JP2021041381A - Distillation stabilization method - Google Patents

Abstract

To provide a distillation stabilization method for realizing stable distillation by using respective substitutes of PCB and TCB even when the PCB and the TCB mixedly exist.SOLUTION: In a distillation stabilization method for separating an object distillate including at least two liquids of the PCB and the TCB by distilling the object distillate in a distillation tower, into a PCB with a concentration increased from that in a distillation initial period, a bottom product including a PCB with a decreased concentration, and a distillate including a PCB with a concentration decreased from that in the distillation initial period. The distillation stabilization method comprises adjusting a concentration ratio of the PCB and the TCB in the bottom product and the distillate by using a PCB analogous substance and a TCB analogous substance so as to return the concentration ratio to a concentration ratio of the PCB and the TCB in the object distillate in the distillation initial period.SELECTED DRAWING: Figure 1

Description

The present invention relates to a distillation stabilization method, and more particularly to a distillation stabilization method that realizes stable distillation by using alternatives of PCB and TCB even when PCB and TCB are mixed.

PCB (polychlorinated biphenyl) has been widely used as an insulating oil for electrical equipment such as capacitors and transformers because of its excellent stability, nonflammability, and electrical insulation. Has become clear and new use is prohibited.

PCB-contaminated equipment such as capacitors and transformers that already contain PCB-containing insulating oil have been recovered and detoxified in special facilities.

Patent No. 536932 Patent No. 5639931

Patent Document 1 includes a cleaning unit for cleaning equipment containing PCB-containing insulating oil with cleaning oil, and a distillation regeneration unit for distilling PCB-containing cleaning oil generated by cleaning to produce regenerated cleaning oil. PCB-contaminated equipment that has a distillation tower for separating the PCB-containing cleaning oil into a distillate having a lower PCB concentration and a canned liquid having a higher PCB concentration than the PCB-containing cleaning oil is harmless. The method of dismantling the chemical equipment is disclosed.

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

However, in the detoxification facilities of Patent Documents 1 and 2, no study has been made on cleaning of PCB-contaminated equipment when TCB (trichlorobenzene) is mixed in PCB.

The present inventor has found that when TCB is mixed with PCB, the separation efficiency of PCB may deteriorate due to the aging of distillation, and the detoxification treatment may not be stably performed.

Therefore, an object of the present invention is to provide a distillation stabilization method that realizes stable distillation by using alternatives of PCB and TCB even when PCB and TCB are mixed.

Other problems of the present invention will be clarified by the following description.

The above problems are solved by the following inventions.

(Claim 1)
Distilled liquid containing at least two liquids of PCB and TCB is distilled in a distillation column, and PCB having a higher concentration than the initial stage of distillation, canned liquid containing TCB having a lower concentration, and a higher concentration than the initial stage of distillation. It is a distillation stabilization method that separates PCB containing PCB with low concentration and TCB with high concentration into distillate.
The concentration ratio of PCB and TCB in the canned liquid and the distillate is adjusted by using a PCB-like substance and a TCB-like substance so as to return to the concentration ratio of PCB and TCB in the liquid to be distilled at the initial stage of distillation. A distillation stabilization method characterized by this.
(Claim 2)
When adjusting the concentration ratio of PCB and TCB in the canned liquid and the distillate so as to return to the concentration ratio of PCB and TCB in the liquid to be distilled at the initial stage of distillation,
The distillation stabilization method according to claim 1, wherein a PCB-like substance and a TCB-like substance corresponding to the reductions of PCB and TCB in the canned liquid and the distillate are added to the distilled liquid. ..
(Claim 3)
The distillation stabilization method according to claim 1 or 2, wherein the PCB-like substance is a solvent having a boiling point close to that of PCB.
(Claim 4)
The distillation stabilization method according to claim 1, 2 or 3, wherein the TCB-like substance is a cleaning solvent having a boiling point equal to or lower than that of the TCB.

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 alternatives of PCB and TCB, respectively.

The figure explaining the basic principle of this invention A processing flow diagram showing an example of equipment for separating PCBs from PCB-contaminated equipment such as transformers containing insulating oil containing PCBs and TCBs. Block diagram showing an example of an embodiment of the present invention

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

The basic principle of the present invention will be described with reference to FIG.

In the distillation stabilization method of the present invention, the case where PCB or TCB is contained as a compound generated by washing from a PCB-contaminated device is targeted.

