JP2001321785A - Method for treating dioxins in liquid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a new technique capable of treating dioxins in a liquid without generating secondary waste. SOLUTION: A method for treating dioxins in a liquid has a process (1) for adsorbing dioxins in the liquid to be treated by an adsorbing material, a process (2) for decomposing dioxins on the adsorbing material while holding a slurry containing the adsorbing material having adsorbed dioxins to 100 deg.C or higher and pressure keeping a liquid phase to obtain a gas-solid-liquid mixed phase containing the regenerated adsorbing material, a process (3) for separating the gas-solid-liquid mixed phase obtained in the process (2) into the regenerated adsorbing material and a gas-liquid mixed phase, a process (4) for returning the regenerated adsorbing material obtained in the process (3) to the process (1) to reutilize the same and a process (5) for subjecting the gas-liquid mixed phase to wet oxidizing treatment in the presence of a catalyst, and gas containing oxygen in a theoretical oxygen amount necessary for decomposing dioxins or more is supplied to the process (2) or (5), or divided to be supplied to the processes (2) and (5).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating dioxins in liquid such as effluent generated from wastewater from various factories such as Incineration Plants, leaching water generated in waste landfill sites, etc .; .

[0002]

2. Description of the Related Art Polychlorinated dibenzo-p-dioxins (PCDD) such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCDD) and polychlorinated dibenzofurans (PCDF) , A dioxin-like compound, coplanar-polychlorinated biphenyl
Dioxins such as (coplana-PCB) have been attracting attention in recent years from the viewpoint of environmental pollution, etc., and their emissions have been reported in the Law Concerning Special Measures against Dioxins, the Law on the Treatment and Cleaning of Waste, and the Treatment law) and the Air Pollution Control Law.

As a method for treating dioxins in a liquid,
There is a method in which dioxins are adsorbed by an adsorbent and removed from the liquid. In this method, an adsorbent that adsorbs dioxins is generated as a secondary waste, and thus the treatment is required.

[0004] Conventionally, high-temperature combustion has been employed as a treatment of an adsorbent having adsorbed dioxins as secondary waste. However, in the treatment method by combustion,
(1) If proper temperature control is not performed, there is a possibility that dioxins are generated in the gas. (2) A large amount of fuel is required for high-temperature combustion, so processing costs increase. There are problems such as.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a new technique capable of treating dioxins in a liquid without generating secondary waste.

[0006]

Means for Solving the Problems In view of the above-mentioned state of the art, the present inventor has repeatedly studied a technique for treating dioxins in a liquid. As a result, they have found that when the adsorbent having adsorbed dioxins in the liquid is treated using a treatment method having a specific step, the above-mentioned problems can be almost achieved.

That is, the present invention provides the following method for treating dioxins in a liquid; A method for treating dioxins in a liquid, wherein (1) a step of adsorbing dioxins in the liquid to be treated to an adsorbent,
(2) maintaining the slurry containing the adsorbent having adsorbed dioxins at a temperature of 100 ° C. or higher and maintaining a liquid phase,
Step of decomposing dioxins on the adsorbent to obtain a gas-solid liquid phase containing the regenerated adsorbent, (3) Separating the gas-solid liquid phase obtained in the above step (2) into the regenerated adsorbent and gas-liquid mixed phase (4) returning the recycled adsorbent obtained in the step (3) to the step (1) for reuse and (5) the gas-liquid mixed phase obtained in the step (3) in the presence of a catalyst. In step (2) or step (5) is supplied with an oxygen-containing gas having a theoretical oxygen amount or more necessary for decomposing dioxins, or a step (2) and step (2). Five)
A method for treating dioxins in a liquid, wherein the dioxins are supplied separately. 2. A method for treating dioxins in a liquid, wherein (1) a step of adsorbing dioxins in the liquid to be treated on activated carbon,
(2) maintaining the slurry containing activated carbon having adsorbed dioxins at a temperature of 100 ° C. or higher and maintaining a liquid phase,
A step of decomposing the activated carbon to which the dioxins are adsorbed together with the dioxins to obtain a gas-liquid mixed phase, and (3) the above step
The gas-liquid mixed phase obtained in (2) has a step of wet oxidation treatment in the presence of a catalyst, and an oxygen-containing gas having a theoretical oxygen amount or more necessary for decomposing dioxins and activated carbon is subjected to the step (2). Or supply in step or step (2) and step
(3) A method for treating dioxins in a liquid, comprising dividing and supplying the dioxins. 3. The catalyst used in the wet oxidation treatment in the step (5) is a catalyst in which at least one selected from the group consisting of a metal and a metal compound is supported as a catalytically active component on a metal oxide carrier or a metal carrier. 3. The method for treating dioxins in a liquid according to 1 or 2 above. 4. 4. The method for treating dioxins in a liquid according to the above item 1 or 3, wherein the adsorbent used in the step (1) is at least one selected from the group consisting of activated carbon, zeolite, acid clay and activated clay.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The method for treating dioxins in a liquid according to the present invention is a method for treating dioxins in a liquid, comprising the following steps (hereinafter sometimes referred to as the "first invention"). ). (1) the step of adsorbing dioxins in the liquid to be treated to the adsorbent, (2) the slurry containing the adsorbent adsorbing dioxins is kept at a temperature of 100 ° C. or higher and a pressure that maintains the liquid phase, and adsorbed. Decomposing dioxins on the material to obtain a gas-solid liquid phase containing the regenerated adsorbent, (3) separating the gas-solid liquid phase obtained in the above step (2) into a regenerated adsorbent and a gas-liquid mixed phase Step, (4) a step of returning the recycled adsorbent obtained in the step (3) to the step (1) for reuse, and (5) a step
(3) a step of subjecting the gas-liquid mixed phase obtained in (3) to a wet oxidation treatment in the presence of a catalyst, and a step of supplying an oxygen-containing gas having a theoretical oxygen amount or more necessary for decomposing dioxins.
It is supplied in (2) or step (5), or is supplied separately in step (2) and step (5).

