JP2003170021A - Method for cleaning exhaust ags and decomposition treatment facility of hardly decomposable halogen compound - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for perfectly cleaning an exhaust gas that cleans an exhaust gas containing a hardly decomposable halogen compound and to provide a facility for withdrawing a hardly decomposable halogen compound, which is suitable for effecting the method of cleaning the exhaust gas, from a vessel and cleaning the vessel and further performing the decomposition treatment of the hardly decomposable halogen compound. <P>SOLUTION: The method for cleaning the exhaust gas comprises steps of an absorbing step that makes the hardly decomposable halogen compound included in the exhaust gas absorbed in an absorbent by contacting the exhaust gas containing the hardly decomposable halogen compound with the absorbent, a cooling step that cools the exhaust gas treated in the absorbing step by a condenser and an activated carbon treatment step that contacts the exhaust gas cooled by the condenser with activated carbon. The facility suitable for effecting the method for cleaning the exhaust gas is also provided. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying exhaust gas containing a refractory halide such as polychlorinated biphenyl (PCB), and a decomposition treatment facility for a refractory halogen compound.

[0002]

2. Description of the Related Art Persistent halogen compounds such as polychlorinated biphenyl (PCB) are generally chemically stable,
It is not easily decomposed in the natural environment (in the present invention, such a halogen compound is referred to as "hardly-degradable halogen compound"). In addition, since these are taken up in animals and plants, accumulated and concentrated, and have serious adverse effects, their production is prohibited today, but they are still difficult to decompose or halogen-containing compounds. The current situation is that a large amount of is stored. Therefore, it is necessary to prevent the persistent halogen compound from being lost or leaked during storage to contaminate the environment, and promotion of detoxification treatment of these persistent halogen compounds has become an important issue. The development of detoxifying treatment technology for persistent halogen compounds has also made rapid progress.

[0003] Examples of such a detoxifying treatment technology for hardly decomposable halogen compounds include "PCB treatment technology guidebook" (edited by Industrial Waste Treatment Business Promotion Foundation, Gyosei Co., Ltd., 1999). , (1) PC
A method of dechlorinating B by adding a hydrogen donor, an additive and an alkali and then heating at 300 to 350 ° C. under normal pressure in a nitrogen atmosphere, (2) sodium hydroxide and hydroxide of PCB A method of converting chlorine in PCB to an alkali salt such as sodium chloride in the presence of an alkali such as potassium and an aprotic polar solvent such as 1,3-dimethyl-2-imidazolidinone, sulfolane and polyethylene glycol dialkyl ether, (3 ) A method of dechlorinating PCB under atmospheric pressure in the presence of a palladium / carbon catalyst with hydrogen gas,
(4) A method of reacting PCB with an organic metal compound such as potassium tert-butoxide by heating is described.

The detoxification treatment of the hardly decomposable halogen compound is carried out by pretreatment equipment for pretreating the hardly decomposable halogen compound or the content of the hardly decomposable halogen compound and the dehalogenation reaction of the hardly decomposable halogen compound. Decomposition reaction equipment,
It is carried out in a facility for decomposing and processing a hardly decomposable halogen compound, which has a post-processing facility for post-processing the reaction mixture. Further, the pretreatment facility also includes a step of extracting the hardly decomposable halogen compound contained in the container from the container and cleaning the container.

From the decomposition reaction equipment or the like for carrying out the dehalogenation reaction of the hardly decomposable halogen compound, environmental pollutants such as the gas of the reaction product and the evaporated hardly decomposable halogen compound (hereinafter, referred to as "the hardly decomposable halogen compound"). Etc.)) is generated. If exhaust gas containing environmental pollutants is directly discharged to the outside, it will recontaminate the natural environment, so it is necessary to remove persistent halogen compounds, etc. from this exhaust gas. ".). In particular, the hardly decomposable halogen compound is a regulated substance, and it is necessary to completely purify the exhaust gas so that even a trace amount does not leak outside.

Further, in order to extract and wash the hardly decomposable halogen compound stored in a container such as a transformer or a condenser, for example, a method using a vacuum heating furnace or a cleaning liquid is used to clean the inside of the container. There is a method of washing. In either method, vapor of persistent halogen compound is generated from the vicinity of the container processing device,
Ventilation with a local exhaust system and its purification are required. Also,
When using a vacuum heating furnace, it is necessary to further purify the exhaust of the vacuum pump.

As a method for purifying these exhaust gases, conventionally, a decomposition reaction facility is connected to an activated carbon packed tower filled with activated carbon, and the exhaust gas is passed through the activated carbon packed tower to prevent decomposition. A method of adsorbing and removing a volatile halogen compound or the like is known (see the above-mentioned "PCB Processing Technology Guidebook" and the like).

However, in this method, it is necessary to replace the activated carbon with a new one when the adsorption amount of the activated carbon is saturated, but since a large amount of the hardly decomposable halogen compound is adsorbed to the used activated carbon. When treating a large amount of used activated carbon, there is a risk that an operator takes in a persistent halogen compound. In addition, since the used activated carbon cannot be used as it is for the dehalogenation reaction of the hardly decomposable halogen compound, it is necessary to take out the hardly decomposable halogen compound and perform the dehalogenation treatment again. The processing work of activated carbon was complicated.