Here, the product PCBs mainly used in Japan include Kanechlor (registered trademark) (KC) and Arochlor, and there are several types of each depending on the number of chlorines and the like. For example, KC500 containing biphenyl pentachloride as a main component, KC1000 obtained by mixing TCB with KC500, KC300 containing biphenyl trichloride as a main component, KC400 containing biphenyl tetrachloride as a main component, and the like can be mentioned.

The boiling point of PCB is 320 ° C. to 360 ° C. for biphenyl trichloride (KC300) and 360 ° C. to 380 ° C. for biphenyl pentachloride (KC500).
The boiling point of TCB (benzene trichloride) is 210 ° C.

When separating and distilling PCB and TCB, two-stage distillation is performed, but the initial conditions are set in the first distillation column, TCB separation column 1000, and when distilled in TCB separation column 1000, the concentration is high. A canned out liquid containing the reduced PCB and the reduced concentration of TCB can be obtained. Since the concentration contained in the obtained canned liquid can be designed in advance according to the initial conditions of the PCB separation column, the initial conditions of the first distillation column 2000, which is the second distillation column, can be set. , The PCB is designed so that it does not go to the distillate between the boiling points of the PCB and the boiling point of the TCB.

Then, the concentration balance of PCB and TCB contained in the liquid to be distilled at the initial stage of operation is well balanced, but the balance of concentration of the liquid to be distilled is gradually lost during the circulation operation.

For example, in the TCB separation tower 1000, the PCB containing the PCB having a higher concentration than that at the initial stage of operation and the TCB having a lower concentration are distilled. Therefore, it was found that distillation separation could not be realized under the above initial conditions.

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

It is considered that the cause is that the boiling points of each of the two components cause boiling point fluctuations such as boiling point elevation or boiling point elevation according to the principle of Clausius-Clapeyron.

Therefore, it is adjusted to supplement the alternative substance that adjusts the concentration balance at the initial stage of operation.

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

Under this condition, when the concentration balance of PCB and TCB of the liquid to be distilled charged in the TCB separation column 1000 gradually changes from the initial stage of distillation, as described above, if the boiling point fluctuates due to the concentration fluctuation, the initial condition is , Distillation separation does not work. Similarly, in the first distillation column 2000 that distills after the TCB separation column 1000, the distillation separation does not go well.

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 at the initial stage of distillation. Therefore, it is prepared by using a PCB-like substance and a TCB-like substance, which are alternative substances in the liquid to be distilled.

The PCB-like substance is preferably a solvent having a boiling point close to the boiling point of PCB, and the TCB-like substance is preferably a cleaning solvent having the same or lower boiling point as the TCB.

For example, as the PCB-like substance, a saturated hydrocarbon solvent can be exemplified, for example, KP-8 (boiling point 274 ° C. to 431 ° C., manufactured by Idemitsu Kosan Co., Ltd.) can be used, and as the TCB-like substance, the cleaning solution HC-250 ( A boiling point of about 170 ° C., manufactured by Tosoh Corporation) and NS Clean 220 (boiling point of about 210 ° C., manufactured by JXTG Energy Co., Ltd.) can be used. In addition to these, KP-8 equivalent products can be used as PCB-like substances, and HC-250 equivalent products and NS Clean 220 equivalent products can also be used as TCB-like substances.

When adjusting to return to the concentration ratio of PCB and TCB in the liquid to be distilled at the initial stage of distillation, PCB-like substances and TCB-like substances corresponding to the respective reductions of PCB and TCB in the canned liquid and the distillate. Is preferably added to the distillate.

Here, each of the reduced amounts of PCB and TCB may be quantitatively analyzed by each compound of PCB and TCB. The addition of the PCB-like substance and the TCB-like substance can be added to the inlet line 1001 of the first distillation column 2000.

FIG. 2 is a processing flow diagram showing an example of equipment for separating PCB from PCB-contaminated equipment such as a transformer containing insulating oil containing PCB and TCB, and FIG. 3 is a block diagram showing an example of an embodiment of the present invention. Is.

Reference numeral 1 denotes an oil drainage cleaning device. This device has two functions, an oil draining device and a rough cleaning device.

A plurality of oil draining devices may be provided, for example, an oil draining device that accepts a transformer or a capacitor that is aged and may leak PCB, an oil draining device that accepts a large transformer or a capacitor that does not leak, a small transformer or a capacitor. It may be an oil draining device that accepts. When draining oil, for example, the internal PCB or TCB-containing insulating oil is drained from a hole made in a casing such as a transformer.