The dioxins in the present invention are 2,3,
7,8-tetrachlorodibenzo-p-dioxin (2,3,7,8-TCD
D) and the like, such as polychlorinated dibenzo-p-dioxin (PCDD), polychlorinated dibenzofuran (PCDF), and coplanar-polychlorinated biphenyl (coplana-PCB), which is a dioxin-like compound. Compounds with different numbers and positions of chlorine are included in PCDD
There are 75 species, 135 in PCDF and 209 in PCB. Of these compounds, 7 PCDDs, 10 PCDFs, and 12 coplanar-PCBs with a flat structure have been identified as hazardous at this time. The dioxins in the present invention mean all these compounds. That is, the dioxins in the present invention also include compounds for which no harm has been confirmed at present.

The dioxin-containing liquid which is the liquid to be treated according to the present invention includes, for example, wastewater from various factories such as waste cleaning plants; leachate generated at waste landfill sites; and washing of ash and soil. Wastewater; sludge generated in various factories can be exemplified. When using sludge, water may be added as necessary. Wastewater containing dioxins and the like can be used as the water to be added. As the liquid to be treated or the water to be added, not only dioxins but also those containing other organic and inorganic substances at the same time can be used.

Hereinafter, the present invention will be described in detail with reference to FIG. FIG. 1 is a flow sheet showing an outline of an example of the present invention.

First, in step (1), dioxins in the liquid to be treated are adsorbed on an adsorbent. For example, the liquid to be treated
1 is led to the treatment tank 2 and the like, in which dioxins in the liquid are adsorbed by the adsorbent.

[0013] The adsorbent used in the step (1) is not particularly limited, and a known adsorbent generally used in the art can be used. Examples of the adsorbent include activated carbon; porous inorganic oxides such as zeolite, alumina, and titania; acidic clay, activated clay, and the like. The adsorbents may be used alone or in combination of two or more. The shape of the adsorbent is not particularly limited, and examples thereof include powder, granules, and molded bodies. When adsorbing dioxins on the adsorbent, if necessary,
You may stir by a stirrer, aeration, etc.

The concentration of the adsorbent in the liquid to be treated can be appropriately set according to the type of the adsorbent, the content of dioxins in the liquid to be treated, and the like. Adsorbent concentration in the liquid to be treated is usually 1 to 100 kg / m ^3, preferably about 20～60Kg /
m is about ^3. Time of contact between adsorbent and liquid to be treated
(For example, the residence time of the liquid to be treated in the treatment tank) is not particularly limited, but is usually about 10 minutes to 3 hours, preferably about 20 minutes to 1 hour. The treatment temperature is not particularly limited and is usually about 0 to 100 ° C, preferably about 0 to 50 ° C. The processing pressure is not particularly limited, and is usually 0 to 15 MPa as a gauge pressure.
It is about G, preferably about 0 to 1 MPaG.

By subjecting to the step (1), a slurry containing treated water and an adsorbent adsorbing dioxins is obtained. The slurry may be subjected to the step (2) as it is. Alternatively, if necessary, the slurry having a desired concentration may be supplied to the step (2), for example, by storing the slurry in the storage tank 5 to precipitate the slurry and extracting the treated water 3 (see FIG. 1).