[0009]

The present invention has been made in view of the above circumstances, and an exhaust gas purification method for completely purifying exhaust gas containing a hardly decomposable halogen compound, and purification of the exhaust gas. The persistent halogen compound suitable for carrying out the method is extracted from the container, the container is washed,
Further, it is an object to provide a facility for decomposing a hardly decomposable halogen compound.

[0010]

Means for Solving the Problems As a result of intensive studies aimed at solving the above-mentioned problems, the present inventors first contacted an exhaust gas containing a hardly decomposable halogen compound with an absorbent,
Then, it was found that exhaust gas containing a hardly decomposable halogen compound can be completely purified by cooling with a condenser and then contacting with activated carbon. When an absorbent that can be used for the dehalogenation reaction of a hardly decomposable halogen compound is used, the absorbent that has absorbed the hardly decomposable halogen compound is recovered, and the hardly decomposed halogen compound contained in the absorbent is collected. The present invention has been completed by discovering that by subjecting a hard-decomposable halogen compound whose outflow to the outside is regulated to a dehalogenation reaction, it is possible to completely and efficiently detoxify the compound. .

Thus, according to the first aspect of the present invention, the hardly decomposable halogen compound contained in the exhaust gas is absorbed by the absorbent by bringing the exhaust gas containing the hardly decomposable halogen compound into contact with the absorbent. Provided is an exhaust gas purification method including an absorption step, a cooling step of cooling exhaust gas treated by the absorption step with a condenser, and an activated carbon treatment step of contacting the exhaust gas cooled by the condenser with activated carbon. .

The purification method of the present invention preferably further comprises a step of passing the exhaust gas cooled by the condenser through a mist separator between the cooling step and the activated carbon treatment step. Exhaust gas generated from a decomposition reaction tank for dehalogenating a hardly decomposable halogen compound is preferable.

Further, in the purification method of the present invention, it is more preferable to use a solvent that can be used for the dehalogenation reaction of the hardly decomposable halogen compound as the absorbent, and the absorbent having absorbed the hardly decomposable halogen compound. It is more preferable to further include a step of recovering the halogenated compound and dehalogenating the hardly decomposable halogen compound contained in the absorbent.

According to the second aspect of the present invention, a pretreatment facility for pretreating the hardly decomposable halogen compound or the content of the hardly decomposable halogen compound, and a decomposition reaction for dehalogenating the hardly decomposable halogen compound. Of a hardly decomposable halogen compound having equipment, an aftertreatment equipment for performing aftertreatment of a reaction product produced by the dehalogenation reaction, and an exhaust gas purification equipment for purifying exhaust gas generated from the decomposition reaction equipment. A decomposition treatment facility, wherein the exhaust gas purifying facility is filled with an absorbent that absorbs a hardly decomposable halogen compound, and the exhaust gas containing the hardly decomposable halogen compound is brought into contact with the absorbent to produce the exhaust gas. An absorption tower for absorbing the hardly-decomposable halogen compound contained in the gas into the absorbent, a condenser for cooling the exhaust gas passing through the absorption tower, and an activity Coal is filled, the decomposition treatment facilities hardly decomposable halogen compound having a cooled exhaust gas and the activated carbon packed column is contacted with the activated carbon by a condenser is provided.

In the decomposition treatment facility of the present invention, it is preferable that the exhaust gas purification equipment further has a mist separator between the condenser and the activated carbon packed tower, and the absorption tower is the decomposition treatment equipment. The solvent that can be used for the dehalogenation reaction of the hardly decomposable halogen compound is filled in, and the exhaust gas containing the hardly decomposable halogen compound is brought into contact with the solvent to make it difficult to decompose. More preferably, the halogen compound is absorbed in the solvent.

Further, in the decomposition treatment facility of the present invention,
It is preferable that the absorbent having absorbed the hardly-decomposable halogen compound is recovered from the absorption tower, and the dehalogenation reaction of the hardly-decomposable halogen compound contained in the absorbent is carried out in the decomposition reaction facility.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The exhaust gas purifying method and the facility for decomposing a persistent halogen compound according to the present invention will be described in detail below. The hardly decomposable halogen compound which is the subject of the present invention is generally a halogen compound which is chemically stable and is not easily decomposed in the natural environment. Examples of the hardly decomposable halogen compound include PCB, dioxins, polychlorinated benzofurans, polychlorinated benzene, and DDT.
And the like; alicyclic halogen compounds such as BHC; and the like.

The harmless treatment of the hardly decomposable halogen compound is
Generally, it is carried out by dehalogenating a persistent halogen compound. The detoxification treatment of the hardly decomposable halogen compound is performed by accepting the hardly decomposable halogen compound or the content of the hardly decomposable halogen compound, and subjecting the hardly decomposable halogen compound or the content of the hardly decomposable halogen compound to the dehalogenation reaction. Treatment of a hard-to-decompose halogen compound having pretreatment equipment for bringing into a state, a decomposition reaction equipment for dehalogenating a hard-to-decompose halogen compound, and a post-treatment equipment for performing a post-treatment of a dehalogenation reaction product Performed at the facility. In addition, the pretreatment step may include a step of extracting the hardly decomposable halogen compound contained in the container and washing the container.

