JP2000063891A - Washing apparatus by supercritical carbon dioxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remote PCB without use of an organic solvent to increase detergent efficiency. SOLUTION: A heating apparatus 14 and an oscillator are mounted on a cover 4 of a chamber 1 in which an item to be washed 3 is disposed and these apparatuses are connected to a power supply via a terminal 16. Supercritical carbon dioxide is supplied into a chamber 1 through a pipe 6 to be contacted with the item to be washed 3 and solubilize to remove PCB attached on the item to be washed 3. When the item to be washed 3 is heated by the heating apparatus 14 or oscillated by the oscillator, molecular mobility of PCB is activated to increase solubility and then the detergent efficiency by the supercritical carbon dioxide is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning device for cleaning and removing organic chlorine compounds (particularly polychlorinated biphenyls) adhering to an object to be cleaned by supercritical carbon dioxide.

[0002]

2. Description of the Related Art Polychlorinated biphenyls (hereinafter referred to as PCBs) have been used as insulating oil in various electric parts such as transformers, capacitors and ballasts. PCB is a mixture of various homologues depending on the number of chlorine and the position of addition of chlorine. Toxicity also varies greatly with each homologue. Especially coplanar PCB
It has been pointed out that the homologues referred to as are as harmful as dioxins. Since PCB is chemically stable and difficult to be excreted, it has a high bioaccumulation potential and the symptoms appear for a long time. It is said to have a function of enhancing general malaise, morbid fatigue, and carcinogenic effects. In addition, it is said that the fetus and the infant are damaged due to the placental permeability and transfer to breast milk. For this reason, the manufacture and use of PCBs has recently been banned.

The various electric parts manufactured and used before the manufacture and use of PCB are prohibited are used as insulating oil in PC.
Since B is used, it cannot be treated as general waste that does not contain PCB, and it must be stored in a special container or burned, alkali catalytic decomposition method (BDC method), supercritical water oxidation method, etc. PCB is disassembled and processed.

Conventionally, when cleaning and removing the PCB adhering to electric parts such as a transformer after the insulating oil is removed, the cleaning is carried out by a supercritical extraction method. For example, in the method for decontaminating a transformer described in JP-A-7-34096, a transformer is placed in an extraction cell, and carbon dioxide in a supercritical state (or pseudocritical state) and a small amount of a cosolvent are supplied. The PCB adhering to the transformer is cleaned and removed. As the co-solvent, an organic solvent such as n-hexane is used, and when it is used, the solubility of PCB is increased, and the extraction efficiency of PCB can be further improved as compared with the case of using supercritical carbon dioxide alone.

[0005]

As described above, conventionally, when cleaning and removing PCB using carbon dioxide in a supercritical state, a small amount of a cosolvent is added to supercritical carbon dioxide. The PCB extraction efficiency is improved. However, the method of adding an organic solvent to improve the extraction efficiency requires a facility for collecting and processing the washed organic solvent, and thus has a problem that the apparatus itself becomes large and expensive. .

Therefore, the inventors of the present invention have studied and improved the extraction efficiency, and as a result, heat the object to be cleaned,
It was confirmed that the extraction efficiency can be improved as in the case of using a co-solvent, because it becomes easy to dissolve when the molecular motion of PCB is activated by vibrating with ultrasonic waves or the like.

The present invention has been made on the basis of the above-mentioned conventional problems and experimental results, and an object thereof is to provide supercritical carbon dioxide capable of improving cleaning efficiency without using an organic solvent. To provide a cleaning device.

[0008]

To achieve the above object, a first invention is a chamber for cleaning an object to be cleaned by contacting the object to be cleaned contaminated with an organic chlorine compound with supercritical carbon dioxide. And a heating device for heating the object to be cleaned is provided in the chamber. In such a configuration, when the object to be cleaned is heated by the heating device, the molecular motion of the organic chlorine compound is activated and the organic chlorine compound is easily dissolved by the supercritical carbon dioxide. Therefore, the organic chlorine compound attached to the object to be cleaned can be efficiently cleaned and removed.

