JP2002097159A - Method of treating pcb - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method of treating PCB oil in a low concentration by reducing the treatment cost by eliminating a procuring process for cooling oil in treating a high concentration PCB. SOLUTION: This method of treating PCB provided with a first process throwing an excess amount of fine particles of sodium metal into a reactor vessel holding low concentration PCB oil of a previously elevated temperature, a second process gradually throwing a high concentration PCB into the reactor vessel holding the low concentration PCB oil and a third process throwing the low concentration PCB oil into the vessel to cool the heat of reaction in the second process, throws the fine particles of sodium metal increasing the amount used in reaction of the PCB and water in the low concentration PCB oil in the first process and previously heated temperature is set at a low temperature equal to the temperature elevated by the reaction of the PCB and water in the low concentration PCB oil and the amount of the low concentration PCB oil thrown in the third process is set by estimating the temperature elevation caused from the reaction of PCB and water in the low concentration PCB oil.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for chemically treating PCB using metallic sodium.

[0002]

2. Description of the Related Art PCBs have been widely used because of their usefulness. However, there are concerns about the effects on ecology and the environment, and production was stopped by 1972.
Use in open applications and new use have been prohibited, and storage has been continued. Regarding these PCB treatments, in addition to the conventional high-temperature incineration treatment, a new chemical treatment method has been recognized and implemented. Among the chemical treatment methods, the metal sodium method is
This method can process both high-density PCB and low-density PCB.

There are so-called “high density PCB” and “low density PCB” in PCB. High concentration PCB is 100% PC
B or 40 ~ used as insulating oil for high voltage transformer
Includes 60% PCB. Low-concentration PCB refers to one that originally used insulating oil that does not use PCB, but was contaminated by PCB due to contamination with PCB.

[0004] This low-concentration PCB-contaminated oil is used for the production of transformers.
This occurred because part of the lines for PCB oil and non-PCB oil were shared in maintenance facilities. Therefore, the type of PCB of the low-concentration PCB contaminated oil is mainly pentachloride PCB,
Usually, benzene trichloride used for adjusting the viscosity of B is also mixed. Most of low concentration PCB is 50pp
m or less.

Among the PCB treatment methods, OSD method, SP method and the like have been proposed as methods using metallic sodium. An outline of the method using sodium metal is to use a sodium sodium dispersion (hereinafter, referred to as “SD”) in which sodium metal fine particles are suspended in a mineral oil at a ratio of about 10 to 40%. It is to dechlorinate PCB.

[0006] A high-concentration PCB is formed by the method using these SDs.
Is treated in a method in which SD is preheated in a reaction tank in a state of being diluted with a mineral oil called base oil, and high-concentration PCB is gradually added thereto.

[0007] Since the reaction between metallic sodium and PCB is an exothermic reaction, it is necessary to appropriately cool while monitoring the temperature during the introduction of high-concentration PCB, and this cooling is performed by a cooler provided in the reaction tank or on the wall surface. It is performed using. However, biphenyl, which is a by-product produced by dechlorination of PCB, polymerizes with each other and increases the viscosity of the liquid phase. Therefore, it is necessary to add mineral oil in consideration of the viscosity of the liquid phase. Therefore, the cooling operation is usually performed by using both the cooler and the supply of the cooling oil.

[0008] Since the by-products have a slightly higher specific gravity than mineral oil, the mineral oil used to dilute the SD and to cool it during the reaction is partially treated by methods such as spontaneous settling, filtering or centrifugation after completion of the treatment. It is recovered and partly polymerized to biphenyl or discharged together with by-products in a form absorbed by by-products. This by-product can be used as fuel in general industry. The processing is performed in a batch system, and the collected cooling oil is reused in the subsequent batches.

[0009]

However, it is necessary to replenish the processing system with mineral oil discharged without being recovered. The amount of cooling oil to be replenished is about ten times that of the PCB to be processed, and the ratio of the cost of cooling oil to the cost of processing is not small at present.

An object of the present invention is to provide a PCB processing method which can reduce the processing cost by eliminating the cooling oil procurement cost during high-concentration PCB processing and can perform low-concentration PCB oil processing. Aim.

