JP6862218B2 - PCB removal method - Google Patents

Description

The present invention relates to a method for removing PCBs for removing PCBs from equipment, storage tanks, etc. (hereinafter referred to as PCB contaminants) contaminated with PCBs.

PCB (polychlorinated biphenyl) has good electrical insulation and is insoluble in water but well soluble in organic solvents and oils, so it dissolves well in transformers and capacitors of electrical equipment, insulating oil for capacitors, adhesives, waxes, and lubrication. It has been used for oils and the like. However, PCBs are currently banned from production because they are highly toxic to living organisms such as carcinogenicity, skin disorders, visceral disorders, and hormonal abnormalities, and tend to accumulate in adipose tissue. In addition, wastes such as electric devices that were produced and used at the time when the production of PCBs was approved cannot be disposed of as they are, and PCB removal work is required.

Conventionally, as a method of removing PCB from PCB contaminants, a method of putting the contaminant in a cleaning tank and immersing it in a cleaning solvent, or a method of vaporizing the solvent and exposing the contaminant to the atmosphere of the vaporizing solvent. (See, for example, Patent Document 1).

If the contaminant is in the form of a container and PCB is attached to the inside, first remove the PCB accumulated at the bottom of the container with a cleaning solvent, and then remove the PCB with a cleaning solvent, and then remove the PCB. There is a method of removing PCB adhering to the inner surface of the container by spray-injecting an aqueous solution containing the above (see, for example, Patent Document 2).

Japanese Patent Application Laid-Open No. 2003-145069 JP 2016-140778

However, the method of immersing PCB contaminants in a cleaning solvent requires a large amount of solvent. Further, the method of exposing the PCB contaminant to the atmosphere of the vaporizing solvent cannot be used when the contaminant has a structure that does not have the strength to withstand the reduced pressure.

Further, the method of spray-injecting an aqueous solution to which a surfactant is added has a problem that cleaning takes a long time and the cleaning power is insufficient. There is also a problem that the treatment of the used aqueous solution is not easy. On the other hand, spraying a solvent to increase the cleaning power is not a safe method because static electricity generated near the nozzle outlet may ignite the solvent.

Therefore, an object of the present invention is to provide a method for removing PCBs for effectively and safely removing PCBs from PCB contaminants.

In order to achieve the above object, the PCB removing method of the present invention is a PCB removing method for removing PCB in a closed structure, and is a PCB placed on the inner surface of the closed structure or in the closed structure. It is characterized by having a solvent ejection step of ejecting a solvent capable of dissolving the PCB into a pollutant from a nozzle at a predetermined discharge pressure at which the solvent does not become atomized.

In this case, it is preferable to supply the solvent to the nozzle by using an air-driven pump.

Further, it is preferable to have an atmosphere adjusting step of filling the closed structure with an inert gas before the solvent ejection step. In this case, nitrogen may be used as the inert gas.

Further, it is preferable to have a grounding step for connecting the closed structure to the reference potential point before the solvent ejection step.

Further, it is preferable that the nozzle is a nozzle that rotates in all directions. The rotation of the nozzle may be performed by using the jet output of the aqueous solution.

Further, the solvent may be circulated and reused.

In the PCB removing method of the present invention, since the solvent is ejected from the nozzle at a predetermined discharge pressure that does not form a mist, the generation of static electricity near the nozzle outlet is suppressed to prevent the solvent from igniting or exploding, and the PCB is effectively used. Can be removed. Further, the risk of ignition or explosion can be further reduced by supplying the solvent using an air-driven pump or ejecting the solvent in an atmosphere filled with an inert gas.

It is a figure which shows the flow of the washing operation in this invention.

The PCB removing method of the present invention is a PCB removing method for removing PCB in a closed structure, and dissolves the PCB in the inner surface of the closed structure or a PCB contaminant placed in the closed structure. It is mainly composed of a solvent ejection step in which a possible solvent is ejected from a nozzle at a predetermined discharge pressure at which the solvent does not become atomized.

Here, PCB is a polychlorinated biphenyl represented by the general formula C ₁₂ H _(10-n) Cl _n (1 ≦ n ≦ 10), and is a compound in which a hydrogen atom of biphenyl is replaced with a chlorine atom. It is a general term for.

In addition, PCB contaminants refer to substances to which PCBs are attached. Specifically, equipment that uses PCBs such as transformers, storage containers and equipment for the equipment, and storage tanks that store PCBs. Etc. are included.