Carbon dioxide has a temperature (critical temperature 31.1 ° C.) and pressure (critical pressure 7.38 M) at which it changes to a supercritical state.
Since Pa) has a lower temperature and a lower pressure than other solvent substances, it becomes a supercritical state with a relatively small energy, and thus is suitable as a solvent for cleaning and removing PCB.
Further, it has an advantage that the extraction reaction is accelerated because of its high thermal conductivity. Supercritical carbon dioxide is supplied to or produced within the chamber.

A second aspect of the present invention comprises a chamber for cleaning an object to be cleaned by contacting the object to be cleaned contaminated with an organic chlorine compound with supercritical carbon dioxide, and vibrating the object to be cleaned in this chamber. A vibrating device is provided. In such a configuration, when the object to be cleaned is vibrated by the vibrating device, the molecular motion of the organic chlorine compound is activated and the organic chlorine compound is easily dissolved by the supercritical carbon dioxide. Therefore, the organic chlorine compound attached to the object to be cleaned can be efficiently cleaned and removed.

A third aspect of the invention is the same as the first aspect of the invention.
The heating device is a high frequency heating device. Such a structure is effective when the object to be cleaned is a metal.

A fourth invention is the same as the first invention,
The heating device is a resistance heating device. Such a configuration is effective when the object to be cleaned is a nonmetal such as ceramics.

A fifth invention is the same as the first invention,
The heating device is a laser generator.
In such a structure, a high heating temperature can be obtained.

A sixth aspect of the invention is the same as the second aspect of the invention.
The vibrating device is an ultrasonic vibrating device. In such a configuration, when the object to be cleaned is vibrated by the ultrasonic vibration device, the molecular motion of the organic chlorine compound is activated, so the organic chlorine compound adhering to the object to be cleaned is efficiently cleaned and removed. can do.

A seventh invention is characterized in that, in any one of the first to sixth inventions, a plurality of chambers are connected in parallel. In such a configuration, a plurality of objects to be cleaned can be cleaned at the same time, so that cleaning efficiency can be improved.

An eighth invention is characterized in that, in any one of the first to seventh inventions, the organic chlorine compound is polychlorinated biphenyl. In such a configuration, since the polychlorinated biphenyl is washed and removed from the object to be cleaned, the object to be cleaned can be rendered harmless,
It can be treated as general waste that does not contain PCB.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments shown in the drawings. FIG. 1 is an exploded perspective view showing an embodiment of a chamber and a lid used in a cleaning apparatus according to the present invention, and FIGS. 2A and 2B are a front view and a bottom view of the lid. In these figures, 1 is a chamber used in a cleaning apparatus for cleaning an object 3 to be cleaned with supercritical carbon dioxide 2, and 4 is a lid for hermetically sealing an upper opening 5 of the chamber 1. The object to be cleaned 3 is made up of electrical parts contaminated by PCB such as a transformer, a condenser, a ballast, etc., and is installed in the chamber 1.

The chamber 1 is made of stainless steel, and is formed in a box shape having an open upper surface of, for example, 3 × 3 × 3 cm,
Supercritical carbon dioxide 2 on 3 of the 4 side walls
Supply pipe 6 for supplying the gas, discharge pipe 7 for discharging the supercritical carbon dioxide 2, and supercritical carbon dioxide 2
One end of a leaking pipe 8 for leaking is connected to each. Further, valves 9, 10, and 11 are provided in the pipes 6, 7, and 8, respectively. A seal member 12 is attached to the upper surface opening 5 of the chamber 1 over the entire circumference in order to improve the sealing performance when the cover 1 is hermetically sealed.

The lid 4 is also made of stainless steel and is a rectangular plate having substantially the same size as the chamber 1, and a heating device for heating the object 3 to be cleaned installed in the chamber 1 on the lower surface side. 14 and a vibrating device 15 for vibrating the object to be cleaned 3 are provided, and both devices 14, 14 are provided on the front surface side.
Four terminals 16 to which 15 is electrically connected are provided in a protruding manner. The terminal 16 is attached to the lid 4 while being electrically insulated.

