JP7140730B2 - Distillation stabilization method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a distillation stabilization method, and more particularly to a distillation stabilization method that achieves stable distillation by using substitutes for PCB and TCB even when PCB and TCB are mixed.

PCB (polychlorinated biphenyl) is stable, non-flammable, and has excellent electrical insulating properties. is revealed and new use is prohibited.

Regarding PCB-contaminated equipment such as capacitors and transformers, which already contain insulating oil containing PCB, measures are being taken to recover them, and detoxification treatment is being carried out at special facilities.

Patent No. 5639932 Patent No. 5639931

Patent Document 1 discloses a cleaning unit for cleaning equipment containing PCB-containing insulating oil with cleaning oil, and a distillation regeneration unit for producing recycled cleaning oil by distilling the PCB-containing cleaning oil produced by cleaning. PCB-contaminated equipment harmless, in which a distillation column is provided in the distillation regeneration section for separating the PCB-containing washing oil into a distillate with a lower PCB concentration than the PCB-containing washing oil and a bottom product with a higher PCB concentration Disclosed is a method for dismantling a decomposing facility.

Patent Document 2 discloses a method for efficiently detoxifying and dismantling the distillation column used in Patent Document 1.

However, in the detoxification facilities of Patent Documents 1 and 2, no consideration is given to cleaning of PCB-contaminated equipment when TCB (trichlorobenzene) is mixed with PCB.

The present inventors have found that when TCB is mixed in PCB, the separation efficiency of PCB deteriorates with the passage of time in distillation, and detoxification treatment cannot be stably performed in some cases.

Accordingly, an object of the present invention is to provide a distillation stabilization method that achieves stable distillation by using substitutes for PCB and TCB even when PCB and TCB are mixed.

Other objects of the present invention will become clear from the following description.

The above problems are solved by the following inventions.

(Claim 1)
The liquid to be distilled containing at least two liquids of PCB and TCB is introduced from the transformer oil receiving tank in which the liquid to be distilled in the early stage of distillation is introduced into the TCB separation column, and distilled in the TCB separation column to contain most of TCB. Separated into a distillate and a bottoms containing a part of TCB and PCB,
The bottoms of the TCB separation column are introduced into a first distillation column, distilled in the first distillation column, and separated into a part of the TCB-containing distillate and a PCB-containing bottoms,
Part of the distillate containing TCB of the first distillation column is received in the first distillation column reflux tank, returned from the first distillation column reflux tank to the transformer oil receiving tank, and the liquid to be distilled in the transformer oil receiving tank. is a distillation stabilization method that distills again,
When supplying a solvent having a boiling point close to the boiling point of PCB and a cleaning solvent having a boiling point equal to or lower than that of TCB to the transformer oil receiving tank, "PCB and the boiling point of the PCB The concentration ratio of "a solvent having a boiling point" and "TCB and a washing solvent having a boiling point equal to or lower than that of said TCB" is at least 2 for PCB and TCB introduced from said transformer oil receiving tank to said TCB separation tower. A distillation stabilization method characterized by supplying and adjusting the concentration ratio of a liquid to be distilled in the initial stage of distillation containing a liquid .
(Claim 2)
2. The distillation stabilization method according to claim 1 , wherein the solvent having a boiling point close to that of PCB is a saturated hydrocarbon solvent.

According to the present invention, even when PCB and TCB are mixed, it is possible to provide a distillation stabilization method that realizes stable distillation by using substitutes for each of PCB and TCB.

Diagram for explaining the basic principle of the present invention A processing flow diagram showing an example of a facility for separating PCB from PCB-contaminated equipment such as a transformer containing insulating oil containing PCB and TCB 1 is a block diagram showing an example of an embodiment of the present invention; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

The basic principle of the present invention will be explained based on FIG.

The distillation stabilization method of the present invention is intended for the case where PCB and TCB are contained as compounds generated by washing from PCB-contaminated equipment.

The PCB products mainly used in Japan include Kanechlor (registered trademark) (KC) and Aroclor, each of which has several types depending on the number of chlorine atoms. For example, KC500 containing pentachlorinated biphenyl as the main component, KC1000 containing KC500 mixed with TCB, etc., KC300 containing trichlorinated biphenyl as the main component, KC400 containing tetrachlorinated biphenyl as the main component, etc., can be mentioned.

The boiling point of PCB is 320-360°C for trichlorinated biphenyl (KC300) and 360-380°C for pentachlorinated biphenyl (KC500).
The boiling point of TCB (trichlorobenzene) is 210°C.