1) Method for Purifying Exhaust Gas The method for purifying exhaust gas of the present invention has an absorption step, a cooling step, and an activated carbon treatment step. In the exhaust gas purification method of the present invention, if the gas contains a hardly decomposable halogen compound, the exhaust gas discharged from any of the above pretreatment equipment, decomposition reaction equipment, and aftertreatment equipment is also an object of purification. Can be

The exhaust gas purification method of the present invention is, for example, as follows:
It can be implemented by the exhaust gas purification equipment 1 shown in FIG. The exhaust gas purification equipment 1 shown in FIG.
3, which purifies the exhaust gas generated from 3, and is basically an absorption tower 2 filled with an absorbent, a condenser 3,
It consists of a mist separator 4 and an activated carbon packed tower 5 filled with activated carbon.

In the exhaust gas purification equipment 1 shown in FIG. 1, the exhaust gas is purified as follows. (A) The exhaust gas generated from the decomposition reaction tank is first cooled by the condenser 6, the solvent vapor is liquefied (condensed), and returned to the decomposition reaction tank. (B) Next, the absorption tower 2 is passed through the seal trap 7.
Sent to. The seal trap 9 is installed to prevent backflow of exhaust gas. Although the condenser 6 and the seal trap 7 are not essential in the present invention, it is preferable that they are respectively installed.

(C) The exhaust gas sent to the absorption tower 2 comes into contact with the absorbent, and the hardly decomposable halogen compounds contained in the exhaust gas are absorbed and removed. The absorbent that can be used is not particularly limited as long as it is a substance that absorbs a hardly decomposable halogen compound or the like, but from the viewpoint of absorption efficiency and efficiency of replacement work of the absorbent, it is preferable to use a liquid absorbent. preferable.

Among the liquid absorbents, in the present invention, they have excellent dissolving power for hardly-decomposable halogen compounds,
It is more preferable to use a solvent that does not interfere with the reaction when the dehalogenation reaction of the hardly decomposable halogen compound is performed, and it is further preferable to use the solvent that is used when the dehalogenation reaction of the hardly decomposable halogen compound is used. . This is because the absorbent that has absorbed the hardly decomposable halogen compound can be used as it is as a solvent for the dehalogenation reaction, and the absorbed hardly decomposable halogen compound can be used for the dehalogenation reaction.

Specific examples of the liquid absorbent include n-hexane, n-hepuan, n-octane, n-decane, kerosene, decalin, liquid paraffin, and electric insulating oil (for example, electricity described in JIS C2320-1993). Insulating oil), hydrocarbons such as heavy oil (for example, heavy oil described in JIS K2205); aromatic hydrocarbons such as toluene and xylene; 1,3-dimethylimidazoline, sulfolane,
Aprotic polar solvents such as polyethylene glycol dialkyl ether; and mixtures thereof. Among these, saturated hydrocarbons such as n-decane, decalin, and liquid paraffin; kerosene, electrically insulating oil, because they have a relatively low vapor pressure, a high flash point, and an excellent ability to absorb persistent halogen compounds. , Heavy oils and other mineral oils;
And the use of mixtures thereof is preferred.

An example of the absorption process using the absorption tower 2 is shown in FIG. In FIG. 2, 9 indicates the flow of exhaust gas and 10 indicates the flow of the absorbent. Here, trans oil is used as the absorbent. Transformer oil is 5-10 liters in total, its flow rate is usually 5 liters / min-30 liters / minute, the flow of transformer oil is produced by diaphragm pump 11, its flow rate is controlled by flow meter 12. There is.

Further, in order to ensure good flow of the transformer oil, the transformer oil is kept at 25 by a heater (not shown).
It is preferable to use by heating to -30 ° C. Absorption tower 2
Is an apparatus for cleaning the exhaust gas by bringing the absorbent and the exhaust gas into contact with each other to cause the absorbent to absorb a hardly decomposable halogen compound or the like contained in the exhaust gas. The size of the absorption tower 2 is not particularly limited and can be appropriately set depending on the flow rate of the exhaust gas to be purified. Absorption tower 2 shown in FIG.
The inner diameter is about 80 mm and the height is about 220 mm, but the diameter of the tower can be various sizes depending on the gas flow rate. Further, the filling amount and the flow rate of the absorbent in the absorption tower 2 can be appropriately set depending on the flow rate of the gas to be purified. For example, if the amount of exhaust gas to be treated is about 20 liters / minute, the column diameter is 80 mm, and the flow rate of the absorbent is about 5 L / hour to 30 L / hour.

Further, a filling section 8 filled with the filling material 14 is provided in the middle part of the absorption tower 2, and while the transformer oil slowly flows through the small gaps of the filling material, the exhaust gas is transformed into the transformer oil. Is in good contact with. There is no limitation on the type of the filler 14 as long as the contact between the exhaust gas and the absorbing liquid is sufficient. For example, homing packings made by assembling wire mesh such as Sruzer packing and Sruzer lab packing, and irregular packings such as Raschig rings and Perlsaddle can be used.

When the absorption amount of the hardly decomposable halogen compound or the like reaches a predetermined concentration, it is necessary to replace a new absorbent. In the absorption tower 2 shown in FIG. 2, since the trans oil, which is the absorbent, is circulated and used in a closed system, the operation of the decomposition reaction facility is stopped, and then the absorbent is replaced. In addition, for example, by connecting a joint to any place of the circulation passage of the transformer oil shown in FIG. 2 and feeding a new absorbent (insulating oil) through the joint, the used absorption from one side is absorbed. The absorbent can be replaced by extracting the agent. According to this method, it is possible to exchange the absorbent while continuing to operate the decomposition reaction equipment.

