator is treated according to the present invention.

FIG. 6 shows a modification of the flow sheet shown in FIG.

FIG. 7 shows a modification of the flow sheet of FIG.

FIG. 8 shows a flow sheet when a fly ash concentration in an aqueous solution is concentrated in a thickener.

FIG. 9 shows another example of a flow sheet when the fly ash concentration in an aqueous solution is concentrated by a thickener.

FIG. 10 shows an exhaust gas containing fly ash discharged from an incinerator,
1 shows an example of a flow sheet when processing is performed by the method of the present invention including two gas-liquid contacting steps.

FIG. 11 is a flow sheet showing a specific embodiment of the flow sheet of FIG.

FIG. 12 shows another example of a flow sheet showing a specific embodiment of the flow sheet of FIG.

FIG. 13 shows still another example of the flow sheet showing a specific embodiment of the flow sheet of FIG.

[Explanation of symbols]

[FIG. 1] 2 solid-liquid separator 3 metal separator 4 copper separator 10 solid-liquid contactor [FIG. 2] 10 solid-liquid contactor 10-A mixing tank 10-B reaction tank [FIG. 3] 40 incinerator (melting) (FIG. 4) 70 boiler 71 cooling device 72 gas-liquid contact device 73 heat exchanger 74 dust collector 75 reaction vessel 76 solid-liquid separation device 77 waste water treatment device [FIG. 5] 1 incinerator 2 waste heat boiler 3 cooling tower 4 gas Liquid contacting device 5 Dust collecting device 6 Storage tank 7 Thickener 8 Dioxin decomposition reaction device 9 Solid-liquid separating device [Fig. 6] 10 Aqueous solution concentrating device (multiple-effect can) [Fig. 7] The same symbols as those shown in Fig. 5 It has the same meaning as the symbol in FIG. [FIG. 8] 60 fly ash slurry preparation tank [FIG. 9] 60 fly ash slurry preparation tank [FIG. 10] 1 first gas-liquid contact step 2 second gas-liquid contact step 3 dioxin decomposition reaction step 4 solid-liquid separation step 5 Wastewater treatment process 6 Fly ash treatment process [Fig. 11] 31 Incinerator 32 Waste heat boiler 33 First gas-liquid contact device 34 Second gas-liquid contact device 35 Wet electric dust collector 36 Dioxin decomposition reaction device 37 Solid-liquid separation device [FIG. 12] 31 incinerator 32 waste heat boiler 33 first gas-liquid contact device 34 second gas-liquid contact device 36 dioxin decomposition reaction device 37 solid-liquid separation device [FIG. 13] The same reference numerals as those shown in FIG. Have the same meaning

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Naoki Sonehara 2-1-1, Tsurumichuo, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Inside Chiyoda Kako Construction Co., Ltd. (72) Inventor Kenichi Imagawa Tsurumi-chuo, Tsurumi-ku, Yokohama-shi, Kanagawa 1-chome No. 1 F-term in Chiyoda Corporation (reference) 2E191 BA12 BC01 BD11 4D002 AA21 AC04 BA02 BA09 BA13 BA14 CA01 CA07 CA20 DA17 DA22 DA23 DA26 EA02 GA01 GA02 GA03 GB01 GB02 GB03 GB08 GB09 GB20 4D004 AA37 AB07 CA35 CA35 CC12 DA01 DA03 DA06 DA10 DA12

Claims (47)