When PCB and TCB are separated and distilled, two-stage distillation is performed. A bottoms solution containing reduced PCB concentration and reduced TCB concentration is obtained. Since the concentration of the bottoms contained in the obtained bottoms can be designed in advance according to the initial conditions of the TCB separation column, by setting the initial conditions of the first distillation column 2000, which is the second distillation column, , between the boiling point of PCB and the boiling point of TCB, is designed so that PCB does not go to the distillate.

As a result, the concentration balance of the PCB and TCB contained in the liquid to be distilled at the initial stage of operation allows distillation to proceed well.

For example, the TCB separation column 1000 distills a liquid to be distilled containing PCB with a higher concentration than at the beginning of operation and TCB with a lower concentration. Therefore, it was found that distillation separation could not be realized under the above initial conditions.

In some cases, a liquid to be distilled containing PCB with a lower concentration than at the beginning of operation and TCB with a higher concentration is distilled. Therefore, it was found that distillation separation could not be realized under the above initial conditions.

The reason for this is thought to be that the boiling points of the two components undergo boiling point fluctuations, such as boiling point elevation or boiling point depression, according to the Clausius-Clapeyron principle.

Therefore, an adjustment is made to compensate for the substitute substance that adjusts the concentration balance at the beginning of operation.

In this embodiment, as an example, the initial conditions for the TCB separation column 1000, which is the first distillation column, and the initial conditions for the first distillation column 2000 are set to a boiling point of 220°C.

Under these conditions, when the concentration balance of PCB and TCB in the liquid to be distilled introduced into the TCB separation column 1000 gradually changes from the initial stage of distillation, as described above, if the boiling point fluctuation occurs due to the concentration fluctuation, the initial condition is , distillative separation goes wrong. Similarly, in the first distillation column 2000 that distills after the TCB separation column 1000, the distillation separation becomes unsuccessful.

Therefore, in the present invention, the concentration ratio of PCB and TCB contained in the liquid to be distilled is returned to the concentration ratio of PCB and TCB in the liquid to be distilled in the initial stage of distillation. Therefore, it is adjusted using a PCB-like substance and a TCB-like substance, which are substitute substances in the liquid to be distilled.

The PCB analogue is preferably a solvent with a boiling point close to that of PCB, and the TCB analogue is preferably a cleaning solvent with a boiling point equal to or lower than that of the TCB.

For example, PCB-like substances include saturated hydrocarbon solvents such as KP-8 (boiling point: 274° C. to 431° C., manufactured by Idemitsu Kosan Co., Ltd.), and TCB-like substances include cleaning solution HC-250 ( Boiling point of about 170°C, manufactured by Tosoh Corporation) and NS Clean 220 (boiling point of about 210°C, manufactured by JXTG Energy) can be used. In addition to these, a KP-8 equivalent can be used as a PCB analogue, and an HC-250 equivalent and NS Clean 220 equivalent can also be used as a TCB analogue.

When adjusting the concentration ratio of PCB and TCB in the liquid to be distilled to the initial stage of distillation, PCB-like substances and TCB-like substances corresponding to the reduced amount of PCB and TCB in the bottoms and distillate, respectively is preferably added to the liquid to be distilled.

Here, each reduced amount of PCB and TCB may be subjected to quantitative analysis of each compound of PCB and TCB. The PCB analogue and TCB analogue additions can be added to the inlet line 1001 of the first distillation column 2000 .

FIG. 2 is a process flow diagram showing an example of equipment for separating PCBs from PCB-contaminated equipment such as transformers containing insulating oil containing PCBs and TCBs, and FIG. 3 is a block diagram showing an example of an embodiment of the present invention. is.

1 is an oil removal cleaning device. This device has two functions: an oil removing device and a rough cleaning device.

A plurality of oil removal devices may be provided, for example, an oil removal device for receiving transformers and capacitors that are likely to leak PCBs due to aging, an oil removal device for receiving large transformers and capacitors that are not likely to leak, and a small transformer and capacitors. It may be an oil removal device that accepts When removing the oil, the PCB- or TCB-containing insulating oil inside is extracted from a hole made in the casing of the transformer, for example.

In this embodiment, the oil removal device can include a large oil removal chamber, a leaked oil removal chamber, and a small oil removal chamber.

After removing the oil as described above, cleaning is performed by a cleaning device. Specifically, the inside of the transformer and capacitor is washed with washing oil. Washing waste liquid is generated by such washing.

The drained oil containing PCB and TCB is sent via line 200 to KC1000 equivalent storage tank 2 . Also, the drained oil containing PCB is sent to the KC500 equivalent storage tank 3 via the line 300 . Washing waste liquid is sent to the washing oil buffer tank 4 via line 400 . In the present invention, cleaning oil is sent via line 200 in addition to the drained oil containing PCBs and TCBs. This is for cleaning the line 200 . Here, KC1000 and KC500 are described above.