The closed structure is a structure of a container or equipment (for example, a vinyl house or the like) used for covering PCB contaminants when removing PCB, in addition to the above-mentioned storage tank, storage container, and storage equipment, and has a lid. Refers to those that can be sealed with doors, seal members, etc.

As a solvent capable of dissolving PCB, a hydrocarbon solvent, a halogen solvent, or the like can be used. For example, if an alkane, alkene, cycloalkane or alkene-based solvent having 8 to 15 carbon atoms (particularly, an alkane or alkene-based solvent having 11 to 13 carbon atoms) or a halogen-based solvent having 1 to 12 carbon atoms is used. good. Specifically, NS220, NS230 (both manufactured by JX Nikko Nisseki Energy Co., Ltd.) and the like can be used. In the present specification, the solvent also includes a solvent after dissolving the PCB in the container.

In the present invention, "mist-like" refers to a state in which innumerable minute liquid particles float in the air and look like smoke. Therefore, "not atomized" means a state in which the particle size is larger than that of the liquid particles in the "atom-like" described above, for example, a state in which the solvent ejected from the nozzle looks like one or more streaks. To say.

The discharge pressure refers to the static pressure of the fluid in the immediate vicinity where the solvent fluid flows into the nozzle. In the present invention, the discharge pressure is set to a predetermined value so that the solvent is ejected from the nozzle without being atomized. The predetermined discharge pressure may be appropriately determined according to conditions such as the shape and cross-sectional area of the nozzle, the flow rate, and the viscosity of the solvent. Here, the discharge pressure can be adjusted by any method via various air-driven or electrically-driven pumps, but it is preferable to adjust the discharge pressure via an air-driven pump for the reason described later. In order to maintain the state in which the solvent is ejected without becoming mist, it is preferable that the discharge pressure can always be monitored by a pressure gauge.

The solvent may be supplied to the nozzle, for example, by connecting the solvent supply tank in which the solvent is stored to the nozzle via a flow path and a pump. In this case, it is preferable to use an air-driven pump as the pump. This makes it possible to prevent the generation of sparks that are expected when the electric drive pump is used and the accompanying ignition of the solvent. Further, since the air-driven pump can adjust the discharge pressure and the discharge amount of the solvent only by changing the pressure of the compressed air, more reliable adjustment can be performed more easily than the electric-driven pump. Therefore, the air-driven pump is suitable for ejecting the solvent from the nozzle at a predetermined discharge pressure that does not form a mist. The air-driven pump is not particularly limited as long as it is a pump that uses compressed air as a power source, but for example, a piston type pump or a diaphragm type pump may be used.

The ejection of the solvent from the nozzle is due to the PCB adhering to the ceiling surface and side surfaces in the closed structure, the PCB adhering to PCB contaminants such as electric devices placed in the closed structure, and the gas in the closed structure. This is done so that the PCB inside can be knocked down by the collision effect. Here, it is preferable to use a nozzle that can rotate in all directions. As a result, the solvent is uniformly ejected in all directions in the closed structure, so that efficient and even cleaning is possible. The nozzle may be rotated by electric power or by utilizing the jet output of the solvent. Further, the nozzle may be slidable up and down so that the height of the injection can be adjusted as appropriate.

The solvent accumulated at the bottom of the closed structure can be discharged by any method, but for example, it may be collected in a waste liquid recovery tank using a pump such as a gear pump. The recovered solvent may be discarded as it is, but it is also possible to return it to a closed structure and circulate it. In this case, although not shown, a removing means for removing PCB from the recovered solvent may be provided. For example, cyclodextrins and organic dibasic acids described in JP2012-229359, JP2012-229360, Japanese Patent Application No. 2012-500601, Japanese Patent Application Laid-Open No. 2012-105307, Japanese Patent Application Laid-Open No. 2012-152416 and the like. A selective fixing agent containing a cyclodextrin polymer in which is sequentially bonded to and is capable of selectively adsorbing a halogenated aromatic compound containing PCBs, and thus can be suitably used as a removing means. In particular, it is preferable to use a selective fixing agent of the type in which cyclodextrin and organic dibasic acids are sequentially bonded and the terminal ester group is capped with alcohols, allyl alcohols, or phenols. When such a selective fixing agent is filled in a column, for example, and the recovered solvent is brought into contact with the column, PCB can be selectively fixed from the solvent. When the recovered oil is brought into contact with the selective fixing agent, it is preferable to treat it under a pressure of about 0 to 0.4 MPa and a temperature condition of −5 ° C. to 30 ° C. Therefore, the removing means may further have suitable pressurizing means and / or heating means.