[Claims] 1. A method for wet detoxification of dioxins, which comprises contacting the dioxins with an aqueous hydrochloric acid solution containing an iron compound in a solid state at a temperature lower than 100 ° C. to decompose the dioxins into harmless substances. A method for wet detoxification of dioxins, characterized in that the method comprises the steps of: 2. The method according to claim 1, wherein the concentration of the iron compound contained in the aqueous solution is 5 mmol or more per liter of water in terms of metallic iron. 3. The method according to claim 1, wherein the concentration of the iron compound contained in the aqueous solution is 10 mmol or more per liter of water in terms of metallic iron. 4. In order to maintain the concentration of an iron compound contained in an aqueous solution at the time of decomposing and detoxifying the dioxins to be not less than 10 mmol per liter of water in terms of metallic iron, an iron compound is externally added. The method according to any one of claims 1 to 3, which is added. 5. The method according to claim 1, wherein the aqueous solution contains a contact promoter.
Any one of the methods (1) to (4). 6. The method according to claim 1, wherein the aqueous solution is irradiated with ultrasonic waves.
Any one of the methods of any one of to 5 above. 7. The method according to claim 1, wherein the aqueous solution contains copper ions, and the concentration of the copper ions is 20 mg / liter or more in the aqueous solution. 8. The method according to claim 1, wherein the iron compound contains a dissolved component, and the dissolved component is in a process of shifting to a solid state. 9. The method according to claim 1, wherein the dioxins are dioxins adhering to a solid. 10. The method according to claim 1, wherein said dioxins are fly ash produced by incineration of waste or adhering to furnace ash. 11. The method according to claim 1, wherein oxygen or an oxygen-containing gas is brought into contact with said aqueous solution. 12. A method for the wet detoxification of incinerator exhaust gas containing dioxin-containing fly ash generated from an incinerator, comprising: an acid solution containing an iron compound in a solid state at a temperature lower than 100 ° C. Contact the aqueous solution,
A wet detoxification method for incinerator exhaust gas, which comprises transferring fly ash in the exhaust gas to an aqueous solution and decomposing and detoxifying dioxins attached to the fly ash in the aqueous solution. 13. The method according to claim 12, wherein the concentration of the iron compound contained in the aqueous solution is 10 mmol or more per liter of water in terms of metallic iron. 14. In order to maintain the concentration of an iron compound contained in an aqueous solution at the time of decomposing and detoxifying the dioxins to be 10 mmol or more per liter of water in terms of metallic iron, an iron compound is externally added. Claim 12 or 13 to be added.
the method of. 15. The method according to claim 12, wherein the aqueous solution contains a contact promoter. 16. The method according to claim 12, wherein the aqueous solution is irradiated with ultrasonic waves. 17. The method according to claim 12, wherein the aqueous solution contains copper ions, and the concentration of the copper ions is 20 mg / liter or more in the aqueous solution. 18. The method according to claim 12, wherein the iron compound contains a dissolved component, and the dissolved component is in a process of transitioning to a solid state. 19. The method according to claim 12, wherein oxygen or an oxygen-containing gas is brought into contact with said aqueous solution. 20. A method for wet detoxification of incinerator exhaust gas containing dioxin-containing fly ash generated from an incinerator and having a temperature of 100 ° C. or higher, wherein the incinerator exhaust gas is brought into gas-liquid contact with a cooling liquid. A cooling step of reducing the temperature of the exhaust gas to a temperature lower than 100 ° C., a gas-liquid contacting step of bringing the exhaust gas obtained in the cooling step into gas-liquid contact with a hydrochloric acid aqueous solution, and a contacting step with the exhaust gas obtained in the cooling step. Hydrochloric acid aqueous solution containing fly ash after contacting the cooling liquid containing fly ash and the exhaust gas obtained in the gas-liquid contacting step, separately or in a unified state,
In the presence of the iron compound in the solid state, the concentration of the iron compound contained in the aqueous solution was adjusted to 1 per liter of water in terms of metallic iron.
A method for wet detoxification of exhaust gas from an incinerator, comprising a dioxin decomposition reaction step of decomposing and detoxifying dioxins in fly ash at a processing temperature of less than 100 ° C. while maintaining the temperature at 0 mmol or more. . 21. A method for wet detoxification of incinerator exhaust gas containing dioxin-containing fly ash generated from an incinerator, wherein the incinerator exhaust gas cooled to a temperature lower than 100 ° C. is brought into gas-liquid contact with a hydrochloric acid aqueous solution. Gas-liquid contacting step, the fly ash concentration step of increasing the fly ash content in the hydrochloric acid aqueous solution containing the fly ash obtained in the gas-liquid contacting step, and the fly ash obtained in the fly ash concentration step were increased. In the presence of an iron compound in a solid state, an aqueous solution of hydrochloric acid containing hydrochloric acid at a concentration of less than 100 ° C. while maintaining the concentration of the iron compound contained in the aqueous solution at 10 mmol or more per liter of water in terms of metallic iron. A method for wet detoxification of incinerator exhaust gas, comprising a dioxin decomposition reaction step of decomposing and detoxifying dioxins contained in the fly ash under processing temperature conditions. 22. The method according to claim 20, wherein an iron compound is externally added to the gas-liquid contacting step and / or the decomposition reaction step.