The cleaning oil is a substance similar to benzene trichloride (TCB), and can be exemplified by hydrocarbon-based high-performance cleaning agents, such as HC-250 and NS Clean 220, as described above.

The boiling point of TCB is 210°C under normal pressure, the boiling point of HC-250 is around 170°C under normal pressure, and the boiling point of NS Clean 220 is around 200°C under normal pressure.

In the present invention, HC-250 equivalents and NS Clean 220 equivalents may be used as long as the boiling point is close to that of TCB.

The removed oil containing PCB and TCB sent to the KC1000 equivalent storage tank 2 and the washing oil are sent to the TCB separation tower 6 via the transformer oil receiving tank 5 and distilled in the TCB separation tower 6 .

In the TCB separation column 6, the temperature is set to separate TCB and PCB for distillation. As a result, the washing oil and TCB are evaporated and obtained as a distillate. The obtained distillate is sent to the TCB separation tower reflux tank 7 .

On the other hand, since PCB does not evaporate in the distillation of the TCB separation column 6, it is obtained as a bottom product. However, a small amount of TCB may remain in the bottoms without evaporation.

Therefore, this bottom product is sent to the first distillation column 8 . In the first distillation column 8, a small amount of TCB and PCB are distilled to separate them. Since the distillate of the first distillation column 8 is only TCB, it is sent to the first distillation column reflux tank 9 and returned to the first distillation column 8 or the transformer oil receiving tank 5 .

The bottom product obtained by distillation in the first distillation column 8 is only PCB because TCB evaporates. This bottom liquid is sent to the KC500 equivalent storage tank 3 .

Part of the TCB collected in the TCB separation tower reflux tank 7 is sent to the TCB analysis standby tank 10 together with the cleaning oil when the PCB concentration is below a predetermined level, and the necessary amount is recovered in the cleaning oil buffer tank 4. .

Next, the drained oil containing PCB is sent to the KC500 equivalent storage tank 3 via the line 300 . The bottoms obtained by distillation in the first distillation column 8 are also sent to the KC500 equivalent storage tank 3 . The collected PCB stored in the KC500 equivalent storage tank 3 is sent to the detoxification treatment facility 50 and detoxified as shown in FIG.

Finally, the cleaning waste liquid containing TCB, PCB, water, and cleaning oil sent to the cleaning oil buffer tank 4 via the line 400, the cleaning oil sent from the TCB analysis waiting tank 10 to the cleaning oil buffer tank 4, and TCB is sent from the washing oil buffer tank 4 to the crude washing water separation tower 11, where it is distilled and separated into water, TCB, PCB and washing oil.

Since the distillate obtained by distillation in the crude washing water separation tower 11 is water, the water is discharged out of the system.

Since the bottoms obtained by the distillation of the crude washing water separation tower 11 are TCB, PCB, and washing oil, they are sent to the crude washing oil recovery tower 12, where they are distilled and separated into washing oil, TCB, and PCB. be done.

Since the distillate obtained by the distillation in the crude washing oil recovery tower 12 is washing oil, this distillate is sent to the crude washing oil recovery tank 13 via the line 401, and the crude washing oil recovery tank 13 The cleaning oil collected in is reused in the oil removal cleaning device 1. This can reduce the amount of new cleaning oil used.

The bottoms obtained by the distillation of the crude wash oil recovery tower 12 contains TCB and PCB, so it is sent via line 402 to the KC1000 equivalent storage tank 2 .

The bottoms containing TCB and PCB are sent to the TCB separation tower 6 through the transformer oil receiving tank 5 together with the above-mentioned extracted oil containing PCB and TCB, and distilled in the TCB separation tower 6 . This distillation has been described above.

The bottom product obtained by distillation in the first distillation column 8 is only PCB because TCB evaporates. This bottom liquid is sent to the KC500 equivalent storage tank 3 . The collected PCB stored in the KC500 equivalent storage tank 3 is sent to the detoxification treatment facility 50 shown in FIG. 3 described later and detoxified.

The washing oil collected in the TCB separation tower reflux tank 7 and part of the TCB are sent to the TCB analysis waiting tank 10 and returned to the washing oil buffer tank 4 through the return line 201 for reuse.

As a result, it is possible to stabilize the distillation when the TCB, PCB, and cleaning oil recovered as the cleaning waste liquid in the cleaning oil buffer tank 4 are distilled by the crude cleaning oil recovery column 12 .

That is, in the crude wash oil recovery tower 12, of the three components of TCB, PCB, and wash oil, the wash oil is distilled and separated. Part may also be separated on the distillate side.