The used absorbent contains a hardly decomposable halogen compound. Therefore, it is necessary to detoxify this product by a dehalogenation reaction. The used absorbent may be directly transferred to a decomposition treatment facility and used for the dehalogenation reaction of hardly-decomposable halogen compounds. You can also use it. It is also possible to separately install a tank for storing the used absorbent, transfer the used absorbent to the tank and store it, and subject each of the fixed amounts to the dehalogenation reaction. In this case, if a solvent that can be used for the dehalogenation reaction of the hardly decomposable halogen compound is used as the absorbent, the used absorbent can be directly used for the dehalogenation reaction. Therefore, the step of separating the absorbent and the hardly decomposable halogen compound becomes unnecessary, and the work efficiency and the risk of recontamination of the hardly decomposable halogen compound in the separation step can be avoided.

(D) The exhaust gas that has undergone the absorption process is sent to the cooling process. In the cooling process, exhaust gas is passed through the condenser 3
By 10 ° C to -10 ° C, preferably 3 ° C to -10
The gas component contained in the exhaust gas is liquefied (condensed) by rapidly cooling to ℃. As the condenser 3, it is preferable to use a deep-cooled condenser, which has a lower cooling temperature than an ordinary condenser and can be rapidly cooled. The cryogenic condenser is not particularly limited, and known ones can be used.

In the absorption step, most of the hardly decomposable halogen compounds are absorbed and removed from the exhaust gas, but a small amount of hardly decomposed halogen compounds may remain in the exhaust gas without being absorbed. By cooling the exhaust gas brought into contact with the absorbent using the condenser 3, it is possible to condense / remove a trace amount of hardly decomposable halogen compound or the like.

That is, the temperature of the exhaust gas that has undergone the absorption process is
It is usually warmed to 20-30 ℃, but condenser 3
Is cooled to 10 ° C to -10 ° C, preferably 3 ° C to -10 ° C, and most of the gas components in the exhaust gas are liquefied and condensed. The condensed liquid is collected by a condenser (not shown). The hardly-decomposable halogen compound or the like collected in the condenser is sent to the decomposition reaction facility for dehalogenation reaction.

(E) The exhaust gas passing through the condenser 3 is sent to the mist separator 4. The mist separator 4 is a separation device for removing mist-like substances (droplet-like substances) from gas. By passing the exhaust gas cooled by the condenser 3 through the mist separator 4, it is possible to completely separate the fine particulate mist-like matter not recovered in the condenser of the condenser 3 from the gas component. The mist separator may be omitted, but it is preferably installed from the viewpoint of prolonging the life of the activated carbon.

(F) Next, the exhaust gas that has passed through the mist separator 4 is passed through the activated carbon packed column 5 filled with activated carbon to perform adsorption treatment with activated carbon. The temperature at which the exhaust gas is brought into contact with the activated carbon is usually 0 ° C to 30 ° C. Further, the amount of activated carbon used is not particularly limited, and the amount of activated carbon can be appropriately set according to the flow rate of exhaust gas and the like.

The activated carbon packed in the activated carbon packed tower 5 is not particularly limited, and any of coconut shell type, wood type and coal type can be used, or granular coal or crushed coal can be crushed and used. . Activated carbon is, for example, after the raw material is carbonized at a temperature of 800 ° C. or lower in an inert residue,
It can be produced by oxidizing and activating at 1,000 ° C. using steam, carbon dioxide gas or the like (called a gas activating method or a steam activating method). In the activation process, the surface of the carbon material generated in the carbonization process is slowly and selectively oxidized, and pores suitable for adsorption are generated. In addition, activated carbon is prepared by mixing chemicals such as zinc chloride as raw materials,
It can also be produced by a method of carbonizing in an inert gas.

According to the purification method of the present invention, the amount of activated carbon used can be greatly reduced as compared with the conventional exhaust gas purification method using only activated carbon. Further, since the hardly decomposable halogen compound adsorbed on the activated carbon is in a very small amount, the life (usable time) of the activated carbon is extended. Therefore, unlike the conventional method, it is not necessary to replace the activated carbon frequently, and the amount of the activated carbon that needs to be replaced is greatly reduced.Therefore, there is a risk that the hard-to-decompose halogen compound adsorbed by the activated carbon is taken into the body during work. It's getting less.

(G) The exhaust gas purified as described above is discharged to the outside. In the purification method of the present invention, the exhaust gas generated from the decomposition reaction tank that performs the dehalogenation reaction of the hardly decomposable halogen compound is targeted for purification. Therefore, since flammable gas such as hydrogen gas may be contained in the exhaust gas, it is preferable to install a safety device such as a flashback preventer (not shown). As described above, the exhaust gas containing the persistent halogen compound or the like can be safely purified.

2) Decomposition Treatment Facility for Persistent Halogen Compounds The outline of the decomposition treatment facility for hardly decomposable halogen compounds suitable for the present invention is shown in FIG. The decomposition treatment facility for the hardly decomposable halogen compound shown in Fig. 3 consists of a pretreatment facility for the hardly decomposable halogen compound or a substance containing the hardly decomposable halogen compound, a dehalogenation reaction facility for the hardly decomposable halogen compound, and a post-treatment facility. An exhaust gas purifying facility for purifying exhaust gas generated from each facility is further installed in each facility.