the method of. 23. The method according to claim 21, wherein the aqueous hydrochloric acid solution having a reduced fly ash concentration obtained in the fly ash concentration step is circulated to the gas-liquid contacting step. 24. The incinerator exhaust gas having a temperature of 100 ° C. or more is sent to the cooling step, and is brought into contact with the cooling liquid to lower the temperature to a temperature lower than 100 ° C., and then sent to the gas-liquid contacting step. 23. The method of any one of to 23. 25. The method according to claim 21, wherein the aqueous hydrochloric acid solution having a reduced fly ash concentration obtained in the fly ash concentration step is circulated to the cooling step and / or the gas-liquid contacting step. 26. The method according to claim 21, wherein the fly ash concentration step is performed using a thickener or a cyclone. 27. A solid-liquid separation step for solid-liquid separation of the fly ash-containing slurry discharged from the dioxin decomposition reaction step, and a part or all of the filtrate obtained in the solid-liquid separation step is concentrated and concentrated. 3. A condensate circulating step for circulating a part or all of the liquid to the dioxin decomposition reaction step.
6. Any of the six methods. 28. The method according to claim 21, wherein the aqueous hydrochloric acid solution containing the fly ash at an increased concentration in the dioxin decomposition reaction step contains a contact promoter. 29. The method according to claim 21, wherein the aqueous hydrochloric acid solution containing the fly ash at an increased concentration in the dioxin decomposition reaction step is irradiated with ultrasonic waves. 30. An aqueous hydrochloric acid solution containing the fly ash at an increased concentration in the dioxin decomposition reaction step contains copper ions, and the concentration of the copper ions is 20 m in the aqueous solution.
30. The method according to any one of claims 21 to 29, which is at least g / liter. 31. The method according to claim 20, wherein the iron compound contains a dissolved component, and the dissolved component is in a process of shifting to a solid state. 32. The method according to claim 21, wherein oxygen or an oxygen-containing gas is brought into contact with an aqueous hydrochloric acid solution containing the fly ash at an increased concentration in the dioxin decomposition reaction step. 33. A method for wet detoxification of incinerator exhaust gas containing dioxin-containing fly ash generated from an incinerator, comprising: a first gas-liquid contacting step of bringing the exhaust gas into gas-liquid contact with a first treatment liquid; A second gas-liquid contacting step of bringing the treated exhaust gas obtained in the first gas-liquid contacting step into gas-liquid contact with a second treatment liquid;
Fly ash captured in the first processing liquid in the gas-liquid contacting step and fly ash captured in the second processing liquid in the second gas-liquid contacting step are separately or united from 100 ° C. At a low temperature, in the presence of an iron compound in a solid state, the concentration of the iron compound contained in the aqueous solution is maintained at 10 mol mol or more per liter of water, in terms of metallic iron, and brought into contact with an aqueous hydrochloric acid solution. ,
A wet detoxification method for incinerator exhaust gas, comprising a dioxin decomposition reaction step of decomposing dioxins contained in the fly ash. 34. The method according to claim 33, wherein the aqueous hydrochloric acid solution in the dioxin decomposition reaction step contains a contact promoter. 35. The method according to claim 33, wherein the aqueous hydrochloric acid solution in the dioxin decomposition reaction step is irradiated with ultrasonic waves. 36. The method according to claim 33, wherein the aqueous hydrochloric acid solution in the dioxin decomposition reaction step contains copper ions, and the concentration of the copper ions is 20 mg / liter or more in the aqueous solution. 37. The method according to claim 33, wherein the iron compound contains a dissolved component, and the dissolved component is in the process of transitioning to a solid state. 38. The method according to claim 33, wherein oxygen or an oxygen-containing gas is brought into contact with the aqueous hydrochloric acid solution in the dioxin decomposition reaction step. 39. The method according to claim 33, wherein the treated exhaust gas obtained in the second gas-liquid contacting step is sent to a mist separation step to remove fly ash and mist contained in the exhaust gas. 40. After the exhaust gas passing through the second gas-liquid contacting step is cooled to a temperature lower than the exhaust gas at the inlet of the second gas-liquid contacting step, the exhaust gas obtained in the second gas-liquid contacting step is cooled. The method according to any one of claims 33 to 39, wherein the method is sent to a mist separation step to remove fly ash and mist contained in the exhaust gas. 41. The method according to claim 33, wherein the pH of the first processing solution is in a range of 2 to 4, and the pH of the second processing solution is in a range of 4 to 6. 42. The method according to claim 33, wherein the second gas-liquid contacting step is performed in the presence of activated carbon. 43. The method according to claim 42, wherein the pH of the first processing liquid is in a range of 2 to 4, and the pH of the second processing liquid is in a range of 2 to 6. 44. The first processing solution and the second processing solution are each an aqueous hydrochloric acid solution containing an iron compound.
43. The method according to any of 43. 45. The method according to claim 33, wherein each of the first processing liquid and the second processing liquid is an aqueous hydrochloric acid solution containing copper ions.
44. The method according to any of 44. 46. The processing liquid containing fly ash obtained in the first gas-liquid contacting step is sent to a fly ash concentration step to increase the fly ash concentration in the processing liquid, and then the dioxin decomposition reaction step is performed. The method according to any of claims 33 to 45, wherein the method is introduced into 47. The fly ash-containing treatment liquid obtained in the dioxin decomposition reaction step is sent to a solid-liquid separation step, where fly ash contained in the treatment liquid is separated, and a part of the obtained separation liquid is separated. The method according to any one of claims 33 to 46, wherein is used as at least a part of the second processing liquid used in the second gas-liquid contacting step.