As a result, the composition components entering the crude wash oil recovery tower 12 are out of balance, which may cause molar boiling point fluctuations (molar boiling point elevation or molar boiling point depression according to the Clausius-Clapeyron principle). If there is a molar boiling point variation among three components or a molar boiling point variation between two components, the distillation operation itself will become difficult, and finally, the separation and stabilization of PCB and TCB will also become difficult.

Therefore, since the washing oil and TCB are returned in the return line 201 of the present invention, the inclusion of the washing oil and TCB returned from the return line 201 in addition to the washing waste liquid reduces the moles of the three components at the time of distillation. Boiling point fluctuation can be prevented, or PCB and TCB molar boiling point fluctuation can be prevented, and stable distillation (stabilization of distillation) can be performed.

At the same time, since the washing oil returned from the return line 201 is added to the washing oil contained in the washing waste liquid by distillation, the amount of washing oil recovered can be increased, and the amount of washing oil recycled can be increased. can. As a result, it is possible to reduce the amount of new cleaning oil used.

In FIG. 2, the recovered PCB discharged from the KC500 equivalent storage tank 3 is sent through a line 301 to the detoxification treatment facility 50 shown in FIG. 3 where it is dechlorinated and detoxified.

The KC500-equivalent storage tank 3 contains PCB-containing extracted oil sent through a line 300 and bottoms obtained by distillation in the first distillation column 8 . The bottoms are PCBs.

As shown in FIG. 3, the PCB sent through the line 300 is detoxified by the detoxification processing facility 50. As shown in FIG. A part of the solvent used in the detoxification treatment facility 50 is returned to the crude washing oil recovery tank 13 via the line 500 as a solvent to be recycled and reused. This allows the solvent to be reused during distillation as a substitute for PCBs as well as for use in detoxification processes.

Furthermore, as the solvent, as described above, KP-8 can be exemplified, and since KP-8 has a boiling point similar to that of PCB, it is sent as a bottom product together with PCB even in distillation, and is sent to the KC500 equivalent storage tank 3. Liquid is fed. As a result, the solvent is sent to the detoxification treatment facility 50 again, so that it can be reused for the detoxification treatment, and the amount of new solvent used can be reduced.

In this embodiment, the solvent returned to the rough washing oil recovery tank 13 via the line 500 and the washing oil returned to the rough washing oil recovery tank 13 via the recovery line 401 are separated into the TCB separation tower 6. It is also preferable to provide an adjustment line (broken line arrow) as shown in FIGS. As a result, a pre-distillation line is formed, and PCB-like substances and TCB-like substances, which are substitutes for PCB and TCB, can be supplied, so that the concentration balance can be adjusted.

1: Oil removal and cleaning device 2: Storage tank equivalent to KC1000 3: Storage tank equivalent to KC500 4: Cleaning oil buffer tank 5: Transformer oil receiving tank 6: TCB separation tower 7: TCB separation tower reflux tank 8: First distillation tower 9: First distillation tower Reflux tank 10: Waiting tank for TCB analysis 11: Crude washing water separation tower 12: Crude washing oil recovery tower 13: Crude washing oil recovery tank 50: Detoxification treatment equipment 200: Line 201: Return line 300: Line 301: Line 400: Line 401: Line 402: Line 500: Line 1000: TCB separation tower 1001: Inlet line 2000: First distillation tower

Claims (2)

The liquid to be distilled containing at least two liquids of PCB and TCB is introduced from the transformer oil receiving tank in which the liquid to be distilled in the early stage of distillation is introduced into the TCB separation column, and distilled in the TCB separation column to contain most of TCB. Separated into a distillate and a bottoms containing a part of TCB and PCB,
The bottoms of the TCB separation column are introduced into a first distillation column, distilled in the first distillation column, and separated into a part of the TCB-containing distillate and a PCB-containing bottoms,
Part of the distillate containing TCB of the first distillation column is received in the first distillation column reflux tank, returned from the first distillation column reflux tank to the transformer oil receiving tank, and the liquid to be distilled in the transformer oil receiving tank. is a distillation stabilization method that distills again,
When supplying a solvent having a boiling point close to the boiling point of PCB and a cleaning solvent having a boiling point equal to or lower than that of TCB to the transformer oil receiving tank, "PCB and the boiling point of the PCB The concentration ratio of "a solvent having a boiling point" and "TCB and a washing solvent having a boiling point equal to or lower than that of said TCB" is at least 2 for PCB and TCB introduced from said transformer oil receiving tank to said TCB separation tower. A distillation stabilization method characterized by supplying and adjusting the concentration ratio of a liquid to be distilled in the initial stage of distillation containing a liquid . 2. The distillation stabilization method according to claim 1 , wherein the solvent having a boiling point close to that of PCB is a saturated hydrocarbon solvent.

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