(1) Pretreatment facility In the pretreatment facility, the hardly decomposable halogen compound or the content of the hardly decomposable halogen compound is received, and fractionation is performed according to the type. The content of the hardly decomposable halogen compound differs in the concentration of the hardly decomposable halogen compound and the property of the member. For example, in the case of electric equipment such as a transformer, the structure and material differ depending on the manufacturer, model number, etc., and it is necessary to carry out subsequent process design according to them.

Examples of the content of the hardly decomposable halogen compound that can be received in the pretreatment facility include wastes containing the hardly decomposable halogen compound. Specific examples thereof include a heat medium containing a hardly decomposable halogen compound, an electric insulator containing a hardly decomposing halogen compound, a hardly decomposing halogen compound for producing a product using a hardly decomposing halogen compound, a contaminated oil containing a hardly decomposing halogen compound, Waste oil containing equipment such as cleaning agent waste liquid containing equipment that uses persistent halogen compounds and waste oil containing persistent halogen compounds and persistent halogen compounds; waste pressure-sensitive paper, insulating paper inside electrical equipment, wipe paper during cleaning, inside electrical equipment Spacers, building materials for earth leakage locations, PP films for capacitor elements, sealants, used protective equipment, wire covering materials, insulating tapes, flame-retardant resins, insulating materials in electrical equipment, electrical equipment such as transformers and capacitors, Containing persistent halogen compounds such as electric equipment containers, heat exchangers, aluminum for capacitor elements, various fasteners in electric equipment, copper wires for transformer windings, etc. ,
Wood, synthetic resin or metals; a hard-degradable halogen compound-treated product containing a hard-decomposing halogen compound; a capacitor containing a hard-decomposing halogen compound; a transformer containing a hard-decomposing halogen compound; and the like.

Among them, kerosene, decalin, electric insulating oil (JIS C2320) containing a hard-to-decompose halogen compound is contained as a substance containing a large amount of a hard-to-decompose halogen compound.
-1993, electric insulating oil), heavy oil (JIS K2
205, heavy oils, lubricating oils, mixtures thereof, and the like. Specifically, it is a transformer or condenser containing a hardly decomposable halogen compound.

The received content of the hardly-decomposable halogen compound is disassembled, cut, broken, fractionated, etc., and washed to recover the hardly-decomposable halogen compound from the disassembled, cut, broken and fractionated products. Done. Examples of the cleaning method include a dipping method, a liquid circulation method, an ultrasonic method, and a bubbling method. The cleaning agent used must have excellent cleaning power, low risk of fire and explosion, low toxicity, and easy drying after cleaning. The hard-to-decompose halogen compound recovered by washing is stored in a storage container together with a detergent, separated from the detergent as needed, and then sent to the next dehalogenation reaction step.

In the case of a transformer or a condenser containing a hardly decomposable halogen compound, the substance containing the hardly decomposable halogen compound is enclosed in a closed container. Therefore, the above-mentioned recovery method by washing or the like is not preferable in terms of work efficiency. Therefore, in this case, it is preferable to perform the operation of extracting the hardly decomposable halogen compound from the transformer or the condenser.

For example, in the case of a PCB-containing transformer (or condenser), the transformer (or condenser)
Fix, and make a hole in the transformer (or condenser) at a predetermined position with a drill or the like, and connect the hole to a vacuum line,
The hard-to-decompose halogen compound can be taken out by sucking the hard-to-decompose halogen compound from the hole while pressurizing the inside of the transformer (or the condenser).

Further, inside the transformer or capacitor from which the persistent halogen compound has been taken out as described above,
The persistent halogen compound that has permeated the fibers may remain. In this case, for example, the inside is washed with a cleaning agent, or a member containing a hardly decomposable halogen compound or a hardly decomposable halogen compound is put in a vacuum heating furnace,
The pressure in the vacuum heating furnace was reduced to 0.01 to 50 mbar,
While continuing to reduce the pressure, the member is heated from 250 ° C. to 650 ° C. to carbonize the member and evaporate the hardly decomposable halogen compound or the insulating oil containing the hardly decomposable halogen compound. By condensing on the exhaust system, the hardly decomposable halogen compound or the insulating oil containing the hardly decomposable halogen compound can be recovered.

Further, the above pretreatment step is carried out in a closed space in order to prevent recontamination of the hardly decomposable halogen compound, and the exhaust gas generated from the space is purified by an exhaust gas purifying facility. It is preferable to discharge it to the outside later. As the purification method, for example, a method of using the inside of an activated carbon packed tower in which activated carbon is adsorbed, or the method shown in FIG.
The method of using the exhaust gas purification equipment shown in 1) and the like can be mentioned. The persistent halogen compound recovered in the exhaust gas purification facility is sent to the next dehalogenation step.

(2) Dehalogenation reaction equipment for hardly decomposable halogen compounds Generally, the decomposition reaction equipment comprises a hardly decomposable halogen compound and a drug (alkali) in a reaction tank together with an activator and a solvent, if desired. It is a facility for carrying out a dehalogenation reaction of a hardly decomposable halogen compound by putting it in and stirring the reaction tank at a predetermined temperature for a predetermined time by using a stirring device.