The slurry obtained in the step (1) may be heated using the heat exchanger 11 or the like, if necessary, before being subjected to the step (2). For example, after heating the slurry to a temperature of about 150 ° C. or higher, it can be led to the empty tower reactor 13 or the like and subjected to the step (2). The heat source of the heat exchanger is not particularly limited, and examples thereof include a method of circulating a high-temperature treatment liquid that has been subjected to the wet oxidation treatment in step (5) described below. Alternatively, a method of installing and heating a heater (not shown) upstream or downstream of the heat exchanger 11, or from the steam generator (not shown) to the step (2) (for example, the empty column reactor 13) And the like). Further, at the time of start-up, as a method of setting the temperature in step (2) (for example, the temperature in an empty tower reactor) to a predetermined temperature, the same temperature raising method as described above can be used.

Next, in the step (2), the slurry containing the adsorbent on which dioxins are adsorbed is kept at a temperature of about 100 ° C. or more and the slurry is maintained at a pressure for maintaining the liquid phase, and the dioxins on the adsorbent are adsorbed. Is decomposed, the adsorbent is regenerated, and a gas-solid liquid phase containing the regenerated adsorbent is obtained. Step (2) is, for example,
This can be performed in an empty tower reactor 13 or the like (FIG. 1).

The concentration of the slurry containing the adsorbent adsorbing the dioxins used in the step (2) is not particularly limited, but is usually about 10 to 200 kg / m ³ , preferably 20 to 100 k / m ^3.
g / m ³ .

The temperature of the slurry in the step (2) is usually about 100 ° C. or higher, preferably about 150 to 350 ° C. The higher the temperature during the reaction, the shorter the processing time, but on the other hand, the equipment cost increases, so the reaction temperature is considered in consideration of the pollutant concentration in the material to be treated, the operating cost, the construction cost, etc. You only have to decide.

The liquid residence time in the step (2) is not particularly limited, but is usually about 5 minutes to 10 hours, preferably 30 minutes to 3 hours.
About an hour.

The pressure in the step (2) is not particularly limited as long as it is higher than a pressure at which the slurry can maintain a liquid phase. The pressure in the step (2) is usually 0.1 to
It is about 30 MPaG, preferably about 0.5 to 15 MPaG.

As a method of maintaining the slurry at a predetermined pressure,
For example, a method using a booster pump 7 or the like can be exemplified.
Alternatively, a method of charging a solid substance into a pressure vessel having a different pressure and / or temperature from the outside can be exemplified. For example,
Japanese Patent Application No. 11-61196 describes that "at normal pressure with the inlet side valve of the solids charging device opened and the outlet valve closed, the solids and liquid are introduced into the charging device, and then the inlet side After closing the valve and increasing the pressure in the device until it becomes equal to or higher than the pressure in the pressure vessel, open the outlet valve and charge the solid fluidized by the liquid into the pressure vessel under pressure. The method can be exemplified, and an apparatus as shown in Fig. 2 can be used as an example.This method is particularly effective when the slurry cannot be pressurized by the pressurizing pump due to a large particle size of the adsorbent. It is.

Next, in step (3), the slurry obtained in step (2) is separated into a regenerated adsorbent and a gas-liquid mixed phase. For separation of the regenerated adsorbent (solid phase) and the gas-liquid mixed phase, for example, a solid-liquid separator 15 or the like can be used. In FIG. 1, the gas-solid mixed phase 14 exiting the superficial reactor 13 is converted into a solid-liquid separator 15.
And separated into a solid phase (regenerated adsorbent) and a gas-liquid mixed phase.

In step (4), the regenerated adsorbent obtained in step (3) is returned to step (1) and reused in step (1).

In step (5), the gas-liquid mixed phase obtained in step (3) is subjected to a wet oxidation treatment in the presence of a catalyst. In the wet oxidation treatment of the gas-liquid mixed phase 17 in the step (5),
For example, a catalytic reactor 18 or the like can be used (FIG. 1). In step (5), dioxins and the like remaining in the gas-liquid mixed phase are oxidatively decomposed.

The temperature of the wet oxidation treatment in the step (5) is as follows:
Although not particularly limited, it is usually about 100 ° C. or higher, more preferably about 150 to 350 ° C. The higher the temperature during the reaction, the shorter the processing time, but on the other hand, the equipment cost increases,
The reaction temperature may be determined in consideration of the concentration of pollutants in the material to be treated, operating costs, construction costs, and the like.

The pressure during the wet oxidation treatment in the step (5) is not particularly limited, but may be any pressure as long as the gas-liquid mixed phase obtained in the step (3) can maintain a liquid phase at a predetermined temperature. The pressure in the step (5) is usually about 0.1 to 30 MPaG as a gauge pressure, preferably about 0.5 to 15 MPaG.