Further, the PCB removing method of the present invention preferably includes an atmosphere adjusting step of filling the closed structure with an inert gas before the solvent ejection step. As a result, the inside of the closed structure becomes anoxic or hypoxic, so that the solvent can be prevented from catching fire even when static electricity is generated near the nozzle outlet.

In this case, the inert gas to be filled may be any gas having a low chemical reactivity, but a rare gas such as helium or argon, nitrogen, carbon dioxide, a gas having a low oxygen content, or the like. Can be used. Since nitrogen can be obtained at low cost, it can be preferably used.

Further, the PCB removing method of the present invention preferably has a grounding step of connecting the closed structure to the reference potential point before the solvent ejection step. As a result, even when static electricity is generated near the nozzle outlet, the static electricity is released to the reference potential point without being retained in place, so that ignition of the solvent can be prevented. In the present invention, it is preferable to connect a material that may be charged to a reference potential point. Further, the electric device such as a compressor may be arranged outside the closed structure.

[Example 1]
A test was conducted to wash the storage tank in which the PCB was stored by the PCB removing method of the present invention. The cleaning operation flow is shown in FIG.

A nozzle 2 for ejecting the solvent is installed inside the storage tank 1 to be cleaned, and the solvent is supplied from the solvent supply tank 20 to the nozzle 2 via the air-driven pump 3 and the flow path 21. It is supposed to be done. As the nozzle 2, a nozzle whose nozzle head rotates 360 degrees by the jet output of the supplied solvent was used (manufactured by Spraying System Japan Co., Ltd.). Further, as the air-driven pump 3, an air piston type pump PST-20SUS (manufactured by Aqua System Co., Ltd.) was used. Further, as the compressor 4 for supplying the driving air of the pump, CFUE37-75 (manufactured by ANEST IWATA) was used. Further, a pressure gauge 5 is installed in the flow path 21 so that the nozzle discharge pressure can be constantly monitored.

Further, inside the storage tank 1, a flow path 61 for flowing nitrogen from the nitrogen cylinder 6 into the storage tank 1 is connected so that the storage tank 1 can be filled with nitrogen. Further, a flow path 71 for recovering the solvent is installed at the bottom of the storage tank 1, and the solvent collected at the bottom of the storage tank 1 is recovered in the waste liquid recovery tank 7 via the gear pump 8. .. As the gear pump 7, a GP type gear pump (manufactured by Ebara Corporation) was used.

Before the washing operation, the storage tank 1 and each device were connected to the ground (not shown), and the storage tank 1 was filled with nitrogen to make the inside of the storage tank 1 oxygen-free.

As the solvent, NS Clean 220P (manufactured by JX Nikko Nisseki Energy Co., Ltd.), which is a hydrocarbon solvent, was used.

Table 1 shows the results of a batch operation in which the amount of solvent ejected in one operation was about 200 kg (for one dedicated drum can) and this was repeated 7 times.

In this test, the PCB concentration could be reduced from 230 mg / kg to 19 mg / kg while preventing the solvent from catching fire. As a result, it was confirmed that the PCB removing method of the present invention can safely and efficiently remove PCBs.

1 Storage tank 2 Nozzle 3 Air drive pump 4 Compressor 5 Pressure gauge 6 Nitrogen cylinder 7 Waste liquid recovery tank 8 Gear pump
20 Solvent supply tank
21 Channel
61 Channel
71 Channel

Claims (8)

A PCB removal method that removes PCBs in a closed structure.
A hydrocarbon solvent (NS Clean 220P / JX Nikko Nisseki Energy Co., Ltd.) capable of dissolving the PCB is added to the inner surface of the closed structure or the PCB contaminant placed in the closed structure. A method for removing PCBs, which comprises a solvent ejection step of ejecting from a nozzle at a discharge pressure of 0.3 MP or less and a unit time ejection amount of 9.1 L / min or less. The PCB removing method according to claim 1, wherein the solvent is supplied to the nozzle by using an air-driven pump. The PCB removing method according to claim 1 or 2, further comprising an atmosphere adjusting step of filling the closed structure with an inert gas before the solvent ejection step. The PCB removing method according to claim 3, wherein the inert gas is nitrogen. The PCB removing method according to any one of claims 1 to 4, wherein a grounding step for connecting the closed structure to a reference potential point is provided before the solvent ejection step. The PCB removing method according to any one of claims 1 to 5, wherein the nozzle is a nozzle that rotates in all directions. The PCB removing method according to claim 6, wherein the rotation of the nozzle is performed by utilizing the jet output of the solvent. The PCB removing method according to any one of claims 1 to 7, wherein the solvent is circulated and reused.

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