The decomposition reaction facility is not particularly limited, and examples thereof include those applicable to various decomposition reaction methods of hardly decomposable halogen compounds. Specifically, a decomposition treatment facility using an alkali metal dispersion method for dehalogenating a hardly decomposable halogen compound using an alkali metal dispersion, a hydrogen donor, an additive and an alkali for the hardly decomposable halogen compound. , A decomposition treatment facility using an alkali catalyst decomposition method (BCD method) that is heated at normal pressure in a nitrogen atmosphere, a hardly decomposable halogen compound, 1,3-dimethyl-2-imidazolidinone, sulfolane, Decomposition equipment using a chemical extraction decomposition method of reacting with an alkali such as sodium hydroxide or potassium hydroxide in an aprotic polar solvent such as polyethylene glycol dialkyl ether,
An organic alkali metal such as potassium tert-butoxide is added to a hard-to-decompose halogen compound and heated to decompose the halogen-containing compound. Catalytic hydrodechlorination method (Pd / C) in which hydrogen is heated at normal pressure in the presence of hydrogenation catalyst such as carbon
Method) is used.

Among these, as the decomposition reaction equipment,
The alkali metal dispersion method is used because the substance balance of the compound derived from the hardly decomposable halogen compound is clear, no harmful substances are produced as by-products, and post-treatment after decomposition is easy. A decomposition reaction facility is preferable, and a decomposition treatment facility using a sodium metal dispersion as an alkali metal dispersion is more preferable.

The decomposition treatment equipment usually comprises a reaction tank with a stirring device, a reaction temperature control device and the like (not shown). The stirring device consists of at least a stirring blade and a stirring motor, the rotation speed of the stirring blade can be freely adjusted, and it is possible to sufficiently stir the hardly decomposable halogen compound and the necessary chemicals, catalysts, solvents, etc., and stabilize the prescribed decomposition reaction. It is preferable to use a stirrer that allows uniform and uniform stirring. The temperature control device is a device for adjusting the temperature in the reaction tank (temperature of decomposition reaction) to a predetermined temperature,
According to the operation management standard of the decomposition reaction equipment determined according to the concentration of the hardly decomposable halogen compound, to ensure proper and safe operation within the standard range of temperature, pressure, etc. from before the reaction to the end of the reaction. It is preferable to have a function of controlling

In any of the above dehalogenation reaction methods, in order to safely carry out the dehalogenation reaction, the dehalogenation reaction is carried out in an inert gas atmosphere such as nitrogen gas or argon gas. Is preferred.

Exhaust gas containing a hardly decomposable halogen compound is generated from the decomposition reaction tank using any of the above dehalogenation reactions. Therefore, it is necessary to completely purify this exhaust gas.

As the cleaning method, the cleaning method of the present invention is used. Specifically, a method using the exhaust gas purification equipment shown in FIG. 2 may be used. In this case, the exhaust gas purification device shown in FIG. 3 is installed in connection with the decomposition reaction tank.

(3) Post-treatment facility The reaction product obtained by dehalogenating the hardly decomposable halogen compound in the decomposition reaction facility is sent to the post-treatment facility. The post-treatment facility separates the decomposition products of the hardly decomposable halogen compounds contained in the reaction products, unreacted chemicals, activators, solvents, etc., and recovers them so that they can be finally discarded or reused. It is equipment to put it into a state.

Specific examples of the post-treatment equipment include a centrifuge, a filtration device, a neutralization washing device, a liquid separation device, a distillation device and the like. Then, using these devices, operations such as separation and recovery of solid content from the reaction product, decomposition of excess alkali content, recovery of solvent, separation of produced salt, separation of catalyst and the like are performed.

For example, a reaction product obtained by dehalogenating a high-concentration hardly-decomposable halogen compound-containing substance using an alkali metal dispersion includes a solvent such as insulating oil and a solid substance (polyphenylene type polymer, insulating oil). , Sodium hydroxide, salt, water, etc.) are included. The post-treatment facility is composed of a centrifuge for separating solid and liquid, a washing device, a liquid separating device, and the like, and the work of separating oil and solid matter is performed using these devices.

When the dehalogenation reaction of the low-concentration hardly decomposable halogen compound is carried out, water is added to the reaction product to obtain a mixture of biphenyls, saline and insulating oil. . Then, after the mixture was washed and allowed to stand, oil, tar and waste water were separated using a separator, the waste water was evaporated by an evaporator, and the obtained solid content was recovered and evaporated. An operation of collecting water as process water by a water recovery device is performed.

In this case, water and alkaline components are recovered from the alkaline washing liquid used for washing with water,
It can be reused as a cleaning liquid for the decomposition product of the hardly decomposable halogen compound. Further, when decomposing a low-concentration hardly decomposable halogen compound-containing substance using an alkali metal dispersion, an activator is added in addition to the alkali metal dispersion and a solvent. The aqueous solution used for washing the decomposed product of the decomposable halogen compound can also be used.

By doing so, post-treatment after decomposition can be carried out in a short step without using a large-scale drainage facility, and highly polar components used in the reaction product can be removed by washing. Moreover, it is preferable that the alkaline component can be discriminated by adjusting the concentration of the alkaline cleaning liquid.

(4) Other Equipment In the facility for decomposing a hardly decomposable halogen compound according to the present invention, although not shown, the decomposing reaction of the hardly decomposing halogen compound is completed and the hardly decomposing halogen compound is decomposed. It is preferable that a measuring facility is further installed to confirm that the content of the compound has reached a certain reference value or less. Examples of such measurement equipment include ECD-GC (gas chromatography with electron capture detector),
GC-MS (Gas Chromato-Mass Spectrometer)
A device for measuring the content of persistent halogen compounds such as etc., or a part of the reaction mixture is sampled (sampling) after a lapse of a predetermined time from the start of the reaction, and this can be purified and measured by the above measuring device Examples include a separation device such as a silica gel column and a purification device for bringing into a state.