As the catalyst used in the wet oxidation treatment in the step (5), for example, a known metal oxide carrier, a catalyst having a catalytically active component supported on a metal carrier or the like can be exemplified. Examples of the catalytically active component include iron, cobalt, nickel, ruthenium, rhodium, palladium, iridium, platinum, copper, gold, tungsten and manganese, selenium, osmium, magnesium, and water-insoluble or poorly water-soluble compounds of these metals. Can be More specific examples of such compounds include oxides of these metals (such as cobalt oxide and iron oxide), chlorides (such as ruthenium dichloride and platinum dichloride), and sulfides (such as ruthenium sulfide and rhodium sulfide). ). The catalytically active components may be used alone or in combination of two or more. The ratio of the catalytically active component can be appropriately set according to the type of the catalytically active component and the like.

The method for loading the catalytically active component on the carrier is not particularly limited, and a conventional method such as an impregnation method can be used.
The support such as a metal oxide support and a metal support is not particularly limited, and those used as known catalyst supports can be used. As the metal oxide carrier, for example, alumina, silica, zirconia, titania, composite metal oxides containing these metal oxides (alumina-silica, alumina-silica-zirconia, titania-zirconia, etc.),
Examples of these metal oxides or metal oxide-based carriers containing a composite metal oxide as a main component, such as a metal carrier,
Examples include iron and aluminum. Among these carriers, zirconia, titania and titania-zirconia having excellent durability are more preferable.

The loading amount of the catalytically active metal is not particularly limited, but is usually about 0.01 to 30%, preferably about 0.01 to 25% of the weight of the carrier.

The shape of the catalyst is not particularly limited.
Examples include a spherical shape, a pellet shape, a columnar shape, a crushed piece shape, a powder shape, and a honeycomb shape. The size of the catalyst used as the fixed bed is, in the case of a sphere, a pellet, a column, a fragment, a powder, or the like, usually about 3 to 50 mm, more preferably 5 to 50 mm.
It is about 25mm. When the catalyst is used by being supported on a honeycomb-shaped carrier, the honeycomb structure has a square opening,
Any shape such as a hexagon or a circle can be used. The area per unit volume, the aperture ratio and the like are not particularly limited, but are usually 200 to 800 m ² as the area per unit volume.
/ m ³ and an aperture ratio of about 40 to 80% are used. Examples of the material of the honeycomb structure include, as the carrier, metal oxides and metals similar to the above-described metals, and zirconia, titania, and titania-zirconia having excellent durability are more preferable.

The amount of the catalyst for forming a fluidized bed in the catalytic reactor is not particularly limited as long as the catalyst can form a fluidized bed in the reactor. When a fluidized bed is formed in a catalytic reactor, the amount of the catalyst is usually 0.1% based on the weight of the liquid phase.
It is about 01 to 20%, more preferably about 0.05 to 10%.
In the case of a fluidized bed, the catalyst is supplied to the catalyst reactor in a state of being suspended in a slurry state in a liquid phase, and the catalyst is settled from the secondary treatment liquid discharged outside the column after the reaction, and centrifuged. It can be separated and recovered by an appropriate method such as separation and reused. Considering the ease of separation and recovery of the catalyst in the step (5), the particle size of the catalyst used in the fluidized bed is 0.15 to
More preferably, it is about 0.5 mm.

The space velocity in the step (5) can be appropriately set according to the type and shape of the catalyst. For example, when the above-mentioned catalyst is filled in a reactor or the like and used as a fixed bed, the space velocity of the liquid is usually 0.1 to 1
About 0h ^-1, preferably 0.3～2H ^- is about ^one. In the case of a fluidized bed, the space velocity of the liquid is usually about 0.1 to 10 h- ¹ ,
Preferably it is about 0.3 to 2 h ^-1 .

The gas-liquid mixed phase 19 obtained in the step (5) is
If necessary, it can be used as a heat source of the liquid to be treated in the heat exchanger 11 as described above. If there is residual energy after use as a heat source of the heat exchanger, the gas-liquid mixed phase 19 obtained in the step (5) may be used, if necessary, in a heat recovery device ( (Not shown) for heat recovery.

The gas-liquid mixed phase 19 subjected to the wet oxidation treatment may be separated into a gas phase and a liquid phase (final treatment liquid) as required. For example, in FIG. 1, the gas-liquid mixed phase 19 from the catalytic reactor 18 is shown.
Is sent to the gas-liquid separator 21 where the gas phase (exhaust gas) 22 and the liquid phase
(Treated water). Since the gas phase 22 is a mixed gas of steam and exhaust gas, it can be guided to a power recovery device such as an expansion turbine to recover power.