In the present embodiment, the degreasing device can include a large degreasing chamber, a leaked product degreasing chamber, and a small degreasing chamber.

After the above oil removal, cleaning is performed by a cleaning device. Specifically, the inside of the transformer or capacitor is cleaned with cleaning oil. Cleaning waste liquid is generated by such cleaning.

The degreased oil containing PCB and TCB is sent to the KC1000 equivalent storage tank 2 via the line 200. Further, the degreased oil containing PCB is sent to the storage tank 3 equivalent to KC500 via the line 300. The cleaning waste liquid is sent to the cleaning oil buffer tank 4 via the line 400. In the present invention, cleaning oil is sent via the line 200 in addition to the oil removal including PCB and TCB. This is to clean the line 200. Here, KC1000 and KC500 are described above.

The cleaning oil is a substance similar to benzene trichloride (TCB), and examples thereof include hydrocarbon-based high-performance cleaning agents. Examples thereof include HC-250 and NS Clean 220 as described above.

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

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

The oil draining and cleaning oil containing PCB and TCB sent to the KC1000 equivalent storage tank 2 is 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 the TCB and the PCB, and distillation is performed. As a result, the cleaning 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, the PCB is not evaporated by the distillation of the TCB separation column 6, so that it can be obtained as a canned liquid. However, even a small amount of TCB may remain in the canned liquid without evaporation.

Therefore, this canned liquid is sent to the first distillation column 8. In the first distillation column 8, a small amount of TCB and PCB are distilled so as 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 canned liquid obtained by the distillation of the first distillation column 8 is only PCB because TCB evaporates. This canned liquid is sent to the KC500 equivalent storage tank 3.

If a part of the TCB collected in the TCB separation tower reflux tank 7 is below the predetermined PCB concentration, it is sent to the TCB analysis waiting tank 10 together with the cleaning oil, and the required amount is collected in the cleaning oil buffer tank 4. ..

Next, the degreased oil containing PCB is sent to the KC500 equivalent storage tank 3 via the line 300. Further, the canned liquid obtained by the distillation of the first distillation column 8 is also sent to the KC500 equivalent storage tank 3. As shown in FIG. 3, the recovered PCB stored in the KC500 equivalent storage tank 3 is sent to the detoxification treatment facility 50 for detoxification treatment.

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 the cleaning oil. The TCB is sent from the cleaning oil buffer tank 4 to the rough cleaning water separation tower 11, and is distilled and separated into water, TCB, PCB, and cleaning oil.

Since the distillate obtained by the distillation of the rough washing water separation tower 11 is water, the water is discharged to the outside of the system.

Since the canned out liquid obtained by the distillation of the rough cleaning water separation tower 11 is TCB, PCB and cleaning oil, it is sent to the rough cleaning oil recovery tower 12 and distilled into the cleaning oil and TCB and PCB to separate them. Will be done.

Since the distillate obtained by the distillation of the rough cleaning oil recovery tower 12 is cleaning oil, this distillate is sent to the rough cleaning oil recovery tank 13 via the line 401, and the rough cleaning oil recovery tank 13 is used. The cleaning oil recovered in the above is reused in the degreasing cleaning device 1. As a result, the amount of new cleaning oil used can be reduced.

Since the canned liquid obtained by the distillation of the rough cleaning oil recovery tower 12 contains TCB and PCB, it is sent to the KC1000 equivalent storage tank 2 via the line 402.

The canned liquid containing the TCB and the PCB is sent to the TCB separation tower 6 via the transformer oil receiving tank 5 together with the oil removal containing the PCB and the TCB described above, and is distilled in the TCB separation tower 6. This distillation has been described above.

The canned liquid obtained by the distillation of the first distillation column 8 is only PCB because TCB evaporates. This canned liquid is sent to the KC500 equivalent storage tank 3. The recovered PCB stored in the KC500 equivalent storage tank 3 is sent to the detoxification treatment facility 50 shown in FIG. 3 described later for detoxification treatment.

The cleaning oil collected in the TCB separation tower reflux tank 7 and a part of the TCB are sent to the TCB analysis waiting tank 10, returned to the cleaning oil buffer tank 4 via the return line 201, and reused.