[0011]

According to the first aspect of the present invention, there is provided a PCB processing method for dechlorinating high-concentration PCB with a metallic sodium dispersion in which SD is suspended in a base oil. In a PCB treatment method using a low-concentration PCB-contaminated oil as a base oil for suspending the SD or a cooling oil during the reaction, the low-concentration PCB preheated is used.
The first step of dechlorinating low-concentration PCB by adding an excessive amount of SD to a reaction tank holding contaminated oil, and gradually inputting high-concentration PCB into this reaction tank holding low-concentration PCB contaminated oil. A second step of dechlorinating high-concentration PCB by using
A third step of introducing low-concentration PCB-contaminated oil for cooling the reaction heat in the step; The amount of water consumed by the reaction with the water in the concentrated PCB-contaminated oil is increased, and the reaction tank is heated in advance. In the third step, the amount of the low-concentration PCB-contaminated oil used for cooling is determined by the amount of PCB contained therein.
Is set in consideration of the temperature rise due to the reaction with water and the water therein.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, as a base oil for suspending SD used in a chemical treatment method of PCB,
Since low concentration PCB contaminated oil is used, high concentration P
By eliminating the cooling oil procurement cost during the CB treatment, the treatment cost can be reduced, and the low-concentration PCB oil treatment can be performed.

That is, when low concentration PCB-contaminated oil is treated using SD, the amount of by-products produced is small,
Most can be recovered as mineral oil. Since the sodium metal method performs the treatment on the same principle at both high and low concentrations, it can be used as a mineral oil for diluting SD at the beginning of the reaction and a low-concentration PCB-contaminated oil for cooling during the reaction.

The PCB treatment according to the present invention is basically a high-concentration treatment, but a low-concentration PCB-contaminated oil is used instead of mineral oil as a base oil to be initially added to the reaction tank. Low-concentration PCB-contaminated oil is obtained by mixing about 50 ppm of PCB into insulating oil, one of the mineral oil products. When this is used as a base oil, when SD is first introduced, slightly mixed PCB reacts with SD and generates heat. The heat of reaction between the PCB and Na is 1500 KJ / mol (PCB pentachloride) from the heat measurement in actual processing.

More specifically, according to the present invention, an excessive amount of sulfur is added to a reaction tank holding a low-concentration PCB-contaminated oil preheated.
A first step of introducing D and dechlorinating the low-concentration PCB;
A second step in which high-concentration PCB is gradually introduced into the reaction tank holding the dechlorinated low-concentration PCB to dechlorinate the high-concentration PCB; A third step of charging the PCB-contaminated oil.

However, since the reaction between PCB and sodium is an exothermic reaction, when it is used as a cooling oil, proper cooling may not be possible. Therefore, preferably, in the first step of dechlorinating the low-concentration PCB, the amount of SD charged is determined by the reaction with the PCB in the low-concentration PCB-contaminated oil and the reaction with the moisture in the low-concentration PCB-contaminated oil. The temperature at which the reaction tank is preheated rises due to the reaction with the PCB in the low-concentration PCB-contaminated oil and the reaction with the moisture in the low-concentration PCB-contaminated oil. Set by lowering by the temperature.

Thus, for example, when SD is added to 50 ppm of PCB-contaminated oil, the temperature rises by about 0.1 ° C. even in consideration of the presence of benzene trichloride. When 500 ppm of contaminated oil is used, the temperature rise is about 1 ° C. In such a concentration, the preheating temperature may be lower than the standard by the following formula (1). Temperature (° C) determined by 0.002 x PCB pollution degree (ppm) ... (1)

The consumption of SD by the PCB in the contaminated oil is about 0.045 g per 1 kg of the base oil when the pollution degree is 50 ppm.
Therefore, an extra amount represented by the following equation (2) may be input in advance. SD (g) determined by 0.0009 x PCB pollution degree (ppm) x base oil amount (kg) ... (2)

Low-concentration PCB-contaminated oil may contain water, which reacts with sodium. The calorific value, standard heat _{(H 2 O; -285.83KJ / mol} , NaOH; -425.
From 61KJ / mol), is _{140kJ / mol (H 2 O)} . From this, assuming that 100 ppm of water is contained, about 0.4 ° C
The temperature rises, but in such a case, the residual heat temperature is set to the following (3)
What is necessary is just to keep it low by the formula. Temperature (° C) determined by 0.004 x water content (ppm)… (3)

In addition, the consumption of SD due to moisture has a content of
At 100 ppm, it will be about 0.3 g for 1 kg of base oil,
As the input SD amount, an extra amount of the following equation (4) may be added to the predetermined amount. Needless to say, if the water in the PCB-contaminated oil is removed in advance by a degasser or the like, the SD consumption can be reduced. SD (g) calculated by 0.003 x water content (ppm) x base oil amount (kg) ... (4)