In the method of the present invention, in step (2), an oxygen-containing gas having a stoichiometric amount or more necessary for decomposing dioxins is supplied. Alternatively, they are supplied separately in the step (2) and the step (5). The supply amount of the oxygen-containing gas in the step (2) is about 0 to 100%, preferably about 30 to 100%, based on the total oxygen supply amount.

The oxygen-containing gas supplied in step (2) and / or step (5) is not particularly limited. The oxygen-containing gas may be, for example, oxygen alone or an oxygen-containing mixed gas such as air or oxygen-enriched air. Alternatively, an oxygen-containing waste gas containing at least one of hydrogen cyanide, hydrogen sulfide, ammonia, sulfur oxides, organic sulfur compounds, nitrogen oxides, and hydrocarbons as impurities can also be exemplified. The method for supplying the oxygen-containing gas is not particularly limited. It is preferable that the pressure of the oxygen-containing gas is increased in advance to a predetermined pressure using a compressor or the like.

The supply amount of the oxygen-containing gas to be supplied in the step (2) or the step (5) (or the total amount when dividedly supplied in the step (2) and the step (5)) is determined by the amount of oxygen contained in the gas. The amount is not particularly limited as long as it is not less than the theoretical amount of oxygen necessary to decompose dioxins into harmless products, and is preferably about 1.05 to 1.5 times the theoretical amount of oxygen.

When the reducing liquid is contained in the liquid to be treated and / or the oxygen-containing gas in addition to the dioxins, the supply amount of the oxygen-containing gas supplied in the step (2) or the step (5) (step ( The total amount of oxygen if contained in the oxygen-containing gas is a product in which the dioxins and the reducing compound are harmless if the amount of oxygen contained in the oxygen-containing gas is divided and supplied in step 2) and step (5).
(E.g., carbon dioxide gas, water, nitrogen, a compound containing sulfate ions, etc.) or more than the theoretical amount of oxygen necessary to decompose, more preferably about 1.05 to 1.5 times the theoretical amount of oxygen Can be. As the reducing compound contained in the liquid to be treated, for example, carbohydrates, fats and oils, organic acids,
Examples include organic substances such as aldehydes and alcohols; nitrogen compounds or nitrogen-containing ions such as amino acids and ammonium ions; sulfur-containing ions or sulfur compounds such as sulfide ions and sulfite ions; and reducing inorganic substances such as iron (II) ions. Examples of the reducing compound contained in the oxygen-containing gas include a nitrogen compound such as ammonia; a sulfur compound such as hydrogen sulfide; and an organic substance such as a hydrocarbon.

In the method of the present invention, activated carbon is used as an adsorbent, and an oxygen-containing gas containing at least the theoretical amount of oxygen required to decompose dioxins and activated carbon is supplied to adsorb dioxins. Activated carbon may be decomposed together with dioxins. In this case, the steps (3) and (4) described above can be omitted. That is, the present invention provides a method for treating dioxins in a liquid, comprising the following steps as a second invention. (1) a step of adsorbing dioxins in the liquid to be treated on activated carbon, (2) maintaining a slurry containing activated carbon having adsorbed dioxins at a temperature of 100 ° C. or higher and maintaining a liquid phase to remove dioxins. Decomposing the adsorbed activated carbon together with dioxins to obtain a gas-liquid mixed phase, and (3) performing a wet oxidation treatment of the gas-liquid mixed phase obtained in the step (2) in the presence of a catalyst, and dioxin In step (2), an oxygen-containing gas having a theoretical oxygen amount or more necessary for decomposing activated carbon and the like is supplied in the step (2), or divided and supplied in the step (2) and the step (3).

The conditions in step (1) and step (3) in the second invention are the same as those in step (1) and step (1) in the first invention.
Same as (5). Various conditions other than the supply amount of the oxygen-containing gas in the step (2) of the second invention are as follows.
It may be the same as (2) or may be supercritical.

In the second invention, in step (2), an oxygen-containing gas of a theoretical oxygen amount or more necessary for decomposing dioxins and activated carbon is supplied, or
In (3), supply separately. The supply amount of the oxygen-containing gas in the step (2) is 30 to 100% of the total oxygen supply amount.
Degree, preferably about 40 to 100%.

Supply amount of oxygen-containing gas in the second invention
(To supply oxygen-containing gas by dividing it, the total amount)
Is not particularly limited as long as the amount of oxygen contained therein is not less than the theoretical amount of oxygen necessary for decomposing dioxins and activated carbon into harmless products, and more preferably 1.05 to 1.5 times the theoretical amount of oxygen. It is about quantity. If the liquid to be treated and / or the oxygen-containing gas contains a reducing compound or ion, the theoretical amount of oxygen required to decompose the reducing compound or ion, dioxins and activated carbon into harmless products As described above, more preferably, an oxygen-containing gas containing about 1.05 to 1.5 times the theoretical amount of oxygen may be supplied.