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

That is, in the rough cleaning oil recovery tower 12, the cleaning oil is separated by distillation among the three components of TCB, PCB and cleaning oil, but since TCB and cleaning oil have relatively close boiling points, one of the TCB together with the cleaning oil. The part may also be separated on the distillate side.

Then, the balance of the composition components entering the crude cleaning oil recovery tower 12 may be lost, and the molar boiling point fluctuation (the molar boiling point elevation or the molar boiling point decrease according to the principle of Clausius-Clapeyron) may occur. If the molar boiling point fluctuates between the three components or the molar boiling point fluctuates between the two components, the distillation operation itself becomes difficult, and finally, the separation and stabilization of PCB and TCB also becomes difficult.

Therefore, since the cleaning oil and the TCB are returned on the return line 201 of the present invention, the cleaning oil and the TCB returned from the return line 201 are included in addition to the cleaning waste liquid, so that the molars of the three components at the time of distillation are included. Stable distillation (stabilization of distillation) can be performed by preventing boiling point fluctuations or preventing PCB and TCB molar boiling point fluctuations.

At the same time, by distillation, the cleaning oil returned from the return line 201 is added to the cleaning oil contained in the cleaning waste liquid, so that the amount of cleaning oil recovered can be increased and the amount of circulating and reused cleaning oil can be increased. it 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 to the detoxification treatment equipment 50 shown in FIG. 3 via the line 301, dechlorinated, and detoxified.

The KC500 equivalent storage tank 3 contains a degreased oil containing PCB sent via the line 300 and a canned liquid obtained by distillation in the first distillation column 8. The canned liquid is PCB.

As shown in FIG. 3, the PCB sent via the line 300 is detoxified by the detoxification processing equipment 50. Then, a part of the solvent used in the detoxification treatment equipment 50 is returned to the rough cleaning oil recovery tank 13 via the line 500 as a solvent for circulation and reuse. This allows the solvent to be reused during distillation as a substitute for PCBs, as well as for use in detoxification treatments.

Further, 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 canned liquid together with PCB even in distillation, and is sent to the storage tank 3 equivalent to KC500. Liquid is sent. 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 the present embodiment, the solvent returned to the rough cleaning oil recovery tank 13 via the line 500 and the cleaning oil returned to the rough cleaning oil recovery tank 13 via the recovery line 401 are separated by the TCB separation tower 6. Therefore, it is also preferable to provide an adjustment line (broken arrow) as shown in FIGS. 2 and 3 for liquid feeding to the transformer oil receiving tank 5 at the time of distillation separation. As a result, a line before distillation is formed, and PCB-like substances and TCB-like substances that are substitute substances for PCB and TCB can be supplied, so that the concentration balance can be adjusted.

1: Degreasing cleaning device 2: KC1000 equivalent storage tank 3: KC500 equivalent storage tank 4: Cleaning oil buffer tank 5: Trans oil receiving tank 6: TCB separation tower 7: TCB separation tower Reflux tank 8: 1st distillation column 9: 1st distillation column Reflux tank 10: TCB analysis waiting tank 11: Rough cleaning water separation tower 12: Rough cleaning oil recovery tower 13: Rough cleaning 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 column 1001: Inlet line 2000: First distillation column

Claims (4)

Distilled liquid containing at least two liquids of PCB and TCB is distilled in a distillation column, and PCB having a higher concentration than the initial stage of distillation, canned liquid containing TCB having a lower concentration, and a higher concentration than the initial stage of distillation. It is a distillation stabilization method that separates PCB containing PCB with low concentration and TCB with high concentration into distillate.
The concentration ratio of PCB and TCB in the canned liquid and the distillate is adjusted by using a PCB-like substance and a TCB-like substance so as to return to the concentration ratio of PCB and TCB in the liquid to be distilled at the initial stage of distillation. A distillation stabilization method characterized by this. When adjusting the concentration ratio of PCB and TCB in the canned liquid and the distillate so as to return to the concentration ratio of PCB and TCB in the liquid to be distilled at the initial stage of distillation,
The distillation stabilization method according to claim 1, wherein a PCB-like substance and a TCB-like substance corresponding to the reductions of PCB and TCB in the canned liquid and the distillate are added to the distilled liquid. .. The distillation stabilization method according to claim 1 or 2, wherein the PCB-like substance is a solvent having a boiling point close to that of PCB. The distillation stabilization method according to claim 1, 2 or 3, wherein the TCB-like substance is a cleaning solvent having a boiling point equal to or lower than that of the TCB.

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