[0061]

Example 1 PCB-containing transformer oil was detoxified by using the facility for decomposing hardly decomposable halogen compounds shown in FIG. First, at the pretreatment facility, oil was removed from the discarded transformer and KC-50048mg / kg, TCB 11mg /
4400k of trans oil containing 54kg / kg of water
g was obtained. Then, this PCB-containing transformer oil 440
0 kg was put into a decomposition reaction tank, the inside was replaced with nitrogen, and then heated until the internal temperature reached 60 ° C. There, 65 kg of sodium metal dispersion (including 11 kg of sodium metal)
, Add 4.31 kg of water, and add 2 at 60-70 ° C.
The mixture was stirred for a time to carry out a dehalogenation reaction.

The exhaust gas generated from the decomposition reaction tank is shown in FIG.
It was sent to the reaction exhaust gas purification equipment shown in for purification. The reactive exhaust gas purification equipment shown in FIG. 4 is the same as the purification equipment shown in FIG. 2, and includes a vent condenser 16 and an empty tank 1.
5, an adsorption tower 17, a cryogenic condenser 18, a mist separator 19 and an activated carbon packed tower 20.

Table 1 shows the results of exhaust gas analysis at points A to E below. A point: Absorption tower inlet B point: Absorption tower outlet C point: Condenser outlet D point: Mist separator outlet E point: Activated carbon packed tower outlet

The exhaust gas was analyzed by using a high resolution gas chromatograph mass spectrometer (GC-MS) after obtaining a measurement sample with the exhaust gas sampling apparatus shown in FIG. That is, the amount of exhaust gas (collection amount) shown in Table 1 was collected from each of the sampling ports A to E, and 250 ml of distilled water (in a gas absorption bottle having an internal volume of 500 ml) was cooled with ice. After passing through, XAD-2-resin (styrene resin adsorbent) tube and diethylene glycol (250 ml) were passed under ice cooling to remove impurities other than persistent halogen compounds to obtain a measurement sample. Was analyzed using high resolution GC-MS.

In Table 1, the abbreviations have the following meanings. Mono-CBs: Monochlorobiphenyl Di-CBs: Dichlorobiphenyl Tri-CBs: Trichlorobiphenyl Tetra-CBs: Tetrachlorobiphenyl Penta-CBs: Pentachlorobiphenyl Hexa-CBs: Hexachlorobiphenyl Hepta-CB-Cs: Heptachlorobiphenyl. Chlorobiphenyl Nona-CBs: Nonachlorobiphenyl Deca-CBs: Decachlorobiphenyl Total-PCBs: Mono-CBs to Dec as described above.
Total amount of a-CBs

[0066]

[Table 1]

Table 1 shows that in the exhaust gas discharged from the outlet of the activated carbon packed tower, hardly persistent halogen compounds were detected, and the exhaust gas was purified almost completely.

Next, the obtained reaction liquid was transferred to a heatable liquid separating device installed in the post-treatment facility. An exhaust gas purifying facility as shown in FIG. 6 is installed on the upper part of this liquid separator. This exhaust gas purification equipment has almost the same structure as the reaction exhaust gas purification equipment shown in FIG. 4, except that there is no absorption tower. That is, vent condenser 2
1, a deep cooling condenser 22, a mist separator 23, and an activated carbon packed tower 24. In addition, in order to prevent backflow, the vent condenser 21 and the deep condenser 22
An empty tank 15 is installed between and.

While stirring the reaction solution, water was added at 10.93 k.
g was added dropwise at 60 to 70 ° C. over 1 hour. After the dropping of water was completed, the mixture was further stirred at the same temperature for 30 minutes to completely decompose the excess metallic sodium dispersion. Then, while raising the temperature of the reaction tank to 80 ° C., the alkaline water was 479.9 k
g (containing 0.3 kg of sodium hydroxide) was added to 30
Stir for minutes. The mixture was allowed to stand at about 80 ° C. for 14.5 hours, liquid was separated into a treated oil layer and an aqueous layer, and the aqueous layer was separated. The separated aqueous layer was recovered by evaporation. The recovered amount was 474.4 kg.

25.6 kg of water was added to the treated oil layer excluding the water layer.
And adding 474.4 kg of the water recovered by evaporation,
The mixture was stirred at 0 ° C. for 1 hour, allowed to stand at 80 ° C. for 5 hours, separated into a treated oil layer and a water layer, and the water layer was separated to obtain a treated oil layer.
This aqueous layer can be reused as alkaline water for washing the reaction solution by adding sodium hydroxide to the aqueous layer and adjusting the concentration so as to obtain a predetermined alkaline concentration.

The treated oil layer obtained as described above is 4465.17 kg in total, and the transformer oil 4440 k
g, water 25.02kg, sodium hydroxide 0.02k
g, 0.1 kg of biphenyl and 0.02 kg of benzene, respectively.

Further, the analysis of the exhaust gas at the F point (outlet of the mist separator 24) and the G point of the exhaust gas purification equipment shown in FIG. 7 was performed in the same manner as the analysis of the reaction exhaust gas. The measurement results are shown in Table 2. The second
Abbreviations in the table have the same meanings as in Table 1.