In the present invention, the above first and second inventions can be combined. That is, when activated carbon is used as an adsorbent in the first invention and it is necessary to replace the activated carbon, the activated carbon can be incinerated with dioxin according to the second invention.

[0045]

According to the method of the present invention, dioxins contained in a liquid to be treated such as waste water can be efficiently treated. Dioxins adsorbed on the adsorbent are completely oxidatively decomposed.

Since the adsorbent can be used repeatedly, no secondary waste is generated. In addition, even when a regenerated adsorbent is used, a stable processing effect is achieved. Further, by using activated carbon as an adsorbent and controlling the amount of oxygen, it is possible to incinerate the adsorbent together with dioxins.

When an oxygen-containing waste gas is used as an oxygen source, the presence of harmful components derived from the waste gas is substantially not recognized in any of the gas phase and the liquid phase.

Further, if necessary, it is possible to efficiently recover electric power and / or heat from high temperature / high pressure exhaust gas and processing liquid.

[0049]

EXAMPLES Examples are shown below to further clarify the features of the present invention. The present invention is not limited to the following examples.

Example 1 Step (1) In a treatment tank, water to be treated (dioxin concentration: 5.9 ng)
The dioxins in -TEQ / L (330ng / L) were adsorbed on the adsorbent. Activated carbon as adsorbent (shape: powder, diameter: 0.1-0.3m
m) was used. The processing conditions are shown below. (TEQ: toxic equivalent, T
(oxic Equivalency Quantity) ・ Adsorbent (activated carbon) concentration of the treated water: 50 kg / m ³・ Residence time of the liquid to be treated in the treatment tank: 30 minutes ・ Temperature: 20 ° C ・ Pressure: 0 MPaG (atmospheric pressure) The dioxin concentration in the treated water obtained by removing dioxins in ()) is 0.048 ng-TE
Q / L (2.3 ng / L). Step (2) In an empty tower reactor, contained in the slurry containing the liquid to be treated and the adsorbent obtained in step (1) (concentration of dioxins in the slurry: 540 ng-TEQ / L (28000 ng / L)) Dioxins on the adsorbent were decomposed. The reaction conditions are shown below.・ Concentration of the slurry containing the adsorbent: 50 kg / m ³・ Temperature of the empty column reactor: 230 ° C. ・ Pressure (gauge pressure) in the empty column reactor: 6 MPaG ・ Retention time of liquid in the empty column reactor: 1.5 h -Air supply amount: 10 times the theoretical air amount required to decompose dioxins Step (3) The gas-solid liquid phase obtained in Step (2) was separated into a regenerated adsorbent and a gas-liquid mixed phase. The dioxins concentration on the regenerated adsorbent was 0.10 ng-TEQ / g (3.0 ng / g). Step (4) The regenerated adsorbent obtained in step (3) was returned to the above step (1) and reused. The regenerated adsorbent exhibited the same dioxin adsorption performance as a new adsorbent. Step (5) Using a catalyst reactor packed so that the catalyst becomes a fixed bed,
The gas-liquid mixed phase obtained in the step (3) was subjected to wet oxidation treatment in the presence of a catalyst. The processing conditions are shown below.・ Catalyst: 2% Ru / TiO ₂ (shape: spherical, diameter: 4-6 mm, amount used: 12 L) ・ Catalyst packing mass per 1 m ^{3 of} catalyst reactor: about 1.5 t ・ Temperature of catalyst reactor: 230 ° C. ・Pressure in the catalytic reactor (gauge pressure): 6MPaG ・ Space velocity in the catalytic reactor: 1h- ^{1 The} gas-liquid mixed phase subjected to wet oxidation treatment is passed through a gas-liquid separator,
It was separated into gas phase and liquid phase (final treated water). The dioxin concentration in the final treated water was 0.008 ng-TEQ / L (0.49 ng / L).

Dioxins in the water to be treated in the same manner as in Example 1 except that various catalysts (shape: spherical, diameter: 4 to 6 mm, usage: 12 L) were used instead of 2% Ru / TiO _2. Was processed. Table 1 summarizes the dioxin concentrations in the final treated water.