As the heating device 14, when the object to be cleaned 3 is a metal, a high frequency heating device having a heating coil 18 is used, and both ends of the heating coil 18 are connected to a high frequency power source via two electrodes 16. Connected. The heating coil 18 has a rectangular coil portion 18a that is wound in five layers at appropriate intervals in the plate thickness direction of the lid body 4. These coil parts 1
When the lid 4 covers the upper opening 5 of the chamber 1 in an airtight manner, the reference numeral 8a has a sufficient size to surround the object 3 to be cleaned in the chamber 1, and a high-frequency current is supplied during cleaning. The object 3 to be cleaned is thereby electromagnetically heated. The heating temperature is about 100 ° C. to several hundreds of ° C., although it varies depending on the material of the article to be cleaned 3. If the object to be cleaned 3 is a non-metal such as ceramics and electromagnetic heating is not effective,
A resistance heating device is used. In this case, the heating coil 18 may be made of a high resistance material and resistance-heated by a low frequency current or a direct current.

As the vibrating device 15, an ultrasonic vibrating device is used. This ultrasonic vibration device 15 is provided with an ultrasonic vibration plate 20 provided on the lower surface of the lid 4 so as to face the object to be cleaned 3, and when an electric current is supplied to the diaphragm 20, the ultrasonic plate 20 and the object to be cleaned 3 Ultrasonic vibration can be generated. The ultrasonic diaphragm 20 is connected to the power source through two terminals different from the terminal 16 to which the heating coil 18 is connected.

Next, the cleaning of the object 3 to be cleaned by the cleaning device equipped with the chamber 1 having such a structure will be described. First, the object to be cleaned 3 is installed in the chamber 1, and the upper surface of the chamber 1 or the row 5 is hermetically sealed by the lid 4. The chamber 1 has an internal temperature and pressure of at least the critical point of carbon dioxide (critical temperature 31.1 ° C, critical pressure 7.38 MPa), for example, an internal temperature of 50 to 90 °.
The internal pressure is maintained at about C and about 15 to 30 MPa.

Next, the valves 9 and 10 are opened, and the carbon dioxide 2 in the supercritical state is introduced into the chamber 1 through the supply pipe 6. The supercritical carbon dioxide 2 is discharged from the chamber 1 through the exhaust pipe 7, but the PC attached to the cleaning object 3 comes into contact with the cleaning object 3 in the middle thereof.
B is washed and removed. The supercritical carbon dioxide 2 has a large diffusion coefficient and a small viscosity, and efficiently cleans and removes the PCB adhering to the object to be cleaned 3.

When cleaning with supercritical carbon dioxide 2, the heating coil 18 of the heating device 14 is energized to heat the object 3 to be cleaned, or the ultrasonic vibration plate 20 of the vibrating device 15 is energized. When the object to be cleaned 3 and the ultrasonic vibration plate 20 are ultrasonically vibrated, or both of these devices are energized to heat the object to be cleaned 3 and simultaneously ultrasonically vibrate, n
As in the case of using a cosolvent such as hexane, the efficiency of cleaning the PCB with supercritical carbon dioxide 2 can be further improved. The reason is that, in both cases of heating and ultrasonic vibration, the molecular motion of the PCB adhering to the object to be cleaned 3 is activated and easily dissolved or released, so that the solubility by the supercritical carbon dioxide 2 increases. It is speculated that this is due to

The completion of cleaning is confirmed by the fact that the PCB sensor (not shown) mounted on the tip side of the discharge pipe 7 no longer detects the PCB. After the cleaning of the object to be cleaned 3 is completed, the opened valves 9 and 10 are closed and the valve 11 of the leak pipe 8 is opened to open the chamber 1 to the atmosphere, and the lid 4 is opened to open the cleaned object. Take out the wash item 3. Since the PCB has been removed from the object to be cleaned 3,
It is harmless to the environment and the human body and is treated as general waste that does not contain PCBs. Next, the object to be cleaned is set in the chamber 1 and the same operation is performed.

[0026]

EXAMPLE Next, an example of cleaning and removing the PCB using the above chamber will be described. [Example 1] Supercritical carbon dioxide at 40 ° C and 100 atm was passed through the chamber 1, and the cleaning object 3 was heated by the heating device 14 to clean the cleaning object 3. As a result, the conventional cleaning using only the supercritical carbon dioxide 2 required 3 hours, but when the heating device 14 was used together, the cleaning could be performed in 1 hour, and the cleaning efficiency was improved. It was Example 2 The object 3 to be cleaned was washed while supercritical carbon dioxide at 40 ° C. and 100 atm was passed through the chamber 1 while the object 3 to be cleaned was ultrasonically vibrated by the vibration device 15. As a result, the conventional cleaning using only the supercritical carbon dioxide 2 took 3 hours, but when the vibration device 15 is used together, the cleaning can be completed in 1.5 hours, and the cleaning efficiency is improved. It was