During the loading of the PCB, the high-density PCB
The reaction heat increases the temperature inside the reaction tank. At this time, cooling oil is supplied while monitoring the temperature. In the present invention, low-concentration PCB-contaminated oil is used as the cooling oil in the third step. In the third step, the input amount of the low-concentration PCB-contaminated oil for cooling is set to be increased in anticipation of the temperature rise due to the reaction with the PCB therein and the reaction with the water therein. . For example, PC contaminated to 50ppm (water is 100ppm)
When the B-contaminated oil is used, the cooling capacity is about 0.5 ° C lower than when non-contaminated mineral oil is used.
(0.4 ° C from equation (3)), so compensation must be made by increasing the input amount. The same applies to the increase according to the water content. The input amount is adjusted while observing the temperature in the reaction tank.

[0022]

[Example] As base oil, contaminated to 50ppm and water content 200pp
350 kg of PCB-contaminated insulating oil containing m
Raise the temperature to 20 ° C. At this time, PC in PCB-contaminated insulating oil
The temperature rise due to B is 0.1 ° C according to equation (1), and the temperature rise due to moisture contained in the insulating oil is 0.8 ° C according to equation (3).
Although the temperature rises by 0.9 ° C., it is sufficiently smaller than the temperature at the time of temperature rise of 120 ° C., and the temperature rise of 120 ° C. is a set temperature with a sufficient margin. While stirring, 50 kg of SD is charged, and then 20 kg of high-concentration PCB is gradually charged.

At this time, the consumption of SD by the PCB in the PCB-contaminated insulating oil is 15.8 g from the equation (2), and the consumption of SD by the same moisture is 210 g from the equation (4), which is 225.8 g in total. However, the input SD amount of 50 kg was a value that fully considered that amount. During charging, the temperature rises due to the heat of the reaction, but low-concentration PCB-contaminated oil at normal temperature is injected into the reaction tank as cooling oil so as not to exceed 150 ° C.

At this time, in consideration of the heat generated by the PCB and moisture in the cooling oil, the cooling oil is supplied in an increased amount to compensate for the temperature rise calculated by the equations (1) and (3). After about 10 minutes from the introduction of the high-concentration PCB, no heat is generated, so the stirring is maintained for about 2 hours. After a lapse of 2 hours, the reaction tank is cooled, 50 kg of water is charged, and the excess sodium is changed to sodium hydroxide, and the treatment is completed.

As described above, according to the present invention, low-concentration PCB contaminated oil, which is processed at high processing cost, is used as base oil and cooling oil during high-concentration PCB processing, thereby reducing low-concentration PCB oil processing cost. Eliminating the cost of procuring cooling oil during high-concentration PCB processing can reduce processing costs.
In addition, the energy used during the production of the cooling oil and the low-concentration PCB treatment can be saved, and the load on the global environment can be reduced.

[0026]

As described above, the present invention eliminates the cost of procuring cooling oil during high-concentration processing, thereby reducing processing costs and also performing low-concentration PCB oil processing. There is an effect that a law can be obtained.

Claims (1)

[Claims] 1. A PCB treatment method for dechlorinating high-concentration PCB with a sodium metal dispersion in which sodium metal fine particles are suspended in a base oil, comprising: Using low-concentration PCB-contaminated oil as cooling oil
In the B treatment method, an excessive amount of metallic sodium fine particles is charged into a reaction tank holding a low-concentration PCB contaminated oil which has been heated in advance to reduce the concentration of low-concentration PCB.
First step of dechlorination of high-concentration P and high-concentration P in this reaction tank holding low-concentration PCB-contaminated oil.
The second to dechlorinate high concentration PCB by gradually charging CB
And a third step of charging the low-concentration PCB-contaminated oil for cooling the reaction heat in the second step. The amount of water consumed by the reaction with the PCB and the reaction with the water in the low-concentration PCB-contaminated oil is increased, and the reaction tank is heated in advance. And the reaction with water in the low-concentration PCB-contaminated oil is set to be lowered by the temperature that increases. In the third step, the input amount of the low-concentration PCB-contaminated oil for cooling is determined by PC
A PCB processing method characterized by being set to increase in anticipation of a temperature rise due to a reaction with B and a reaction with water therein.