[0052]

[Table 1]

Example 2 Step (1) In a treatment tank, water to be treated (dioxin concentration: 5.9 ng)
The dioxins in -TEQ / L (330ng / L) were adsorbed on the adsorbent. Activated carbon as adsorbent (shape: powder, diameter: 0.1-0.3m
m) was used. The processing conditions are shown below. And adsorption treated water of the adsorbent (activated carbon) Concentration: 50 kg / m ³ · processing residence time of the liquid to be treated in the bath: 30 minutes Temperature: 20 ° C., & Pressure: 0 MPaG (atmospheric pressure) dioxins in step (1) Dioxin concentration in the treated water obtained by treating
Q / L (2.3 ng / L). Step (2) In an empty tower reactor, contained in the slurry containing the liquid to be treated and the adsorbent obtained in step (1) (concentration of dioxins in the slurry: 540 ng-TEQ / L (28000 ng / L)) Dioxins on the adsorbent were decomposed. The reaction conditions are shown below.・ Concentration of slurry containing adsorbent: 50 kg / m ³・ Temperature of empty tower reactor: 270 ° C ・ Pressure in empty tower reactor: 8.8 MPaG ・ Liquid residence time in empty tower reactor: 3.0 h ・ Air supply: 1.5 times the theoretical amount of air required to decompose dioxins and activated carbon The activated carbon used as the adsorbent was all decomposed. Step (3) Using a catalyst reactor packed so that the catalyst becomes a fixed bed,
The gas-liquid mixed phase obtained in the step (2) was subjected to wet oxidation treatment in the presence of a catalyst. The processing conditions are shown below.・ Catalyst: 2% Ru / TiO ₂ (shape: spherical, diameter: 4-6 mm, usage: 12 L) ・ Catalyst packing mass per 1 m ^{3 of} catalyst reactor: about 1.5 t ・ Temperature of catalyst reactor: 270 ° C.・ Pressure (gauge pressure) in the catalytic reactor: 8.8 MPaG ・ Space velocity in the catalytic reactor: 0.33 h ^{-1 The} gas-liquid mixed phase subjected to the wet oxidation treatment is passed through a gas-liquid separator.
It was separated into gas phase and liquid phase (final treated water). The dioxin concentration in the obtained final treated water was 0.004 ng-TEQ / L (0.14 n
g / L).

Except for using various catalysts (shape: spherical, diameter: 4 to 6 mm, amount of use: 12 L) in place of 2% Ru / TiO ₂ , the water to be treated was processed in the same manner as in Example 2. Of dioxins were treated. Table 2 shows the concentration of dioxins in the final treated water.
Summarized in

[0055]

[Table 2]

Example 3 Except that a nitrogen-sulfur-containing gas was used as the oxygen-containing gas,
Dioxins in the water to be treated were treated in the same manner as in Example 1. The concentrations of nitrogen compounds and sulfur compounds in the oxygen-containing gas are shown below. _{· H 2 S: 1300ppm, NH} 3: 5300ppm, HCN: using all of the catalyst used in the 80ppm Example 1 was subjected to dioxins process water to be treated. In any case, the concentration of dioxins in the final treatment liquid was determined in Example 1.
Was equivalent to the value in. In each case, the concentrations of nitrogen compounds and sulfur compounds in the gas phase (exhaust gas) finally obtained in step (5) were as follows.・ H ₂ S and HCN: not detected, NH ₃ : less than 0.1 ppm, NOx: 0.05
Less than ppm, SOx: less than 0.01 ppm Example 4 Dioxins in water to be treated are treated in the same manner as in Example 1 except that wastewater containing organic substances, nitrogen compounds and sulfur compounds other than dioxins is used as the liquid to be treated. did. The properties of the liquid to be treated are shown below.・ COD _Cr : 35000mg / L, total nitrogen: 1500mg / L, total sulfur:
65 mg / L Dioxins in the water to be treated were treated using all the catalysts used in Example 1. Regardless of which catalyst was used, the concentration of dioxins in the final treatment liquid was equivalent to the value in Example 1. Regardless of which catalyst was used, the concentrations of nitrogen compounds and sulfur compounds in the gas phase (exhaust gas) finally obtained in step (5) were as follows. -NOx: less than 0.05 ppm, SOx: less than 0.01 ppm From the results of Examples 3 and 4, when the liquid to be treated contains nitrogen, sulfur, or the like, or when an oxygen-containing exhaust gas is used as the oxygen-containing gas. Even in this case, it was found that an exhaust gas and a final treatment liquid substantially free of ammonia, nitrogen oxides (NOx), sulfur oxides (SOx), dioxins and the like can be obtained.

[Brief description of the drawings]

FIG. 1 is a flow sheet showing an example of the method of the present invention.

FIG. 2 schematically shows an example of an apparatus that can be used to maintain a slurry at a predetermined pressure in step (2) of the present invention.