Here, in the above embodiment, an example using one chamber has been shown, but it is also possible to connect two chambers in parallel for cleaning.
During cleaning, the supply of supercritical carbon dioxide and the leakage of gas are alternately performed in each chamber and the cleaning is continuously performed, whereby the cleaning efficiency can be doubled. In addition, the cleaning efficiency can be further improved by increasing the number of chambers.

As the heating device 14, a high frequency heating device,
A laser generator may be used instead of the resistance heating device. In that case, a transparent window may be provided on the lid 4, and a laser beam from, for example, a YAG laser arranged outside the chamber 1 may be irradiated through the transparent window to heat the object to be cleaned in the chamber. Even in such a structure, the cleaning efficiency can be improved as in the case of using the electric heating coil 18 or the ultrasonic vibration plate 20.

In the above-described embodiment, the example in which the supercritical carbon dioxide 2 is supplied to the chamber 1 has been shown. However, the present invention is not limited to this. Good. In that case, normal carbon dioxide may be introduced into the chamber 1 by a pressure pump, and the inside may be maintained at the critical temperature and the critical pressure of carbon dioxide or higher. Further, in the above-described embodiment, the example of the electric component contaminated with PCB as the object to be cleaned has been described, but the cleaning of the object to be cleaned contaminated with other organochlorine poison similar to PCB It goes without saying that it is also effective.

[0030]

As described above, the cleaning apparatus using supercritical carbon dioxide according to the present invention can improve the cleaning efficiency without using an organic solvent such as n-hexane. It is possible to realize simplification and cost reduction of the device itself without requiring equipment for doing so.

[Brief description of drawings]

FIG. 1 is an exploded perspective view showing an embodiment of a chamber and a lid used in a cleaning apparatus according to the present invention.

2A and 2B are a front view and a bottom view of a lid.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Chamber, 2 ... Supercritical carbon dioxide, 3 ... Cleaning object, 4 ... Lid body, 5 ... Opening part, 6, 7, 8 ... Piping, 9, 1
0,11 ... Valve, 14 ... Heating device, 15 ... Vibration device,
16 ... Terminal, 18 ... Heating coil, 20 ... Ultrasonic vibration plate.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shiro Nishi             3-19-3 Nishi-Shinjuku, Shinjuku-ku, Tokyo Japan             Telegraph and Telephone Corporation (72) Inventor Yukitoshi Takeshita             3-19-3 Nishi-Shinjuku, Shinjuku-ku, Tokyo Japan             Telegraph and Telephone Corporation F-term (reference) 4D056 AB18 AC24 BA16                 4H003 DA15 DB01 DB02 DC04 EA31                 4H006 AA04 AB70 AD10 BD82

Claims (8)

[Claims] 1. A chamber for cleaning an object to be cleaned by contacting the object to be cleaned contaminated with an organic chlorine compound with supercritical carbon dioxide, and a heating device for heating the object to be cleaned is provided in the chamber. A cleaning device using supercritical carbon dioxide. 2. A vibration device for vibrating the object to be cleaned is provided with a chamber for cleaning the object to be cleaned by contacting the object to be cleaned contaminated with an organic chlorine compound with supercritical carbon dioxide. A cleaning device using supercritical carbon dioxide, which is provided. 3. The cleaning device for supercritical carbon dioxide according to claim 1, wherein the heating device is a high-frequency heating device. 4. The cleaning device using supercritical carbon dioxide according to claim 1, wherein the heating device is a resistance heating device. 5. The cleaning apparatus for supercritical carbon dioxide according to claim 1, wherein the heating device is a laser generator. 6. The cleaning device for supercritical carbon dioxide according to claim 2, wherein the vibration device is an ultrasonic vibration device. 7. The cleaning apparatus for supercritical carbon dioxide according to claim 1, wherein a plurality of chambers are connected in parallel. . 8. The cleaning apparatus for supercritical carbon dioxide according to claim 1, wherein the organic chlorine compound is polychlorinated biphenyl. .