[0073]

[Table 2]

As shown in Table 2, the exhaust gas discharged from the activated carbon packed column outlet (point G) contained almost no persistent halogen compounds (polychlorinated biphenyls).

[0075]

As described above, according to the present invention,
An exhaust gas purification method for completely purifying exhaust gas containing a hardly decomposable halogen compound, and a decomposition treatment facility for a hardly decomposable halogen compound suitable for carrying out the method for purifying the exhaust gas are provided.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of an exhaust gas purification equipment for carrying out an exhaust gas purification method of the present invention.

FIG. 2 is a conceptual diagram showing an absorption tower 2 portion when the absorption step of the exhaust gas purification method of the present invention is performed using the exhaust gas purification equipment shown in FIG.

FIG. 3 is a schematic view of a decomposition treatment facility for a hardly decomposable halogen compound according to the present invention.

FIG. 4 is a conceptual diagram of reaction exhaust gas purification equipment used in the examples.

FIG. 5 is a conceptual diagram showing an apparatus for obtaining a measurement sample for analyzing exhaust gas.

FIG. 6 is a conceptual diagram of an exhaust gas purifying apparatus for post-treatment equipment used in Examples.

[Explanation of symbols]

1 ... Exhaust gas purification equipment 2, 17 ... Adsorption tower 3 ... condenser 4, 19, 23 ... Mist separator 5, 20, 24 ... Activated carbon packed tower 6, 16, 21 ... Bent condenser 7 ... Seal trap 8 ... filling 9 ... Exhaust gas flow 10 ... Flow of adsorbent (trans oil) 11 ... Diaphragm pump 12 ... Flowmeter 13 ... Reactor 14 ... Post-treatment tank 15 ... Empty tank 18, 22 ... Cryogenic condenser

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B09B 3/00 B01D 53/34 134F (72) Inventor Tetsuo Otsuka Nakagoki-gun, Niigata Prefecture 950 Fujisawa, Japan Soda Co., Ltd. Nihongi Factory F-term (reference) 2E191 BA13 BC01 BD11 4D002 AA21 AC10 BA02 BA04 BA13 CA07 DA33 DA41 DA56 EA02 EA07 GA01 GB05 GB11 4D004 AA07 AA12 AA22 AB06 AB07 CA02 CA04 CA07 CA12 CA15 CA22 CA34 CA40 CC04 CC12

Claims (9)

[Claims] 1. An absorbing step of causing the absorbent to absorb the hardly-decomposable halogen compound contained in the exhaust gas by bringing the exhaust gas containing the hardly-decomposable halogen compound into contact with the absorbent. An exhaust gas purification method comprising: a cooling step of cooling the treated exhaust gas with a condenser; and an activated carbon treatment step of bringing the exhaust gas cooled by the condenser into contact with activated carbon. 2. Between the cooling step and the activated carbon treatment step,
The exhaust gas purification method according to claim 1, further comprising a step of passing exhaust gas cooled by the condenser through a mist separator. 3. The exhaust gas purification method according to claim 1, wherein the exhaust gas is an exhaust gas generated from a decomposition reaction tank for dehalogenating a hardly decomposable halogen compound. 4. The exhaust gas purification method according to claim 1, wherein a solvent that can be used in a dehalogenation reaction of a hardly decomposable halogen compound is used as the absorbent. 5. The method according to claim 1, further comprising a step of recovering the absorbent having absorbed the hardly decomposable halogen compound and performing a dehalogenation reaction of the hardly decomposable halogen compound contained in the absorbent. Exhaust gas purification method described. 6. A pretreatment facility for pretreating a hardly decomposable halogen compound or a substance containing a hardly decomposable halogen compound, a decomposition reaction facility for dehalogenating a hardly decomposable halogen compound, and the above dehalogenation. A post-treatment facility for performing a post-treatment of a reaction product generated by the reaction, and a decomposition treatment facility for a persistent halogen compound having an exhaust gas purification facility for purifying exhaust gas generated from the decomposition reaction facility, The exhaust gas purifying facility is filled with an absorbent that absorbs the hardly decomposable halogen compound, and the exhaust gas containing the hardly decomposable halogen compound is contacted with the absorbent, whereby the hardly decomposable gas contained in the exhaust gas is decomposed. An absorption tower that absorbs a halogen compound into the absorbent, a condenser that cools the exhaust gas that has passed through the absorption tower, and activated carbon are packed, A decomposition treatment facility for persistent halogen compounds, which has an activated carbon packed tower for contacting the exhaust gas cooled by a condenser with the activated carbon. 7. The decomposition treatment equipment for a hardly decomposable halogen compound according to claim 6, wherein the exhaust gas purification equipment further comprises a mist separator between the condenser and the activated carbon packed tower. 8. The absorption tower is filled with a solvent that can be used in the dehalogenation reaction of a hardly decomposable halogen compound performed in the decomposition treatment facility, and exhaust gas containing a hardly decomposable halogen compound is used as the solvent. The decomposition treatment facility for a hardly decomposable halogen compound according to claim 6 or 7, wherein the solvent is made to absorb the hardly decomposable halogen compound contained in the exhaust gas by bringing it into contact with each other. 9. An absorbent having absorbed a hardly decomposable halogen compound is recovered from the absorption tower, and a dehalogenation reaction of the hardly decomposable halogen compound contained in the absorbent is carried out in the decomposition reaction facility. A decomposition treatment facility for the hardly decomposable halogen compound according to any one of 6 to 9.