[Explanation of symbols]

Reference Signs List 1 liquid to be treated (e.g., wastewater containing dioxins) 2 treatment tank 3 treated water 4 high-concentration slurry containing adsorbents adsorbing dioxins 5 storage tank 6 slurry 7 boosting pump 9 oxygen-containing gas 11 heat exchanger 13 empty tower Reactor 14 Gas-solid-liquid mixed phase 15 Solid-liquid separator 16 Return of regenerated adsorbent 17 Gas-liquid mixed phase 18 Catalytic reactor 19 Gas-liquid mixed phase from catalyst reactor 18 21 Gas-liquid separator 22 Gas phase (exhaust gas) 23 Liquid phase (Final treatment liquid)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B01J 23/30 B01J 23/30 M 23/42 23/42 M 23/44 23/44 M 23/46 23 / 46 M 301 301M 311 311M 23/52 23/52 M 23/72 23/72 M 23/745 27/057 M 23/755 C02F 1/28 ZABA 27/057 1/72 Z C02F 1/28 ZAB C07B 35 / 06 1/72 37/06 C07B 35/06 C07C 25/18 37/06 C07D 319/24 C07C 25/18 B01J 23/74 301M C07D 319/24 321M (72) Inventor Ryosuke Ito Chuo-ku, Osaka-shi, Osaka 4-1-2 Hiranocho Osaka Gas Co., Ltd. F-term (reference) 4D024 AA04 AA10 AB02 AB04 AB11 AB13 AB14 BA02 BA06 BA07 BA13 BA14 BB01 BB05 BC04 CA01 DA07 DA08 DB23 4D050 AA12 AA13 AB07 AB14 AB17 AB19 AB31 AB35 AB41 AB42 AB55 BB01 BC01 BC02 BC06 BC07 BD02 BD06 BD08 CA06 CA20 4G069 AA03 BA01A BA02A BA03A BA04A BA04B BA05A BA05B BA17 BA20A BB02B BB04A BB04B BB08A BB09A BC10A BC10B BC31A BC31B BC33A BC33 BC66B BC BC74B BC75A BC75B BD09A BD09B BD12A CA05 CA10 CA19 DA06 EA02Y EA18 EB12Y EB18Y EC03Y EC04Y 4H006 AA02 AC24 AC26 BA05 BA14 BA15 BA16 BA19 BA20 BA22 BA23 BA24 BA26 BA30 BA36 BA37 BA55 BA60 BC10 BC11 BE30

Claims (4)

[Claims] 1. A method for treating dioxins in a liquid, comprising:
(1) the step of adsorbing dioxins in the liquid to be treated to the adsorbent, (2) the slurry containing the adsorbent adsorbing dioxins is kept at a temperature of 100 ° C. or higher and a pressure that maintains the liquid phase, and adsorbed. Decomposing dioxins on the material to obtain a gas-solid liquid phase containing the regenerated adsorbent, (3) separating the gas-solid liquid phase obtained in the above step (2) into a regenerated adsorbent and a gas-liquid mixed phase Step, (4) a step of returning the recycled adsorbent obtained in the step (3) to the step (1) for reuse, and (5) a step
(3) a step of subjecting the gas-liquid mixed phase obtained in (3) to a wet oxidation treatment in the presence of a catalyst, and a step of supplying an oxygen-containing gas having a theoretical oxygen amount or more necessary for decomposing dioxins.
A method for treating dioxins in liquid, which is supplied in (2) or step (5), or is supplied separately in step (2) and step (5). 2. A method for treating dioxins in a liquid, comprising:
(1) a step of adsorbing dioxins in the liquid to be treated on activated carbon, (2) maintaining a slurry containing activated carbon having adsorbed dioxins at a temperature of 100 ° C. or higher and maintaining a liquid phase to remove dioxins. Decomposing the adsorbed activated carbon together with dioxins to obtain a gas-liquid mixed phase, and (3) performing a wet oxidation treatment of the gas-liquid mixed phase obtained in the step (2) in the presence of a catalyst, and dioxin Characterized in that the method comprises supplying an oxygen-containing gas in an amount not less than the theoretical oxygen amount required for decomposing species and activated carbon in the step (2), or separately supplying the oxygen-containing gas in the step (2) and the step (3). For treating dioxins in liquid. 3. The catalyst used in the wet oxidation treatment in step (5) is a catalyst in which at least one selected from the group consisting of metals and metal compounds is supported on a metal oxide carrier or a metal carrier as a catalytically active component. The method for treating dioxins in a liquid according to claim 1 or 2, wherein: 4. The method for treating dioxins in a liquid according to claim 1, wherein the adsorbent used in the step (1) is at least one selected from the group consisting of activated carbon, zeolite, acid clay and activated clay. .